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Mach Discussion => General Mach Discussion => Topic started by: kolias on January 08, 2011, 04:34:51 PM

Title: Power Supply Unit
Post by: kolias on January 08, 2011, 04:34:51 PM
Power Supply Unit

Not very good with the electrical staff so I hope someone can help.

I have 4 Keling motors (the spec sheet is attached for more info) which I will connect as Unipolar and as per spec sheet that gives me 3.0A per motor or 12.0A total.

Besides the motors I will have 4 drivers and one BOB from Probotix. Each driver is 3A, 42V output rating whatever this means and they also say that the voltage should be limited to about 42V DC. So I guess I figured that I need another 12.0A for the drivers.

The BOB is listed as 12 to 40V capables of at least 100mA, so I figured 1.0A here. I will also have 8 LED lights and a small fan so lets say another 2.0A

Total Amps I need = 27A. So I bought a power supply 12V DC / 29A / 350 Watts.

Do you see any problem with the power unit I purchased? Any suggestions?
Title: Re: Power Supply Unit
Post by: HimyKabibble on January 08, 2011, 05:36:08 PM
"Do you see any problem with the power unit I purchased?" - Yes.  What you really want is about a 37V/10A supply.  12V is nowhere near enough to get decent performance from those motors.  The ideal voltage for the motors is given by 32 times the square root of the motor inductance (in mH), which gives about 47.5V.  This is assuming bipolar parallel mode, which is what you want to use.  But your drivers are rated for 42V maximum, so you want to stay a bit below that maximum rating, so knock it down to 37V.  The current rating of the supply should be about 70% of the sum of all the motor currents, or about 8.5A.  Round that up to 10A.  You won't get best performance out of this setup, as the drivers are not well matched to the motors.  You will be losing about 25% of the potential torque, since your drivers won't allow you to run full rated current on the motors (4.2A for the motors, vs 3A for the drivers).

Regards,
Ray L.
Title: Re: Power Supply Unit
Post by: ger21 on January 08, 2011, 05:38:06 PM
You don't need 3 amps for the motors and drives. Just 3 per set.The drives don't draw any current, they just pass it to the motors.
 A 15 amp supply is probably plenty.
Title: Re: Power Supply Unit
Post by: ger21 on January 08, 2011, 05:39:50 PM
Yes, as Ray said, 12V is too low. Speed is proportional to voltage, so a 36V power supply would give you 3 times more speed.
Title: Re: Power Supply Unit
Post by: kolias on January 08, 2011, 06:17:04 PM
Glad I asked, so I will get another power supply around 36V DC / 10 - 15A

Thank you
Title: Re: Power Supply Unit
Post by: kolias on January 08, 2011, 06:29:33 PM
The only place I know to buy power supply is
http://cgi.ebay.com/12V-DC-29A-350W-Regulated-Switching-Power-Supply-/370412404026?pt=LH_DefaultDomain_0&hash=item563e4cbd3a

The best I can see are: 22-26VDC / 14.6A, 26-30V / 13A, 36V / 9.7A. Don't know why but seems as the voltage increases the Amps decreases

Any suggestions?
Title: Re: Power Supply Unit
Post by: RICH on January 08, 2011, 06:47:05 PM
Try    Camtronics        as they sell power supply kits. 

RICH
Title: Re: Power Supply Unit
Post by: kolias on January 08, 2011, 07:03:45 PM
Try    Camtronics        as they sell power supply kits. 

RICH

Thanks RICH but did not see any power supply at Camtronics-CNC. I have purchased everything and all I need now is the Power Supply
Title: Re: Power Supply Unit
Post by: Hood on January 08, 2011, 07:14:48 PM
You can easily make your own power supply, Bob Campbell has a good pdf describing how to do it, heres the link.
http://campbelldesigns.net/files/power-supply-part-1.pdf

Hood
Title: Re: Power Supply Unit
Post by: RICH on January 08, 2011, 07:23:12 PM
Don't know where you looked but:

power supply 36V 25A $125 ( email me at dmauch@seanet.com I do not want to sell power supply kits to unqualified people.

Power Supply ( email me at dmauch@seanet.com I do not want to sell power supply kits to unqualified people.
110 primary 33VDC at 20A ideal for the 600 oz in Ametch motors and others.

RICH

Title: Re: Power Supply Unit
Post by: kolias on January 08, 2011, 07:30:00 PM
You can easily make your own power supply, Bob Campbell has a good pdf describing how to do it, heres the link.
http://campbelldesigns.net/files/power-supply-part-1.pdf

Hood

An excellent article Hood, thank you

That is a project in itself and for sure I will give it a try after I finish my CNC
Title: Re: Power Supply Unit
Post by: HimyKabibble on January 08, 2011, 07:32:30 PM
This would work perfectly: http://www.antekinc.com/details.php?p=170

Regards,
Ray L.
Title: Re: Power Supply Unit
Post by: kolias on January 08, 2011, 07:42:25 PM
Don't know where you looked but:

power supply 36V 25A $125 ( email me at dmauch@seanet.com I do not want to sell power supply kits to unqualified people.

Power Supply ( email me at dmauch@seanet.com I do not want to sell power supply kits to unqualified people.
110 primary 33VDC at 20A ideal for the 600 oz in Ametch motors and others.

RICH




I looked at camtronics-cnc.com, no power supply there

$125 for a power supply plus shipping is a lot and I will assume thats US$. The ones I mentioned above are from China at about $40 shipping included. In 2009 I bought one from the same place 27V DC / 13A about $35.00 shipping included. My motors are 282oz-in and I guess I dont need the high Amps

Thanks anyway
Title: Re: Power Supply Unit
Post by: kolias on January 08, 2011, 07:50:13 PM
This would work perfectly: http://www.antekinc.com/details.php?p=170

Regards,
Ray L.


I do appreciate the help from all here but this unit is also an expensive power supply ($US116.00 shipping included). Perhaps I will have to purchase one but I have to look at all alternatives.

The one you mentioned from Antek is 35V DC / 8.6A and cost US$116.00. The ones I mentioned earlier from eBay one is 36V / 9.7A and cost US$40.00 shipping included. I tend to believe that the second will do the job
Title: Re: Power Supply Unit
Post by: HimyKabibble on January 08, 2011, 08:51:43 PM
You get what you pay for.  Those E-Bay supplies are switching power supplies., which are not the best thing for steppers.  They are also brand X Chinese-made power supplies, and a number of people have had problems with other such supplies.  Don't be surprised if it doesn't work well, or goes up in smoke.  Saving pennies by buying cheap motor drivers, and cheap power supplies is what leads to flaky machines, and supports the old myths about steppers being inherently unreliable....

Regards,
Ray L.
Title: Re: Power Supply Unit
Post by: kolias on January 08, 2011, 09:19:01 PM
Ray I do apologize but I understand that the products in US are much superior than from China or Hong Kong. However I made a mistake and already bought a power supply for $40.00 which is not good enough as you pointed out and now I have to buy another one which will be another $40.00. My budget is limited.

When I make another CNC then I will go to Antek which seems a good place and I didn’t know about them before.

I do appreciate your time and help

Title: Re: Power Supply Unit
Post by: Hood on January 08, 2011, 09:54:39 PM
kolias
 it is very easy to make a power supply for steppers, a transformer (toroidal is normal) a rectifier and a capacitor or two. Dont know the prices in North America for these but I am sure it will work out cheaper than buying a ready made one.


Hood
Title: Re: Power Supply Unit
Post by: RICH on January 08, 2011, 10:25:40 PM
FWIW,
Common mistakes:
1. Not considering the future use of the controller
2. Inadequate power supply
3. Second rate / problematic drives
4. Inadequate stepper motors

So you buy all at a bargain and save $A.....
Then you rebuy and to get what you needed or wanted in the first place $B

So $B - $A= may be nothing but agrivation and wasted money

Take you time, build the controller yourself, buy once and save money, know how it all works and can repair it, ....nice good feeling........$ cost in the long run = priceless

You CAN do it all......, ;)

RICH

Title: Re: Power Supply Unit
Post by: kolias on January 08, 2011, 10:48:33 PM
I totally agree with all above and I would have liked to build my own power supply but my knowledge with electrical is very basic. In addition, although Montreal is a big city the stores to supply electronics is only one and all the clerks there are students who know nothing to give me a hand. Talking about rectifiers and capacitors etc. is like Chinese to me LOL.

Anyway I'm reading the document which Hood send me and looks simple enough. I like to read it again and see if I can figure out how I can do it and where to purchase the staff.
Title: Re: Power Supply Unit
Post by: kolias on January 10, 2011, 09:26:06 AM
kolias
 it is very easy to make a power supply for steppers, a transformer (toroidal is normal) a rectifier and a capacitor or two. Dont know the prices in North America for these but I am sure it will work out cheaper than buying a ready made one.


Hood


I ordered the new power supply from China (25 days delivery!!!) and in the mean time I printed the pdf document you sent me from CambellDesigns and I study it to see what I can get out of it. Would I get any help here if I decide to go ahead and build one myself? I mean the questions I will have may sound stupid to you but I know very little about electrical let alone build a power supply.

First step is to size the items I need and then go to my local store and see if they are available and how much they cost. My local store have tons of electronic parts which they are stored in bins and you must know exactly what you are looking for otherwise you are lost since there is no help from the store.
Title: Re: Power Supply Unit
Post by: Hood on January 10, 2011, 09:36:47 AM
Yes you will get help here I am sure, I am no electrical whiz but its straight forward enough, must be I managed ::) But there are lots of guys here that are experts so you will be sure to get answers.

Hood
Title: Re: Power Supply Unit
Post by: Hood on January 10, 2011, 09:39:03 AM
Oh and by the way, when you are not sure its always best to ask, especially where electricity is concerned.
Hood
Title: Re: Power Supply Unit
Post by: kolias on January 10, 2011, 11:52:34 AM
Oh and by the way, when you are not sure its always best to ask, especially where electricity is concerned.
Hood

That is 100% correct and I always do, thanks
Title: Re: Power Supply Unit
Post by: kolias on January 10, 2011, 02:54:59 PM
To size the components of the power supply unit I follow the steps from the .pdf document Hood provided earlier. http://campbelldesigns.net/files/power-supply-part-1.pdf

I also attach a snapshot of my motors spec in case I misinterpreted something. Please note that the drivers for my motors are Unipolar and we cant change this for now. So I have 4 motors and each is 2.76VDC, 3.0A and I came up with the following:

Desired power supply voltage: 2.76 * 20 = 55.2VDC

Desired transformer voltage: 55.2 / 1.4 = 39.42VAC (This I don't understand; assuming this 39.42VAC is the household voltage where the transformer will be plugged, all households are either 120VAC or 220VAC)

Then I calculate the desired transformer current:
3.0A * 4 motors = 12.0A * 0.67 = 8.04A
39.42 * 8.04 = 316.93VA (if this is correct what will be the next transformer std size?)

Next comes the size of the filter capacitor: (I don't know where this item is located in the schematics provided by “cambelldesigns”)
C = (80000 * 8.04) / 69 = 9321.73uf (here I’m in the dark because I don't understand which current and voltage the “cambelldesigns document uses).

So the above is the 1st step in the selection of the components. If someone can check the above and answer my questions will be appreciated/
Title: Re: Power Supply Unit
Post by: Hood on January 10, 2011, 04:18:47 PM
Before going any further what is the max voltage your drives can handle as that will determine the calculations.
Hood
Title: Re: Power Supply Unit
Post by: kolias on January 10, 2011, 06:00:36 PM
In the exact words the manufacturer (Keling) said: "You can use the power supply from 24-72VDC"
Title: Re: Power Supply Unit
Post by: Hood on January 10, 2011, 06:32:09 PM
Ok well I would go as high as I could on the voltage, most recommendations are for up to 25 x  motors rated so  about 70V Dc would be ideal. AC would then be 70/1.4= 50v which will be a standard toroidal I would imagine, 110v primary 50v secondary.


Next VA would be 50 x 8.04 = 402VA so probably 500VA would be a standard size, doesnt matter if you go more than the calculated value for this but dont go lower, although 400VA would be close enough I would think if thats what you found..

So toroidal transformer with 110v primary  50v secondary and 400VA or more


Capacitance needed would be  (80000 * 8.04) / 70 = 9188uF So you are looking for a capacitor of that capacitance and a voltage of at least  your DC voltage. If you cant get capacitors of that capacitance value you can link 2 or more  in parallel (positive to positive and negative to negative) to get to the value required.


Hood
Title: Re: Power Supply Unit
Post by: Hood on January 10, 2011, 06:43:28 PM
Oh and also should have mentioned you can go higher on the capacitance if required.
Hood
Title: Re: Power Supply Unit
Post by: kolias on January 10, 2011, 08:09:49 PM

Capacitance needed would be  (80000 * 8.04) / 70 = 9188uF So you are looking for a capacitor of that capacitance and a voltage of at least  your DC voltage. If you cant get capacitors of that capacitance value you can link 2 or more  in parallel (positive to positive and negative to negative) to get to the value required.

Hood

So capacitance 9188uf and voltage 50VDC?
I dont know what is available but can I go higher on the 50VDC?

Is filter capacitor and capacitor the same item?

And how about the bridge rectifier? What specs I need to buy this one?

Thank you Hood
Title: Re: Power Supply Unit
Post by: RICH on January 10, 2011, 09:04:19 PM
The capacitor is a capacitor but the word "filter" comes into the description  because it takes out some of the ripple that stills exists after the rectifier has changed the AC to DC.
Said a different way, you have a flowing river of AC which is turned into a lake of DC, the bigger the lake the less ripple in the waves you will see in the lake at the discharge.
If you want to have a bigger lake, no problem. You will find that the standard formula provides for say 10 percent ripple and you can have less if you increase the size of the capacitor which is good.

The capacitor ( about the size of a beer can ) in mine is way over size as compared to the calculated value. So when your dumpster diving though the bins just look at the cap and it should give the Uf and also say it's good for like 1000Volts ( the volt rating should be better than say 20 - 50 % over the power output voltage ). A lot of the bigger ones will say 1000 volts. Buy 2 or three if they are real cheap....think i bought five of them  for $2 each.

RICH
Title: Re: Power Supply Unit
Post by: kolias on January 10, 2011, 09:51:22 PM
Thanks RICH, good explanation

Title: Re: Power Supply Unit
Post by: Hood on January 11, 2011, 02:26:22 AM
Dont go any higher than the 50vac secondary on the transformer as that will put you over the max for your drives. When you rectify and smooth  AC the DC value is approx 1.4 times greater hence 50vac becomes 70vdc.  You can go a bit less on the 50vac secondary but try and keep at the 50 or close.

As for the rectifier, you need it to be rated at least for the 70vdc and 8 amp that you calculated for.

Hood
Title: Re: Power Supply Unit
Post by: stirling on January 11, 2011, 05:39:12 AM
In the exact words the manufacturer (Keling) said: "You can use the power supply from 24-72VDC"
This appears to be at odds to what you've said at the beginning of your post where you stated 42V max. Are you mixing up max recommended motor V with max driver V. (The motors are Keling - not the drivers).

Certainly if the drivers are these http://www.probotix.com/stepper_motor_drivers/ProboStep (http://www.probotix.com/stepper_motor_drivers/ProboStep) (which are the only unipolar drives I can see at Probotix) then the max V is 44V.

From your link the (unipolar) motor inductance is 2.2mh, therefore your "ideal" voltage for "max" speed & torque is 32 * sqrt 2.2 = 47.4636704 Vdc. BUT this is over the 44V limit of your drives. You said your supplier recommended limiting to 42V - a tad below the limit of 44V.

So 42Vdc gives a transformer secondary of 42/1.414 = 29.7029703VAC.

Generally (in the UK anyway) transformer secondarys come in 12, 15, 18, 22, 25, 30... VAC so your nearest fit is 25VAC which will give you 35.35Vdc. This as has been stated earlier is not the "ideal" for your motors but it's the best you can do with your drivers.

Unless of course I've cocked up somewhere  :)

Ian
Title: Re: Power Supply Unit
Post by: kolias on January 11, 2011, 06:48:24 AM
Thank you Ian for your input and lets see if I can clarify the data.

Keling told me by email that for the 4 motors I have the voltage range on my power supply should be from 24-72VDC

Probotix states in their manual that the 4 drivers I have the power supply voltage should be limited to about 42VDC (your link for the drivers is correct)

I thought about it that the transformers secondary must be available in certain std. size and my next question here would have been what size my choice should be. So you have answered my question before I even asked. I will get one at 25VAC

There is something that confuses me and I would like it to be clarified. You said the transformers secondary comes in .......25VAC. I thought that these transformers have a primary side which is the AC volts and a secondary side which is the DC volts. So is the 25 volts AC or DC?

Thanks for your time
Nicolas
 
Title: Re: Power Supply Unit
Post by: Hood on January 11, 2011, 07:03:51 AM
No a transformer just steps the AC voltage down  from the input to the output so you still need to rectify and smooth the Ac to make it DC.
Hood
Title: Re: Power Supply Unit
Post by: RICH on January 11, 2011, 07:16:52 AM
The secondary would be AC and depends on the ratio of the primary to secondary windings. Some transformers have multiple taps on the secondary windings
 so you have a choice of voltages available. The AC is then is made into DC by the rectifier. That component is is usualy a group of diodes which clip off the tops and bottoms
the AC sine wave. The AC sine wave is sort of like a female who has a period which is  repeatable over time with a highs and lows.

RICH
Title: Re: Power Supply Unit
Post by: Hood on January 11, 2011, 07:19:06 AM
The AC sine wave is sort of like a female who has a period which is  repeatable over time with a highs and lows.

RICH


Brave man ;D
Title: Re: Power Supply Unit
Post by: kolias on January 11, 2011, 07:25:43 AM
LOL..........thanks Rich, now I get it but I should have thought about before by myself. Guess too much to digest at once.

So now that Ian said to get a transformer with 25VAC secondary, what will be the VA of this transformer? 402VA?
Title: Re: Power Supply Unit
Post by: Hood on January 11, 2011, 07:29:14 AM
Nope, 25v x 8.04A = 201VA although as said before, more will not harm.
Hood
Title: Re: Power Supply Unit
Post by: kolias on January 11, 2011, 08:33:12 AM
Sounds good so far, I'm going to this store this morning to see what is available regarding toroidal transformers, capacitors and rectifiers.

Then I would like to know what gauge wiring I should use plus I want to put a fuse on both the incoming 110VAC and outgoing 25VDC. Before I proceed with the build I will post a wiring schematic including materials list and if all is ok then I will do my purchasing. Who knows, I might have a new power supply even before the one I ordered from China arrives LOL......

Nicolas
Title: Re: Power Supply Unit
Post by: kolias on January 11, 2011, 09:26:44 AM
The attached is part of the last page from the CambellDesigns document and I have some questions:

1- When he says all ground wires should be attached to one point, does this mean AC and DC ground?

2- Then he says to run a wire from the + terminal on one of the capacitors to a terminal strip because later    you will run a wire from the terminal to the fuse block. What this fuse is for?
Title: Re: Power Supply Unit
Post by: Hood on January 11, 2011, 01:54:48 PM
I am not sure  about the mains wiring in North America so dont really want to comment too much regards question 1 but dont get confused with the neutral of an AC circuit and Gnd. Your transformer will likely only have two wires on the primary or possibly 4 but they are live and neutral and none is a gnd wire. If your mains has live neutral and gnd then you would normally have the Gnd connected to the Gnd stud.


Regards question 2, the positive wire from the cap will be the positive you use to feed your drives, the 0v coming from the negative terminal on the capacitor. The positive is fused in that example but I am wondering if that is actually a good idea and will let others that have more knowledge comment on that.

Hood
Title: Re: Power Supply Unit
Post by: kolias on January 11, 2011, 03:26:32 PM
I have two pilot lights rated for 110VAC which I want to install on the control station for my CNC. Would they work if I supply them with 40VDC?

Also I have a toggle switch rated 10A, 250VAC which I want to control 8 LED lights. Would this switch work if I connect it to 12VDC?

I dont confuse the ground, neutral and line on the 110V circuit. I just wanted to know if I can connect the ground from the 110VAC along with the ground (Black wire) from a DC circuit

Well the store close by does not have any toroidal transformers neither rectifiers but they do have a large selection of capacitors
10000uf, 25V, $3.99 (that thing is HUGE)
8200uf, 25VDC, $2.99
5500uf, 25VDC, $1.99

When I buy the capacitor(s) how do I secure them to my board? I noticed on the .pdf document from Cambel that he has some kind of pipe clamps at the bottom. Do I buy these clamps separetly?

Anyone knows an online store to buy the toroidal transformer and rectifier?
Title: Re: Power Supply Unit
Post by: Hood on January 11, 2011, 04:49:17 PM
You can buy the capacitor clamps or secure with cable ties(zip ties?) or even a dab of silicone sealant on the base and stick them down.
Hood
Title: Re: Power Supply Unit
Post by: BR549 on January 11, 2011, 07:28:16 PM
MAke SURE on your caps that you over rate the voltage rating. Do not use 25dcv caps on a 40 vdc system.

Just a thought, (;-) TP
Title: Re: Power Supply Unit
Post by: kolias on January 11, 2011, 08:32:10 PM
Thanks for bringing it up, a very good tip
Title: Re: Power Supply Unit
Post by: kolias on January 12, 2011, 08:36:22 AM
The conclusion so far is:

1) I would like to know if I can connect the ground wiring from tha AC along with the Ground (Black) from the DC (I plan to use a metal bar on my board and connect the AC ground plus the DC black wire there)

2) It seems that toroidal transformers are not easily available. Searching on the web I found no places where I can purchase them and eBay does not have the size I want. Antek has them but they are out of stock. Anyone knows where I can buy them?

3) Rectifiers seems that is easy to purchase

4) As I understand now, the capacitor has to be a multiple of 50VDC or perhaps more? Anyone can suggest a safe combinations (uf / vdc)?
Title: Re: Power Supply Unit
Post by: kcrouch on January 12, 2011, 10:44:12 AM
Signal transformer has lots of items that will do for you. signaltransformer dot com
They can make up any toroidal transformer that you need as well as having lots of other transformers in stock. Check out their MPI series too.
Kenny
Title: Re: Power Supply Unit
Post by: Hood on January 12, 2011, 11:00:19 AM
The conclusion so far is:

1) I would like to know if I can connect the ground wiring from tha AC along with the Ground (Black) from the DC (I plan to use a metal bar on my board and connect the AC ground plus the DC black wire there)
My commercial lathe and mill had/have the AC Earth (as we call it) connected to the stud, DC 0V is not as far as I can recall (possibly internally in the power supply the connect to earth)but all shields are.
2) It seems that toroidal transformers are not easily available. Searching on the web I found no places where I can purchase them and eBay does not have the size I want. Antek has them but they are out of stock. Anyone knows where I can buy them?

I am from the UK but every place that sells electronics in the UK sells toroidal transformers so I would imagine the USA places such as DigiKey would also.

4) As I understand now, the capacitor has to be a multiple of 50VDC or perhaps more? Anyone can suggest a safe combinations (uf / vdc)?


As was said by me, Rich and lastly Terry you need the voltage to be above the DC voltage of your supply, it can be as high a voltage rating as you can get but dont go lower and as Rich pointed out best 20% higher than your supplies output. Capacitance is similar, except it can be what you calculated (dont need the 20% more that the voltage does) or higher but again never lower.

Hood
Title: Re: Power Supply Unit
Post by: kolias on January 12, 2011, 08:41:03 PM
Ok we are getting somewhere now.......

Gerry helped me to locate the transformerand it looks good
http://www.mpja.com/prodinfo.asp?number=7846+TR

For the capacitor I will get one from the store in my area, around 30 – 50 VAC, 10000 – 20000uf

For the bridge rectifier the choices I see from the same store as the transformer are:
400PIV, 15A
1000PIV, 15A
50PIV, 25A
400PIV, 25A
50PIV, 35A

Dont know what PIV means, is my choice in one of the above?
Title: Re: Power Supply Unit
Post by: kolias on January 13, 2011, 09:09:08 AM
No one can help with my previous post?

I would like to know if the transformer looks ok
If the capacitor selection range is ok
Bridge rectifier selection

If no answer, perhaps I should go to another forum to finalize this projects?

Thanks
Title: Re: Power Supply Unit
Post by: Hood on January 13, 2011, 09:49:44 AM
Transformer should be fine, think toroidals are less noisy but it should be fine.

Capacitor would be best 50v or hiigher with  capacitance of 20,000uF or higher

PIV means Peak Inverse Voltage I would probably go overkill on the rectifier and get the 400/25 one.

Hood
Title: Re: Power Supply Unit
Post by: stirling on January 13, 2011, 10:25:14 AM
No one can help with my previous post?

I would like to know if the transformer looks ok
If the capacitor selection range is ok
Bridge rectifier selection

If no answer, perhaps I should go to another forum to finalize this projects?

Thanks


Kolias - I'm going to put my mod hat on just for a second. Your last post is unfair to all the very knowlegable people who have spent a lot of time helping you. Whilst people love to help as much as they can it's also up to you to try to do as much as you can for yourself. Your first two questions have been answered several times by several people and your third... I just typed PIV Bridge Rectifier into google and I got over 7000 results with the 1st on the list telling me all I could ever want to know.

You are of course free to go to any other forum if you think this one isn't good enough but I doubt VERY much that you'll receive as much help and patience as you have here.

mod hat back off  :)
Title: Re: Power Supply Unit
Post by: kolias on January 13, 2011, 11:20:57 AM
ok so we now have settled all the major components:
The transformer as posted before, capacitor 50V or higher & 20000uf or higher, rectifier 400/25
Tonight I will try to post a schematic for comments and then I will proceed with purchasing.
A BIG thanks to all involved here

Stirling regarding your comments I guess you got me wrong. At the beginning of this post Hood, who has been the only one providing most of the answers, had mentioned:

Yes you will get help here I am sure, I am no electrical whiz but its straight forward enough, must be I managed ::) But there are lots of guys here that are experts so you will be sure to get answers.

Hood

Therefore when I received no answers I thought Hood was waiting for others to reply and when there was no reply from others I thought perhaps I should go elsewhere to get my answers. I must say the intention was NOT to insult anyone or this forum but only to get more help and get going with this project.

I love this forum and all people and it has been a great help on this project and for Mach3

As for the Google search, I try not to use it a lot regarding electrical because I’m really green with this staff. Reading something on Google depends on my interpretation and since I know nothing I may interpret it wrongly and this I don’t want since the consequences can be disastrous.

AGAIN, asking to go to other forum was NOT to insult anyone but rather to help

Title: Re: Power Supply Unit
Post by: kolias on January 13, 2011, 06:23:41 PM
Here is my schematic and all comments will be appreciated.

I have already made a control station box (1/4” plywood, 20”x 18”x 12” high) which is intended to house the drivers and BOB and there is space to build the power supply unit inside this box. As you can see on my schematic I connect the ground from the AC supply to a ground metal bar and in the same bar I connect the black wire from the DC. I dont know if this is correct.

The other point I’m not sure is the size of the fuses; I have 10A fuse for the AC and DC but not sure if this is sufficient.
Title: Re: Power Supply Unit
Post by: RICH on January 13, 2011, 06:45:41 PM
Quote
control station box (1/4” plywood)

Strongly suggest a metal enclose.

RICH
Title: Re: Power Supply Unit
Post by: kolias on January 13, 2011, 07:38:24 PM

Strongly suggest a metal enclose.

RICH


A couple years ago when I built my old CNC, I had asked a friend about the control box and he suggested against a metal enclosure to avoid the possibility of sort circuit between wires touching the metal enclose.

Can I ask why a metal enclosure is suggested ?
Title: Re: Power Supply Unit
Post by: ger21 on January 13, 2011, 08:10:38 PM
I don't know much about electronics, but I know that you shouldn't have a fuse in your AC ground wire. The fuse defeats the purpose of the ground.
Title: Re: Power Supply Unit
Post by: RICH on January 13, 2011, 08:39:42 PM
Quote
Can I ask why a metal enclosure is suggested ?

Metal is not combustable and will contain a spark,fire, smoke,  and to some degree an explosion.

The metal enclosure acts as a shield thus preventing  transmitting and recieving spurious signals.

The metal enclosure allows for grounding. Should a wire break and touch the box , the box is grounded / it is bonded to the ground wire and such provides a less resistive path to ground. You could think of this as the same reason for having a ground wire run along with the other wires in a shield.

The box is basicaly a junction box and code may require you to put it in a metal enclosure.

Not to argue with your friends advice but I disagree with your friends advice. (Don't let him do any wiring in your house  ;))

RICH

 
Title: Re: Power Supply Unit
Post by: kolias on January 13, 2011, 08:44:18 PM
I don't know much about electronics, but I know that you shouldn't have a fuse in your AC ground wire. The fuse defeats the purpose of the ground.

Sorry Gerry but my sketch is not clear enough. The fuse is installed on the black wire (Line) of the 120VAC cable.

The ground wire is broken to allow me only to write 10A Fuse
Title: Re: Power Supply Unit
Post by: kolias on January 13, 2011, 08:48:16 PM
Thank you RICH

I agree with your points and so a metal box will be used for the new power supply unit.

BTW my friend doesn't even know what house wiring is LOL
Title: Re: Power Supply Unit
Post by: kolias on January 14, 2011, 05:19:14 PM
I went to purchase the capacitors from my local store but I couldn’t find anyone with 50VDC or more neither with 20000uF or more. The closest I found were:

15500uF, 25VDC
10000uF, 25VDC
8200uF, 25VDC
5500uF, 25VDC
34000uF, 15VDC
25000uF, 15VDC
10000uF, 10VDC

Can someone tell me if a combination of the above is suitable?

If not, then I will have to purchase them from the Web

Thanks
Title: Re: Power Supply Unit
Post by: Hood on January 14, 2011, 05:37:19 PM
No, you need the voltage to be above what your supply is, you may get away with some the same but I definitely wouldnt risk it and definitely not lower. Capacitance is not a problem as you can link in parallel to get the capacitance required but you cant do that with the voltage I am afraid.
If you wish to pay the postage to Canada (I think thats where you said you were) I probably have some capacitors here that I could give you, would have to check tomorrow when I get to the workshop, let me know.
Hood
Title: Re: Power Supply Unit
Post by: RICH on January 14, 2011, 05:37:42 PM
Nic,
We already told you. The  voltage rating must exceed the output voltage by some amount. The uF can be more than calculated
but preferable not less.

You wouldn't put a circuit breaker or fuse which is less than required for the amps you will draw, it explodes, like wise you wouldn't put
a capacitor  not rated for the voltage you will use.

RICH
Title: Re: Power Supply Unit
Post by: kolias on January 14, 2011, 07:01:46 PM
Alright, somehow I knew that we can’t add the voltage but wasn’t sure. Yes Rich you told me that the voltage must be higher but you never told me we can add the capacitance but not the voltage LOL. Sounds silly but simply I don’t know about this staff.

Thank you Hood for the offer, sure I don’t mind to pay the postage (yes I’m in Canada) but I don’t know how I can do that. Anyway let me know what is required and I will do it

You would think that I’m in the North Pole because today I spend about 3 hours driving around checking some local stores for capacitors, toroidal and bridge rectifiers but no luck. Mostly they have IC staff.

Thanks
Title: Re: Power Supply Unit
Post by: Hood on January 14, 2011, 07:05:02 PM
I will check tomorrow and see what I have, hope I remember ::)

Hood
Title: Re: Power Supply Unit
Post by: Hood on January 14, 2011, 07:13:32 PM
Just thought I better mention something else as you are new to this stuff. Capacitors store a charge and this can be quite a high voltage and they are dangerous because they can discharge very quickly, so never touch the terminals of a capacitor unless you are sure it is discharged or it could cause serious injury. It can take quite a while for a capacitor to discharge naturally so if you need to do any work on the circuit you really need to discharge it first to make sure there is no danger. I usually put a household light bulb across the terminals to do that, not sure if its a standard way to do it but seems to work for me, hopefully someone will chime in if it could be dangerous.
Hood
Title: Re: Power Supply Unit
Post by: kolias on January 14, 2011, 07:43:47 PM
Thanks for the tip Hood, much appreciated

I'm waiting for someone to chime in and tell me if I can connect the AC ground wire with the DC black (ground) wire. I mean since I will have a metal box to build the unit, do I attach both the AC and DC ground to the metal box wall?
Title: Re: Power Supply Unit
Post by: RICH on January 14, 2011, 10:03:08 PM
One of the questions to get a ham radio license is:
What is the first thing one should do before working on a power supply or amplifier?
Make sure sure the capacitor's are discharged.

Hood is right on as they can be dangerous. IE; my friend who knew better happen to touch the capacitor terminal, voltage arc  entered the little finger and came out at the thumbs knuckle, which he kind of no longer has. I always waite and then check with a volt meter that it reads zero. A light bulb in a socket works as it acts as a bleed off resistor, but , the meter should still read ZERO. You can have a sized resistor accross the terminals of the capacitor to act as a bleed resistor.

I take the ground wire of the supply cord and bond / attach to the metal case. The DC ground goes to a seperate post which is attached to the cabinet. All DC grounds go to that post.

BTW,

You and only you are completely responsible for all associated power supply building and design. Any and all advice, comments, etc given in this post are not to be considered absolutely safe or correct. The user requesting or using posted information assumes all risk associated with information in this thread.
RICH
Title: Re: Power Supply Unit
Post by: kolias on January 15, 2011, 12:15:12 AM
Thanks Rich, I like the voltmeter test too and I will use it. The bleed off resistor I will leave it for later until I get to know more about this staff.

Grounding the AC ground to the metal box sounds good and that is what I was planning. The DC black wire I will attach it to a ground bar inside the metal box as you said. I still have to work it out in my mind to see why they have to be separate since indirectly both grounds are connected together (through the metal box) but eventually I will get it.

As for the responsibility of the project of course I know that I’m responsible and nobody else. As you may have noticed I ask a lot of questions, sometimes stupid, and the reason is that I must understand what I’m doing. I will not proceed to build this project until I know exactly what is going on and I feel confident enough to do it.

Thanks for all the help
Title: Re: Power Supply Unit
Post by: kolias on January 15, 2011, 07:38:30 AM
I’m planning this weekend to order the transformer and rectifier online and at the same time I would like to order the fuse and fuse holder

I think I will not install a fuse on the 110VAC incoming line but definitely I will have a fuse on the outgoing DC line.

Since my transformer has an output of 24VDC @ 10A (12V-0V-12V) should I get a 10A fuse or 15A or 20A?

Thanks
Title: Re: Power Supply Unit
Post by: HimyKabibble on January 15, 2011, 10:24:04 AM
I’m planning this weekend to order the transformer and rectifier online and at the same time I would like to order the fuse and fuse holder

I think I will not install a fuse on the 110VAC incoming line but definitely I will have a fuse on the outgoing DC line.

Since my transformer has an output of 24VDC @ 10A (12V-0V-12V) should I get a 10A fuse or 15A or 20A?

Thanks


That is completely backwards.  Put the fuse on the AC input, NOT on the DC output.  If the fuse on the DC blows while the machien is moving, the back EMF frpm the motors can blow the stepper drivers.  Plus, with no fuse on the input side, if the transformer develops an internal short, you'll be completely unprotected, and could havd a fire.

Regards,
Ray L.
Title: Re: Power Supply Unit
Post by: Richard on January 15, 2011, 10:42:22 AM
Antec has rectifier modules on ebay -  $25 For 50v 30A ,or 80V 25A. Probably the best way for you to go.
Visit his store and you will also find fuse modules
Title: Re: Power Supply Unit
Post by: kolias on January 15, 2011, 04:01:44 PM
Thank you Ray, it shows how much I know about power supply units LOL.

So I will only install a fuse on the incoming AC (black wire). Since this is 110VAC, 15A circuit should I put a 15A fuse? perhaps less?

And how you install a fuse on the 110VAC? with the same fuse holder they sell for the DC circuits? or perhaps a 15A breaker?

Richard thanks for the tip but we have settled the bridge rectifier; Hood suggested earlier a 400PIV, 25A which I will purchase from mpja.com at $2.70 (item #5248 BR)
Title: Re: Power Supply Unit
Post by: HimyKabibble on January 15, 2011, 04:10:35 PM
Thank you Ray, it shows how much I know about power supply units LOL.

So I will only install a fuse on the incoming AC (black wire). Since this is 110VAC, 15A circuit should I put a 15A fuse? perhaps less?

And how you install a fuse on the 110VAC? with the same fuse holder they sell for the DC circuits? or perhaps a 15A breaker?

Richard thanks for the tip but we have settled the bridge rectifier; Hood suggested earlier a 400PIV, 25A which I will purchase from mpja.com at $2.70 (item #5248 BR)


The primary power will be roughly equal to the secondary power.  Since the secondary is 24V/10A, that's 240W.  Since the input is 120V, the input current will be roughly 240W/120V = 2A.  You want to use a larger fuse, for some safety margin, so I'd go with something in the 3-5A range.  You'll also NEED a slow-blow fuse, to prevent it from blowing due to the turn on transient caused by the large capacitors.  Use a 3AG style fuse, and any style holder that will accomodate it, and is rated for >120V AC, will be fine.

Regards,
Ray L.
Title: Re: Power Supply Unit
Post by: kolias on January 15, 2011, 04:28:01 PM
Thank you Ray, much appreciated
Title: Re: Power Supply Unit
Post by: kolias on January 15, 2011, 04:43:50 PM
Sorry Ray to bother you again; I found the fuse holder but all the fuses are “fast blow general use electronic type” and either 2A, 4A, 5A etc. There are no slow blow fuses

Fuse Holder
http://www.mpja.com/prodinfo.asp?number=4476+FH

Fuse
http://www.mpja.com/prodinfo.asp?number=15781+FU

Would you happen to know any other place I can purchase them?

Thanks
Title: Re: Power Supply Unit
Post by: HimyKabibble on January 15, 2011, 04:54:47 PM
http://www.amazon.com/s/ref=nb_sb_noss?url=search-alias%3Delectronics&field-keywords=3AG+Slow+Blow+Fuse&x=14&y=17
Title: Re: Power Supply Unit
Post by: Hood on January 15, 2011, 05:00:40 PM
Never made it to the workshop today, hopefully tomorrow I will and will try and remember to look for the caps.
Hood
Title: Re: Power Supply Unit
Post by: kolias on January 15, 2011, 11:00:23 PM
Updated schematic for comments
Title: Re: Power Supply Unit
Post by: Hood on January 16, 2011, 11:15:12 AM
Diag looks ok to me but maybe best wait for the  electrical guys to comment, oh would go for the 5 amp fuse myself.

Have 2 of these caps, if you want them PM me your address and I will send them off ASAP.
As seen in the pic they are  15,000uF and 80v +-20% so should be fine for you, hopefully there are no restrictions sending capacitors by airmail.
Hood
Title: Re: Power Supply Unit
Post by: kolias on January 16, 2011, 11:40:31 AM
Thank you Hood very much for your help, its appreciated a lot

I feel more confident when I get comments on my diagram and I hope the electrical guys can also give me some comments to confirm all is ok. I will go with the 5A fuse. Ultimetly ff course I’m the responsible person but will be nice to have an ok

I sent you my address by PM and again much appreciated. Dont either if there are restrictions sending caps by airmail but honestly I dont believe so.
Title: Re: Power Supply Unit
Post by: stirling on January 16, 2011, 12:11:46 PM
Kolias - Don't know if anyones raised this yet but it looks as though you have a double primary and double secondary transformer there. Wiring is not complicated but you need to be aware of how they need to be configured. Generally speaking it looks like you'll need your primaries in parallel (for 120Vac) and your secondaries in series (for 24Vac). Also you'll need to establish the phases of the windings or that fuse might well come in handy (hopefully there'll be some marking or whatever). To cover my *rse Please check it out - don't take this as instruction - just a cautionary heads up.

Ian
Title: Re: Power Supply Unit
Post by: HimyKabibble on January 16, 2011, 12:12:58 PM
Your schematic looks fine.  Personally, I would connect the DC and AC grounds together at a single point.  Better to have them tied together at one point intentionally, than to have a connection occur later on it's own, and create all kinds of flaky problems.  It will save you some grief down the road.

When you get around to wiring up E-Stops, limits, etc. always use shielded cables, and connect the shield to that same ground point ONLY at the electronics box, NEVER at the far end, and NEVER at both ends of the cable.

BTW - It would also be wise to wire in a relay for E-Stop, that cuts the AC power to the transformer.  There are many ways to wire an E-stop, but the most direct, and certain is best.  You NEVER want to depend on the software working properly for your E-stop to work, and it's best not to depend on the BOB either.  The simpler the better when safety is concerned, as it reduces the number of potential failure modes.

Regards,
Ray L.
Title: Re: Power Supply Unit
Post by: stirling on January 16, 2011, 01:06:07 PM
If the fuse on the DC blows while the machien is moving, the back EMF frpm the motors can blow the stepper drivers.
Ray - This just caught my eye whilst browsing. I wonder if this is why this fuse arrangement has been taken out of geckodrives's current version of their "step motor basics guide". I have the older version on file and saw that the DC quick blow fuses (between PS and drive) had disappeared on the latest version. Surely Mariss didn't make a mistake - oh no is nothing dependable any more :)

Ian
Title: Re: Power Supply Unit
Post by: HimyKabibble on January 16, 2011, 01:17:03 PM
If the fuse on the DC blows while the machien is moving, the back EMF frpm the motors can blow the stepper drivers.
Ray - This just caught my eye whilst browsing. I wonder if this is why this fuse arrangement has been taken out of geckodrives's current version of their "step motor basics guide". I have the older version on file and saw that the DC quick blow fuses (between PS and drive) had disappeared on the latest version. Surely Mariss didn't make a mistake - oh no is nothing dependable any more :)

Ian

I'm surprised it was ever in there.   Mariss has recommended against fusing the DC side for many years.

Regards,
Ray L.
Title: Re: Power Supply Unit
Post by: stirling on January 16, 2011, 01:45:01 PM
http://www.geckodrive.com/upload/Step_motor_basics.pdf (http://www.geckodrive.com/upload/Step_motor_basics.pdf)

Page 10

Ian
Title: Re: Power Supply Unit
Post by: kolias on January 16, 2011, 01:52:30 PM
Now I like all these answers and thanks all for your time........

Ian, the transformer was suggested to me by ger21 who was kind to send me a link where to buy it and I know that I may have trouble wiring it up but when I get it I will post a picture of it along with all the wiring hanging out from it and I will ask what else? more questions. Thanks Ian for pointing out this critical point.

Ray that was a question which always was puzzling me but I was not sure if I could connect the ground from the AC along with the ground (black) from the DC. Now that you confirm this point, I will do as you say – much easier anyway. I always use shielded cables and I do connect the shield as you mentioned. For the motors I use 22 gauge cable with 5 wires on it and for the limits / Estop I use 18 gauge with BLK / RED on it. That’s what I did with my 1st CNC and seems it worked just fine. I would have liked to go heavier on the motors cable but my local store had only 22 gauge available with 5 wires

Regarding the relay for the Estop I did pursue this subject on my 1st CNC machine with a Swedish guy from the CNCZone forum who was extremely helpful. I did buy 2 relays and was ready to install them based on his schematic but then I got tied up with other work and never installed the relays. I still have the relays and left space in my new control station for them and later I will install them. I know that is not wise to depend on software for the Estop and thanks for pointing out this item

Title: Re: Power Supply Unit
Post by: HimyKabibble on January 16, 2011, 02:53:02 PM
A Bit Of The Logic Behind Grounding And Shielding....

For all practical purposes, ALL electrical conductors have resistance.  When current is passed through those conductors, that resistance causes voltage drop.  The greater the current, or resistance, the greater the voltage drop.  If the current is pure, constant DC, this voltage drop will be constant.  But, if we're operating in the real world, this is almost never the case.  The voltage drop will add "noise" to the signal, and the shape of that noise will be more or less the same as the shape of the current.  So, where, in an ideal world, you night have a 35V DC supply driving a constant 35V into your load (motor or electronics), you will instead have a noisier, lower voltage, signal present at the load.  So, what happens if you run a wire from the power supply, to your motor drivers, and from there on to your electronics?  The motor drivers will introduce a lot of noise into BOTH the power and ground wiring.  This noise will then be passed along to the electronics, possibly leading to the electronics misbehaving, because the noise may "look" like a signal to the electronics.  If, however, you run one set of wires from the supply to the motor drivers, and a completely separate set from the supply to the electronics, the electronics will not "see" the noise introduced by the motors and drivers, making the electronics operate more reliably.  The whole point here is to provide a dedicated path from the power supply to each "load", so noise introduced in one part of the system does not get into other parts of the system.

Similarly, you want to ideally have one, and only one, path the power, and ground can take.  Electricity will always take the path of least resistance.  If you provide more than one path, SOME of the current will go down each path, creating the possibility for current to take a path that will introduce noise into places you don't want it.  This is part of the reason you generally don't want to ground the shield on both ends of a shielded cable, as it creates the possibility for current to flow through the shield, rather than through the ground conductor, and that current can induce noise, through inductive coupling, into the signals carried on all of the conductors in the cable.  Make the current go where you WANT it to go, don't let it find just its own way.

There are two generally "safe" ways to make ground connections.  One is to bring all the ground wires to a single point, and tie them all together there.  The other is to create a VERY low-resistance ground bus, using terminal strips, heavy ground cables, or a ground plate.  The E-box for my big mill is a 24"x24"x12" steel box.  In it, I've mounted a 24"x24"x1/4" aluminum plate, to which ALL the electronics are mounted.  This box contains the entire PC (all removed from its case, and all the bits re-mounted to the door of the enclosure), the servo power supply (dual 72V@20A supplies), a giant E-Stop contactor to cut the AC to the power transformer, rectiifers and filter caps, all the servo drives, the VFD for the 3HP spindle motor, three breakout boards, relays for coolant, pwoer drawbar, etc, a Modbus controller, four fans, and some other odds and ends.  Everything is open, and in rather close physical proximity, but from the very first time I powered it up, it has worked absolutely rock-solid reliably, with no glitches or flakiness whatsoever, despite having the VFD inches away from the PC, which is inches from the servo drives, etc..

The AC line (220V, plus neutral, plus AC ground) comes into one side of the box, through a fuse, then goes directly to a terminal strip.  From the terminal strip, I branch off separate wires to power the VFD and servo power supply transformer.  The AC ground connection is tied, through a heavy conductor, to the 1/4" plate to which most of the electronics are mounted.  There are additional heavy conductors from the terminal strip to the enclosure itself - one to the main enclosure, one to the door, where the PC electronics are mounted.  ALL DC ground connections are to the 1/4" plate.  The separate ground connections for all the high-current AC devices ensures there can be no AC ground currents flowing through the 1/4" plate.  The 1/4" plate itself acts as a very low resistance ground conductor.  Since the currents drawn by all the electronics are relatively small, there is no real possibility of ground currents through the plate causing any measurable voltage drops, or noise injection, into any of the electronics.

All I/O cabling is shielded, with the shields connected ONLY at the BOB, or whatever device they connect to.  Where appropriate (limits, E-Stop, etc.), I try to use higher voltage I/Os (limit switches, etc), and ALWAYS provide good, stiff pull-up resistors (100-300 ohms) on logic-level inputs, to make it much more difficult for noise to false-trigger an input signal.   If you follow a similar, simple layout, you will rarely have problems with noise, ground loops, and other such problems.

Regards,
Ray L.
Title: Re: Power Supply Unit
Post by: kolias on January 16, 2011, 04:12:03 PM
Thank you for taking the time Ray to educate me, very interesting.

One thing I noticed: you are saying that you use 1/4" aluminum plate which you mount your electronics plus you use this 1/4" aluminum plate to connect your grounds. I thought that aluminum is not a good conductor and I was planning to use a steel flat bar 1/8” thick to mount all the grounding wires.

Is it better to use an aluminum bar because of its low resistance?
Title: Re: Power Supply Unit
Post by: Hood on January 16, 2011, 05:08:04 PM
I thought that aluminum is not a good conductor and I was planning to use a steel flat bar 1/8” thick to mount all the grounding wires.



Alu is quite a good conductor, lots of high voltage power cables are Alu, its not as good as copper but a heck of a lot cheaper. Another place its often used is transformers in big welders.
Hood
Title: Re: Power Supply Unit
Post by: HimyKabibble on January 16, 2011, 05:08:18 PM

When there is that much metal involved, the difference in conductivity between steel and aluminum is negligible.  You have to get into pretty small wires, or pretty high currents for that to be of any concern.

Regards,
Ray L.
Title: Re: Power Supply Unit
Post by: kolias on January 16, 2011, 06:53:15 PM
That is a pretty impresive cabinet Ray and very well organized, thanks for sharing

I will assume the big round piece at the bottom of your cabinet is a toroidal transformer; the 2 big cables going to a terminal strip to the left and the 2 going to a board above it are they covered with some kind of a jacket? what kind it is?

Also when you say “The AC ground connection is tied, through a heavy conductor, to the 1/4" plate” how big of a conductor we are talking here? like 12 or 10 gauge?
Title: Re: Power Supply Unit
Post by: HimyKabibble on January 16, 2011, 10:14:30 PM
Yes, some of the wiring is covered with split plastic tubing, available from most electronics stores, and some hardware stores.  Like this:

http://www.allelectronics.com/make-a-store/item/SLT-14/1/4-SPLIT-LOOM-TUBING//1.html

The ground wires should be at least as big as the biggest wires on that supply.

Regards,
Ray L.
Title: Re: Power Supply Unit
Post by: kolias on January 17, 2011, 08:16:19 AM
I was reading through a document from the web and noticed two paragraphs saying:

“There is a special consideration if the power supply voltage will be at or near the maximum
voltage rating of the drive. If the motor will be rapidly decelerating a large inertial load from a high
speed, care has to be taken to absorb the returned energy. The energy stored in the momentum
of the load must be removed during deceleration and be safely dissipated. Because of its
efficiency, the drive has no means of dissipating this energy so it returns it to the power supply. In
effect, instead of drawing current from the power supply, the drive becomes a source of current
itself. This current then may charge the power supply capacitor to destructive voltage levels.

If more than one drive is operating from the power supply this is not a problem since the other
drive will absorb this current for its needs, unless of course it is decelerating as well. For this case
or for a single drive it may be necessary to place a voltage clamp across the power supply in the
form of a zener diode. The voltage of this diode must be greater than the maximum expected
power supply voltage, yet low enough to protect the drive. A good choice would be either 82 volts
or 91 volts as standard values.”

Based on the above two paragraphs, I don’t want to sound like an expert or go against this forum’s knowledgeable people but I would like to know if we have sized the capacitors big enough to accept the motors deceleration energy or if I should install a voltage clamp across the power supply.

Title: Re: Power Supply Unit
Post by: stirling on January 17, 2011, 08:48:09 AM
Hi Kolias - yes this is from the document I linked above - the geckodrive "stepper motor basics guide".

Personally I wouldn't worry too much about this. Note the opening sentence that you've quoted - "There is a special consideration if the power supply voltage will be at or near the maximum voltage rating of the drive."

Your PS voltage is going to be 34Vdc and your drive's limit is (if I remember correctly) 42Vdc. Not what I'd call "at or near" - others may disagree.

Even if you DID decide to be concerned - the solution would be the voltage clamp - not to increase the capacitor's rated voltage - others may disagree.

Ian
Title: Re: Power Supply Unit
Post by: kolias on January 17, 2011, 03:22:18 PM
Ok Ian sounds good

I was disappointed today because yesterday I email my order to mpja.com (Canadians can’t order online) and today they phoned and said that they can only ship to Canada by UPS. Items imported to Canada with any carrier company go thru custom brokers and you pay their service fee, a minimum of $45.00 plus they add all taxes and duties and it becomes a very expensive item whatever you ordered.

With USPS you don’t have the above because items are processed in Canada by the Canadian Post Office who they only check the parcels at random. If you are the unlucky one then you pay all the taxes and duties but there is no brokers fee. On my present CNC I got all my items for free but on my 1st CNC I was caught once and had to pay $35.00.

So now I have no transformer and no bridge rectifier and the online stores I know they don’t have these items with my specs. I will try again to see if I can find another place to order these parts
Title: Re: Power Supply Unit
Post by: kolias on January 18, 2011, 09:42:51 AM
I have located some transformers and bridge rectifiers and have list them in the attached one page Word document.

Can someone pls suggest which one meets my specs?

Thanks
Title: Re: Power Supply Unit
Post by: Hood on January 18, 2011, 11:04:20 AM
For the transformer I would say probably this as the best

Avel Y236652 250VA 25V+25V Toroidal Transformer
Your Price:  $53.48 EA   
Sku 122-625: In Stock

Few others you could use but are overkill or getting right on the max voltage your drives can accept so probably not worth taking the chance.


Link to the rectifier is not working for me.

Got your caps sent off today, took them yesterday but they wouldnt accept as the plastic lathe tool box, I had them in, wasnt big enough for the customs label ::) Put them in a jiffy bag and posted today, they say 4 to 5 day delivery.

Hood



Title: Re: Power Supply Unit
Post by: kolias on January 18, 2011, 01:32:28 PM
ok I will order the transformer you suggested Hood (unless there is another snag and fail again – seems I dont have a good luck sourcing my parts LOL

Digi-key have a weird site so I will copy the specs, like the transformers and post it back for suggestions

Much obliged for the caps and your help
Title: Re: Power Supply Unit
Post by: kolias on January 18, 2011, 01:57:35 PM
Here is a selection of bridge rectifiers
Title: Re: Power Supply Unit
Post by: Hood on January 18, 2011, 02:13:40 PM
Any of them would be fine as far as I can see. All are at least 3 times the current and 2.5 times the voltage ratings you are looking at so there should be no problems.
Hood
Title: Re: Power Supply Unit
Post by: kolias on January 18, 2011, 03:08:44 PM
Alright I will order the toroidal and rectifier tonight, thanks for your help
Title: Re: Power Supply Unit
Post by: kolias on January 18, 2011, 08:12:03 PM
The last item to purchase for this power supply unit will be the metal enclosure.

Approx. what size box we are talking about?
Noticed in the local stores that they come in various size and they dont have any holes for ventilation. Do I punch some holes on the side?

The cable for the 110VAC will be 14AWG two conductors + the copper ground wire.
What size wiring from the toroidal to the 110VAC terminal strip?
And what size wiring from the toroidal to the rectifier and capacitors?

Thanks
Title: Re: Power Supply Unit
Post by: alenz on January 19, 2011, 03:03:23 AM
Nicolas,
Re. your power supply enclosure. I built up a power supply that used the identical 24V MPJ transformer that you first selected. It all fit rather nicely into an old scrap desktop PC power supply case. I scrapped the electronics and only kept the metal case, cooling fan and power cord. A piece of Radio Shack printed circuit board mounted on standoffs was used to mount the components.  Milled some straight line trace isolation cuts in the copper to end up with an equivalent printed circuit board.  The newer PC power supply cases are a bit smaller but then I think the toridal transformer that you intend to use will be considerably smaller than the rather huge MPJ one that I used. And old PC’s are essentially free.
I couldn’t believe the prices quoted for metal enclosures.  So I made a separate one for the drives out of inexpensive Ace hardware acrylic sheet. Just couldn’t see spending more for an empty metal box than the electronic components that went inside. Of course a proper metal enclosure even tho a bit more expensive would result in a more porofessional job.
Al
P.S.
Disclaimer: I’m not qualified to make any recommendations where electricity is involved but note that the plastic case only has low-voltage components and the potentially lethal mains voltages are in a grounded metal case. I am sure that there are technical reasons why this is not good practice, but the bottom line is that it has been 100% trouble free for going on ten years now.
al
Title: Re: Power Supply Unit
Post by: stirling on January 19, 2011, 04:48:22 AM
The last item to purchase for this power supply unit will be the metal enclosure.

Approx. what size box we are talking about?
Noticed in the local stores that they come in various size and they dont have any holes for ventilation. Do I punch some holes on the side?

The cable for the 110VAC will be 14AWG two conductors + the copper ground wire.
What size wiring from the toroidal to the 110VAC terminal strip?
And what size wiring from the toroidal to the rectifier and capacitors?

Thanks

your toroidal already has the wires. Just wire the primary side to your strip and secondary to your rectifier - job done.

Box size: I'm just going to throw in another heads up just in case. Your toroidal will (should) come with fixing bolt and a large "washer". You bolt through the washer and on through the toroidal to your mounting plate. DO NOT allow any part of the metal case to come into contact (or even that close) with the top of the bolt or the washer. (It will short the transformer and that fuse will come in handy again).
Title: Re: Power Supply Unit
Post by: kolias on January 19, 2011, 08:17:45 AM
It is true that the metal enclosures are quite expensive and I must balance my cost vs a good looking job. For my needs, a PC case although a very good alternative will be too bulky. I know a place that they sell among others old metal switch boxes of various sizes and I will pick one after I get the toroidal and my other parts to figure out how much space I need. You did a nice looking job with yours Al.

stirling that is one thing that scares me about this project – creating a short circuit somewhere. What you said it puzzles me though;

“You bolt through the washer and on through the toroidal to your mounting plate. DO NOT allow any part of the metal case to come into contact (or even that close) with the top of the bolt or the washer.”


Why it matters if any part of the case may come close with the top of the bolt? This bolt will be mounted to the bottom of the case which is metal anyway!!! Am I missing something?

Still I would like to know: Do I need any ventilation holes on the metal enclosures?

What size wiring from the rectifier to the capacitors?
Title: Re: Power Supply Unit
Post by: HimyKabibble on January 19, 2011, 09:45:45 AM
Look on E-Bay for enclosures.  Mine was a brand-new Hoffman 24"x24"x12" heavy gauge steel NEMA enclosure I got on E-Bay for $99!

You should allow for airflow, but for such a small supply, I very much doubt forced ventilation is required.

If the bolt mounting the power transformer is in any way connected to anything electrically, then it was horribly mis-applied.  The transformer should have a rubber insulator top and bottom completely isolating it from the bolt and "washer".

Regards,
Ray L.
Title: Re: Power Supply Unit
Post by: kolias on January 19, 2011, 10:18:48 AM

You should allow for airflow, but for such a small supply, I very much doubt forced ventilation is required.

If the bolt mounting the power transformer is in any way connected to anything electrically, then it was horribly mis-applied.  The transformer should have a rubber insulator top and bottom completely isolating it from the bolt and "washer".

Regards,
Ray L.

Sorry not clear to me; the metal enclosures here are just a box with cover with no openings whatever on sides. When you say I should allow for ventilation do you mean That I should drill some holes on the sides of the box?

Now I get it with the toroidal but I will post some pics to see how we mount it, it seems critical to me

And no one to tell me the wire size from the rectifier to the capacitors ?
Title: Re: Power Supply Unit
Post by: stirling on January 19, 2011, 12:01:14 PM
If the bolt mounting the power transformer is in any way connected to anything electrically, then it was horribly mis-applied.  The transformer should have a rubber insulator top and bottom completely isolating it from the bolt and "washer".
Yes of course there are rubber washers and of course they should be used, but this is not the point I was trying to make. Incidentally they (the rubber washers) don't electrically isolate anything that isn't already isolated - they are there as a belt and braces thing to prevent the coil insulation from waring through and causing a short. But as I say this is not the point I was attempting to make.

I don't care how much the transformer is electrically iscolated from the bolt and washer - the case must STILL NOT touch the top of the bolt. Why? because then the case, plate and bolt effectively create a ring of metal through the transformer torus. This effectively creates another secondary and worse  a secondary of ONE turn (think about the current) and worse still a short circuited secondary.
Title: Re: Power Supply Unit
Post by: Hood on January 19, 2011, 12:14:08 PM
Still I would like to know: Do I need any ventilation holes on the metal enclosures?

What size wiring from the rectifier to the capacitors?


Yes, ventilation would be needed, whether its holes or slots or just a bit cut out maybe with gauze covering to stop fingers getting in.

Dont know anything about your wiring sizes in the USA, here we are mm2 but whatever the USA gauge is that can handle your current plus a bit extra should be fine.

Hood
Title: Re: Power Supply Unit
Post by: kolias on January 19, 2011, 12:39:42 PM
So I will make sure that there is at least 1" clear between the top of the bolt and the case
Title: Re: Power Supply Unit
Post by: kolias on January 19, 2011, 02:51:28 PM
Still I would like to know: Do I need any ventilation holes on the metal enclosures?

What size wiring from the rectifier to the capacitors?


Yes, ventilation would be needed, whether its holes or slots or just a bit cut out maybe with gauze covering to stop fingers getting in.

Dont know anything about your wiring sizes in the USA, here we are mm2 but whatever the USA gauge is that can handle your current plus a bit extra should be fine.

Hood


So I got the ventilation question answered, thanks Hood

The 2mm translates to 12 or 14AWG here if I'm right which I find it kind of heavy

Hopefully someone can let me know the wiring size from the rectifier to the capacitors and then I will feel more confident
Title: Re: Power Supply Unit
Post by: Hood on January 19, 2011, 03:02:37 PM
I was meaning mm² (cross sectional area) not 2mm wire.

Looks like you still cant Google ;D

http://www.geocities.com/CapeCanaveral/Lab/9643/MIL_STD_975_wire.htm

Hood
Title: Re: Power Supply Unit
Post by: Hood on January 19, 2011, 03:10:06 PM
Heres another
http://www.csgnetwork.com/wiresizecalc.html
Title: Re: Power Supply Unit
Post by: kolias on January 19, 2011, 03:40:35 PM
So it is 14AWG, thanks
Title: Re: Power Supply Unit
Post by: kolias on January 20, 2011, 07:27:57 AM
I just noticed that the power supply I have ordered from China it is called “Switching Regulated Power Supply”

I wonder what the difference with the one I will build is. Any pros / cons between the two?
Title: Re: Power Supply Unit
Post by: stirling on January 20, 2011, 09:05:42 AM
Well remember that doc I linked to back in post #86 - the stepper basics guide from geckodrive? Here's a quote from page 11.

"The drive works best with unregulated power supplies though regulated linear and switching
power supplies may also be used. What matters is the power supply must have a large output
capacitor and an unregulated supply intrinsically has one.
If a linear regulated or a switching supply is to be used, then a large capacitor should be placed
across the output terminals. A 2,000 to 10,000 uF capacitor should do."

However, I note that this has apparantly been dropped from the latest version of this doc http://www.geckodrive.com/support.aspx?q=10005#Power%20Supplies (http://www.geckodrive.com/support.aspx?q=10005#Power%20Supplies)

Make of that what you will

Ian
Title: Re: Power Supply Unit
Post by: kolias on January 20, 2011, 09:32:38 AM
Thank you for your time Ian, so much to absorb in such a sort time
Title: Re: Power Supply Unit
Post by: kolias on January 20, 2011, 03:15:25 PM
I have ordered the rectifier but have a hell of the time to get the transformer due to high cost

Parts-express.com they have a toroidal for $53.48 + $44.82 shipping
The Antek which Ray.L suggested is $90.00 + $26.00 shipping
Plitron who are in Canada have also one for $107.65 but minimum order is $250.00 !!!!

So the best deal I guess is the one which Gerry suggested (picture attached) from mpja.com at $18.95 + shipping by UPS + brokers and custom fees which I estimate them to be $50.00 to $70.00

My question is why the transformer on the attached picture is so inexpensive and the toroidal seems so expensive. Are they so different?

And the transformer on the attached picture what kind it is? I would like to search other sites to see if I can find one which they will ship to Canada by regular post.

Never thought that it will be so difficult to get the parts for this project
Title: Re: Power Supply Unit
Post by: rrc1962 on January 20, 2011, 03:22:02 PM
You can probably buy an unregulated power supply with toroidal transformer from Keling for less than what you can build it for.  He has a 38V, 15A for $139. 
Title: Re: Power Supply Unit
Post by: kolias on January 20, 2011, 06:02:42 PM
You can probably buy an unregulated power supply with toroidal transformer from Keling for less than what you can build it for.  He has a 38V, 15A for $139. 

Very good info, however I would have liked to build one myself for the experience providing that it doesn't cost me an arm and a leg

Thanks
Title: Re: Power Supply Unit
Post by: Hood on January 20, 2011, 06:28:15 PM
What voltage are your mains in Canada?
Title: Re: Power Supply Unit
Post by: kolias on January 20, 2011, 08:11:34 PM
What voltage are your mains in Canada?

Household voltage here enters each house at 220V and then at the main panel is split to 220V for all major appliances like cooking stove, oven, electric heating, air conditioning etc. and 110V for all lights and wall outlets
Title: Re: Power Supply Unit
Post by: HimyKabibble on January 20, 2011, 10:17:17 PM
That transformer should work fine.

Regards,
Ray L.
Title: Re: Power Supply Unit
Post by: kolias on January 22, 2011, 10:19:56 AM
To summarize all the discussions above, I made this small Excel file which can be useful next time a beginner like me asks the same questions.

People with no experience should not use this file before someone knowledgeable approves it just in case I have misinterpreted some data. After the approval, all cells can be locked except the input (yellow) cells.

If there are any suggestions to improve / modify this file, let me know and I will do it.
Title: Re: Power Supply Unit
Post by: kolias on January 26, 2011, 05:26:05 PM

Got your caps sent off today, took them yesterday but they wouldnt accept as the plastic lathe tool box, I had them in, wasnt big enough for the customs label ::) Put them in a jiffy bag and posted today, they say 4 to 5 day delivery.

Hood


I received them today Hood including the holding clamps (very thoughtfull of you) , very much appreciated, let me know how I can repay you

I'm still looking for the transformer, never thought it will be so difficult. As I said previously I ordered the rectifier, fuse holder and the 5A fuse but I dont want to pay right now about $100.00 for the transformer because half of this cost is the shipping charges and I feel its a ripoff.

I have a friend in US and he is looking for me to get one locally and then he will ship it to my by US post
Title: Re: Power Supply Unit
Post by: Hood on January 26, 2011, 06:45:26 PM
Good to hear it :)

There has to be some electronics/electrical places in Canada that you could get the transformer from, for the size you are looking for I could get one here probably around £30 delivered.
Hood
Title: Re: Power Supply Unit
Post by: Hood on January 26, 2011, 06:54:49 PM
Quick google  brought up Newark and here is one, cant remember the exact specs you were needing but if this isnt right then I am sure there will be one there.
http://canada.newark.com/multicomp/mcta225-25/toroidal-transformer/dp/38K4918

Hood
Title: Re: Power Supply Unit
Post by: kolias on January 26, 2011, 08:12:06 PM
Well, I dont know whats wrong with me but that place you found Hood looks great. They have the attached picture transformer for CAD$51.47 + $12.00 shipping by courier. That is a good deal but I’m not sure about the specs. If you look at the photo at the bottom it says “secondary current secondary series 4.5A” which sounds low to me.

Anyway if you say that is ok, I will order it otherwise the 30 pounds you suggested delivered also sounds good and if we choose to go this way I can send you a money order in pounds.

BTW what I need is 201VA or more, 25VAC
Title: Re: Power Supply Unit
Post by: Hood on January 27, 2011, 02:27:43 AM
Sorry about the £30 bit, thas what I can get one for in this country, it would cost a foryune to send it across to you I think. I was just surprised that you could not get one in Canada about a similar kind of price.

Yes I noticed the 4.5Amp bit but think its a typo, if you download the data sheet you will see its 4.5Amps per secondary and there are 2 secondaries so that would be 9 amps total. Also if you work it out 9 amp x 25v = 225VA
BTW you would be connecting the secondary in parallel rather than series as series would give you 50VAC
Hood
Title: Re: Power Supply Unit
Post by: GrahamIT on January 30, 2011, 06:59:33 PM
I went to purchase the capacitors from my local store but I couldn't find anyone with 50VDC or more neither with 20000uF or more. The closest I found were:

15500uF, 25VDC
10000uF, 25VDC
8200uF, 25VDC
5500uF, 25VDC
34000uF, 15VDC
25000uF, 15VDC
10000uF, 10VDC

Can someone tell me if a combination of the above is suitable?

If not, then I will have to purchase them from the Web

Thanks


I haven't read all this thread yet (only up to page 7), so this may have already been answered...

If you can't find the correct size capacitor, you could always buy more of the same size lower voltage ones and wire them in series to get over your operating voltage. Series means wiring + to - in a line... So 3 x 15500uF @ 25V in series would give you in effect 1 capacitor of 15500uF @ 75V.

If you bought 6 of these 15500uF 25V capacitors, wired 2 sets of 3 in series and then took those 2 sets of three and wired them in parallel, you'd end up with the equivalent of 1 capacitor of 31000uF @ 75V.

I know it sounds weird to do it that way, but I usually work with what I can get my hands on at a reasonable price too.

Graham
Title: Re: Power Supply Unit
Post by: kolias on January 30, 2011, 07:08:30 PM
Thanks for the tip Graham nice to know, I think we discussed connecting them in series or parallel, I forget too, but Hood send me the capacitors I need and I'm all set for now.
Title: Re: Power Supply Unit
Post by: HimyKabibble on January 30, 2011, 07:11:37 PM
That's really not a good practice with electrolytics, unless you provide a LARGE voltage safety factor, which kinda defeats the purpose.  The tolerance on the capacitance of large electrolytics is typically very broad (like +/-30%), which means some will charge MUCH faster than others, which means some can have considerably more voltage across them than others when connected in series.

Regards,
Ray L.
Title: Re: Power Supply Unit
Post by: GrahamIT on January 30, 2011, 07:49:45 PM
That's really not a good practice with electrolytics, unless you provide a LARGE voltage safety factor, which kinda defeats the purpose.  The tolerance on the capacitance of large electrolytics is typically very broad (like +/-30%), which means some will charge MUCH faster than others, which means some can have considerably more voltage across them than others when connected in series.

Regards,
Ray L.

That's why I suggested 3 x 25V types in series to give a 75V capability, they should easily handle the 40 or so volts being used in this circuit with almost a 40% margin for safety. It's always worth a try if you can't get the correct size. They don't exactly go off like a hand grenade, just monitor the voltage across them individually and make sure they don't get too warm :)

...and I thought the purpose was to get up and running as quickly as possible :P
Title: Re: Power Supply Unit
Post by: rrc1962 on January 30, 2011, 07:53:22 PM


If you bought 6 of these 15500uF 25V capacitors, wired 2 sets of 3 in series and then took those 2 sets of three and wired them in parallel, you'd end up with the equivalent of 1 capacitor of 31000uF @ 75V.



If I'm not mistaken, the total capacitance in a circuit with capacitors in series is reduced.  If I'm figuring right, the total capacitance for three 15500uF caps in series would be about 5200uF.  To maintain a total capacitance of 15500uF you would have to have three 46500uF caps.  That said, I'm not sure total capacitance even matters that much in a power supply.

In the above example, the 2 sets of three would equal about 5200uF each then putting those sets in parallel would raise the total capacitance to about 10400uF.
Title: Re: Power Supply Unit
Post by: GrahamIT on January 30, 2011, 08:31:07 PM


If you bought 6 of these 15500uF 25V capacitors, wired 2 sets of 3 in series and then took those 2 sets of three and wired them in parallel, you'd end up with the equivalent of 1 capacitor of 31000uF @ 75V.



If I'm not mistaken, the total capacitance in a circuit with capacitors in series is reduced.  If I'm figuring right, the total capacitance for three 15500uF caps in series would be about 5200uF.  To maintain a total capacitance of 15500uF you would have to have three 46500uF caps.  That said, I'm not sure total capacitance even matters that much in a power supply.

In the above example, the 2 sets of three would equal about 5200uF each then putting those sets in parallel would raise the total capacitance to about 10400uF.

Oops... I forgot that bit,  I got the voltage bit right though, it's been a while since I've done any electronics.. Though I seem to remember being able to draw off odd voltages at low currents into a regulator between the capacitors to use when no other source was available. Though I may have been dreaming :P

http://www.electronics2000.co.uk/calc/series-parallel-capacitor-calculator.php (http://www.electronics2000.co.uk/calc/series-parallel-capacitor-calculator.php)
Title: Re: Power Supply Unit
Post by: HimyKabibble on January 30, 2011, 08:37:20 PM
Yes, you're absolutely correct.  Capacitors in series combine the same way resistors do in parallel.  Similarly, capacitors in parallel combine the same way resistors do in series.  So, two 10,000 uf capacitors in series will give 5000 uF,in parallel will give 20,000 uF.

"That said, I'm not sure total capacitance even matters that much in a power supply." - It matters VERY much, if you don't want your output voltage to sag during the low phases of the AC input.  Too little capacitance will result in output voltage ripple.  The higher the current, or the lower the capacitance, the larger ripple.  On a stepper motor, that will lose torque, and top speed, and could, in extreme cases, cause the stepper driver to misbehave.

Regards,
Ray L.
Title: Re: Power Supply Unit
Post by: kolias on January 30, 2011, 08:52:57 PM
Hey Ray, I dont understand what you are saying but I try.... I only wish I knew a fraction of what you know......

Anyway its nice to have you here to help people like me
Title: Re: Power Supply Unit
Post by: alenz on January 30, 2011, 10:56:49 PM

Nicolas,
I know better than to butt in but re capacitors………………
I think you are seeing viewpoints from two opposite sides of the spectrum. Perhaps (just guessing) one from a professional who designs commercial products to meet a certain spec and a hobbyist that just wants to build something that will do what he wants with the parts at hand (even tho it's not optimal). I say don't worry about the second decimal when dealing with components that have a 20% tolerance to begin with. Try to stay in the ballpark and it should turn out just fine. Our steppers may not be operating at 100% (how would we know?) but if they are doing what we want then as hobbyist we are happy. Ignorance is bliss.
Al
P.S. Fire away, I'm flameproof<grin>
P.S.S. I deeply respect the wealth of knowledge of both of the above unnamed posters.
AL
Title: Re: Power Supply Unit
Post by: kolias on January 31, 2011, 12:12:51 AM
I totally agree Al, as a hobbyist we just want things to run and forget about the details. Nothing wrong with that.

But electronics has always fascinated me and I always want to learn more, just for the fun of it. In this case I value the time people spend to teach others their knowledge.

We all try to help each other, isn’t it wonderful?
Title: Re: Power Supply Unit
Post by: alenz on January 31, 2011, 12:23:43 AM
Agreed, my sentiments exactly :).
Title: Re: Power Supply Unit
Post by: Hood on January 31, 2011, 03:55:49 AM
The problem then arises that when things are going wrong Mach is blamed and the lack of capacitance is overlooked ;D

Hood
Title: Re: Power Supply Unit
Post by: kolias on February 08, 2011, 10:26:31 PM
Soon I will be starting putting together this power supply unit and I have 2 questions

First from the attached picture how do I know which is the +/- terminal on each capacitor? I noticed one of the terminals is lighter color than the other so perhaps the darker terminal is the + ?

Second and from my recent post "Power supply overheating" I learned that this unit may generate about 250 watts of power and subsequent heat. Therefore should I make allowances on the metal enclosure I will get to have a fan for cooling ?
Title: Re: Power Supply Unit
Post by: Atlas56 on February 08, 2011, 11:34:32 PM
Here is a list of the basic capacitor parameter you should consider when selecting a capacitor. This is only a starting point as there are other parameters to consider when selecting a capacitor for a power supply.

Series type
Manufacturer
Tolerance
Lifetime @ Temp.
Operating Temperature
Features
Ripple Current
ESR (Equivalent Series Resistance)
Impedance
Mounting Type
Package
Case Size
 ???
It would be better to consider the power as only the small part of the total system design. If your system contains just one motor, power supply and controller it’s must simpler to design than a system with 4 motors and 4 controllers which all maybe interacting because of a common power supply design.

Good luck.
 ::)
Title: Re: Power Supply Unit
Post by: HimyKabibble on February 08, 2011, 11:42:15 PM
The information you were given in that other thread is absolutely incorrect.  If it were, you'd have to put twice as much power into the input of the supply as you get from the output, which is NOT the case.  The supply will NOT be dissipating 250W.  The only significant power dissipation in the supply itself will be in the bridge rectifier, which may be dissipating a few watts, and that only when the supply is providing high current to the motors, which it should never be doing for very long.  It should be heat-sinked (i.e. - mounted to a metal plate, smeared with silicone grease at the interface). 

Those are some gnarly looking capacitors.  How old and.or abused are they?  Old electrolytic caps do not perform well, and can go "boom".  On the blue plastic sleeve you should see a minus sign, or a string of them, running the length of the capacitor, near one of the terminals.  That is the minus terminal.  Do NOT power it up unless you are certain it's connected correctly, or it WILL go BOOM as soon as you apply power!

Regards,
Ray L.
Title: Re: Power Supply Unit
Post by: kolias on February 09, 2011, 12:35:49 AM
Thanks Ray for your input

Since the information on the other thread is incorrect, why that 36VDC power supply unit has its cooling fan going on for so often? is it normal?

Regarding  the rectifier, I attach a picture of it which shows a thin aluminum plate at its base. Is this sufficient to dicipate heat or I should mount it in another piece of aluminum? And we just bolt it down through the hole it has in the center?

Calling those capacitors “some gnarly looking capacitors” Hood is not going to like that because he was good enough to send them to me all the way from Scotland since I could not find anything similar. There is a string of dotted lines running the length of the capacitor but I thought that was part of the label because under those dotted lines are the specs of the capacitor. I know nothing about capacitors so I will let Hood inform that they will NOT go BOOM when I apply power.

Thanks again
Title: Re: Power Supply Unit
Post by: kolias on February 09, 2011, 12:36:37 AM
Sorry forgot the cap picture
Title: Re: Power Supply Unit
Post by: HimyKabibble on February 09, 2011, 12:41:07 AM
Perhaps your other supply simply has a defective temperature sensor?  Is the air coming out of the supply warm?

Go to Radio Shack, or any electronics store, and buy a small tube of silicone heat sink grease.  Put a thin coating on the underside of the rectifier, and bolt it yo your metal enclosure.

If Hood sent you those caps, I"m sure they're fine.  The dashed line running up the side is the minus indicator, so the near terminal is the minus.

Regards,
Ray L.
Title: Re: Power Supply Unit
Post by: Hood on February 09, 2011, 03:25:31 AM
Yes the caps should be fine they look a bit grungy as they were in the junk drawer in my outside store but they should be fine and unless they have degraded during transit your pics are making them look a lot nastier than they actually do ;)

As Ray has said the  line down the side denotes the negative terminal.
Hood
Title: Re: Power Supply Unit
Post by: kolias on February 09, 2011, 07:17:03 AM
No, the air coming out of the 36VDC power supply is not warm

Alright I will get the silicone heat sink grease and follow instructions.

And now I know the negative terminal on the capacitors. I will assume that I have to solder my connections to these capacitors

Is it ok to apply heat to these terminals to solder my wiring?

Thank you both
Title: Re: Power Supply Unit
Post by: Hood on February 09, 2011, 07:39:00 AM
Yes, soldering is no probs, thats why the top plastic outer is slightly melted as when I went to post them to you I had to de-solder the wires I had on them, only prob was the only soldering Iron I had handy was a big wolf one with a 1 inch square  tip so not easy to get in ;D

Hood
Title: Re: Power Supply Unit
Post by: kolias on February 15, 2011, 11:44:40 PM
From the 3 main items on this power supply unit (toroidal, rectifier, capacitors). which will generate the most heat that needs to be dissipated ?

Toroidal was to be delivered today but the courier got stuck in the snow and delivery will be tomorrow. I will then make a layout and post a photo for comments before starting mounting the items.

 
Title: Re: Power Supply Unit
Post by: HimyKabibble on February 15, 2011, 11:54:07 PM
None of them should generate a great deal of heat.  Heat sink the rectifier, just in case.  The transformer should only get hot if you run it for sustained periods at high current output, which should never happen.  The capacitors should NEVER get hot.

Regards,
Ray L.
Title: Re: Power Supply Unit
Post by: kolias on February 16, 2011, 05:19:10 PM
Thanks Ray for the info

The unit just arrived and here is a photo along with my questions:

Do I remove the clear plastic that is wrapped around the unit?
When I mount it, the wires coming out should be at the top or the bottom?
There is one metal washer and two rubber washers along with one bolt. How do I use these?

On the unit it is written: Noratel, 953 2846, Model TA225/25     LK 0923A
I went to Noratel.com but no more info is available with the above numbers

I have also attached a .PDF data sheet from where I bought the unit which has the wiring coming out of the unit. The BLU & GRY are hold together with some kind of tape and the same for the VIO & BRN

Thanks
Title: Re: Power Supply Unit
Post by: HimyKabibble on February 16, 2011, 09:58:14 PM
Do NOT remove the clear plastic.

Wires can be at the top or the bottom - doesn't matter.

Put one rubber piece on the mounting surface, then the transformer, then the other rubber piece, followed by the large metal washer, then install the bolt.  Do NOT over-tighten the bolt - just enough to keep the transformer from going anywhere.

If you're AC source is 110/120V, connect the Violet and Blue wires together, and connect to one side of the AC supply.  Connect the Brown and Gray together, and connect to the other side of the AC source.  If your AC source is 220/240V, connect the Brown wire to one side of the AC source, and the Blue wire to the other side.  Connect the Violet and Gray wires together, and seal the connection up in some heat-shrink tubing.

Connect the Orange and Black wires together, and connect to one AC input of the rectifier.  Connect the Red and Black wires together, and connect to the other AC input of the rectifier.  Connect the capacitors with the - terminals to the - terminal of the rectifier, and the capacitor + terminal to the + terminal of the rectifier.

Regards,
Ray L.
Title: Re: Power Supply Unit
Post by: kolias on February 16, 2011, 11:12:29 PM
Thank you Ray

I find it strange to leave the clear plastic on, looks to me that is going to burn or something but I will follow your instructions, What purpose it serves any way

Mounting sounds good, no problem here.

I’m on 110/120V so when you say connect to one side of AC supply does it matter if it is Line or Neutral (Black or White)?

There is a mistake on the secondary side, I think

You say to connect Orange and Black together and connect to one AC input of the rectifier. Then connect the Red and Black (you mean the YELLOW) and connect to the other AC input of the rectifier.

So I take a piece of wire and connect it to the PLUS of one Capacitor then continue and connect the same wire to the PLUS of the next Capacitor and then the same wire I connect to the PLUS of the rectifier.

Then I do the same with the MINUS

Thanks again
Nicolas
Title: Re: Power Supply Unit
Post by: kolias on February 16, 2011, 11:34:01 PM
Kolias - Don't know if anyones raised this yet but it looks as though you have a double primary and double secondary transformer there. Wiring is not complicated but you need to be aware of how they need to be configured. Generally speaking it looks like you'll need your primaries in parallel (for 120Vac) and your secondaries in series (for 24Vac). Also you'll need to establish the phases of the windings or that fuse might well come in handy (hopefully there'll be some marking or whatever). To cover my *rse Please check it out - don't take this as instruction - just a cautionary heads up.

Ian

By wiring as Ray suggested, do I take care what is mentioned above by Ian?
Title: Re: Power Supply Unit
Post by: HimyKabibble on February 17, 2011, 12:10:48 AM
I’m on 110/120V so when you say connect to one side of AC supply does it matter if it is Line or Neutral (Black or White)?
>> Correct

You say to connect Orange and Black together and connect to one AC input of the rectifier. Then connect the Red and Black (you mean the YELLOW) and connect to the other AC input of the rectifier.
>> Yes, I meant Red and Yellow, not Red and Black.  Sorry!

So I take a piece of wire and connect it to the PLUS of one Capacitor then continue and connect the same wire to the PLUS of the next Capacitor and then the same wire I connect to the PLUS of the rectifier.
>> Correct

Then I do the same with the MINUS
>> Correct

By wiring as Ray suggested, do I take care what is mentioned above by Ian?
>> Yes.

Regards,
Ray L.
Title: Re: Power Supply Unit
Post by: kolias on February 17, 2011, 08:34:59 AM
Sorry but I must be sure that I understand correctly”

So the VIOLET & BLUE together will connect to LINE (Black) and the BROWN & GRAY together will connect to NEUTRAL (White) of the AC Supply. Correct?

The GROUND (bare copper wire) from the AC supply will connect to the Aluminum box somewhere along with the NEGATIVE (Black) from the Capacitors. Correct?

I still would like to know what is the purpose of the clear plastic wrap around the Toroidal body. To me looks like a fire hazard
Title: Re: Power Supply Unit
Post by: Hood on February 17, 2011, 10:11:15 AM
Not sure what your mains supplies are like in Canada, here in the UK we are 240v single phase, ie between a live and neutral we get 240v. What are you between live and neutral? If 110v then conneection as you have said is fine.

The plastic cover I am not sure what its for, presume just protection so that the laquer on the wires is not easily damaged thus causing a short. Dont worry about it being a fire hazard, my Bridgeport has had power to it for 5trs or more constantly and has not gone up in flames yet. Here a pic.
Hood
Title: Re: Power Supply Unit
Post by: kolias on February 17, 2011, 03:37:04 PM
Thanks Hood, yes our mains here have 110V between Live and Neutral and so we put to bed the AC connections.

I hope someone will chime in and say what the plastic wrap is for, just to learn although I think it makes sense in what you are saying. Nice job on your Bridgeport.

Here are some pictures on what I did today. The box cover is 9”x 6.5”x 4” High and each side is made of two aluminum sheets 23 gauge and all are riveted together. I still have to drill some holes on the sides for ventilation.

The base is made of two aluminum plates each 1/8” thick and they are bolted together on the exterior with two aluminum bars each 1/4" thick by 1/2" wide.

The items are now screwed to the base and I would like to know if we all agree that the location of each is correct.

The rectifier has not yet the silicone on its base in case I have to move it.

The bottom of the two capacitors is NOT touching the aluminum box bottom, it is about 1/8” higher. Don’t know if it is good idea to touch the bottom or not. I can easily lower it by loosen the clamps.

There is plenty of space around and on the top of the toroidal but for my education I would like to know what would happen if the toroidal body touches the aluminum box. I would have liked to install the box inside my control station sitting on its side but since the toroidal is so heavy I’m afraid that it may slide and touches the aluminum sides
Title: Re: Power Supply Unit
Post by: kolias on February 17, 2011, 06:13:05 PM
Questions remained to be answered:

Should the capacitors touch the base of the box? Now they sit about 1/8” off the base and supported with the clamps.

Can I install to unit on its side? In this case I have to tighten the toroidal so it will not slide

What would happen if the toroidal touches the sides of the aluminum box?

I have an aluminum ground bar in my control station now and all DC grounds (Black wire) go there. Should I also connect in this ground bar the ground (bare copper wire) from the AC? Good / bad idea to do so?

Title: Re: Power Supply Unit
Post by: larryc on February 17, 2011, 09:40:22 PM
Hi do not take the plastic wrap of the transformer it holds the windings together. If you take it off the transformer will buzz as the current goes through it. the windings will not be held tight. Also if you take the wrap of and say some day you whant to take the transformer out to get it repaired it will fall apart on you... Oh and that transformer does not get hot neither does the capacitor or recifiers. Well not if they are big enough and they looik okay I have made the same power supply 3 years ago for my machine and they have never got hot or even warm. The geko drives for the motor though will get warm. Just warm. I have mine put on a 1/4 inch aluminum plate just bigger than the drives wide and long enough for all the drives on one plate. Put a computer fan at one end facing the plate even they  Havent got warm after that. only thing that gets warm are the motors.. and even after 4 or 5 hours they should not get to hot to touch. Just as warm as coffee.good luck.
Title: Re: Power Supply Unit
Post by: kolias on February 17, 2011, 10:14:14 PM
Thank you Larry, that is a very good info
Title: Re: Power Supply Unit
Post by: larryc on February 18, 2011, 09:00:12 AM
are you at the power supply level all ready. how does you machine work.
Title: Re: Power Supply Unit
Post by: kolias on February 18, 2011, 02:17:31 PM
are you at the power supply level all ready. how does you machine work.

Larry the machine is working and you can see the video at

http://www.youtube.com/watch?v=xJvCtoMv814

I just want to replace the existing switching 36V power supply with the one I'm building now
Title: Re: Power Supply Unit
Post by: kolias on February 18, 2011, 02:20:24 PM
Here are the wiring pictures of the unit

Hopefully someone will tell me if all looks ok before I plug it in
Title: Re: Power Supply Unit
Post by: Hood on February 18, 2011, 05:15:00 PM
Looks fine to me, only thing I would say is I would have the black wire (DC 0V) go to a terminal as well for easy connection. I never put my 0V to the base plate but the document seems to suggest that you should and I think others in the thread have also said so.

Hood
Title: Re: Power Supply Unit
Post by: kolias on February 18, 2011, 05:21:00 PM
Looks fine to me, only thing I would say is I would have the black wire (DC 0V) go to a terminal as well for easy connection. I never put my 0V to the base plate but the document seems to suggest that you should and I think others in the thread have also said so.

Hood


I agree with you Hood, I will put the Black lead (0V) to the terminal as well until someone here tells me otherwise

Thank you
Title: Re: Power Supply Unit
Post by: HimyKabibble on February 18, 2011, 09:14:53 PM
Looks OK, except:

1) The wire gauge you used on the secondary circuitry looks light.  It should be the same gauge as the wires coming out of the transformer.
2) The way you have the ground wired is fine, but it will make connection easier if you also run it to the terminal strip.
3) It gives me the willies seeing those AC line wires so close to that sharp sheet metal edge in the last photo....

Regards,
Ray L.
Title: Re: Power Supply Unit
Post by: kolias on February 18, 2011, 10:15:13 PM
Thanks Ray for your input

1) I agree the Black wire is smaller but that’s the only Black wire I had available and wanted to finish. I will zip to the store tomorrow and get the same size as the other ones
2) Having the DC ground where it is gives ME the “Willies” LOL. I will leave the AC ground as it is and take the DC ground to the terminal strip.
3) I agree did not look right although that sheet metal edge would not even cut was. But I removed the edge as you can see from the attached photo

Much obliged for your help
Title: Re: Power Supply Unit
Post by: kolias on February 19, 2011, 01:04:18 PM
Well it is done and all seems right.

I did the test in steps (with the help of a friend); first I only apply power to the toroidal and measure the output voltage which was 26.5ACV

Then connect the toroidal leads to the rectifier and measure the DC volts which was 23.9DCV

Then connected the capacitors and I get at the terminals 36.2DCV

Now I will install the new power supply inside the control station and connect the motors etc.

Thank you all so much for such a wonderful experience and a special thanks to Hood who inspired me to go through this experience and also sent me the two capacitors on his own expenses.
Title: Re: Power Supply Unit
Post by: Overloaded on February 19, 2011, 01:15:53 PM
You have done a great job Nicolas. It looks really nice.
I'm not sure if it was mentioned earlier, but be very careful with the stored energy in those caps !
Some folks recommend a resistor across them to bleed them off for safety.
Again, great job !
Russ
Title: Re: Power Supply Unit
Post by: kolias on February 19, 2011, 01:31:29 PM
Thank you Russ

Yes the stored energy inside the caps, which I didn't know before, it was mentioned to me by Hood and others

As to the resistor, I will leave it for now; I had enough heart breaking experience today testing the new unit LOL