Hello Guest it is March 28, 2024, 04:02:59 PM

Show Posts

This section allows you to view all posts made by this member. Note that you can only see posts made in areas you currently have access to.


Messages - robertspark

111
General Mach Discussion / Re: Any help / suggestions please?
« on: October 10, 2016, 08:33:23 AM »
I didn't finish this one off.... 'll have a go here, but I've kind of lost my chain of thought...

There is a bit of waffle over here on the UK earthing arrangements..... basically although the nomenclature is UK based, if you consider the wiring arrangements it kind of covers every possible permutation of the incoming earth....
https://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwj2o6ycm9DPAhXKJsAKHZUuDeMQFggfMAA&url=http%3A%2F%2Felectrical.theiet.org%2Fwiring-matters%2F16%2Fearthing-questions.cfm%3Ftype%3Dpdf&usg=AFQjCNGgVmZa42MaWWheFH0je93n2TQVdg&sig2=12kT_2cmztOW93h4-zaNaA&bvm=bv.135258522,d.d24

Because cnc systems work on lower voltages, we have step down transformers or switched mode power supplies.

Both of these allow for electrical isolation of the primary (mains) and secondary (lower voltage) sides and all use some form of transformer (two / more coils of wire wrapped around a ferrite [iron] core).

Because of this electrical isolation, you really want to separate out the secondary side 0v, Vcc- or ground connections because they will never be at exactly the same zero volt potential as the primary side because of the load characteristic trying to reduce the potential differences between the two wires when under electrical load. ......    its this electrical isolation that means that the are not true "ground" voltages but can be offset slightly which will lead to some current flow

Lots of people just join them all together and in some cases link them to the earthing point which makes it even worse.... because it can create earth leakage currents.

112
General Mach Discussion / Re: Any help / suggestions please?
« on: October 08, 2016, 07:06:26 AM »
Ahh.... earth's are a different matter...

People get very confused by earth's... vcc-.... 0v..... gnd.... and think they are all the same.... they are not!

Ask yourself what is earth?

It is essentially the 0v with respect to everything else...

Electrically.... mains voltage side... it is created at the substation transformer by grounding the centre tap of the transformer....  the transformer will be in one way or another a star wiring configuration.... so as the three electrical phases move 120 degrees out of sync the star point provides a common 0v point.... and because this is grounded at the transformer literally by driving earth rods or more correctly laying an earthing mat in the ground this provides the earth point.....

Now the next problem is your wiring arrangement... they vary across the world... but essentially you need a live (hot wire) and another wire... in the rest of the world (non 2 or 3 phase) this is called the neutral phase.... and it is essentially the centre tap of the transformer..... same as the earth.... sort of.....

These two wires are required .... now there is a choice by the local electrical requirements... with a separate protective earth can be sought by laying of an earth mat... and or driving earth rods into the ground (same as the mat) .... or connecting onto the neutral or a combination of the two....

...2 phase (common with USA 110v and remote uk supplies plus others I suspect too) and 3 phase are a little different...

.....I need to do this over a few posts as I have children demanding lunch (uk time)

113
General Mach Discussion / Re: Any help / suggestions please?
« on: October 08, 2016, 06:04:19 AM »
Looks neat... note... I've edited one of my previous posts as my autocorrect on this phone is killing my messages and changing the text to any old thing it thinks...

114
General Mach Discussion / Re: Any help / suggestions please?
« on: October 08, 2016, 06:02:25 AM »
Yes, sounds Ok... suggest maybe splitting your drive power supply from your bob.

I have 50v ac to each of my drives... 24v to my bob... then a 5v supply to my ess (when I ran an ess... now moved on... same principle applies). None of the zero volt lines are joined... plus because the bob has optoisolators within it it separates the 5v  motion controller signals from my machine side 24v signals.... plus the dries have optoisolators in them.... hence the ability to feed them directly off their own power supply (which does just happen to be ac) ... but I did a similar thing when I ran lesser 42v drives too

115
General Mach Discussion / Re: Any help / suggestions please?
« on: October 08, 2016, 05:46:17 AM »
Also remember if you have a 5v power supply for example, when you measure the no load voltage it may be say 5.2v... then when you apply the rated load on it it now measures 4.9v.... those voltages are with respect to the power supplies vcc+ and vcc- lines... ie the voltage is pulled closer together under load.... now when you join all the zero volt lines together you will try to pull those zero volt lines voltages upward too and change the offset voltage with respect to the other power supplies vcc+ outputs

With simple electronics and electrical circuits this is not seen as a problem but with high speed data communication (usb for example ) where the data is offset and has high and low status voltages for the different state a change in the offset voltage that's different... it looses packets plus the controller (FPGA) may lockup because the voltages they work in are minute differences with very little current flow)

Edit: man this autocorrect is killing my messages!

116
General Mach Discussion / Re: Any help / suggestions please?
« on: October 08, 2016, 05:29:44 AM »
Its the reason why we use optoisolators and optocouplers.... to separate the circuit out... by joining the grounds you are effectively getting ride of the main benefit of the optoisolator/ optocoupler (other benefits being dissimilar voltages interface)

117
General Mach Discussion / Re: Any help / suggestions please?
« on: October 08, 2016, 05:26:00 AM »
Because you create the ground loop as unfortunately the power supplies do not output zero volts but the zero volt lines are offset from each other...

Suggestion.... if you have a voltmeter... break the dinrail... so that all the zero volt lines are seperate... then test the voltages between each of the zero volt lines with respect to reach other, that is your offset voltage... and creates your ground loop (which the SS will be particularly unhappy about and the cause of much annoyance to you)

118
General Mach Discussion / Re: Ess Smoothsteper speed problem
« on: October 08, 2016, 04:50:01 AM »
Smooth Stepper spindle setup is here:
http://www.warp9td.com/index.php/faq/faq-mach3#Spindle

really you are best having a look at the Warp9 website which has come on loads over the past year and is much more helpful (all thanks to Andy at Warp9).

The website supersedes any manuals you may have as they were never completed (one thing always lacking with SS + warp9.... like driver updates [back in your box rob!])

Anyway.... have a look at the FAQ on the warp9 website as there are a number of items within the configuration pages of mach3 that do not relate to the SS as they are configured on the SS-configuration / plugin page as them must be loaded directly to the FPGA upon mach3 resart .... hence the reason why after changing any settings you must restart mach 3 so that the FPGA is reset and the new config settings are uploaded.... yes its a pain but the way it works.... once its setup you don't need to do it but get a backup of your xml file and save it somewhere safe (online storage .... googledrive... dropbox whatever)

119
General Mach Discussion / Re: Moving to a new PC
« on: October 08, 2016, 04:40:38 AM »
WOW! I thought that nice tidy method of programming died with DOS!

Its how all programs should be made in my view, MAC's used it up to a few years ago but now they spread stuff all over the place.

Nice.

Whether or not the uSB bus is fast enough for the job i don't know but its interesting :)

Don't forget Mach3 came out a looooong time ago now and was based upon a continuance of code.....

Yes... depends on your usb stick..... + how you are motion controlling too (usb motion controller?).... I'm not sure how much of the programme is loaded and if there is any calls from the files once it's loaded....  (I wouldn't do it but I have a dedicated offline PC with one purpose in life).

I don't "think" it will work with mach4 though..... also if you are running a big g-code file I'm not sure how much use the programme may make of any swap files (or files that act like swap files, that may be in the mach3 programme folder) to buffer motion and look ahead

120
General Mach Discussion / Re: Any help / suggestions please?
« on: October 08, 2016, 04:35:18 AM »
How have you wired the two power supplies?

Please tell me you did not join the (+) and (-) together..... (that will kill one of you PSU's if they are SMPSU's as the voltage outputs are never exactly the same or align as load kicks in which means one will backfeed into the other)

How many drives do you have?

If you take my scenario.... I have 4 drives X, X' Y and Z   .... I use a toroidal transformer with two windings.... one winding feeds two drives ... the other winding feeds the other two drives ....  (my drives are ac input [so much easier!])  ...

essentially I'd feed two (and or your occasional extra drive) off one of the psu's and then the other two off one of the other PSU's