Messages

1841

General Mach Discussion / Re: Toroidal transformers vs standard IE

« on: March 30, 2008, 10:33:11 AM »

KNS - I think you're right to just go ahead and build it and see what happens. With respect I'm wondering why you asked in the first place. Throughout the whole thread, no one has said it won't work. If you mean by work, will the axes move? then probably yes. If you mean will you get the performance you need then with the info you've given it's not possible to say yes or no - and again that is basically what everyone has said.

There are however a couple more issues I'll throw into the pot - make of them what you will.

Gecko say that (and I quote) "In a all cases the power supply should be no less than 4 times or no more than 25 times the motor's rated voltage. The motor may not run as smoothly as possible if the power supply voltage is less than 4 times the motor's rated voltage".

Will it rotate, probably yes.

One other thing is that with the 65V motor, you are in no way going to get the performance from the gecko that you've paid for. That poor little gecko is going to be sitting there going - why me? - I'm a thouroughbred race horse - why am I pulling this cart?

Finally a note about calculating your PS current requirements. With friendly respect to Sam, you don't just add up your motor's rated currents. Chopper drives do not draw their apparant load. The total will be at most 2/3 of the sum of the motors rated currents and with 4 wire motors it will be nearer to 1/3. hence the value I stated in my previous post.

1842

General Mach Discussion / Re: Toroidal transformers vs standard IE

« on: March 29, 2008, 07:23:22 AM »

Let's go with what you've said you've got and look at what will happen.

You have 2 motors - 1 power supply so... both motors will be presented with the same voltage by your geckos i.e. the 54Vdc of your PS.

Your 65Vdc rated motor will be UNDER driven by a factor of 54/63 or ~0.8 and your 4.8Vdc rated motor will be OVER driven by a factor of 54/4.8 or ~11.5.

Now - current: your going to be using a gecko for each motor to drive them independently - yes? So... the gecko driving the 65Vdc/5.4amp motor should have its current-set resistor set appropriately so that it does not DELIVER more than ~5.4amps. Now onto your other 4.8Vdc/8.4amp motor: A gecko can deliver a MAX of 7amps so that is what it will deliver to that motor - period. Geckos, being chopper drives are current limiting devices - they will only deliver the current they are set to deliver. You can NOT "draw" more, V=IR does not apply here as it would in a simple "linear" dc circuit.

So the bottom line is: Firstly, you're under driving one motor in terms of voltage - this will affect the usable speed you can usefully get the motor to before it stalls. - will it be enough - well that depends on your application and more info would be needed to comment usefully. Secondly you're current starving the second motor and that will reduce it's torque over the whole range of speeds it can operate at. - is it enough? - same answer as before.

Regarding the often stated 10-20 V overdrive factor - this is totally dependant on application. To determine this empirically you would start by running your motor at the labelled voltage (Vx) and increase speed under the required load until it stalls. If that stall speed is insufficient for your application you up your voltage by Vx and repeat. As a rule of thumb the overdrive ratio of the voltage is proportional to the stall speed at a given load. i.e. 10 x V = 10 x stall-speed.

A couple of observations on things you've said:

I was told by Pacsci to just hook them up in parallel and go with it. Do you see any problem with this?

Yes, it's meaningless. They're FOUR wire motors - it is not possible to wire them in parallel.

I am going to be using a 54vdc 800 watt power supply with these drives.

Your 2 drives are going to require ~4.2Amps in total from your PS. Your PS can source ~14.8 Amps so that will not be a problem.

1843

VB and the development of wizards / Re: Tool changer routine with hot swap

« on: March 28, 2008, 03:30:06 PM »

Hi Terry

No problem. I order by tool, you order by slot. Just loop through my tools and read each slot. Then use the slot to index the appropriate DRO.

e.g.

assuming your first gcode var is #1000 and your slot 1 DRO number is 1000 AND that you use consecative vars and DROs (which would be weird if you didn't)

numTools=8
gcodeVarBase=999 (or whatever i.e. 1 less than the first you use)
droBase=999 (or whatever i.e. 1 less than the first you use)

for tool = 1 to numTools
  slot = GetVar(gcodeVarBase + tool)
  SetUserDRO(droBase + slot, tool)
next

Ian

1844

General Mach Discussion / Re: cnc machine running when start windows 2000

« on: March 28, 2008, 02:00:55 PM »

Hi jd1uth

seems your saying before you even start Mach right?

Maybe you have a printer driver in there as well as the pulse engine and a document in W2Ks print queue? - just a (wild) thought...

Whatever, best not to start windoze with the rig switched on. Whilst booting a PC and loading W2K, the parallel port is chucking out all sorts of garbage. Turn your machine off until it's is up at least - preferably wait until Mach is up and running.

1845

VB and the development of wizards / Re: Tool changer routine with hot swap

« on: March 28, 2008, 10:29:41 AM »

Hi Terry - now you're starting to take the p*ss 

(PS - for 0x378 (C hex style) use &H378 (BASIC hex style)

Hi Terry - with regard to your last question to Graham - you need to read my earlier reply about the format of hex strings in BASIC. The syntax is &H0378 or whatever address you're using. The &H is instead of Grahams 0x at the front of the string.

A word of caution which I hope isn't too late. You have to be VERY careful which port or address you write to - you can seriously screw up your system - even trash the hard disk if you're not careful.

1846

General Mach Discussion / Re: Online forum has exceded Yahoo membership as of today.

« on: March 28, 2008, 07:47:31 AM »

It would be nice to have just a one stop shop forum and of course this should be it - any thoughts in the pipeline on this? bye bye Yahoo?

1847

General Mach Discussion / Re: Toroidal transformers vs standard IE

« on: March 28, 2008, 07:31:51 AM »

covered by Hood and Remberto but...

ain't google the mut's nuts 

"The toroidal transformer has the ideal shape for producing a transformer with the minimum of material. The high efficiency which is obtained with this type of transformer enables it to be conservatively rated without incurring size or weight penalties.

There are no loose laminations or air gaps in the toroidal design which, together with the virtual absence of any external field, makes the toroidal transformer particularly suitable for those applications where electrical and mechanical noise must be kept to a minimum."

1848

VB and the development of wizards / Re: Tool changer routine with hot swap

« on: March 28, 2008, 07:02:57 AM »

Hi Terry

Would you happen to know of a way to do a DOS command from inside of machVB if so then I can send the file to the printer with the DOS Print command?

Dim cmd As String
cmd = "print c:\test.txt"
Shell ("cmd.exe /c" & sCommand)

(With thanks to Shuja Ali)

Ian

1849

VB and the development of wizards / Re: Tool changer routine with hot swap

« on: March 27, 2008, 12:07:40 PM »

LOL - you can't go around saying things like that. Last time I said that about someone's software they looked at me like I'd said their daughter had a face like a horse 

1850

VB and the development of wizards / Re: Tool changer routine with hot swap

« on: March 27, 2008, 11:21:34 AM »

Yes, It seems that although the printer object itself is recognised, none of its methods or properties are available (I tried a few) - zippo. Hence your message of "object doesn't support this property or method". I think this is one for Brian perhaps. I'm sure he'll be delighted.