Two Drivers on One Motor??

[MillworkMike]

Just wondering if something like this would work?? Any input would be great. Thanks!

[fizzissist]

I had a bipolar parallel girlfriend once. She didn't work.
But, I don't think she was wired right.

[MillworkMike]

Lol!! I got one them now... and i know for sure shes not wired right!!

[doorknob]

I don't know the actual answer, however in giving the idea some thought, my guess is that it may work after a fashion, but with possible problems or complications.

So, the following is just a guess:

The motor drivers probably are sending a chopped current to the motor windings. However the chopper circuits in both drivers would not be synchronized with each other, so on a "microscopic level", both A windings (and also both B windings) are unlikely to be driven with the same current at the same instant. In addition, both A windings (and both B windings, too), are likely to be closely coupled to each other (they may in fact be set up as "bifilar" windings - that is, they are likely to be closely-spaced, parallel windings). So, the drive signals applied to one of the A windings will be coupled into the other A winding (and vice-versa, and similarly for the pair of B windings).

Thus, the actual, resultant currents through the windings are probably going to be different from what each drive expects to see. So, the current-regulating circuitry within each drive may operate erratically. If the current through each coil is behaving erratically, then the operation of the motor may be erratic as well. I wouldn't rule out the release of a bit of smoke, either.

Of course, i could be completely off base. I suppose that it's possible that the current-regulating circuitry within each drive might actually end up in sync with each other. But I wouldn't bet on it happening.

Someone else who either has actual experience trying this or who has more detailed experience with chopper drive design principles may chime in and provide better info, though...

[judleroy]

I would think that even with two drives you would still only get 3 amps of power to your 6 amp motor.
judleroy

[RomanLini]

I know something of chopper driver principles. Judleroy is right you would still get only 3 amps, although you would effectively get "double" the voltage to the motor (which is good for higher speed).

But I would really recommend not doing it! In the case of a missed or glitched step pulse it will cause disaster, and there is a very real chance of feedback instability as there is no mechanism to synchronise the chopping frequency and the magnetic phenomenon inside the motor is very complex.

[MillworkMike]

Thanks for the input guys! :-)

[tommylight]

That might just work, although i never tried it, just be careful with wiring, do it EXACTLY as on your picture. Anything else and it fry the drives for sure. It is 2 AM here so i am off to bed but i would give it a try for sure. Again, WARNING, any of the motor outputs on the drives connected to the output on the other drive through the motor windings will kill your drives, both of them most probably.
Regards,
Tom

[MillworkMike]

Thanks Tommy.... Anybody else think this "Might just Work"??

[robe_uk]

Originally Posted by MillworkMike Thanks Tommy.... Anybody else think this "Might just Work"??

No, I think its more likely to ''might NOT work'', I would agree with doorknob and think the drives would be fighting against eachother.

I guess the question has to be ask, why not just buy the correct drives to start with? the cost of one 6Amp drive would be less than the cost of 2 3Amp drives, if its a case you have a load of 3Amp drives and thats why you want to use them I would say sell them and buy the correct drive and be done with it, then you'll not be worrying every time you power up is it going to work and more than likely when you really need it to work, it wont.

Rob

[MillworkMike]

Hey Rob....

Just so you know this is just a curiousty thing.... something I was wondering if it would work or if anybody has ever tried.

So.. yeah... Thanks for the "INPUT" Buddy!!

[tommylight]

Ok,i can see that this is getting out of hand, so here it goes: today i was busy and i am dead tired and tomorrow it is going to be even worse since i have to mount and install 4 huge led signs ( the smallest one being 6x1 M ), but as soon as i get 15 minutes of free time i will try it and report back. I have a lot of geckodrives and some others but i will try it with geckos since i got used to changing mosfet's on them.... WARNING !!!! ALL the geckos that came dead to me were dead due to ignorance of a friend of mine who doesn't understand a single thing about electronic but non the less he wires them and destroys them at a rate of 1.5 drives per build, i had mine for over a year and i have done absolutely everything possible to them short of changing the polarity of the power supply ( that will kill them for sure ) and they NEVER failed!
Anyway i would love to kill one or two of them since i have gotten my dirty little mints on some 75545 mosfets rated at 80V and 75A aaaand with a bit of tweaking i can have geckos that will easily do 30A per motor winding!!! BUUUUUT, again but, i have tried to kill a G320 for nearly a week just to have an excuse to change the mosfets but it just wont die under normal conditions.
Stay tuned...
Tom