On Friday 31 October 2014 20:24:54 Kirk Wallace did opine And Gene did reply: > On 10/31/2014 03:36 PM, Gene Heskett wrote: > ...snip > > > That could be an SOA failure, where a bug spends too much time in the > > transition between on and off and punches thru. > > > > TBT, most darlingtons are too slow, particularly for power drivers, > > to be suitable for such usage, and I would expect a relatively high > > failure rate. > > > > Servo, or steppers? > > > > Cheers, Gene Heskett > > NEMA42 steppers at 45V and 8 amps. The PWM sounds like it is in the > audio range or pretty close. These drives have worked pretty well for > the handful of years that I have had the machine, plus it is around > thirty years old.
All the more reason to not putz with them, replace them. The difference in the technology is amazing. The big brother to the 2M542, there are 2 that I'm aware of, will go as high as 80 volts & 7 something amps. My 7 $50/copy 2m542's (50 volt, 4.2 amps) have been absolutely bulletproof, and the one driving the Z on my lathe is driving an 8 wire triple-stack Nema 23 in parallel mode running wide open at that 4.2 amps from about a 39 volt supply. I bought a spare when I bought them, and its still in the box in the tool cabinet next to the lathe. That was about 4 years ago now. The PWM is up around 25 khz & inaudible to me. The only thing I hear is the motors singing as the step rate varies. Something like this: <http://www.ebay.com/itm/Nema34-Stepper-motor-driver-DM860A-7-8A-256micsteps-24-80VDC-CNC-Router-LONGS-/151329396996?pt=LH_DefaultDomain_0&hash=item233bef5904> And still only 50 bucks a copy. Its also NOT a leadshine, which I believe mine are. But thats the first link I hit on fleabay, maybe better deals yet. There is also this one: <http://www.ebay.com/itm/LeadShine-DM1182-2-4-Phase-Digital-Stepper-Motor-Driver-80-150VAC-0-5-8-2A-/121455690755?pt=LH_DefaultDomain_0&hash=item1c4752c403> at $160, but its 8.2 amps with a built in AC supply rated 80-150 VAC input. Having the builtin supply saves $ in the long run if you don't have a big enough supply now, having to cobble up a 2kw plus 75 or so volt supply for this "bigger" iron. The increased voltage these drivers can handle sure makes a heck of a difference in top speeds and in how fast they can accelerate. If your are running on 45 volts now, the AC powered driver will pretty close to triple both the accels and the top speeds. All of these are opto-isolated inputs and can microstep by large numbers. I run mine at 8x. 4x worked but growled a lot louder. Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> US V Castleman, SCOTUS, Mar 2014 is grounds for Impeaching SCOTUS ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
