re:RE: max chopper voltage
Posted by
ballendo@y...
on 2000-10-05 17:03:39 UTC
A-Alan wrote(in response)to: >my post Additions interspersed below
my drivers, either through usage, or misuse(backdriving). The L298
does not have the inherant "protection" diodes of most MOS devices
and I wanted to point out to those on the list that they may wish to
increase the diode specs over the SGS recommendations.
A-so )near the switching transistors.
EXACTLY RIGHT! I use 470uf, low ESR (this means Equivalent Series
Resistance, for those who don't already know, and has to do with the
capacitor efficiency in this usage)
A-MOST IMPORTANT, by far, is to have a good board layout and use good
A-grounding practices. This cannot be stressed enough !
EXACTLY RIGHT AGAIN! THIS IS THE KEY! (Alan, have we stressed this
enough? :-) )
A-the stepper board could arise that would screw up the PS, but if it
A-did, it would have to be a pretty crappy supply and definitely not
A-worth using.
A-And there's no need for the regulation a typical switcher supplies
A-when used with a chopper drive, meaning that the extra cost is just
A-money out the door. ( This is certainly NOT the case with a non-
A-chopper drive,though )
Agreed. But I have seen these "crappy" supplies cause people to tear
their hair out(been several years ago, though. Things are better
now,IMO). But it was the PS affecting the driver chopping, not the
other way around.
A-My opinion would be that if you have a quality switcher around of
A-suitable capacity, there's no reason not to use it. But there's no
A-reason to go out and buy one if you don't.
Key word, quality. Agreed.
A-found in a typical shop could influence the performance of a
A-properly designed, properly constructed stepper controller.
Exactly what we're talking about here. PROPER design,PROPER
construction. A lot of "marginally designed, marginally constructed"
setups ARE doing good service now, but sometimes a working system
stops for what SEEMS to be "no apparent reason", when it is actually
this design and construction issue popping up. This is like the
cordset thread(playing now in egroups CCED)where you "could" use it
for 3 phase, and it "would" work electrically, but IF someone came
along later and didn't know, there's a SERIOUS problem!
A-Improper design, poor construction, LONG cable distances, or bad
A-grounding ( inside or outside the box ) certainly will, but a well
A-designed, well built controller six feet from the PC and six feet
A-from the machine it controls will not suffer from almost any
A-external electrical influence.
Alan
Alan, Thank you for your reply.
Ballendo
>Well, the 851 is both higher voltage and higher current, so a personUsing 23SS(single stack) to 34 DS's. The key here is I have not blown
>would guess that you're running some healthy motors.
my drivers, either through usage, or misuse(backdriving). The L298
does not have the inherant "protection" diodes of most MOS devices
and I wanted to point out to those on the list that they may wish to
increase the diode specs over the SGS recommendations.
> I believe the power supply is a significant part of the success atA-More important is to have a fast, low ESR electrolytic ( 220uf or
> higher volts/amps. Mine use a 40,000mfd electrolytic, with a hi-freq
> disk cap and bleeder resistor.
A-so )near the switching transistors.
EXACTLY RIGHT! I use 470uf, low ESR (this means Equivalent Series
Resistance, for those who don't already know, and has to do with the
capacitor efficiency in this usage)
A-MOST IMPORTANT, by far, is to have a good board layout and use good
A-grounding practices. This cannot be stressed enough !
EXACTLY RIGHT AGAIN! THIS IS THE KEY! (Alan, have we stressed this
enough? :-) )
>I have heard conflicting info re: switching PS with chopper-drivesA-It's POSSIBLE that some sort of beat frequency between the PS and A-
>so I don't do it. Mariss???
A-the stepper board could arise that would screw up the PS, but if it
A-did, it would have to be a pretty crappy supply and definitely not
A-worth using.
A-And there's no need for the regulation a typical switcher supplies
A-when used with a chopper drive, meaning that the extra cost is just
A-money out the door. ( This is certainly NOT the case with a non-
A-chopper drive,though )
Agreed. But I have seen these "crappy" supplies cause people to tear
their hair out(been several years ago, though. Things are better
now,IMO). But it was the PS affecting the driver chopping, not the
other way around.
A-My opinion would be that if you have a quality switcher around of
A-suitable capacity, there's no reason not to use it. But there's no
A-reason to go out and buy one if you don't.
Key word, quality. Agreed.
> Also like to use toroid <snip>A-I cannot conceive of how any external "interference" likely to be
A-found in a typical shop could influence the performance of a
A-properly designed, properly constructed stepper controller.
Exactly what we're talking about here. PROPER design,PROPER
construction. A lot of "marginally designed, marginally constructed"
setups ARE doing good service now, but sometimes a working system
stops for what SEEMS to be "no apparent reason", when it is actually
this design and construction issue popping up. This is like the
cordset thread(playing now in egroups CCED)where you "could" use it
for 3 phase, and it "would" work electrically, but IF someone came
along later and didn't know, there's a SERIOUS problem!
A-Improper design, poor construction, LONG cable distances, or bad
A-grounding ( inside or outside the box ) certainly will, but a well
A-designed, well built controller six feet from the PC and six feet
A-from the machine it controls will not suffer from almost any
A-external electrical influence.
Alan
Alan, Thank you for your reply.
Ballendo