On Thursday 08 October 2009, Andy Pugh wrote: >2009/10/8 Sven Wesley <svenne.d...@gmail.com>: >> Sounds like a very clean setup. Then it would be really easy to make an >> amplifier board (with opto isolation) that just enhance the signal, >> right? No need to by step/dir drivers then. > >True, though we desicussed this on IRC a few days ago, and cradek >pointed out that you don't get the chopper-controlled current limits >that you have with a commercial driver, so either you run at motor >rated voltage and are limited to low speeds, or you have large banks >of resistors and capacitors to create a constant-current source in a >1970s style. > And that is so retro, not to mention the latter is hugely, grossly inefficient. Most if not all of the commercial driver units from the xylotex on up, control the actual motor currants actively with a chopper regulator running at ultrasonic speeds. That is very easily 10-50 times more efficient. Because this can't be done cleanly with the L298 based drivers, even they fall by the side when step rates get above 100hz. I cooked several of them trying.
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