On Tuesday 27 October 2020 04:14:14 Gene Heskett wrote: I put the 2nd one in.
The dir signals are solid, going slightly above 5 volts even. The pwm starts outputing pulses at input of .04, either polarity, into the pwmgen value. At that point it is not steady as the pwmgen has decayed into pdm, and is a 200ns pulse, raising the input high enough to get a steady train of 200ns pulse at a 2 kilohertz rate, its holding at about 107F for temps. This is with a much smaller 12 volt motor, and escapee from a dosage pump used in hospital setting. About an inch each way, teeny little thing. raising the input to .2 results in a steady train of pulses, 400ns wide at 2 khz. And the chip temp is about 160F. At a .3 input, the pulses are around 600ns and the temp is 178F At a .35 input, pulses are 800ns, temp is about 190F At a .4 input, pulse are a full microsecond, and temp is 200F Running it up to around .8, the little motor finally started, but well above 200F as it didn't run long enough to get a reading from my IR thermometer. Thermal shutdown. Internal slew rates from way undersized gate drivers are the problem. Rise and fall times of the input signals are under 10ns, so they definitely are not a problem. Got to find something that doesn't have such glacial switching times, I've wasted long enough with this poor thing. Some of these class D audio stuff runs at 500 khz, so as far as running a motor, can be made into dc amplifiers. And I think I have an idea for a fast enough driver, involving a miller run-up and a sample-hold. Start a reset to zero miller circuit with the rising edge of the pwm, let it run up to whatever, sampling the charge on the falling edge of the pwm, hold that sample until the next pulse. Or something like that should be fast enough. :) 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) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/gene> _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
