Gene, I've got a ton of these chips driving motors. They work fine. Just write the software to the datasheet spec. If the chip is getting hot and the motor is not mechanically stalled then you are doing something wrong. For debug/development replace the motor with a 100R power resister and then you know 100% no more then 1/4 amp is flowing through it. Place a volt meter on the resister and watch the voltage change with PWM duty cycle Put an amp meter on the power supply. A motor not under load running at 50% PWM shouldn't use even one amp. The chip will not be even warm
One of the best investment you can make is a $10 logic analyzer. The they can collect data on 8 pins at once. Put on on every pin When I do a direction change I ALWAYS go through a "brake" mode on the way. I've never once seen a car with a 150 audio amp driving the wind shield wipers. The problem is you are trying to futz with both a new-to-you chip and LCC at the same time. I keep an Arduino around for leaning how controller chips work. Arduino is a very simple and clean environment for experiments. In fact there is an example program in the IDE for testing PWM controlled motor where you control the speed with a three terminal pot. On Mon, Oct 26, 2020 at 6:56 PM Gene Heskett <ghesk...@shentel.net> wrote: > On Monday 26 October 2020 20:33:40 Jon Elson wrote: > > > On 10/26/2020 06:48 PM, Gene Heskett wrote: > > > But the switching losses in the olimex board, even at only > > > a 1 kilohertz pwm are killers, getting it hot enough to > > > burn a finger in just 2 or 3 seconds. So, I need a d2a to > > > drive one of the 150 watt class D audio boards after > > > shorting the inputs hi-pass filters caps. And I have the > > > feeling that even as sweet as the SpinX1 is for knocking > > > around a vfd, that it won't be fast enough for this, so > > > I'll need a real d2a that I can shove fresh data thru at > > > servo-thread speeds. Looking for likely suspects I might > > > be able to drive from the 7i76D sserial extension bus. > > > Suggestions? > > > > I'm guessing the thing was designed for 50 Hz PWM or > > thereabouts. That might actually be OK for a spindle motor. > > Clearly NOT OK for a positioning servo. > > > Jon, Its a car seat positioner driver, claims very low milliohm on r's. > $13 on fleabay. Looks promising, but write checks it can't cover even > with a 1 kilohertz pwm. Rated up to 10 kilohertz. Either that or the > first one is fubared. I bought two, and its not hard to change. I'll > measure the rise and fall times being delivered to it tomorrow too on > the chance the Sainsmart bob is slow. Manual claims up to 10 Mbits/S at > any output. For driving switches, thats bordering on cook it slow. 10ns > rise and fall would be a heck of a lot better. Designed for car seats, > in cmos circuits, rated on time delay is 100 to 300us, off time is 85 to > 255us. > > And change of direction is 600 to 1800us. In polite language, that > explains it all. For starters, there is no measureable lag coming out of > the 7i76 for a direction reversal. So with our drive, this thing > probably has 150us of shoot thru time for any dir signal change. I > could probably design an interfacing circuit that would fix that, but > IMNSHO that is the semi designers job. And STM failed, miserably. > Thats not a problem in this particular circuit, but that geological rise > and fall times for the pwm are a killer, even at 1 kilohertz. At 50 hz, > maybe. At 10KHz, nearly instant overtemp shut down at 170C. Sigh... > > Thanks Jon. > > > > > _______________________________________________ > > Emc-users mailing list > > Emc-users@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > 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 > -- Chris Albertson Redondo Beach, California _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
