Alan B
100 GW
Jeremy Harris said:I'm playing with a bog-standard linear motor control chip, that does everything in hardware. The only reason for trying it out is that it is a simple solution that's easy to use with very few extra components. The downside is that the chips I've got (MC33033) aren't for new designs, but they were dirt cheap! The FET drivers are now 8 pin DIP NCP5181s, mainly because these better suited to the board layout than the TI drivers I was originally looking to use. The FETs are IRFP4368s. I have all the components and the board layout done, but I'm tied up fitting a new bathroom for the next week................
The MC33033 seems ideal for a really simple controller. It runs on the 12V or so FET drive power line, has an on-chip 6.2V reference supply for the Hall sensors and the throttle pot, has an on-chip current sense comparator with a 100mV threshold, can go from forward to reverse on the fly by switching one pin (handy for those building retro-direct gearboxes) and does cycle-by-cycle current limiting at the PWM rate, so is potentially quite robust when it comes to fault conditions. In terms of external component count you're looking at just a tiny handful of passive components, plus the drivers and FETs.
If I want to do some fancy stuff later on, then I can intercept the throttle and current sense lines to make the chip sing any tunes I want, using a small, slow supervisory micro.
I've attached the data sheets, if you're interested.
Jeremy
View attachment 1
Looks like that chip will make for a very low parts count! Nice!