fechter wrote:Hmm.. previous post didn't make it...
Anyway, nice job on the controller.
I think you found my list of desirable features and actually made one. Current mode throttle rocks, so does adjustable regen and cycle by cycle current limiting. I'll be real interested in how you implemented the sensorless mode too.
Right now the sensorless is simple crossing detection of the back-emf voltage equaling half the battery supply voltage, with various levels of digital filtering, and that works good enough down to about 5 kph, but for really low speed and/or low duty cycle measurements I'm going to try implenting measuring the back-emf during the PWM off phase as well, looking for the point when it crosses ground, and that should enable operation down to just 1-2 kph, effectively a standstill.
fechter wrote:Next challenge will be to make a fully sensorless one that can start from a dead stop just like a sensored one. Think about that one as you are pedaling across the country...
That's going to be required if I want this controller to work with the internally geared/freewheeling motor setups in sensorless mode (required for some hubs like the Tongxin units), so it's on the agenda for sure.
fechter wrote:I'm split on the epoxy. Great for water proofing. Sucks for future repair. If the smoke gets out of one part, the whole thing will be scrap (except for a few of us armed with pans of boiling water and dental picks).
Can you get through epoxy with boiling water? I seriously tried just about everything including acetone baths to not much avail. Certainly at this stage potting in epoxy was a bit premature, and I fried both my primary and backup controller when the golden motor overheated and (presumably) shorted the 5V hall line to one of the motor phase windings, and there was no way to do a repair. So when I rebuilt earlier this week I left the controller circuit serviceable, sealed in a nice polycarbonate enclosure.