Just in case anyone was wondering, I haven't abandoned the project!
Been busy with other things, but in my limited time I've been finalizing the circuit design and laying out boards for the prototypes. I think I'm still going to do some tweaking before I send them off for manufacture, but the first layout iteration is complete. The current design is a 2-board stack, but I'm considering making it a 3-board stack. The advantage would be a more compact footprint and modular functionality.
Here's the feature set for the prototype:
- Custom hall-based 3-phase current sensor. The sensor should have fully-linear range of >300A, >200A, or >150A depending on the sensitivity of the sensors used. Sensor is fully isolated and insulated from the phase wires - the current design just has 3 0.25" dia holes which the phase wires pass through. I have some 8 ga wire which passes through easily.
- Interfaces to standard 5V e-bike throttle, hall- or pot-based. 5V supply is provided to the throttle. Currently both gain and offset adjustments are included.
- Option for either pass-thru throttle or closed-loop current-based throttle (selectable by jumper).
- Throttle filtering with separate up/down ramp times if desired (ramp-down time <= ramp-up time). Filtering can be disabled by removal of a capacitor.
- Option for throttle "boost" which provides temporary 10-30% (set by fixed resistor) increase in throttle gain. Boost is activated by a momentary pushbutton.
- Phase current limiting via 2 separate limits (works for either direct or closed-loop throttle). One limit has a fast, aggressive response, the second has a slower, integrating response which is less aggressive.
- Includes servo interface directly to ESC with adjustable min/max pulsewidths. Pulse rate is set via a fixed resistor (50 Hz nominal). Prototype is designed to drive ESCs only, but future versions will have a 0-5V output to drive a standard controller instead.
- Current design generates 5V supply directly from the battery. Future versions will probably make that optional, either internal 5V supply or taken from an external BEC, and will probably use a switching regulator rather than the current linear regulator.
The prototype does not have forward/reverse capability, low-speed lockout, or LED indicators but those may be added later. I had to cut off the feature set somewhere and the above list included most of the features which were easy to add. The prototype also does not include any additional safety features. I am open to suggestions about what people would like to see there. I think safety features are important, but might also annoy the user, so a balance is needed and feedback will guide the decision.
More to come - comments appreciated!