adrian_sm wrote:Fantastic work Justin. Great list of new features. Especially like the automatic battery gauge, and the whole concept of making the CA the central brain that can work with any controller.
Hey Adrian, nice work on completing the tidy Brainbox too btw! It's no small feat to go from a concept/prototype into a first small scale production run like that,,, i would know
1) Torque Limit
If you have a constant power limit, torque drops as speed increases. Some systems may benefit from being able to set a maximum "torque" based on Volts*Current / Speed. This makes sense to me as most drive trains are torque rather than power limit.
Yes, I think this might have come up in the RC-CA thread as well. Torque limit also works best from the perspective of protecting controller mosfets and motor phase wires and connectors. IF the throttle output of the CA is mapped properly and the controller takes the throttle signal as a direct control of the PWM duty cycle, then the CA should be able to estimate the motor current from
Motor Current ~= Battery Current / (Act Throttle Output / Full Throttle Output)
And hence could set up a limit accordingly. Doing it as Volts*Current / Speed is an interesting approach but it wouldn't reflect the torque at lower speeds well where the efficiency of the motor is poor. It's looking at input power / speed, while what we'd want to be looking at (for motor torque / phase current) is output power / speed.
2) Throttle Rate Limit
I am a bit of a special case, but I actually use a separate rate limit for throttle down. It smooths the disengagement of my friction drive. Would be nice if this option was possible on the CA.
3) Large Screen vs Small Screen
Are you only offering the large screen CA in the future? Has the smaller screen version been permanently discontinued?
We still keep the small screen LCD's and membrane overlays on hands for OEMs (like the stealth bomber), and if anyone wants to take on doing a small form factor enclosure for these and offering it that would be great. The actual footprint of the small LCD PCB is just 80mm x 36mm, and we made sure that the V3 CA boards would fit within this boundary. So in principle you could make a fairly small box around it. The old hammond enclosures we used to machine for the application were 100mm x 50mm.
4) Temp Limit
Have you decided on how you will be implementing any limitting features baseed on the temperature sensor input?
Right now you set a threshold temp and a maximum temp:
The current limit automatically starts to scale linearly downwards when you hit the thresh temp, until it reaches 0 amps when you reach MaxTemp. I don't think anything more than this is really needed for effective overtemp protection, but if you have other ideas I'd be curious. I don't personally push many items to their thermal limit in my own ebike usage.