onewheelskyward said:
Bike setup: phaserunner x2, Grin all axle motor up front, bafang mg60 in back. Grin dual motor shunt in the middle.
Here’s my problem- the CA connected to the shunt can tell me overall power output but I need to limit by speed for an event, and the shunt CA can't read speed at all. If i connect a CA directly to one of the phaserunners I can get speed but that CA cannot affect both motors at once. How can I either limit speed on both motors or, ideally, get speed information into the shunted CA?
You can add a simple wheelspeed sensor like this
https://ebikes.ca/ca-speedo.html
to either wheel, and wire that to the ground and speedo wire of the CA-SA shunt connector. No need to change any other wiring on the bike.
If you can't get the grin one, you can use one from a cheapo bike speedometer, or you can use any reed switch and magnet (like door-window security sensors) that creates a change in the signal when the magnet passes it. The N.O. type is what is used in the typical speedo sensor. For any wheel sensor with one magnet on the wheel spokes, the CA "number of poles" gets set to 1. (otherwise, match the number of magnets you use--I use three to give faster response of speed changes at low speeds from a stop)
If a wheel sensor is not an option, you can run a wire from the speedo wire of the CA-SA shunt connector to the speedo output wire of the PR that runs the Grin All Axle hubmotor in the wheel. As long as that PR's speedo output wire provides a signal from one of the motor's halls, then your CA can read that signal. For this the number of poles needs to match half the magnets in the motor. That's usually 46 magnets, so 23 poles. If the PR is not set up to output one of the hall signals to the speedo wire, you could hack a wire from any of the hall signals directly to the speedo wire of the CA-SA shunt connector.
ONce you have a wheel speed sensor feeding into the CA, you can then setup whatever speed limiting you like in it's menus, and it will then affect whatever system(s) that the CA is outputting a throttle signal to.
Personally, I prefer a standalone wheel sensor, because there are two ways you can destroy a CA if the speedo uses a motor hall. It's a rare event, but the possibility exists, and I prefer prevention whenever I can manage it.
The first I haven't had myself, but others have had various electronics destroyed by it: If something happens to the motor phase / hall wiring (axle damage, etc) that causes a short between any phase wire and the hall signal wire hooked to the CA speedo wire, then the CA MCU (and controller, and motor hall sensor) can be destroyed by the high voltage passed thru the short from the phase wire.
The second: I had an incident where somehow the shunt wiring cable at the exit of the CA-SA shunt split the jacket around the wiring, and something (vibration?) eventually also split the insulation around some of the wires inside. Then the speedo wire shorted against the battery positive wire in that cable, and it blew up the CA MCU and the motor hall sensor (and I think the controller; I cant' remember). I probably still have the fried CA somewhere....
Not a very likely occurence....but really bad consequences if it does.
So now I only use standalone speed sensors for the CA.
