Expected resistance range for pot throttle on VEC500

[Jbunn]

I am considering changing my motorcycle throttle from the Hall sensor that shipped with my VEC500 to a potentiometer type (a Domino 0 - 5K ohms) throttle.  When the VEC500 is put into potentiometer mode, what is the expected ohm range?

Thank you!

John

[Bikemad]

Hi John andto the forum.

The controller basically uses the voltage signal being output from the potentiometer (rather than resistance values) to control the motor power/speed.
The potentiometer effectively operates as a simple variable voltage divider which varies the signal voltage relative to rotary movement.

If the overall resistance of the potentiometer is too low, it could overload the +5V supply.
Conversely, if the resistance is too high, the voltage drop could reduce the amount of usable travel of the potentiometer.

I have previously suggested using a 10k Ohm potentiometer as a throttle control for the VEC controllers, which has been proven to work fine:



The 2k Ohms and 1.5k Ohms resistors shown in the diagram above are required to ensure the throttle signal voltage stays within the controller's working range:



Without these resistors, the Throttle voltage range protection is likely to be activated at both ends of the potentiometer's travel (i.e. below 0.7V or above 4.0V) causing the motor to cut out (accompanied by a 12 beep/blink error code).

If the resistors are not used, the Throttle voltage range protection enable value would need to be set to 2:Disable to prevent the 12 beep/blink error from being triggered. However, this could prove to be extremely dangerous if the ground wire going to the potentiometer suddenly failed due to vibration etc. (and became completely disconnected) while the controller was powered up, as the motor could then start running at maximum speed, regardless of the potentiometer position! 

A 5k Ohms potentiometer should work fine, as it would only be placing ~1mA load on the +5V supply, but you would probably need to use lower value resistors 1 kOhm on the +5V supply and 750 Ohms on the ground wire (with a 5k Ohms potentiometer) to keep the signal voltage within the expected range.

Alan
 

[Jbunn]

Hello Mike!  Thanks for the response.  I've given up on the idea of a pot based throttle and am going with a hall based throttle.  Most of the reason is on the hall from Domino, it has a microswitch which is closed when the throttle is in the off position.  This switch is to be wired to the low brake connector on the controller.  My understanding is that's how you enable regen on the VEC500 controller.  I ran some brief tests, and closing that circuit stops power to the motor, and the wheel stops rather quickly.  (it's on a motorcycle on a lift with the rear wheel off the ground.  The only issue remaining is the controller beeps when the circuit is closed.  Is there a way to turn off beeping on regen?  Please don't tell me I'm going to sound like a delivery truck in reverse every time I ease off the throttle.

Thanks!!

[Bikemad]

Hi John,

Unfortunately I am not aware of any way to stop the beeping when the regenerative braking is active apart from physically removing the beeper from inside the controller.

If you wired another switch in series with the throttle switch it would allow the regen to be turned off when not required, which would be very useful if you wanted to use cruise control, simply coast without braking, or even use hand signals while riding.

If the throttle had a much stronger spring in the microswitch (or possibly a rubber "O" ring around the microswitch operating plunger) it would only activate regen when you intentionally twisted the throttle backwards to the fully closed (regen) position. 

Alan