Quick and Dirty - Electric Scooter 3-Wire Test Throttle

I ordered a new 36v scooter motor controller without a new 3-wire throttle. While I wait for my new throttle to arrive, I made a quick and dirty project to simulate the throttle for my new controller.

I made another project to also convert my current 2-wire throttle into a 3-wire setup and it works fine - it's just either ON or OFF, with no fine control in between. You can check out that instructable here - https://www.instructables.com/id/Quick-and-Dirty-U...

Parts you'll need for this project are:

1 variable resistor;

2 resistors;

Some 3-core wire (or just 3 wires);

3 spade terminals.

The 3-wire throttles use a hall effect sensor in the grip. The motor controller sends it circa 5v and depending on how hard you have your throttle on, it sends back a voltage in the range of 0.85v to 4.0v.

0.85v - Zero throttle.

4.0v - Full throttle.

I think some motor controllers also check for the presence of this 0.85 volts on startup, so if it's not present, the controller won't work.

Anyway, this simple voltage divider circuit simulates exactly the same effect using three resistors. I used 2% resistors to try and keep it fairly accurate - it's also what I had in the box.

The image here shows how I wired-in the resistors at the 3-pin connector of the motor controller.

Works like a charm - has smooth, full range of speed control from 0 to 100% using the variable resistor.

As I was just using this as a test circuit, I didn't bother too much with making it neat. I had an old broken network cable I used for the 3 core cable.

I was able to hang it over the handlebars of the scooter while I took it for a test run. Not recommended as it's a pain to coordinate braking, steering and keeping your eye on the road while adjusting the speed.

I guess if you had one of these DC motor controllers, you could re-purpose it for other things, and using this method of speed control might be much better than trying to use an old throttle off a scooter.

I hope this helps anyone trying to understand their scooter and/or motor controller a bit better.