Rev Limiter

The motor should be limited to under 5,500 RPMs. Pieces start falling off of the motor above that limit. The controller has the ability to read the motor RPM and make sure that it does not exceed this value.

The RPM sensor sends out 4 pulses per revolution, but the controller is expecting 2 pulses per revolution. This calls for a frequency divider that can divide the frequency by 2.

A frequency divider can be implemented using a type of Flip-Flop circuit. Let's say you had a push button that activates a light. When you push the button, the light comes on. Push it again. and the light goes off. So, you pushed the button twice and the light came on once. Four pushes and the light would come on twice. Hence, it is a frequency divider.

This is a photo of my circuit. It has an input Schmitt Trigger, and produces a sharp square wave output. Here is a demonstration of how it operates: Click Here