Speed sensor

Thread Starter


Joined Jul 25, 2007
I want to implement my own speed sensor which will be used to monitor the

speed of a 3Vdc motor of an electric car. Any idea on parts to be used are

welcome, as i have no idea how to implement it.


Joined Jan 17, 2007
If you want to know the rotation rate of the wheels:

Your car, probably has a gear box. Since the motor is running of 3V, I assume that the gearbox is small, and the gears re made of plastic. You can put a little steel screw near the edge of th gear. then you can sense the screw with a Hall effect sensor fixed to the gearbox case near the rim of the gear. As the gear is rotating, the output of the Hall effect sensor will go up as the screw passes by the sensor. You can count the maxima per second and get the rotation speed of the wheels.

Alternatively, you can use an optical beam interruption sensor. Drill a hole in the gear. Put an LED on one side and photodetector on the other side. Again, count the strobes on the photodetector.

Alternatively, you can use a reflective optical sensor. Paint a black strip radialy on the gear, or attach a little reflector (aluminum foil will do). Shine the LED onto the gear and look for reflected light with detector.