Question about rotary encoders

Looking for a low cost incremental rotary encoder to measure shaft speed on a low rpm application.

I'd like to use one of those low cost encoder switches without detents, but will they last if used at 100 to 200 rpm? They're usually used with a knob like a potentiometer, not connected to a shaft...

Anyone had any experience using them like this?

Don't need great precision or huge number of divisions per rotation.


Can you give more information on the project? What are you trying to achieve?


Which encoder to use depends a lot on which motors you're using.

Here are some encoders for a small motor with a shaft extending from the rear of the motor.

While it's certainly possible to add encoders after the fact, I think it's much easier to find motors which include encoders.

Thanks for the suggestions, the Pololu one looks great. These aren't being used on a motor, just on a shaft to measure the speed of an assembly.

If you can add stripes to divide up a gear or wheel, you can use optical sensors to detect the dark and light areas.

One problem with using a single sensor (one of the dots is an IR LED, the other is the sensor) is you can't tell the direction of rotation.

If you add a second sensor in a way which prevents both sensors from transitioning at the same time, you can detect the direction of rotation.

Here's another servo with two sensors.

Using the same striped disk, the two sensors could keep track of the servo's position.

Normally, you'd have more stripes. The confined space where I was adding the encoder, limited my options or how many stripes to use.

DIY optical encoders can require some experimentation in order to get reliable output. The IR light doesn't always reflect off white surfaces and not all black surfaces absorb IR.