Youmile 5Pcs Speed Measuring Sensor IR Infrared Slotted Optical Optocoupler Module Photo Interrupter Sensor for Motor Speed Detection or Arduino with Encoders

I hadn't noticed that the photo-interrupters are mounted on little printed circuit boards. I don't know what voltage they can work off, but they seem happy with my Raspberry Pi's 3.3V. Just 3 connections: power, ground and output.In case anyone's interested in the dimensions, the mounting holes are 3.2mm diameter, 21mm between centres, and the gap for the slotted wheel is 6mm wide.

I am pleased with this purchase. The optocouplers worked without a problem and they fitted neatly in the pre-cut holes in the robot car kit I bought (see image above) -something I was concerned about. The wheel encoders are fine, made of good quality plastic and they fit those yellow gear motors that are so popular.I would recommend this product for purchase.

Used it as a temp for a Dyno it was fine for anything up to about 750cc but could not handle most 1000cc +It is not designed for use at the speeds that a Motorcycle Dyno can run but it held up well, the speed is pretty accurate up to about 155,then it gives up. I have had to change to a different sensor but keep a couple of these just in case.

They work well. Making and breaking the beam produces a nice clean square wave on my oscilloscope.

A great item to learn about programming with

Bought these to have speed vector input to 2wd robot, but 3 out of 5 failed!

One of the sensors was missing. I only received four.

These are great little sensors with lots of documentation and guides on youtube about them. They are perfect for working with speed and arduino's and seem relatively accurate for the price. They arrived well packaged and worked out of the box which is great for ease of use.