- on Miscellaneous Electronics
- Published in issue 7/2002 on page 0
Low-cost Position Sensor
Ever wanted to build a positioning encoder? Here’s one and you do not even need any sensors. The circuit uses an LED as a light emitter and another LED as a light receiver. This is possible due to the ability of the LED to generate a very tiny current when light is shining into it, almost like a small solar panel. A red LED is used because tests indicated that they gave the best results. It is possible though to use a different colour than red and the best combination might be found by trial and error. Please note that not all red LEDs give the same result, so you might have to get hold of a few different types and then find the best one.