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Project Help and Ideas » Seeking help to build an optoswitch circuit

December 15, 2012
by Steelers
Steelers's Avatar


Can anyone give me some direction on building a circuit that uses an LED Infrared Emitter and Detector?

I want an output to go high whenever the emitter beam is physically blocked and no longer seen by the detector.

Anyone have a schematic or basic instructions?

Thanks, Dan

December 16, 2012
by pcbolt
pcbolt's Avatar

Dan -

It would depend on the type of detector you are using. If it is a photo transistor type, you would start by hooking one end of a resistor to the 5v supply and the other end to the positive lead (usually called drain) of the photo transistor. The other end of the transistor goes to ground. The point where the resistor and transistor connects is where you need a wire going to your MCU. When the light is on, the transistor should conduct and the wire should read a low voltage (closer to ground). When no light is on the transistor, very little current will flow to ground so your wire will read close to 5v.

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