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How Do I Design a Circuit With an Infrared Detector?

Infrared (IR) detectors have many applications, but the most common one is in electronics. For example, remote controls have photodiodes that send signals to phototransistors that are in devices such televisions. Photodiodes and phototransistors are sensitive to light. Diodes and transistors are semiconductors.

To design a circuit with an IR detector, determine how the circuit should behave. Some circuits are designed to complete actions in the presence of IR, while others will complete actions only in its absence. The properties of the detector also need to be taken into consideration. These include the component's viewing angle and whether it can detect visible light or not. To practice, build a circuit that emits a sound when it detects infrared radiation.

Things You'll Need

Phototransistor
Piezo buzzer
Flashlight
Remote
9-volt battery
Battery holder
Solderless breadboard
Jumper wires

Instructions

- 1
  Connect a battery holder to the solderless breadboard. Do this by inserting its red lead into one of the rows near the red stripe and its black lead into one of the rows near the blue stripe.
- 2
  Study the data sheet or package to determine the phototransistor's collector and emitter leads. For a phototransistor with two terminals, the collector lead is normally the shorter one.
- 3
  Add the phototransistor to the breadboard so its leads are in different columns. Place a jumper wire between the collector lead and the row that the red lead of the battery holder is in.
- 4
  Place the plus side of the buzzer into the same column that the emitter is in. The minus side will fall into a different column. Attach a wire between the minus side of the buzzer and the negative lead of the battery holder. Add the battery to the holder.
- 5
  Shine the flashlight on the phototransistor, moving it until the proper detection angle is found. The buzzer will make a continuous sound. Remove the flashlight and replace it with the infrared remote. Click it on and off rapidly, and then hold its button down. The buzzer will make a series of noises such as buzzes and chirps, depending on the remote being used.

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