Infrared detector

 

Just to get in the mood for Opto electronics circuits here's a little warm-up project.

You know-how frustrating it is when you try your remote control and nothing happens, is controller working, are the batteries flat or is there bigger problem? Now you have a test device.

Using this circuit you can carry out tests of infrared remote controls used in television sets, stereos, and videos etc. Infrared light will cause the LED to switch on.

 

Circuit Diagram

Components list

T1,T2 transistors BC 308
T3 photo-transistor
LED light emitting diodes
C 1 capacitor 100 pF.
C 2 electrolytic 47uF
R1,2,4 270 Ohms
R3 1M

Construction notes

Take care when carrying out the connection of the LED and of the photo-transistor. Both are identified with legs of different lengths see figure 1 for details

Both daylight and artificial light include a considerable proportion of the infrared spectrum, therefore the infrared detector will react to ordinary daylight. To overcome this, place the photo-transistor into a black cardboard tube approximately 50mm long and 4mm in diameter.

To test for infrared place remote controls etc at distance between 3 to 10 cm in front of the photo-transistor

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