IR Rays are invisible to human eye, so it is very difficult to check the working of IR LED. Usually we use a Mobile camera to test IR LED since the pink light from the IR LED becomes visible in digital camera. We can make a simple IR LED tester so that, before using it in the project, we can confirm whether it is good or not. Lot of IR LEDs are also in our Junk box. So we can check all IR LEDs and discard the damaged ones. The same tester can be used to check all ordinary LEDs, Photo diodes, Silicon and Germanium diodes etc.
Use a two pin socket as test points A and B.
IR LED / LED Testing
When the IR LED or Ordinary LED is connected to the Test points – Anode to A and Cathode to B, Green LED in the tester lights to indicate that the IR LED is good. Reverse the direction. If the Green LED still glows, the IR LED is shorted.
If the LED is the ordinary type, it also lights along with the Tester LED.
Connect Cathode to A and Anode to B. Green LED lights if the Photodiode is good. Reverse the direction. If the Green LED still glows, the Photodiode is shorted.
Same procedure as the IR LED testing.