The most common problem for infra-red (IR) remote control is the failure to transmit the pulsed infra-red light. The circuit shown in the schematic diagram below is an IR remote control handset tester. This device is very useful and easy to use, and could quickly identifying a faulty remote control handset. An operative remote control handset will generate a pulsed infrared light that falls upon D1, which creates a pulse waveform across R1. The signal from D1 is capacitively coupled to the base of TR1, and the amplified signal is coupled to C2 to a pulse stretching circuit based around TR2, C3, and associated components. In this circuit, whenever infrared light is received by D1, driver transistor TR3 conducts and illuminates the LED D2. By giving an initial flash of D1 when the switch S1 is first closed, this device can self-test its own battery. The photo-diode should be a 940nm type. The type of the transistors are not crucial. This remote control tester circuit will operate from a 6 to 12 V rails power supply.
