You can switch on this short duration White LED Lamp using the TV remote. The lamp turns off automatically after 3 minutes. It gives sufficient light in the room if you want to locate the remote buttons.
The circuit uses the IR Sensor module TSOP 1738 to trigger the circuit.
The IR sensor gives 5 volts output in the standby state which inhibits the PNP transistor from working. This keeps the monostable timer built around IC1 off. CD 4538 is a 16 pin precision monostable/astable timer IC more reliable than the IC 555 and is free from false triggering. Its output turns high at power on and turns low when the trigger pin 5gets a low-to-high transition pulse. Its pin7 is high in the standby state and sinks current when it is triggered.
IC1 is wired as a short duration monostable timer with the timing elements R3 and C3. So when the remote is focused to the IR sensor and any of the buttons is pressed, output of IR sensor turns low and triggers the PNP transistor T1. The high output from the collector of T1 gives a low-to-high transition pulse to the trigger pin 5 of IC1 and the monostable triggers. Once it is triggered, its output sinks current for 3 minutes to light the LEDs.
Resistor R4 keeps the trigger pin of IC1 low to get quick low –to- high transition when T1 conducts.
CD 4538 Pins
The circuit can be powered with a 6 volt battery or 6 volt regulated power supply. Fix the unit on the roof to prevent false triggering while using the remote for TV operation.
Filed Under: Electronic Projects