IR obstructer

IR Obstructer Using 555 Timer

We know that IC 555 is a popular timer chip used to make timer circuit. The 555 timer operates in three modes like monostable, astable and bistable modes. In monostable mode, the timer acts as a one-shot pulse generator. In astable mode, the timer acts as a free running multivibrator. And in bistable mode, the timer acts as a schmitt trigger. It has many applications in linear ramp generator, pulse width modulation, time delay generation and etc. in this article we are going see about IR obstructer using 555timer.

From the below circuit, here we are using 555timer where pin1 is connected to ground (GND) and pin2 is connected to pin6 which is threshold pin of timer. The pin3 is connected to base of a transistor BC547 whose emitter is connected to GND and collector is connected to power supply through IR diode / LED D1 and a Resistor. The pin4 of timer is connected to pin7 through resistor R2 of 1k again pin7 and pin5 are shorted together in between two capacitors C1 of 0.01µF, C2 of 0.01µF and a potential divider of 2.2k. The pin8 of the timer is connected to power supply.

In this, the 555 timer used is in free running astable multi-vibrator mode at a frequency of 38 KHz and a duty cycle of about 60%. The said pulses drives a transistor Q2 the collector of which powers an IR diode D1 through 100Ω resistor from the power supply 6V DC. As the receiving unit of any T.V receives 38KHz pulses from its own remote, continuous stream of 38KHz pulses so generated by an external timer circuit superimposes and overrides the remote signal resulting in making the T.V remote sent pulses scrambled. Thus the T.V is not able to respond the required pulses from the T.V remote to take any action such as channel change, volume up, down etc.