As 555 timer is very popular and handy chip I'm going to show an amazing project by using a timer. This chip works in three modules like monostable, a stable and bistable mode. We will discuss all the modes. The timer acts as a one shot pulse generator ( it generates pulses ). In stable mode it acts as free running mutivibrator. And in bistable mode it works as a Schmitt trigger. It has a number of applications in linear ramp generator , time delay generation , pulse width modulation and things like that. But now we are going to see the IR instructor with 555 timer. Here is its circuit diagram. Thanks to those who made this design.
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| IR BLOCKER- 555 TIMER |
THINGS REQUIRED:
555 timer
Resistors
Capacitors
Transistor BC547
LED power supply.
In this circuit big block is of timer IC. Its pin 1 is connected to ground ( GND) and pin 2 is with pin 6, because it is threshold pin of ic.the pin 3 is connected to the base of a transistor BC547 whose emitter is connected to GND and the collector is connected to the power supply via ID diode /LED D1 and a resistor. The pin 4 of the timer is connected to pin 7 via resistor R2 ( of value 1k ) and finally pin 7 and pin 5 are shorted together in between two capacitors C1 and C2 of value 0.01µF and a potential divider of 2.2k. The pin8 is connected with a power supply.
WHAT'S HAPPENING IN THIS CIRCUIT ?
As engineers we should know what's happening in this circuit, because we are not ordinary technicians. The 555 timer used is in free running astable multi vibrator mode. It's raining at a frequency of 38 KHZ and duty cycle of about 60 %. Tv remote control works at a frequency of 38KHZ so we create waves of frequency of 38KHZ too. So this will superimpose with the radiation of remote control and make it scrambled/jam ( not working condition). Thus the tv is will not able to respond the required pulses which is came from remote control anymore such as channel change, volume up, down etc.
Pulses drives the transistor Q2 the collector of which powers and IR diode D1 through a 100ohm resistor from the DC power supply of 6V.
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