IR LED emits infrared light, and used in TV remotes. This Infrared is received by the receiver TSOP17XX (TSOP 1738used in TV). TSOP17XX receives the modulated Infrared waves and changes its output. TSOP is available in many frequency ranges like TSOP1730, TSOP1738, TSOP1740 etc. Last two digits represent the frequency (in Khz) of modulated IR rays, on which TSOP responds. Like for example TSOP1738 reacts when it receives the IR radiation modulated at 38Khz. TSOP output is active low, means it becomes LOW when IR is detected.
In this remote controlled switch circuit we are using TV remote to ON/OFF the AC light by pressing any button of remote, and using the TSOP1738 at receiver end. Receiver circuit is connected to AC appliance via Relay, so that we can control the light remotely. We have used IC 4017 to convert it into a push ON, push OFF switch. Go through this article to understand the IR Transmitter and Receiver.
[Also check: TV Remote Control Jammer Circuit]
Normally when we press any button of TV/DVD player remote, Light glows and as soon as we release Button, it becomes OFF. Now it can be converted into a PUSH ON and PUSH OFF toggle switch using IC CD4017. IC CD4017 is a CMOS decade counter IC. It can produce output at the 10 pins sequentially, i.e. it produces output one by one at the 10 output pins. Output is switched to one pin to another by applying a clock pulse at pin 14. Learn more about IC 4017 here.
When firstly, power is applied to IC 4017, output at PIN 3 (Q0) is HIGH, when we press the button of IR remote, then a LOW to HIGH clock pulse is applied to PIN 14 (first clock pulse) and output at Q0 becomes low and PIN 2(Q1) becomes HIGH. PIN 2 triggers the RELAY module, and the AC light becomes ON. Now this position will remain until the next clock pulse. If we press the Button of IR remote again (second clock pulse), output at Q1 becomes LOW and Q2 becomes HIGH. This will deactivate the Relay and switch off the light. And because Q2 is connected to the RESET pin 15 of 4017, it will reset the IC and again output at Q0 becomes HIGH and Q2 becomes LOW (initial state). So it works like a toggle switch.
Circuit Diagram of Remote Controlled Switch
Output of TSOP1738 oscillates at the rate of 38KHz, which is applied to clock pulse of 4017. So we have connected a 1uF capacitor across the output of the TSOP so that this 38KHz pulse train is counted as one clock pulse to the IC 4017.
We can also use the IR transmitter circuit to ON/OFF the Bulb, this IR transmitter circuit produces modulated IR at 38KHz like a TV remote. Also we can replace Bulb with any AC appliance, which is to be controlled by remote control.