The previous month, I made an Electric board relay-controlled circuit. Using the exact schematics and circuit diagram, I want to build an IR controlled Electric extension board. Keeping the form factor in mind, I designed a PCB and ordered it from JLCPCB. And JLCPCB is the sponsor of this project; PCB manufacturing service is just available for $2.

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  • 4 channel controller
  • IR remote compatible
  • Range <50 meter
  • Low power consumption
  • Indicator light for each channel
  • Small and 5volt operatable

Working in Brief:

The infrared signal from Remote is received by the Receiver section of the board (containing TSOP1738 IR receiver). Then this binary code is given to the microcontroller to process the signal. This Binary is converted in HEX code; then, there will be an ON/OFF action according to every pressed button. The microcontroller made its corresponding digital pin to high to control the relay system and then AC mains.


Here is a separate tutorial on decoding IR remote using Arduino.

Components required:

  • SPDT relay x4
  • BC547 transistor x4
  • PC817 optocoupler x4
  • Atmega328p or Arduino
  • Crystal 16Mhz x1
  • 1k Resistor x 10
  • 10k resistor x1
  • 22pf capacitor x2
  • 100nf capacitor x1
  • Screw terminals x4
  • 5mm red led x4
  • 100ohm resistor x1
  • 9v battery OR 5v supply
  • 1N4007 Diode x4
  • TSOP 1738- IR receiver x1

Circuit diagram:

Schematic_RELAY IR_2022-01-24.png

Breadboard schematics:


For one channel, Try this by placing a led Instead of relay, If this one work fine then go ahead.



Extension Board:

Here we have four outputs to connect to our 4-channel relay system. But the space inside the wooden box of extension is significantly less. So, we extended it using another wooden stick to solve the problem of space.

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All the components are fixed inside the wooden box and glued correctly; make sure while making connections with TSOP1738, the wire length is not too long and use copper wires. Also, add a capacitor between the two legs of TSOP (470uf can do the job perfectly).

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Use thick copper wire while making connections of AC mains. Then there will be a low dropout of voltage, and it will not overheat the circuity.




Here, we are using the SMD version of the microcontroller and headers is given to program the microcontroller. Now let’s program the microcontroller, Connect the pins in this format, and upload the code simply using Arduino as the ISP function. For more info, check this post.



Every button in IR remote has different hex number data, if we want to turn ON/OFF a device, we need two buttons of IR remote. One to switch ON and other one to switch OFF the same device.

Similarly, here we are making 3 channel relay controllers, that’s why we need 6 different buttons. Also, when we want to switch ON/OFF all the devices at same time, we need two more buttons. In total our IR remote should have 8 buttons.

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When remote release IR hex data, it will be captured at receiver end and microcontroller decode the data, immediately turn ON/OFF the respective pin.

This code only controls the digital pins of Arduino. To switch ON/OFF any load we cannot directly mount relay on any microcontroller without controlling and switching circuit. That’s why here we are using a combination of optocoupler and NPN transistor as a switch to control the relay properly. Optocoupler is used to control transistor and further relay and mains load. Download the proper IR library from Here.

Version 1:

I posted version ONE of this circuit some time ago, but one is also working well. Circuit is designed on a general purpose holed pcb. You may get more info about the code, circuit from here.



JLCPCB is the one of the most popular PCB makers. Price is just $2 for 2, 4 and 6 layer PCB. They just launched new purple solder mask, aluminum Pcb and 3d printing service in very low cost. Pcb quality is not compromised at any cost. Check them out right now from Here.


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