4-Channel Relay Driver Module Circuit


BySaddam 4

4-Channel Relay Driver Module

In this project, we will make a 4-Channel Relay Driver Circuit for relay based applications. In this circuit, we have designed an isolated PCB for 4 relays. By using this Relay Board, we can operate 4 AC appliances at a time. We have put a three pin screw terminal blocks (NC, Nuteral, NO) for connecting appliances. Here we have provided PCB layout, circuit diagram and gerber files, so that you can build or directly order this Relay Driver Module.


Components Required:

  1. SPDT relay 12v -4
  2. 817 Optocoupler -4
  3. Transistor BC547 -4
  4. SMD LEDs -5
  5. PCB (ordered from EasyEDA) -1
  6. Terminal Block 3 pin -5
  7. 1N4007  Diode -1
  8. 1k Resistor -9
  9. Burg sticks male -1
  10. Power supply
  11. Microcontroller or Arduino for demonstration
  12. Connecting wire


Relay Driver Circuit Explanation:

In this 4-Channel Relay Driver Circuit we have used an optocoupler to trigger the NPN transistor which further drives the relay. And optocoupler will be triggered by the active LOW signal. Here we have used 12v 10Amp relay in this PCB board, you can also use 5v relays.

4-channel relay driver module circuit diagram


Working and Demonstration:

For demonstrating the working of this Relay Module, we have used an Arduino Uno board for controlling relays. We have connected all four relays with Arduino at 8,9,10 and 11th pins (In1, In2, In3, and In4). We have used 12v adapter for powering the circuit. Then we have connected 220VAC bulb at the terminal block of the PCB board and AC supply is also applied to the board.

demonstrating 4 channel relay driver module using arduino

Below is the Arduino Code which we have used to demonstrate this Relay module:

#define rly1 8
#define rly2 9
#define rly3 10
#define rly4 11

void setup() 
  pinMode(rly1, OUTPUT);
  pinMode(rly2, OUTPUT);
  pinMode(rly3, OUTPUT);
  pinMode(rly4, OUTPUT);

void loop() 
    digitalWrite(rly1, HIGH);
    digitalWrite(rly2, HIGH);
    digitalWrite(rly3, HIGH);
    digitalWrite(rly4, HIGH);
    digitalWrite(rly1, LOW);
    digitalWrite(rly2, LOW);
    digitalWrite(rly3, LOW);
    digitalWrite(rly4, LOW);

Also check the Video at the end of this article.


Circuit and PCB Design using EasyEDA:

To design this Relay Driver Circuit, we have chosen the online EDA tool called EasyEDA. We have previously used EasyEDA many times and found it very convenient to use compared to other PCB fabricators. Check here our all the PCB projects. After designing the PCB, we can order the PCB samples by their low cost PCB fabrication services. They also offer component sourcing service where they have a large stock of electronic components and users can order their required components along with the PCB order.

While designing your circuits and PCBs, you can also make your circuit and PCB designs public so that other users can copy or edit them and can take benefit from there, we have also made our whole Circuit and PCB layouts public for this Relay Driver Module, check the below link:



Below is the Snapshot of Top layer of PCB layout from EasyEDA, you can view any Layer (Top, Bottom, Topsilk, bottomsilk etc) of the PCB by selecting the layer form the ‘Layers’ Window.

top layer of 4 channel relay driver module PCB


You can also view the PCB, how it will look after fabrication using the Photo View button in EasyEDA:

Photo view of 4-channel relay driver module PCB


Calculating and Ordering Samples online:

After completing the design of PCB, you can click the icon of Fabrication output above. Then you will access the page PCB order to download Gerber files of your PCB and send them to any manufacturer, it’s also a lot easier (and cheaper) to order it directly in EasyEDA. Here you can select the number of PCBs you want to order, how many copper layers you need, the PCB thickness, copper weight, and even the PCB color. After you have selected all of the options, click “Save to Cart” and complete your order, then you will get your PCBs a few days later. And you may go with your local PCB vendors too with Gerber output of PCB layout. They are fabricating the PCB at very low rate which $2.

ordering pcb for 4 channel relay driver module


After few days of ordering PCB’s I got the PCB samples

PCB samples of 4 channel relay driver module circuit


Soldering: after getting these pieces I have mounted all the required components over the PCB connected it with Arduino for demonstration.

soldering components on 4 channel relay driver module PCB

Also check the Video below.


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  • sagor saha's picture
    sagor saha
    Aug 31, 2017

    in your schematics, you showed two +5v, i am bit confused.. Could you explain?

  • Mohit Arora's picture
    Mohit Arora
    Sep 02, 2017

    Sir, your creative ideas are very helpful for us but your explanation is not very good please make it good (this is a request)........

  • Ralph Hulslander's picture
    Ralph Hulslander
    Sep 02, 2017

    You need a constant signal, I want to have a latching relay.
    Single high pulse for ON then a high pulse for OFF.

  • Aswinth Raj's picture
    Aswinth Raj
    Sep 04, 2017

    If you want to latch it with two high pulses, then using a 555 timer is bistable mode will help. You have to design this additional circuitry.

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