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Arduino - 4-Channel Relay Module

When we want to control 4 high-voltage devices such as pumps, fans, actuators... We can use multiple relay modules. However, there is a simpler way is to use a 4-channel relay module. A 4-channel relay module is a combination of 4 relays on a single board.

A 4-channel relay module vs 4 x 1-channel relay modules:

A 4-channel relay module has simpler wiring.
A 4-channel relay module uses less space.
A 4-channel relay module is cheaper.
The programming is the same.

Hardware Required

1	×	Arduino UNO or Genuino UNO
1	×	USB 2.0 cable type A/B
1	×	4-channel Relay Module
1	×	Jumper Wires
1	×	(Optional) 9V Power Adapter for Arduino
1	×	(Recommended) Screw Terminal Block Shield for Arduino Uno
1	×	(Optional) Transparent Acrylic Enclosure For Arduino Uno

Or you can buy the following sensor kit:

1

×

DIYables Sensor Kit 30 types, 69 units

Please note: These are Amazon affiliate links. If you buy the components through these links, We will get a commission at no extra cost to you. We appreciate it.

About 4-Channel Relay Module

Pinout

4-Channel Relay Module Pinout

A 4-channel relay module has the following pins:

Power pins for relay boards

DC+: connect this pin to 5V pin of power supply
DC-: connect this pin to the GND pin of the power supply and also to the GND pin of the Arduino

Signal pins:

IN1: this pin receives the control signal from Arduino to control relay 1 on the module
IN2: this pin receives the control signal from Arduino to control relay 2 on the module
IN3: this pin receives the control signal from Arduino to control relay 3 on the module
IN4: this pin receives the control signal from Arduino to control relay 4 on the module

Output pins: NCx (normally closed pin), NOx (normally open pin), COMx (common pin),

NC1, NO1, COM1: These pins connect to a high-voltage device that is controlled by relay 1
NC2, NO2, COM2: These pins connect to a high-voltage device that is controlled by relay 2
NC3, NO3, COM3: These pins connect to a high-voltage device that is controlled by relay 3
NC4, NO4, COM4: These pins connect to a high-voltage device that is controlled by relay 4

For detail of how to connect relay to high-voltage, what are differences between normally closed and normally open, see Arduino - Relay tutorial

It also has 4 jumpers to select between the low trigger and the high trigger for each relay individually.

Wiring Diagram

4-channel relay module consumes considerable power. Therefore, we should NOT power the module directly from the 5V pin of Arduino. We need to use external 5V power for the module instead.

So, we need to use three power sources:

A 5V power adapter for Arduino
A 5V power adapter for the 4-channel relay module
A higher-voltage power adapter (12VDC, 24VDC, 48VDC, 220AC...) for things that are controlled by the 4-channel relay module
Wiring diagram with three power sources. Power supply for Arduino (not included in the image) can be via either USB cable or power jack.

Arduino 4-channel relay module wiring diagram

This image is created using Fritzing. Click to enlarge image

We can reduce the number of power adapters by using a single 5V power source for both Arduino and the 4-channel relay module.

Arduino 4-channel relay module wiring diagram two power source

This image is created using Fritzing. Click to enlarge image

※ NOTE THAT:

If 4 devices that are controlled by a 4-channel relay module use the same voltage, we can use a single high-voltage power adapter for all. However, if they use different voltages, we can use different high-voltage power adapters independently.

How To Program For 4-Channel Relay Module

Initializes the Arduino pin to the digital output mode by using pinMode() function.

pinMode(PIN_RELAY_1, OUTPUT); pinMode(PIN_RELAY_2, OUTPUT); pinMode(PIN_RELAY_3, OUTPUT); pinMode(PIN_RELAY_4, OUTPUT);

Control the relay's state by using digitalWrite() function.

digitalWrite(PIN_RELAY_1, HIGH); digitalWrite(PIN_RELAY_2, HIGH); digitalWrite(PIN_RELAY_3, HIGH); digitalWrite(PIN_RELAY_4, HIGH);

Arduino Code

/* * Created by ArduinoGetStarted.com * * This example code is in the public domain * * Tutorial page: https://arduinogetstarted.com/tutorials/arduino-4-channel-relay-module */ #define PIN_RELAY_1 2 // the Arduino pin, which connects to the IN1 pin of relay module #define PIN_RELAY_2 3 // the Arduino pin, which connects to the IN2 pin of relay module #define PIN_RELAY_3 4 // the Arduino pin, which connects to the IN3 pin of relay module #define PIN_RELAY_4 5 // the Arduino pin, which connects to the IN4 pin of relay module // the setup function runs once when you press reset or power the board void setup() { Serial.begin(9600); // initialize digital pin as an output. pinMode(PIN_RELAY_1, OUTPUT); pinMode(PIN_RELAY_2, OUTPUT); pinMode(PIN_RELAY_3, OUTPUT); pinMode(PIN_RELAY_4, OUTPUT); } // the loop function runs over and over again forever void loop() { Serial.println("Turn on all"); digitalWrite(PIN_RELAY_1, HIGH); digitalWrite(PIN_RELAY_2, HIGH); digitalWrite(PIN_RELAY_3, HIGH); digitalWrite(PIN_RELAY_4, HIGH); delay(1000); Serial.println("Turn off all"); digitalWrite(PIN_RELAY_1, LOW); digitalWrite(PIN_RELAY_2, LOW); digitalWrite(PIN_RELAY_3, LOW); digitalWrite(PIN_RELAY_4, LOW); delay(1000); }

Quick Steps

Copy the above code and open with Arduino IDE
Click Upload button on Arduino IDE to upload code to Arduino
Listen the click sound on relays.
See the result on Serial Monitor.

COM6

Send

Turn on all Turn off all Turn on all Turn off all Turn on all Turn off all Turn on all Turn off all

Autoscroll Show timestamp

Clear output

9600 baud

Newline

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Function References

The Best Arduino Starter Kit

See the best Arduino kit for beginner

See Also

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