Connecting a relay to ARDUINO UNO

Microcontrollers generally have no pin I / O capable of providing high current, such as to trigger an engine, high-current LED or lamp. Digital pin ARDUINO UNO provide a DC voltage of 5 volts accurate and maximum current up to 40 mA.

This topic will be presented techniques for using relays, which is nothing more than an electromechanical switch, comprising a coil that acts as a solenoid, which by electromagnetic action triggers a lever, causing the closure of the contacts of the relay. With this component can trigger high current loads and different voltages.

For this project we will use Relay (Metaltex ML2RC1-6V), which you can trigger AC loads of 127V / 15A and 250V / 10A or DC loads up to 110V / 15A. Its activation is made with a 6V DC voltage but may use the voltage of 5 volts without problems.

But in order to use a relay connected to ARDUINO, we have to use an intermediate component. We will use a transistor as an electronic key for the activation of the relay, this is due to the fact that the relay requires a current of 40 to 100 mA to your drive. Further on we will see how to do the calculations for the use of this important component.

Below the wiring diagram:

Circuit schematic:

Material list :

Ref. Des.	Name	Value
D1	Diode General	1N4148
RY1	RELAY, SPDT	Metaltex ML2RC1-6V
R1	RESISTOR	2K2
Q1	NPN	BC 548
R2	RESISTOR	1K
L1	LED	Red one

Program :

// the setup function runs once when you press reset or power the board
void setup() {
  // initialize digital pin 13 as an output.
  pinMode(7, OUTPUT);
}

// the loop function runs over and over again forever
void loop() {
  digitalWrite(7, HIGH);   // turn the LED on (HIGH is the voltage level)
  delay(3000);              // wait for 3 seconds
  digitalWrite(7, LOW);    // turn the LED off by making the voltage LOW
  delay(1000);              // wait for a second
}

This simple program is used only to demonstrate the operation of the relay.