Lab set Program-2

Develop a program to interface a relay with Arduino board

Objective

To control an LED through a relay module using Arduino. This simulates switching of loads via relay control.

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Learning Outcomes

By the end of this experiment, students will be able to:

• Understand how a relay works as an electronic switch.

• Interface a relay with Arduino Uno.

• Control external loads (here, LED) using digital output pins.

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Components (from Tinkercad Palette)

• Arduino Uno

• Relay Module (5V, single channel)

• LED (any color)

• 220Ω Resistor

• Breadboard

• Jumper wires

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Circuit Wiring

1. Relay Module Connections

   • VCC → Arduino 5V

   • GND → Arduino GND

   • IN → Arduino Digital Pin 7

2. LED as Load (through Relay switching)

   • LED Anode (+) → Relay COM terminal (through 220Ω resistor)

   • LED Cathode (-) → Arduino GND

   • Relay NO (Normally Open) terminal → Arduino 5V

(This wiring makes the LED glow only when relay closes the circuit.)

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Step-by-Step in Tinkercad

1. Open Tinkercad → Circuits → Create New Circuit.

2. Place Arduino Uno, Relay Module, LED, and Resistor.

3. Wire Arduino pin 7 to Relay IN pin.

4. Connect LED and resistor between relay COM and GND.

5. Connect Arduino 5V to Relay VCC and LED via NO terminal.

6. Simulate → LED will blink ON and OFF as relay switches.

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Arduino Sketch

// Program: Relay with LED load
int relayPin = 7;   // Relay control pin

void setup() {
  pinMode(relayPin, OUTPUT);   // Set relay pin as output
}

void loop() {
  digitalWrite(relayPin, HIGH);   // Relay ON → LED ON
  delay(2000);                    // Keep ON for 2 sec
  digitalWrite(relayPin, LOW);    // Relay OFF → LED OFF
  delay(2000);                    // Keep OFF for 2 sec
}

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How It Works

• The Arduino sends a digital signal to the relay input pin.

• When signal is HIGH, relay coil energizes and closes the NO contact, completing the LED circuit → LED glows.

• When signal is LOW, relay opens → LED goes OFF.

• This demonstrates how Arduino can control devices through relays.

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Common Mistakes & Quick Fixes

• Relay not clicking? → Check VCC and GND connections.

• LED never glows? → Ensure LED is connected via NO terminal and not NC.

• LED very dim? → Use correct resistor (220Ω).

• Wrong pin? → Verify relay IN is wired to pin 7 in both hardware and code.

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Viva / Check-Your-Understanding

1. What is the role of a relay in circuits?

2. Why can’t we directly connect high-power loads to Arduino?

3. What is the difference between NO and NC contacts in a relay?

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Extensions (Mini-Tasks)

• Modify the code to blink LED faster (0.5 sec ON/OFF).

• Use two LEDs and control them alternately using the relay.

• Replace LED with a motor or lamp in simulation.

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Lab Record (Suggested Headings)

• Title of Experiment

• Objective

• Components Required

• Circuit Diagram

• Arduino Code

• Output

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Thinkercad Link:

https://www.tinkercad.com/things/ekpvaAzYTyT-labset-prog-2