Tools

Raspberry Pi Motor Control with Relay

Theory

Controlling external electrical devices such as DC motors through a microcontroller like the Raspberry Pi requires safe interfacing methods. One such approach involves the use of a relay switch—an electrically operated switch that isolates and manages high-power components using low-power signals from the Raspberry Pi. This experiment focuses on demonstrating how to use a relay module to control a DC motor from the Raspberry Pi's GPIO pins.

Components and Their Functions

1. Raspberry Pi

  • Acts as the main controller in this experiment.

  • Sends GPIO signals to the relay module based on the control logic.

  • Operates at 3.3V logic level, which is compatible with most relay modules.

  • Cannot directly drive high-current devices like motors, so it relies on the relay for switching.

    Raspberry Pi

2. DC Motor

  • A rotary electrical machine that converts electrical energy into mechanical rotation.

  • Operates on the principle that a current-carrying conductor in a magnetic field experiences a force, producing motion.

  • Used here as the output device, powered by an external source and activated through the relay.

  • Common in robotics, automation, and electronics for its simplicity and ease of control.

    DC Motor

3. Relay Module (5V)

  • An electromechanical switch that uses a small electrical signal to control a higher-powered circuit.

  • It uses a GPIO pin on the Raspberry Pi to activate its internal switch.

  • Provides electrical isolation and safely controls the motor’s higher voltage, protecting the Raspberry Pi.

  • This module allows control over the DC motor's power supply using logic signals.

    Relay Module

4. 9V Battery

  • Provides an external power source for the DC motor, preventing the Raspberry Pi from bearing the current load.

  • Powers the motor when the relay closes the circuit.

    9V Battery

Explanation of Each Connection

  1. Connect the Relay to the Raspberry Pi
  • Connect the 3.3V pin (Physical Pin 1) of the Raspberry Pi to the VCC pin of the relay to supply power.
  • Connect a GND pin (e.g., Physical Pin 9) of the Raspberry Pi to the GND pin of the relay to complete the control circuit.
  • Connect GPIO21 (Physical Pin 40) of the Raspberry Pi to the Input pin of the relay to control its switching mechanism.
  1. Connect the Relay to the Motor and Battery
  • Connect the COM (Common) pin of the relay to the positive (+) terminal of the 9V battery.
  • Connect the NO (Normally Open) pin of the relay to the positive (+) terminal of the DC motor.
  • Connect the negative (-) terminal of the 9V battery to the negative (-) terminal of the DC motor to complete the motor circuit.
  1. Verify Connections
  • Double-check all physical connections to ensure accuracy, polarity, and proper wire placement.
  • Ensure the breadboard layout matches the circuit diagram.
  1. Software Execution
  • After completing all the wiring, click the “Code” button followed by the “Submit” button in the software interface (if applicable).
  • This will trigger the GPIO logic to activate the relay and control the motor.