DC Motor Speed Control Experiment

Overview

This experiment demonstrates how to control the speed of a DC motor using a Pulse Width Modulation (PWM) signal. By adjusting the duty cycle of the PWM signal, you can control the average voltage supplied to the motor, thus regulating its speed.

Components Required

• DC Motor
• 555 Timer IC
• Transistor (NPN - 2N2222 or similar)
• Resistor (10kΩ for the potentiometer)
• Capacitor (0.1µF)
• Potentiometer (10kΩ)
• Power Supply (9V or 12V, depending on the motor rating)
• Breadboard and connecting wires

Procedure

Follow these steps to build and test your DC motor speed control circuit:

1. Set up the 555 Timer IC in astable multivibrator mode to generate a PWM signal.
2. Connect the output of the 555 Timer IC to the base of the NPN transistor through a current-limiting resistor.
3. The collector of the transistor connects to the positive terminal of the DC motor, and the emitter connects to ground.
4. Use the potentiometer to adjust the duty cycle of the PWM signal, which in turn controls the average voltage supplied to the motor.
5. Apply power to the circuit and observe the motor's speed. Adjust the potentiometer to change the motor speed.

Expected Result

The motor speed will change based on the duty cycle of the PWM signal. A higher duty cycle increases the average voltage, thus increasing the motor speed. A lower duty cycle reduces the speed of the motor.

Important Notes

• Ensure the transistor you use can handle the current drawn by the motor.
• Monitor the motor's temperature if running for extended periods, as high current can cause overheating.
• The potentiometer allows you to fine-tune the motor speed by adjusting the PWM signal.