DIY DC Motor Speed Controller Making at Home || 12V Fan Speed Controller

Controlling the speed of a DC motor is essential for many DIY electronics projects, from robotics to model cars. In this tutorial, we will create a DC motor speed controller using the 75N75 MOSFET and a few other common components. This project is perfect for hobbyists and enthusiasts looking to gain hands-on experience in electronics.

Components Needed

• 75N75 MOSFET
• 10K Resistor
• 10K Variable Resistor (Potentiometer)
• NE555 Timer IC
• 1nF Capacitor
• 1N4007 Diode
• AC Terminal Block
• PCB
• DC Motor
• Power Supply (suitable for your motor)

Tools Required

• Soldering iron and solder
• Wire cutters/strippers
• Multimeter

Before we start assembling the components, it’s essential to understand the basic workings of the circuit. The NE555 Timer IC is used in astable mode to generate a Pulse Width Modulation (PWM) signal. The duty cycle of this PWM signal is controlled by the 10K variable resistor, which in turn controls the speed of the DC motor. The 75N75 MOSFET acts as a switch, controlling the power supplied to the motor based on the PWM signal.

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At first, I create a Schematic Diagram on EasyEDA online PCB design software. Then I convert my Schematic Diagram into a PCB design with 2 Layers. After completing my design I will order PCB from JLCPCB .

Place the NE555 Timer IC on the Breadboard:

• Connect pin 1 to the ground.
• Connect pin 8 to Vcc (your power supply, typically 12V for this setup).

Configure the NE555 Timer:

• Connect pin 4 (Reset) to Vcc.
• Connect pin 2 (Trigger) and pin 6 (Threshold) together.
• Place the 10K resistor between pin 7 (Discharge) and Vcc.
• Connect the 10K variable resistor between pin 7 and pin 6.
• Place the 1nF capacitor between pin 6 and ground.
• Connect pin 5 (Control Voltage) to the ground through a small capacitor (usually 10nF).

Set Up the PWM Output:

• Connect pin 3 (Output) to the gate of the 75N75 MOSFET.

Connect the MOSFET:

• Connect the source pin of the 75N75 MOSFET to the ground.
• Connect the drain pin of the 75N75 MOSFET to one terminal of the DC motor.
• Connect the other terminal of the DC motor to the VCC through the AC terminal block.

Add the Diode:

• Place the 1N4007 diode across the motor terminals to protect against back EMF. Ensure the cathode (marked end) is connected to Vcc.

1. Double-check Connections: Ensure all connections are secure and correctly placed according to the schematic.
2. Power Up: Connect the power supply. The motor should start spinning. Use the 10K variable resistor to adjust the speed of the motor. The motor speed should change as you vary the resistance.
3. Troubleshooting:

• If the motor doesn’t spin, check the power supply and all connections.
• Use a multimeter to verify the output from the NE555 Timer IC.

Once the circuit works perfectly on the breadboard, you can solder it onto a PCB for a permanent setup. This step involves carefully transferring each component and wire connection from the breadboard to a solderable perf board or custom PCB.

You have successfully created a DIY DC motor speed controller using the 75N75 MOSFET, NE555 Timer IC, and a few other components. This basic yet effective speed controller can be used in various projects, providing you with a reliable way to control motor speeds. Happy building!

Heat Sinks: If you’re driving a large motor, consider adding a heat sink to the MOSFET to dissipate heat.

Power Supply: Ensure your power supply matches the voltage and current requirements of your motor.

Component Substitution: If you can’t find a 75N75 MOSFET, look for an alternative

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