555 PWM Motor Controller
π Overview
Build a PWM motor controller around the classic 555 timer: a potentiometer sets the duty cycle, which drives a MOSFET and gives you stepless speed control of a DC motor.
A classic hands-on exercise from electronics basics - a few dollars of parts, a breadboard or a PCB, and you learn how PWM works along the way.
π§° What you need
- NE555 timer chip x1
- N-channel MOSFET (IRFZ44N or similar) x1
- 10k potentiometer (speed knob) x1
- Freewheel diode x1-2
- 5mm screw terminals, DC power jack, assorted resistors and capacitors
- Breadboard/perfboard + jumper wires
π§ Step by step
Gather the parts
The 555 is the most common timer chip and costs pennies
Pick an N-channel power MOSFET like the IRFZ44N to drive a DC motor
Schematic and breadboard
The author provides the schematic: a 555 oscillator with potentiometer duty-cycle control feeding the MOSFET
Build it on a breadboard first, then solder the PCB once it works
Key detail: put a freewheel diode across the motor so back-EMF cannot kill the MOSFET
Solder it
Solder the board starting with the low-profile parts and working up
A heatsink on the MOSFET is worth adding - it gets hot at high current
Connect the motor
The motor goes to the MOSFET drain and the potentiometer to the control input
Keep the motor within the MOSFET and power supply ratings
Power it
Connect the supply through the DC jack at the motor's rated voltage
Do not exceed the voltage rating of the chip or the MOSFET
Play and tune
Turn the potentiometer and the motor sweeps smoothly from stopped to full speed
Changing the capacitor value changes the frequency - judge it by sound and smoothness
You can add an indicator LED or a power switch later
π‘ Tips
- Get the freewheel diode the right way round: cathode to supply positive, anode to the motor terminal - backwards and it pops
- The 555 usually runs in the tens of kHz; if you cannot hear a whine, that is ideal
- For more linear control, add fixed resistors at each end of the potentiometer to limit its range