PWM fan or LED dimmer
Variable brightness or speed from a knob. A 555 oscillates at about 1.4 kHz; two diodes steer the charge and discharge currents through opposite halves of the pot, so turning it changes the duty cycle but not the frequency. A logic-level MOSFET switches the 12 V LED strip (or fan) fully on and off, so it barely warms up.
Build it in the labGuided build, test sheet and fault finding, free in your browser.
Parts list
- Bench power supply
- 555 timer
- 3 × Resistor
- Potentiometer
- 2 × Signal diode
- 2 × Film capacitor
- N-channel MOSFET
- 12 V DC LED bulb
Test procedure
Each test has an expected value and a pass range, like a factory test sheet:
- Pot at 25 %
- Pot at 75 %
How it works
What it does: Variable brightness or speed from a knob.
Build it (guided or ready-made), then run its test procedure below. Every test has an expected value and a pass range, just like a factory test sheet.
Background
The standard dimmer for LED strips, 12 V fans and motors.