This project implements an LED dimmer using Pulse-Width Modulation (PWM) generated by a 555 timer.
The PWM drives an N-channel MOSFET (IRFZ44N) which switches the LED load. Adjusting the potentiometer changes the PWM duty cycle and therefore the perceived brightness of the LED.
- 555 Timer IC (Astable PWM generator)
- IRFZ44N N-channel MOSFET
- 50kΞ© Potentiometer
- 1kΞ© Gate resistor (R1)
- 1N4148 Diode (for PWM shaping)
- 1N4007 Diode (flyback protection)
- Capacitor (C1)
- LED load
The 555 timer is configured in astable mode to produce a square wave whose duty cycle is adjustable using the potentiometer.
Two diodes (1N4148 and 1N4007) separate the charge and discharge paths of the timing capacitor, allowing independent control of ON and OFF durations.
The approximate duty cycle is:
[ D = \frac{R_A + R_B}{R_A + 2R_B} \times 100% ]
Here:
- RA = 1kΞ©
- RB = 50kΞ© (Potentiometer)
As RB increases, the duty cycle decreases β the LED becomes dimmer.
The PWM output from the 555 is connected to the Gate of the MOSFET through R1.
- When PWM is HIGH, the MOSFET conducts, powering the LED.
- When PWM is LOW, the MOSFET turns OFF, cutting current to the LED.
Thus, varying the duty cycle controls the average LED current and brightness.
A logic-level MOSFET (e.g., IRLZ44N) is ideal for low-voltage control.
- 1N4007 Flyback Diode: Protects the circuit from voltage spikes (important if the load has inductance).
- 1N4148 Diode: Creates asymmetric charge/discharge paths in the timing network.
- C1 Capacitor: Provides timing and decoupling stability.
- R1 (1kΞ©): Limits gate charging current and prevents ringing.
A PWM frequency between 500 Hz and 2 kHz ensures:
- Smooth LED dimming (no visible flicker)
- Efficient switching with low heat loss
At 10% duty cycle, the LED is dim.
At 90% duty cycle, the LED appears bright.
- Smart home lighting dimmers
- Automotive interior lighting
- Solar lighting controllers
- General LED brightness control
Sreyas Kishore
This project is licensed under the MIT License.