LED Dimmer

This control method is called Pulse-Width Modulation (PWM). It allows the LED to operate at its nominal current during the “ON” portion of the cycle, so there is no color shift. There are many ways to implement PWM dimming in an LED driver circuit. The “Live” (interactive) example above shows one method. It uses a 555 Timer to control the PWM switching frequency and duty cycle.

In that schematic, you can change parameter values and run new simulations to see the effect. The key dimming parameters are the potentiometer setting, which controls the relative RC charge and discharge time constants of the 555 timer and therefore the duty-cycle of the PWM. Also, the capacitor c2 value controls the PWM switching frequency.