Pwm Led Dimmer Circuit. Before we get start building a 1 watt led dimmer circuit first consider a simple circuit as shown in figure below. Instead of varying the brightness by varying the supply current with a variable resistor or transistor it is accomplished by varying the ratio of on time vs off time.
Leds can be dimmed in two ways. Before we get start building a 1 watt led dimmer circuit first consider a simple circuit as shown in figure below. Also the linear fashion in which an led is affected by current and voltage makes them the ideal candidate for pwm in terms of control.
However the external pwm will not work because during the off periods of the pwm cycles the internal filter capacitor will keep the led circuit switched on and thus the pwm will not be effective.
The are different types of pwm circuits. The main principle of this circuit is to generate a pulse width modulation pwm signal with the help of the good old reliable 555 timer ic and vary the power being delivered to the leds and hence achieving the effect of led dimming. Arduino based led dimmer using pwm pulse width modulation this led dimmer is an arduino uno based pwm pulse width modulation circuit developed to get variable voltage over constant voltage. So if this filter capacitor is removed then the bulb could be dimmed externally through a pwm.
