PWM LED Dimmer/ Brightness Control by 555 Timer With Video Simulation


Posted on Feb 6, 2014

How to change the brightness of aLED Whether led lights are dimmable Is it possible to adjust the brightness of LEDs LED is basically a diode, when the forward voltage exceeds 0. 7 volt, it starts to glow, and if the forward voltage is less than 0. 7 volt, it will be in the OFF state. What happens if we are providing a high voltage to the LED so


PWM LED Dimmer/ Brightness Control by 555 Timer With Video Simulation
Click here to download the full size of the above Circuit.

as to increase the brightness Will it be a practical solution No, it will lead to the burning of LED. So what we can do to adjust the brightness of LEDs Here Circuits Gallery comes with a simple LED brightness control circuit using (Pulse Width Modulation) PWM method. It is also called PWM LED dimmer circuit diagram. By changing the pulse width of square wave, it is possible to control the brightness of LED. We have already discussed about the PWM signal generation before. Here NE555 timer IC is used to produce PWM signals. Our new circuit is based on 555 timer IC. You can use this circuit as a dimmer switch for LED lights. This PWM concept is also applicable for lamp dimmer switches too. But here we are explaining about 555 led dimmer. At the instant of powering ON the circuit, output will be 5V, because the voltage at the 2nd pin (trigger pin) is less than 1/3 Vcc. [Read Astale Multivibrator for getting familiarized with 555 timer]. At the very next moment, the output voltage will reach the capacitor via the 10k © potentiometer and diode D2 so that the capacitor starts charging with a time constant RdR1C (where Rd is the forward resistance of Diode D2). Here the charging and discharging path is entirely different since it is isolated by diodes D1 and D2 (refer above images). If the potentiometer midpoint is at 50% (middle), we will able to get 50% duty cycle (square waves of equal pulse width).




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