Tag Archives: light dimmer

AC load dimmer using triac

Triacs-based dimmers are based on the principle of controlling the phase of AC voltage applied to the load and are specially designed for resistive loads such as incandescent or halogen lamps. Mike from Electronics-Lab has shared this simple TRIAC AC load dimmer circuit that can handle AC power up to 400VA. The circuit is working by controlling the phase of the 220 VAC voltage allowing the load to be powered for less than 360ยบ of the full sine wave. Powering the load for smaller period than full sine wave delivers less power, so it has a dimming effect on the load.

AC load dimmer

Lab 9: Pulse Width Modulation (PWM) using PIC CCP module


Pulse width modulation (PWM) is a technique of controlling the amount of power delivered to an electronic load using an on-off digital signal. The fraction of the period for which the signal is on is known as the duty cycle. The average DC value of the signal can be varied by varying the duty cycle. The duty cycle can be anywhere between 0 (signal is always off) to 1 (signal is constantly on). Suppose, if the signal has +5 V while it is on and 0 V during off condition, then by changing the duty cycle of the signal, any voltage between 0-5 V can be simulated. This method is commonly used for controlling speeds of DC motors and brightness of lamps. This lab session will talk about how to generate a PWM signal using the PIC16F628A microcontroller and control the brightness of an LED with it. PIC16F628A has a built-in hardware, called Capture/Compare/PWM (CCP) module, to generate a PWM signal.

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