Now, one terminal of the POT is connected to anode of a Diode (preferably 1N4148) while the other terminal of the POT is connected to cathode of another diode.Also, a 0.1μF Capacitor is connected between Pin 6 (or Pin 2) and GND. The Trigger pin (Pin 2) and threshold pin (pin 6) are shorted and the Wiper Terminal of the POT is connected here.Hence, a decoupling capacitor of 0.01μF is connected between pin 5 and GND. Pin 5 or the voltage control pin is not used in this application.For resetting the IC, in case of an error while circuit is working, connect the RESET pin to GND for a Second and then connect it back to 12V. The reset pin also directly connected to the 12V as shown in the circuit diagram. The 12V DC supply is given to the VCC Pin for operating voltage of 555 timer.Circuit Diagram of PWM LED Dimmer Using 555 It has a wide range of applications like lamp dimmers, motor control, joysticks etc. It has features like timing for micro seconds through hours, adjustable duty cycles and ability work in various voltage levels etc. The 555 Timer IC can work in three different modes of operation: Astable, Monostable and Bistable operations. ![]() The output of the IC can be taken from the out pin i.e. Pin 4 is the Reset pin and it is used to reset the complete IC. Pins 2, 6 and 7 are the Trigger, Threshold and the Discharge Pins. The operating voltage may vary from 3v to 15V. The pin 8, which is the VCC pin, is used to give the main supply voltage to the IC. Pin Diagram of the 555 Timer IC is shown in the following image. It is one of the most popular ICs and is used for a variety of applications like Timer, Oscillator and Pulse Generation. The 555 Timer is an 8-pin Integrated Circuit available in Dual-in-Line Package originally developed by Signetics. Related Post: LED Lamp Dimmer Circuit A Brief Note on 555 Timer IC The generated PWM Signal is then applied to a bunch of LEDs and based on the Duty Cycle of the PWM Signal, the intensity of the LEDs can be high or low. The 555 timer is used to generate a PWM signal with the help of a few passive components. The following image depicts the block diagram of the PWM based LED Dimmer using 555 Timer IC.Ī 12V DC source is used to power the entire circuit including the 555 timer IC and the LEDs. Using PWM technique, the mount of power delivered to a device is varied and hence, if we can control the pulse width of the signal, we can easily control the device like making a simple DC Motor to rotate slow or fast or to dim the intensity of an LED. Here, in our project, the PWM Technique is used for dimming the LEDs. If you want to control the speed of the motor, PWM plays a key role. The Pulse Width Modulation (PWM) plays an important role in controlling the a lot of 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. In this project, we will see a PWM based LED Dimmer using 555 Timer IC. Circuit Diagram of PWM LED Dimmer Using 555.
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