LED ramping circuit.

john February 28, 2010 6 Comments

Description.
In this circuit the intensity of LED will vary in a ramping fashion. The circuit consists of three ICs: Two 555 timer ICs and one LM393 op-amp. IC1 and IC2 are wired as oscillators to produce 10 KHz and 1 Hz frequencies respectively.These two frequencies are given to the inputs of the op-amp LM393.LM393 is wired as a comparator and its output will be a PWM signal. This PWM signals controls the FET Q1 to drive the LED. The LED will rise from OFF state to full brightness slowly and then slowly fades to OFF state and this operation repeats. The resistor R4 controls current through the LED.

Circuit diagram with Parts list.
led-ramping-circuit

Notes.

  • Assemble the circuit on a general purpose PCB.
  • The ICs must be mounted on holders.
  • The power supply for this circuit can be anything between 3 to 12V.
  • I recommend 6V for this circuit.
  • The effect can be varied by changing the values of C1, C2, R1 or R2.
Comments
  • sanchu
    October 3, 2014

    what is the application of this circuit?

  • Brandon Cooper
    November 29, 2012

    Can I decrease the resistance of R1 and add more than 1 LED in series with one another?

    Thank you
    Brandon Cooper

    • seetharaman
      October 7, 2014

      You can use 3 red LEDs by reducing the resistance R4 to 47 ohms. With yellow LEDs remove R4. White LEDs you can use only one. But you can parallel more LEDs,and the limiting current is 200 mA.

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    Many people do not know how to wire LED lights due to the accuracy required in the circuit values and the number of LEDs to use in a lighting circuit. For the circuit to work, you need to use accurate values for voltage, current, and resistance.

  • jayesh
    August 2, 2011

    Very Gooooooooooooooooooddddddddddddd ///////////’;’;

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