Flashing Light with Triacs

This flashing light circuit uses triacs to generate an intermittent light with variable frequency. Additional components are the D1 diode and semi adjustable potentiometer R2. The trigger capacitor C1 is increased from 0.1 µF to 220 µF so that the triacs can be ordered for several successive periods. C1’s loading time is longer, so that the lamp flashes with one pause of several periods.

Blinking frequency can be adjusted with P1. Semi-adjustable potentiometer R2 regulates the current gate. This setting affects the lighting duration of the lamp because it also establish the C1’s discharging time.

Triac Flashing Light Circuit Diagram

triacs flashing light circuit diagram


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  • Eduardo Mendes

    I build it and it works fine.
    It seems very handy for simple usages like the flash light of an automatic gate openning.
    For those in trouble to make it work I sugest to check the polarities of the diode, capacitor and triac itself.

  • Palurdo

    This circuit works like a charm with a 220V/35W Xmass light string. The small changes i did were replacing the triac with a MAC97A6 (a cheap TO92 triac that can control up o 120W max). The ER900 with a more easy to find DB3 diac, and replaced the 6,8k+100k pot series with a 100k 1/2w fixer resistor, and the 1k preset with another 680R 1/4W fixed resistor that i had lying around. The circuit blinks close to every second with a brief yet noticeable flashing. The capacitor was 220uf/50V but i’m considering replacing it wit a 1000uF/50V for extending the flashing period and the on time.

  • Sivanand

    There are some serious mistakes in this circuit.
    1) The capacitor’s value should be 0.1Mfd/600volts.
    2)The dimmer control pot should be 470Kilo Ohms not 100K.
    3)There is no need of BY126 or In4004 diode just make a short.
    4)The 6.8K resistor’s value should be increased to 15Kilo Ohms.
    5)The Ik preset can also be avoided, make a link across.

    • Palurdo

      It is a schematic for a light flasher not for a light dimmer, now that you realize it your comment is nonsense.


      is it ok if i used triac BT136? and also the capacitor i used 10uF!!!! this components will affect the function of the circuit??? answer please thanks!!!!!

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