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Dim 12V Light Bulb with 555 IC

This light dimmer is used to dim the intensity of 12V light bulbs using the well-known 555 timer that is configured as an astable multivibrator. The pulses from pin 3 are used to control the VMOS transistor BUZ20, BUZ72 or 10N10. The maximum dissipated power must not exceed 40 watts. You may use the transistor without a heatsink if the power does not exceed 10 watts.

The 555 IC powering is done through D2 diode and is filtered using C3 capacitor. The resistors can be 0.25W or 0.5W with a tolerance of ±5%.

Schematic of 12V Light Dimmer Circuit

12v dim light bulbs schematic

7 Comments

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  • Marshall Moon

    I wana make a light switch that will be oparated by photo diode and can also be operated manualy by on/off switch.i wana also include timer on it.help plz

    • Kuberkoos

      In my country (South Africa) you can buy a security light that includes a day/night switch plus a timer to set the “on” time for very little money. It is simple to add a manual on switch to that.
      In other words it is not worth the time, money and effort to build one.
      However, if you want to build one there are numerous circuits available on the ‘net, Try to Google “day/nite switch, and if you do not find anything, let me know.

  • Kuberkoos

    I’ve made bigger boo-boos than that! 🙂

  • Kuberkoos

    When the lamp is in the “on” position, the voltagedrop over it is 12v minus Vdrop over the transistor: say ±0,5V. Right?
    Then the voltage between the lamp/transistor/diode junction and Neg will be ± 0.5 volt. The 555 cannot operate on that.

    • Popescu Marian

      I think the light bulb was placed in the wrong place so I have modified the schematic and now I think is right.

  • Kuberkoos

    Will this circuit work as it is????

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