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I want to use a TRIAC as a switch for an AC light bulb and turn on the bulb when it gets dark and turn it off when it gets light using an LDR.

I want to fully cut off the bulb below a certain intensity of light and fully turn it on above that level. Is this possible?

ocrdu
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Divakar Aryal
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1 Answers1

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Yes, it can be done. You can check for these two things online:

  1. Triac circuit interface with a microcontroller.

  2. LDR circuit to generate logic HIGH and LOW.

Once you have these figured out, you can use LDR ckt output to drive the triac ckt instead of MCU.

Note: Make sure light from bulb does not fall on the LDR. Otherwise, the circuit will go into a feedback loop and bulb will keep turning ON and OFF repeatedly.

Whiskeyjack
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  • @user263983 - sorry, didn't get you. What do you mean by 3d. PS will be required for sure, but I am not suggesting MCU. LDR ckt output can directly drive the triac. BTW, my answer is just a guide around what to look for. OP will have to look at a few circuits, put them together and then ask questions if he finds a problem. – Whiskeyjack Jan 23 '23 at 10:39
  • Sorry, 3d was typed by mistake. But power supply is essential, even without MCU. – user263983 Jan 23 '23 at 15:00
  • @user263983 - totally agree. OP will need a psu. depending upon his use case, a simple 2-4 mA PSU can be made using a diode, cap, zener and resistors. – Whiskeyjack Jan 23 '23 at 17:44