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120Vac Night Light

Discussion in 'LEDs and Optoelectronics' started by orion311976, Feb 29, 2012.

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  1. orion311976


    Sep 23, 2011
    I have a 120v/4W bulb night light w/ an on/off switch. I'm removing the switch to add a photoresistor and not sure what else I need- I got a BT169D transistor, photoresistor, and I think I need a resistor but not sure of the size. Anyone got any ideas?
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    Using those components, at the safest approach is a separate low voltage power supply to power the circuit which operates a relay that in turn switches the mains to the bulb.

    edit: personally I'd be more inclined to use a LED as a night light. If 4 watts as too much to leave on continuously, then a LED with its much higher efficiency is going to consume far less power.
    Last edited: Mar 1, 2012
  3. BobK


    Jan 5, 2010
    Or, you could go to the dollar store and get one for $1 that already has a photo sensitive switch. For a learning experience, buy two and take one apart! I suspect it uses an LDR + a triac.

  4. orion311976


    Sep 23, 2011

    Actually I have taken one apart to get parts for an LED night light I was building, but never thought to draw and label the circuit for future reference in my files. I have since been taking very detailed notes and drawings being careful not to make that mistake again. I have been thinking off cleaning out this bulb base and use it to build an LED bulb with the screw in base. Thanks for the help.... P.S. This project was for fun and a challenge to check my electrical learning knowledge.
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