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Need Light Sensor for Making Circuit to Turn On Or Off

Discussion in 'LEDs and Optoelectronics' started by The Heater, Nov 21, 2018.

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  1. The Heater

    The Heater

    Nov 21, 2018
    Hi, all:

    I am not an electrical engineer. I am a chemist and an attorney. I love doing auto electric, restore cars and work on cars and motorcycles and do car audio installations as a hobby.

    My question is what do I need to search for on DigiKey or Mouser to find a light sensing device that is very small that I can mount anywhere that just has two wires going to it? The purpose is to turn on some accessory LED light strips I want to mount on a sport bike for accent lighting. I want to tie a relay into the headlamp circuit and power the lighting from a sub panel I put in the bike. But I want something to control the power so the lights only go on at night. For those not familiar with motorcycles, the headlamp goes on whenever the ignition key is in the "on" position. 12 DC system.

    It needs to be very small. I have a light modulator for the headlamp on this bike that uses a micro sized controller and a light sensing device that just looks like a tiny dome sticking out of the end of a two wire pigtail with a rubber cover over the base where the wires go in. I can put my own waterproof heat shrink tubing on the wire entry area but need something that would mount on the end of a wire circuit and then could be just zip tied to a mirror or body work on the bike.

    So far I have found some things that are called "ambient light sensors" and "phototransistors".

    Thanks for the help.
  2. kellys_eye


    Jun 25, 2010
    To do it with two wires and in a small package you need to remotely mount the actual sensor from the controlling electronics.
    There are many light-sensitive switching modules that are available and extending the wire connections to the light-sensitve part of it (be it a phototransistor or a light dependent resistor etc). Use some two-core cable and heat shrink at the connections.

    Typical light sensing switch kit

    Light switch.png

    The sensor itself is the small item at the bottom labeled 'LDR'

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