How to make a light activated switch

Discussion in 'General Electronics Chat' started by zuse2000, Feb 27, 2008.

  1. zuse2000

    Thread Starter New Member

    Feb 4, 2008
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    How can I make a switch for a circuit that is turned on and off using light I need that when light stimulates it it is turned on and remains on till light stimulate it again to turn it off
     
  2. DC_Kid

    Distinguished Member

    Feb 25, 2008
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    i dont have all the schematic info for you, but you can use a photo voltaic cell with a op-amp which can drive a flip-flop. one flash on, one flash off, etc.
     
  3. mik3

    Senior Member

    Feb 4, 2008
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    You can use an LDR (light dependent resistor) connected to a simple transistor amplifier and then a flip-flop.
     
  4. mozikluv

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    Jan 22, 2004
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  5. DC_Kid

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    Feb 25, 2008
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  6. thingmaker3

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  7. tatenda

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    Feb 29, 2008
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    how can make a system which prevents light above a certain intensity reaching the plants in a greenhouse using light activated switch
     
  8. zuse2000

    Thread Starter New Member

    Feb 4, 2008
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    Thanks for the replies but I need a schematic to use because I am not profecional in addition in the provided schjematic does the switch stays on till light switches it off again or it simply stays on as long as light is there because I need a schematic for the first case where the switch stays on after short exposure to light and goes off and stays off after another short lighht exposure
    Thanks again for the help
     
  9. nomurphy

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    Aug 8, 2005
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    Stand next to the switch, when you see the light, flick the switch.
     
  10. beenthere

    Retired Moderator

    Apr 20, 2004
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    Use the light activated circuit in the link, but use 12 volts instead of 6. Also use an impulse latching relay. Digi-key has one, part# PB513 @ $45.38 that's good for 15 amps on the contacts. And it's DPDT so you can spread the loads out a bit.
     
  11. DC_Kid

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    Feb 25, 2008
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    this had me rollin ... :)


    auto shading glass panels (i believe they go clear when electric field is applied). its gotta be some sort of feedback system. as the light level on photo-voltaic cell goes up the glass panel gets darker, etc, keeping the incoming light level where you want it. in real basic terms a NPN bipolar can work. voltaic cell is setup to just bias the base. some load is connected between +v and collector. signal to panel is taken right from the collector. as transistor is driven harder the voltage at the collector will decrease, thus less electric field on the panel and the darker it gets. not really sure if this theory is real world practical, but its a basic start.
     
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