Photo resister - how can I reverse it function

Discussion in 'General Electronics Chat' started by booggaville10, May 28, 2013.

  1. booggaville10

    Thread Starter New Member

    May 28, 2013
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    Please help me. I've just started getting into electronics and I've made a Jaycar project with a photoresister. The idea of the project is when it is in the dark the buzzer sounds. How can I get the buzzer to sound when it's light and go off in the dark? Is this an easy task?

    Thanks for your time!!
     
  2. MrChips

    Moderator

    Oct 2, 2009
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    It's easy if we can see the circuit diagram.
     
  3. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    Yes if you post the circuit diagram we can help.
     
  4. firebreather

    New Member

    May 27, 2013
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    Hi, boogaville, i'm too a beginner, hmm....
    Most probably you must've used transistor in your circuit. Transistor acts as an invertor. i.e
    when you've connected the buzzer btw the collector and +ve end of supply, and if it
    sounds,then it will notsound when connected btw. the collector and emitter
    terminals, and vice versa. So try exchanging the connections..hope it works..
     
  5. MrChips

    Moderator

    Oct 2, 2009
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    There are a half dozen ways to solve the problem. We begin after we see the circuit diagram.
     
  6. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    Generally speaking, there is a much better way to do it, but we need the schematic.
     
  7. Ramussons

    Active Member

    May 3, 2013
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    You are also likely to end up with a blown transistor!

    Ramesh
     
  8. #12

    Expert

    Nov 30, 2010
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    Not likely. This will change the circuit into an emitter follower and have not enough voltage as its output.
     
  9. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    The simplest form is 9 V battery, + to one leg of LDR, other leg to + [red] of solid state buzzer, RS 273-060, - [black] buzzer to - battery. LDR used about 1 in dia., 50 Ω bright light, 1M Ω dark.
     
  10. #12

    Expert

    Nov 30, 2010
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    This is the basic shape of what you need. Give numbers about voltage, current, of the buzzer and photocell, to get answers about the transistor and resistors.
     
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