How to make LDR working identically?

Discussion in 'Analog & Mixed-Signal Design' started by Shubhankar, Jun 30, 2016.

  1. Shubhankar

    Thread Starter New Member

    Jun 30, 2016
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    Hello there,
    I am making dimmer using my Arduino Board for my home. I am using LDR for dimming the light. But I am facing one problem that all LDR's are not working identically. I found that every time I am getting different value on same intensity of light using different LDR's. So how can I achieve this?
     
  2. #12

    Expert

    Nov 30, 2010
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    1) Hardware, use resistors to make the LDRs similar
    2) Software, Make a look-up table for each LDR
    3) Start over, Use a better sensor.
     
  3. AlbertHall

    Well-Known Member

    Jun 4, 2014
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    Comprehensive, except possibly:
    4) Don't worry about it!
     
  4. dannyf

    Well-Known Member

    Sep 13, 2015
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    By calibrating them to the same output under identical lighting.
     
  5. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    Any minor change in outdoor light coming into a window will cause a different ADC value. Even reflections of where you are standing relative to lamps and the various reflections in the room - there is lots of possible differences on a minute by minute basis.
     
  6. #12

    Expert

    Nov 30, 2010
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    You're thinking on a micro scale. I have a drawer full of CdS sensors, and they are so dissimilar that I have to choose which range I want to work in before I start designing. Less than 1k, several k, dozens of k ohms at twilight levels. This range would look problematic to a software program. As an analog designer, I cope with this in hardware. Find the right range, slow down (integrate) the output to discard small interference factors, go to logic section.
     
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  7. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    I just wanted the OP to understand the variabilities within his room with on LDR before tries to match a second to it - what ever his methodology might be or what ever his expectation for his design.
     
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