LED colour change when temperature rise/fall

Discussion in 'The Projects Forum' started by blackstallion, Feb 21, 2012.

  1. blackstallion

    Thread Starter New Member

    Jan 13, 2012
    8
    0
    Hi everyone...i have this project of water level detector. Im planning to add a feature which is...the LED level indicator will change color when cold/hot water is in the water tank. I want the LED to light ups in blue for cold water and light ups red for hot water.

    I have been searching the circuit for the temperature dependence LED but still not found any.

    Can anyone give ideas on how to achieve the intended feature? any circuit reference available?

    Any supportive comments are welcome. Thanks
     
  2. Felo

    Member

    Feb 20, 2012
    91
    13
    I have never seen such thing as temperature dependant LED, as I see it, the fast way to achieve this is use a low pin count MCU and a temp. sensor sucha as LM35 or the digital DS12XX, write the apropriate code for this and voila!!! If you take such endeavor, many people here would be willing to help, but please be super specific with you requirements
     
  3. Ron H

    AAC Fanatic!

    Apr 14, 2005
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  4. luvv

    Member

    May 26, 2011
    186
    31
    Like Felo said a pic makes everything just a matter of programming.

    But for people like me w/ zero knowledge of programming a analog solution may be more appropriate.

    If it where me, i would use a op amp as comparator and have the output drive the gates of a pnp/npn mosfet.

    This is a ghetto way of doing it,but works ......

    Perhaps someone else will suggest a better way that don't involve coding.

    -luvv-
     
  5. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    First, pick your sensor. Then pick your range.

    Then you need to design an analog circuit that does what you want with voltage swing.
     
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