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IR Temperature Sensor

Discussion in 'Electronic Basics' started by [email protected], Mar 1, 2009.

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  1. Guest

    I am attempting to construct a temperature sensor that will activate
    several relays when the thermometer senses temperatures above 150
    degrees Celsius, or ignition point for decayed wood. Unfortunately I
    have only been able to find this plan online, which has far more
    features than I need.

    If anyone knows of a circuit diagram that would be more to my needs or
    has suggestions of any sort, I would be extremely grateful. If you
    have any questions feel free to email me at .
  2. Guest

    By IR sensor I mean like the kind you can find in a computer mouse or
    motion detector, that can detect infrared energy (heat) and change the
    resistance based on this (I think that is how they work, anyway). I am
    trying to build a circuit where once the sensor is giving the correct
    signal back, a relay will be tripped, activating another circuit I am
  3. Guest

    Google had a number of hits for me using "temperature activated relay
    circuit". This page has a simple circuit. Week18, Relays.pdf

    A computer mouse is not doing ir. And I think most house alarms do
    motion, not ir either. Is what you mean to say that you need to be
    able to point it at the heat source rather than have the sensor on the
    heat source? Like these?

    If so that will take a more complex circuit.
  4. Nemo

    Nemo Guest

    tranerm asks
    If you base your circuit on an IR sensor you will have a lot of
    problems, because IR is everywhere. You'll get false positives from
    normal lights and even clever circuits which try to auto-adjust for the
    average background level can get fooled by, say, a cloud passing across
    the sun. Also - how are you going to calibrate it? And protect the high
    gain circuitry from RF pickup when someone uses a mobile phone below it?

    May I suggest a simpler approach like this:

    this kind of component, a "thermal switch", is widely available. I used
    one recently partly because I noticed this particular shape is some kind
    of standard, so even if that manufacturer goes bust Honeywell and some
    other bunch will still stock them.

    The main problem with this item is that it is normally closed. But if
    you're happy to burn a bit of power and continuously power a relay
    (20mA?) that's OK. An IR circuit would burn a bit of power anyhow.
  5. Guest

    Sorry about the false diagram and not enough info):
    I am building a small turret that will first seek brightness (in a
    dark room, so for example, a candle) and then when the IR sensor is
    facing it, activate a series of relays, some ceasing motion of the
    'turret' and one trggering a pump which will squirt a spray of water
    in the direction of the candle or other type of flame. The distance is
    required because I want to be able to move the candle and still have
    the turret track a different location. If possible, I would also like
    to have the sensor indicate once the temperature has gone
    significantly below combustion point and track a different target. If
    possible. Thank you for your patience and assitance:)
  6. Guest

    I will be runninf it off a a wall wart so power won't be a problem,
    but the interference probably would be. I am trying to build a small
    'turret' that will first seek brightness (in a dark room, so for
    example, a candle) and then when the IR sensor is facing it if the IR
    sensor detects heat above a certain level, activate a series of
    relays. One or two of these will shut down the motors moving the
    turret, and another will activate a small pump that will squirt water,
    extinguishing the flame. From there, if possible I would like it to
    seek another target if the detcts temp below a certain level. (however
    this is purely an extra) I want to be able to switch the locations of
    the candle, so I can't reallly just run temp relays back and forth
    either, unfortunately. Thank you incredibly for your help:)
  7. Jasen Betts

    Jasen Betts Guest

    The Nintendo Wii handset (available separately) has in it a neat
    little infrared image sensor that is quite capable of sensing rthe
    direction of a candle flame. it doesn't have a simple output that
    you can wire straight to a motor driver though, you'd have to put
    a microcontroller in-between to interrogate the sensor.

    some electronics hobby mag did an article on it a while back.

    And there's stuff on the web too.

    so buy a used wiimote and rip the image senor out of it.
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