Simple Thermal Project

Discussion in 'The Projects Forum' started by mustafagtgt, Dec 2, 2009.

  1. mustafagtgt

    Thread Starter New Member

    Dec 2, 2009
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    Hi, I am new this thread and I would like some help and advice on how I can constuct a simple thermal device. :)

    I am thinking of using a thermistor which is a type of resistor which varies with tempreture. I would like to know How I can impliment this resistor affectivly in a working circuit with other neccesary components. My main aim is to contrust a device that reacts to a shift in Room tempreture.

    General temperature related to human comfort can vary from 20.0 Celsius to 25.0 Celsius. I will programme the device to indicate when the temperature has risen above 26.0 Celsius allowing some flexibility and also I when the temperature has fallen below 15.0 Celsius.
    A Red LED will turn on when Tempreture has risen above 26 Celsius
    A Blue light will turn on when Tepreture has fallen blow 15 Celcius
    How can I create this? :confused:
    Thank you
     
  2. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    Is this a homework problem?
    Can you use an LM35 instead of a thermistor?
     
  3. mustafagtgt

    Thread Starter New Member

    Dec 2, 2009
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    What exactly is a LM35?

    I am actually doing a Project at College and for my Project I chose to do make a a sensor which turns a Red LED or Blue LED depending on the room temperature...
     
  4. SgtWookie

    Expert

    Jul 17, 2007
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    Then this is a homework assignment, and should be in the Homework Help forum.

    An LM35 is a temperature sensor that is available in a TO-92 plastic case. These are sometimes called "three legged critters".

    If you supply it a certain voltage level, it will output a voltage that can be read in °C.

    You could use that output in conjunction (with the assistance of) a "window comparator" circuit to light your LEDs.

    Google is your friend.
     
  5. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    I provided a link to the datasheet...:rolleyes:
     
  6. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    Why dont you just borrow my wife. She doesn't need an electronic circuit to tell if the house temperature is less than 69.9degF :D
     
  7. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    Hmmm, I'm gussing she might be equipped with the "high dB audible alarm option"?
    :D
     
  8. logans-electronics

    Member

    Sep 1, 2009
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    This will get you started. I used in an inverting op amp to vary the fan speed based on temp....I also added a 16 led array for a visual indicator. The FET has a 4 volt drop to the fan. I had to build this backwards. Find your VSAT- the GOS drop of 4 volts. I had to play around with the gain structure to get what I needed....Hope that it atleast gives you some start...:)

    Mesure your resistance at the tempurature values you need....sounds weird but I placed my thermistor in a curling iron on high and turned it off(attach a thermometer also)...it will slowly cool down enough where you can get half way decent measurements. This is how I determined my gain and RI and RF resistors.
     
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