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Temperature transmission

Discussion in 'Electronic Design' started by varun kumar, Feb 19, 2007.

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  1. varun kumar

    varun kumar Guest

    Hi everyone,

    I'm doing a project on "measurement of temperature using a Rover"
    AS a part of this we need to measure the temperature of the
    surroundings and transmit this temp. value. For transmiting the
    temperature I decided to use FM transmission and for temp. sensing
    decided to use LM35.For displaying temperature value at the reciever
    decided to atm microcontroller(89c51)

    So if any one knows the details regarding this Temperature
    transmission . plz send me the details.

    Components used are:
    lm35 (temperature sensor)
    FM transmitter and reciever
    at89c51 (microcontroller)
  2. I suggest you make a voltage to frequency converter, to
    change the temperature signal to an audio tone. Use that to
    modulate the FM transmission. At the receiving end, you
    change the frequency of the tone back to voltage, or measure
    the frequency, digitally, and convert to temperature with a
    look up table. There are lots of ways to do voltage to
    frequency, from a 555 and LM2907. But there are also
    temperature sensors that output frequency, directly.
    See page 6 of:

    Or you could convert the temperature signal to a variable
    duty cycle digital signal (variable mark/space ratio), and
    modulate the FM with one of two tones for the two variable
    times per cycle. You would have to convert the received
    pair of tones back to the two digital values (see LM567 )
    so that the duty cycle can be measured by the micro.
  3. (snip)

    Another one on page 10:
  4. SR

    SR Guest

    i like to tell something abt the same project, that is temperature
    indicator using,v r doing digital thermometer,it consist of a
    sensor,LM35 which is acting as a current to voltage converter, n the
    output of the sensor will b given to an ADC whose output is in digital
    format.This digital format information is our temperature whcih is in
    the form of voltage.Inorder 2 convert it to corresponding temp,v uses
    a microcontroller,ie 89c51.And the output of the mc wil provide to the
    LCD display.

    And if it is needed v can provide additional facilities like
    temp range indicator etc.acually i wan ur help inorder 2 modify the
    same project with additional ideas ie using this same principle other
    than temp measurement can v do somethin else with the same
    extra fittings.thank u
  5. Max and min temperature, logging to a file for the year, humidity with
    a different sensor, air pressure with an other sensor, wind speed and
    direction with yet an other sensor..., radioctivity with [], light
    sensor for the shades, and count the sunny days, rain sensor, sound
    pressure sensor, lightning detector, CO detector, other gasses detector,
    passive IR detector, etc...
  6. linnix

    linnix Guest

    Location, location and location. We would like to log the absolute
    location of an unstable hillside. With heavy rains for the past few
    days here, I wish we have it in place already.
  7. Tim Wescott

    Tim Wescott Guest

    Why not measure temperature using an MG or a Citroen?

    John P.'s suggestion of using analog telemetry is good if all you're
    ever going to do is measure one thing. If there's any hint that you'll
    want to measure other quantities consider using some low rate digital
    telemetry. I'd suggest 300 baud FSK, or perhaps 1200. This should be
    easy to implement, it should work just dandy with the serial output of
    your microprocessor, and you'll be able to send just about anything you
    can dream up.


    Tim Wescott
    Wescott Design Services

    Posting from Google? See

    "Applied Control Theory for Embedded Systems" came out in April.
    See details at
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