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Humidity sensor

Discussion in 'Electronic Basics' started by Chris Fowler, Nov 20, 2003.

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  1. Chris Fowler

    Chris Fowler Guest

    I'm looking for a schematic that will allow me to build
    a humidity sensor and attach to me serial port. I'll then
    write software under Linux to read the port and display
    meaningful data. Any links?

    Chris Fowler
  2. Lord Garth

    Lord Garth Guest

    Humidity sensors are generally capacitive. You could use
    one to vary the frequency or pulse width of an oscillator
    which you would then count or time.

    If you really want to build the sensor, you might try something
    that shrinks or expands in response to humidity....human hair comes
    to mind.
  3. Chris Fowler

    Chris Fowler Guest

  4. Rich Webb

    Rich Webb Guest

    Thermometrics makes some inexpensive resistive relative humidity sensors
    that work OK in battery-powered apps. Recently had to replace one in an
    outdoor wireless RH + temperature sending unit that had a bad experience
    with Hurricane Isabel. Humidity sensors, as a rule, prefer not to spend
    excessive amounts of time submerged in brackish water...

    The Thermometrics HSP15P (Newark 39C2249) is reasonably affordable for
    small qty purchases. Specs at

    Couple that with a few passives, a microcontroller with a built-in UART,
    and a small power supply.
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