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Thremopiles and Pyroelectrics — Parallax Forums

Thremopiles and Pyroelectrics

LoopyBytelooseLoopyByteloose Posts: 12,537
edited 2005-12-10 17:13 in General Discussion
Can anyone explain the differences in simple terms.

From what I read, I believe that thermopile generates a·DC voltage in realationship to temperature.

And the pyroelectrics generate an AC voltage in relationship to temperature when you have an aperture opening and closing at a regular rate.· It seems they usually have a spinning wheel·with appropriate holes placed in front of them.

I was hoping that I could use the pyroelectrics as a replacement to thermopiles in Jens' flight controller, but it seems like I need to provide a lot of extra hardware.

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"When all think alike, no one is thinking very much.' - Walter Lippmann (1889-1974)

······································································ Warm regards,····· G. Herzog [noparse][[/noparse]·黃鶴 ]·in Taiwan

Comments

  • PJAllenPJAllen Banned Posts: 5,065
    edited 2005-12-10 15:59
    From "Modern Dictionary of Electronics", R.F. Graf, Sixth Ed.,1991:

    thermopile -- A group of thermocouples connected in series-aiding. Specifically:
    1. A device used to measure radiant power or energy
    2. A source of electric energy
    3. Battery of thermocouples, consisting of alternate rods of antimony and bismuth suitably joined and connected to a galvanometer

    Thermopiles are used for the measurement of heat where thermometers cannot be employed.

    pyroelectric material -- A material which produces electrical output when subject to a change in temperature

    pyroelectric effect -- Also called pyroelectricity. The redistribution of the charge in a crystal that has been heated. The crystal is left with a net electric dipole moment - i.e., the centers of the positive and negative charges are separated.

    pyrometer --
    1. An instrument used to measure elevated temperatures (beyond the range of mercury thermometers -- Anybody remember Mercury?) by electric means. These include immersion, optical, radiation, resistance, and thermoelectric pyrometers.
    2. A temperature measuring instrument incorporating a sensor and a readout device.
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2005-12-10 17:13
    PJ,
    Thanks, but I have been search and reading quite a bit about the Pyroelectrics being IR motion detectors that are used in security.
    The dictionary really doesn't get me into enough detail for applications.

    We are talking about two very distinct deviews. One measures temperature in the IR spectrum, the other measures movement [noparse][[/noparse]of warm bodies]. Both seem to be really interesting


    I have two PIR or Pyroelctrics here that are rated as 30meters distance and will view motion from left to right as different from right to left [noparse][[/noparse]or up to down versuse down to up]. Someone wanted to have something like them on a bot that could chase his dog. It seems feasible and I would love to have my Toddler exhibit such behavior - uncanny. These seem better suited for watching your front lawn and backyard.

    On the other hand, I still want to buy some Thermopiles, but I cannot locate another outlet aside from Digikey. Does anyoone have suggestions? Digikey wants $16USD each for the little guys.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    "When all think alike, no one is thinking very much.' - Walter Lippmann (1889-1974)

    ······································································ Warm regards,····· G. Herzog [noparse][[/noparse]·黃鶴 ]·in Taiwan
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