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temp control help

Discussion in 'General Electronics Discussion' started by ghost1356, May 12, 2015.

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  1. ghost1356


    May 12, 2015
    I know very little about electronics outside of an introductory class at community college so bare with me. I am a vaper and there have been some temperature sensing devices coming out lately utilizing the interesting properties of nickle wire to detect when the temperature is getting to hot and turning the power off or back on accordingly. This is cool technology but I was wanting to do it without having to buy a whole new set up. With some research I found something called a thermistor. I was wondering if someone here could help me integrate this into my RDA. Essentially an RDA is a device that shorts a positive and negative post with a coil that the user builds. The coil heats up the saturated wick inside it and makes vapor. The way I understand it if you were to wire this thermistor in parallel with the coil when the coil got too hot the thermistor would "sense" that and the current would travel through that instead. The big problem I'm running into is the coils we are building are between .2Ω and 1.5Ω and I can't seem to find a thermistor that would work with any of these and be able to withstand the 300 degrees Celsius. Any help is greatly appreciated.
  2. poor mystic

    poor mystic

    Apr 8, 2011
    :) Hi Ghost
    Are you yet lurking in some machine?
    Welcome to the forum.

    Thermistors are used to sense temperature, and I believe that high temperature thermistors are available.
    However they cannot be simply wired across your heating coil and left to short out the supply when things get too hot. Is that what you'd had in mind?

    Usually, the thermistor is supplied with a very stable voltage, which drives a current through the device. This current is temperature dependent; it rises and falls as thermistor temperature falls and rises, usually, I think. So the resistance of the thermistor changes, and that's useful to engineers wanting to make measurements.
    To use the thermistor in your circuit you would need to build the temperature sensing circuit, and another circuit to drive some kind of switch (could be a relay or a transistor) to control heating.

    I think the nickel heating wire is probably used in exactly the same way in your existing device, so my guess is that you'd achieve very little.
    davenn likes this.
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