Thermal control

Discussion in 'The Projects Forum' started by Friendlyguy, Dec 20, 2013.

  1. Friendlyguy

    Thread Starter New Member

    Dec 20, 2013
    First I should say I'm new to electronics and have very little experience. that said, I need help with a thermostat I'm making for a mini electric heater. I want to use a thermistor so I have the advantage of variable control of current but know little about them or how to size them...any help would be great!
    3 watt heater @29 volts from a 35 va ac xfmr running at under two amps.
    At this point I'm using a bi metal thermal device and short cycling.
  2. MikeML

    AAC Fanatic!

    Oct 2, 2009
    A thermistor is just a temperature sensor; it will not control your heater by itself. Starting from just a thermistor, you will effectively be building an electronic thermostat, likely with a relay or SSR at its output to actually switch the heater. Is that what you were thinking of doing?
  3. #12


    Nov 30, 2010
    Short cycling: move the bimetal farther away or add mass to it to slow it down.
    As MileML said, there is no such thing as a thermistor that will do this job, however, I have a thermistor circuit that will, with a bit of modification. Adding variable current control is a whole 'nuther matter.
  4. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    How are you getting your 29V (AC? DC?) from the 35VAC tranny?
    How do you want current to vary as a function of temperature?
  5. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    "typically" with heaters you just keep turning them on and off to maintain a set temperature instead of trying to vary the current.