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120VAC 40watt heater

Discussion in 'Electronic Design' started by Jamie M, Feb 9, 2013.

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  1. Jamie M

    Jamie M Guest


    I have an application (home brewing Kombucha) that requires a small
    heater to increase the temperature for the fermentation to work
    properly. Does anyone have a link to a cheap readily available
    120VAC 40watt heater that can work in ambient heating the air with no
    fan? I am using a 40watt incandescent lightbulb right now, but it
    isn't ideal as the Kombucha is supposed to ferment with low light, and
    tinfoil on the bulb causes too much overheating.

  2. Jasen Betts

    Jasen Betts Guest

    a heating pad. try a brewing, hardware, or garden shop.
  3. Pimpom

    Pimpom Guest

    Some ideas off the top of my head -
    Use a 25W incandescent lamp if 40W with the tinfoil shield
    is too much.
    Put a 1-amp diode in series with the lamp to reduce power by
    You could also coat the bulb with matt black spray paint
    instead of tinfoil..
    Use a wirewound resistor(s) in place of the lamp.
  4. Guest

    Some pet stores will have ceramic heating elements that are designed
    to screw into a normal lamp socket, for keeping pets warm. Example:

    Omega sells a number of heaters that might do what you want. This is
    one example
    but there are many others. (You'll have to order it from them; they
    don't have stores.)

    For either of the above heaters, if you buy a standard 120 V "dimmer
    switch" with a knob - designed to control incandescent lamps - it will
    also work to adjust the output of the heater. Mount it in an electrical
    box with a standard wall outlet and a cord.

    A coffee mug warmer seems to only be about 17 or 18 watts:

    Standard disclaimers apply; I don't get money or other consideration
    from any companies mentioned.

    Matt Roberds
  5. Syd Rumpo

    Syd Rumpo Guest

    Connect two or more lightbulbs in series so they run at half (or third
    etc) their rated voltage and glow red rather than 'white'. How many?
    Don't know, filament resistance is lower at lower temperatures, so try
    it and measure the current to find the wattage.

    Lightbulbs operated at a lower than rated voltage will last more or less
    for ever, and the 40W is spread out among two or more.

    And what's more, I've learned a new word.


  6. They call them "cartridge" style. Cooler surface than "immersion"
    style. Because of the greater surface area. I'm sure that other
    solutions are even better, but also more costly. Putting this type
    *inside* a block of say aluminum with a food grade polish or such, would
    spread the heat further and make it even more efficient in your process

    You can also (you actually have to) use duty cycle (PWM) to make a higher
    wattage unit operate at a lower temperature ( a simple light dimmer
    switch will work on a DC heater element).

    one example with a 30W version

  7. Put a dimmer switch in front of the lamp. Turn the damned light down.

    Get a nice big spotlight bulb and use the dimmer to regulate the
    surface temp of the bulb. Immerse. Voila.
  8. I've used a 'heater tape'* and Variac for that type of thing.
    Heater tape might be expensive... but maybe something at the hardware
    store to stop outdoor pipes from freezing.

    George H.
    * a resitive element in a woven high temperature fabric, with 1/2 of
    an AC plug on each end... you clip the plug together after wrapping
    the tape around something.
  9. Jamie M

    Jamie M Guest


    I think I will go with a lightbulb painted with high temperature exhaust
    pipe paint and bake it to keep the paint fumes down. That is similar
    to the light socket ceramic elements that Matt mentioned which would be
    perfect. Also I am using a cheap digital thermostat from ebay:

    Thanks guys for the tips!

  10. Jamie M

    Jamie M Guest

    Kombucha? :) It is a pretty nice drink, and inexpensive to make, just
    need the scoby to get started, if anyone wants one mailed out let me

  11. Pimpom

    Pimpom Guest

    Oops, that's correct. But it will still reduce the heat
    output substantially, perhaps enough for the OP's purpose.
  12. Jamie M

    Jamie M Guest

    Yep that's probably a good idea, after one coat of black paint the
    lightbulbs are still giving off light, and I don't trust the paint
    to not give off fumes.

  13. Jamie M

    Jamie M Guest


    One thing I was wondering about, is how the yeast get their nutrients,
    normally when making beer, you will need to add nutrients with the
    yeast, like vitamins and minerals, (or buy something like "turbo yeast"
    with the nutrients already added). But with Kombucha, its just black
    tea and refined white sugar, so I'm a bit curious if adding nutrients
    would give different results.

  14. Oppie

    Oppie Guest

  15. josephkk

    josephkk Guest

    Lookup heat tape.

  16. Guest

    Just be sure you are not getting heat tape designed to keep things
    from freezing. Some of them have high resistance at temperatures a
    bit above freezing.

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