twelve volt microwave

Discussion in 'The Projects Forum' started by studiousscholar, Jul 15, 2008.

  1. studiousscholar

    Thread Starter New Member

    Jul 15, 2008
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    0
    I saw an article on the web several years ago describing how to convert an AC microwave to twelve volts. I have tried to find it but have been unable to. If any one has seen it and remembers where it is I would greatly appreciate if he would post it here. Failing that I would have to start from scratch. I don't think it would take much more than rewinding the primary of the transformer and a simple FET drive. The microwave I have in mind uses a simple dial timer. I would leave the timer and turntable on AC and have the output of the timer drive a relay for the DC. The advantage of this is to reduce the losses from an inverter. Even for a 600 watt microwave the loss through even an efficient inverter is not negligible. The microwave will actually use about 850 watts. The amperage (around 80) should be within the range of some readily available FETs.
     
  2. KMoffett

    AAC Fanatic!

    Dec 19, 2007
    2,577
    231
    If a 12vdc microwave is your end goal, not building a converter, here's one.
    http://www.thewavebox.com
    I was just thumbing through some back issues of "Nuts and Volts" and ran across it on page 11 of the August 2007 copy.

    Ken
     
  3. studiousscholar

    Thread Starter New Member

    Jul 15, 2008
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    0
    I don't mean to sound whiny but I am semi indigent. Most of my income for the next several months is already allotted to pay debts. I really live in my van. Hence the need to limit the wear and tear on the alternator, inverter and battery. I already have the microwave. I use it A LOT. Since the losses are not merely cumulative but multiplicative, this is more than just a cool project. I really need it. This big of a load is especially hard on the deep cycle battery which I have to have for lights etc. I just had to buy a new one. It was not cheap. It would still start the truck but I couldn't cook anything. Any improvement here would be a big improvement.
     
  4. Norfindel

    Active Member

    Mar 6, 2008
    235
    9
    I'm not sure if it would work at all, but instead of rewinding the microwave's transformer, it would be easier to use a 12v to (microwave input voltage) transformer. The bad news is that the transformer would need to be big to power the microwave, but at least you don't need to modify the microwave oven. On a second thought, shouldn't the losses be similar, either way you do it?

    What about cooking with gas? "Canned" gas should be cheaper than buying a new battery, or at least would mean you must pay less money more often.
     
  5. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Sorry about your financial situation. I hope that you can work that out, and that times improve.

    First, opening the chassis of the microwave means that you would have to use an RF "sniffer" on it when you closed it back up to ensure that there were no radiation leaks. High-power RF leaks will cause severe health problems for you, particularly since you are in such close quarters with the device.

    Secondly, the microwave was designed to work as efficiently as possible with the power supply that it was designed for. Attempting to modify the transformer, which was designed for operation at 120v 60Hz, to a high frequency boost inverter (or whatever it requires) would be virtually certain to have less efficient operation.

    Thirdly, the inverter that you already have is probably in the realm of 90% to 94% efficient.

    I can only suggest that without a good deal of engineering, attempting to improve upon your existing setup would require a lot of resources for a very minimal payback; perhaps a few percent improvement. Without adequate resources, the project could end disasterously - and you would be without a microwave.

    Cooking/heating with flammable gas or fluids in your vehicle, or storage of the same, is something that I strongly recommend against. One small mistake, and you could lose everything - including your life.

    If you commute to work or the like, consider using the waste heat of your engine to cook and reheat food. A few vegetables and a slab of fish wrapped up in some aluminum foil, and placed on a hot intake manifold for a half-hour makes for quite a tasty meal. Wrap it up beforehand, stick it on the intake, and drive. This also works well with Mexican-type food; a wet foil-wrapped burrito.
    This Google search will give you a lot of ideas for engine-cooked meals:
    http://www.google.com/search?hl=en&q=engine+cooking

    Something else you should consider is:
    http://www.google.com/search?hl=en&q=solar+reflector+oven
    to use solar heat. That way you won't use any energy at all. You could make a useable oven out of nothing more than some aluminum foil and some coat hangar wire, or for larger, some baking racks from a junked stove.
     
    Last edited: Jul 18, 2008
  6. Norfindel

    Active Member

    Mar 6, 2008
    235
    9
    Sorry, i thinked he said he was on a camper, my mistake.
    At least here, it's common for campers to come equipped with gas to cook. Of course, the gas can is outside the camper, and it would be wise to close the gas (on the outside) after use.

    Studiosscholar: Maybe if you live on a sunny place, you can try this: http://www.solarcooking.org
    I had seen that some people are using this to cook on Salta (Argentina), in a Discovery Channel program. Salta is very sunny and hot, however.
    Cannot think on anything else. Good luck, man.
     
    Last edited: Jul 18, 2008
  7. Gadget

    Distinguished Member

    Jan 10, 2006
    613
    0
    Im sorry, but I cant see the problem with using an inverter. I think efficiencies may be similar, as you are going to have to do something inefficient with the 12v to generate the HT and filiment volts anyway. And if it has a digital timer circuit as well. .. .....
    The other thing to remember is a 600 watt microwave probably consumes well over a thousand watts as well.... check the rear panel for consumption.
     
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