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ac or dc or does it even matter Answered

I just saw a video on the web about a heater made out of a coffee can and some other odds and ends. My question is, its a 12v dc contraption. Can I use 12v ac instead ( like splice a 12v plug for a keyboard or something ) or will it not work? I can be more detailed if needed but i didnt want to post where or what the video was exactly since Im not sure Im allowed.


you can use AC for the coils but you'll need a ac to dc converter for the fan my advice, play it safe, just go buy one from the store

Im so poor I cant afford to pay attention, building it is really the only option. Plus, I just want to make something.

the diode you would want could be salvaged from an old auto alt. just look for the type with internal regulator (allmost all of them today )GM had used internal for 30 years.mounted to the inside back housing they look like little metal flower pots. a ohm meter will show polarity .or... a jumper wire to "short out " a part of the nichrome element would let the heater run on a lower input also lowering the output of heat. one point if it was made for 120vac and convert it to 12v it will take 10x the amps to run.

the device they show is a severe fire risk. if the fan stops it'll heat up and get hot enough to melt isolation of wires etc you need thermal sensor (best - electromechanical thermostat from a boiler) to shut down the heat if it heats too much the heat wire can be connected to mains power. just use wire with 100 X (110 V) or 400 X (240 V) more resistance to get the same power if you run it on ac do it in full metal enclosure connected to earth and protect with 30 mA or lower rcd. this way youll be safe if a wire touches it from inside as high current 12 V supply you cn use a computer power supply. get some blown ones from a computer repair center for free. in most the problem is just capacitors that can be replaced easily. you can get 200 - 300 W out of them (at 60 % load which leaves a safe margin even for bad supply) for heat fan below 150 - 200 W i'd use a computer cpu cooler with something that heats pressed hard under it. maybe a very thin iron plate welded to 2 conductors. this is safer (no exposed red hot wire) but still requires thermal sensor protection


9 years ago

Aight, got a 1350 watt heater i picked up at a local flea market for 7 bucks, I want to reduce the power usage but still get decent heat. What are my options here?

you can connect a diode (of appropriate current and voltage) in series with the heating element to 1/2 its power

Thats sort of beyond me, although if you told me what i was looking for (the diode) Im sure I could read up on how to implement it. I did a google search on it but only found specific heaters and not really any general information.

you need simple diode in us (110 volt) forward current 15 A reverse voltage 200 V in 240 volt countries forward current 7.5 A reverse voltage 400 V diode with better parameters is better

. If there is more than one heating element, disconnect one (or more).

basic heating elements dont mind ac / dc electronics mind - they need dc only i think its ok to link to the video the power supply you use should be of sufficient current too - otherwise you may overload and damage / burn it

. Yep. Heating elements couldn't care less whether they receive AC or DC. AC is usually measured using RMS ( root mean square ), so 12VAC has the same "heating value" as 12VDC.
. You can buy (or salvage) a 12VAC fan.
. I've never seen a wall wart with enough capacity to drive much of a heater.
. All in all, 12V (DC or AC) is probably not the best choice for space heating applications - too much current is required.

how much power would you suggest then? Im following another ible on making a dc power supply out of an old pc ps i have here ( 250w max 20.3v i think if I combine all the rails) would that be enough?

. It depends on how much heat you want. A 250W heater will put out roughly the same amount of heat as 2½ 100W incandescent lamps.

I only need enough heat to warm, oh, 2 office cubicles maybe. Perhaps less. My work bench is in my basement, its crowded down there, uninsulated and only maybe 20% warmer than the outside temp. Maybe i could rig a UPS for power, I dont know.

get some packaging materials and aluminium foil (for fire proofing) and insulate for the space heater - you may want to employ the lightbulbs to work and thats all