DIY Power Resistor: 5 Steps

First , hello , I am glad to be here on instructables.com

This is my first instructable.

This is one simple way to create power resistor at home.
I needed 0,33 ohm resistor with some larger wattage so I decide to create one, instead of buying one. I always say, creating is much more fun then buying.

Step 1: Video

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I created small video with these steps

Step 2: Coating Mass

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You will need jointing filler to create mass for coating, to protect resistor wire from oxidation, and to provide heat transfer from wire to environment.

Step 3: Prepare Wires

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You need one old high wattage resistor ( I had one 10W 100 ohm ) to use wire from it.
You will have to destroy it, and take high resisting wire of desired length-resistance. You also need some copper wire as connectors.

Step 4: Prepare Mold

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Also you will need small piece of tin to create mold.

Step 5: See Results

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This is semi finished, and finished resistor after drying.

This is very interesting! What did you make using this homemade resistor?

Thanks, I am creating variable power supply so I needed it on output stage.

ha, that's exactly how I landed here. I need 12x 0.05 ohms at 100W.

Yes, it is possible to create any resistance and any power.If one does not have precise ohm meter it is possible to measure , let say 2 ohms wire, and calculate with the length of 2 ohm wire desired resistance. Also combining wires in parallel we can get desired resistance and higher power.

Thanks for this one. Actually, since I don't have those old resistors/resistor wire I'll try the pencil way. It's needed for a battery tester with something around 10-20 Ohms.

you're welcome, you can try with pencil graphite rod, you just have to be careful since graphite rod is quite fragile.

I have just tried it out. 1cm of graphite had around 10 Ohms. I connected it to my power supply with 5 Volt. And that made the resistance drop constantly so the 500 mA increased and soon crossed 2 A with nice little smoke clouds. It looks like I need some resistor wire which does not change that much when heated.

Sorry for this :-) I did not have time to try this with graphite rod.You can check this web page <a href="http://www.troelsgravesen.dk/graphite.htm" rel="nofollow">http://www.troelsgravesen.dk/graphite.htm </a> where this guy noted that these graphite rods are actually NTC resistor, so that why you probable got this result, I am not sure.Anyway, for resistor wire you can try heating elements from some old hairdryer, old electric furnace...etc. but I think the best result is when tae wire from some old resistor.

No worries. I simply heated it until it blew off. BANG!I'll probably go for my distributor. I need three 17 Watt resistors at 12 Ohms. Each at about 1€. My broken hairdryer is already on the dump :-/

Might one also use a piece of graphite rod of the kind used in mechanical pencils? Anyone know the resistance of a 0.5 mm HB pencil lead, per centimeter?

I just tried a measurement. 1 cm of 0.5mm HB rod had about 50 ohms, so it seems that one would need a very short piece, or a much wider rod, or a thin layer between 2 conductors.

I did not try this, but the principle would be almost the same, except that we would have different way of connecting of resisting element to the connecting copper wire.Anyway, I don't if it is allowed, but I will give you link to a page where one guy tested pencil graphite on electrical resistance:http://www.troelsgravesen.dk/graphite.htm

When there are no electronics suppliers nearby, this is very handy to know. Thanks.

You're welcome, and you are right, in my town there is no electronics shop, I wold have to drive 30-40 km ( and spend 10 euros ) just to by some of these.But I also like to make(and destroy :-) ) things , so this was both useful and fun to me.I hope this idea will be useful someone sometimes.

I admire your determination and problem solving abilities in creating this custom power resistor, well done, it looks very profesional.

Thank you, I needed few of these resistors 0,33 and 0,1 ohm and thought to buy them, but then I asked myself "can I make them?" and started to think about that and this is the result.