DIY Power Resistor

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

I created small video with these steps

Step 2: Coating Mass

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

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

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

Step 5: See Results

This is semi finished, and finished resistor after drying.

Comments

[awe070707]

hi, i need resistor 40ohm 360w for my project. can i use 40ohm 10w resistor and make new create mass for coating?. and any calculation size coating for 360w resistor?
TQ.

[Billyatams]

The mass keeps the heat inside. It is likely that the wire in your 10W resistor will fail if you supply sufficient current to produce 360 watts of power. I would suggest wrapping nichrome or steel wire on a high temperature insulating material and placing the device inside of a small cage. The cage should allow easy air passage to allow heat dissipation to the atmosphere. I’m going to give this a try this week for a 5kW resistor. Should be fun!

[stanleyford]

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?

[stanleyford]

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.

[kobyx]

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

[kumudugayashan]

Awesome, I'm trying this

[aswinsharif1412]

As commented by other reader.."when there are no electronic suppliers nearby.." ..yes we sometimes need to reinvent the wheel. Might worth to try to use motorbike brake cable, sunk into mortar for heat dissipation. Somebody in my country use that for inrush prevention (soft starter) for running power tool

[seamster]

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

[kobyx]

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

[MakinThings]

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

[kobyx]

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.

[acheide]

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

[kobyx]

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.

[BeachsideHank]

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

[kobyx]

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.