Better Homemade Resistors

Homemade resistors that are better than the pencil lead carbon and low-ohmic wirewound resistors people normally make.

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For some time now I have been trying to make practical homemade resistors. While using pencil lead works fine it's near impossible to get high resistance values and the resistors made are bulky and fragile. Also on the internet are dozens of sets of instructions on how to make low-ohmic wirewound resistors with nichrome. Though all of these work they just aren't great. Size and durability are major issues as well as the fact that high resistance values are impossible to achieve. I want to change this and push the envelope of homemade components.

I currently do not know all the details of the project myself as due to the nature of the project it is very much about experimentation. When I do find a viable construction method I will definitely post the design features and capabilities. Until then if you have any suggestions let me know.

  • Metal oxide first attempt

    Spockopolis09/29/2014 at 23:05 0 comments

     I figured the easiest way to make a metal oxide resistor would be to fill a tube with iron oxide and put wire in the end. I did just this. A got a short length of 3mm OD glass tubing, placed a peice of 14AWG copper wire in one end, poured powdered iron oxide (made from steel wool) into it, and placed another wire in the other end. When I connected my meter I discovered an annoying fact. Iron Oxide (FeO2) is completely non-conductive. I think after that fail carbon composite is my best shot.

  • Carbon composite second attempt

    Spockopolis09/26/2014 at 22:04 0 comments

    To try to increase the strength of the resistors I replaced the clay with plaster. I mixed 5/8 of a teaspoon plaster of Paris with  1/8 of a teaspoon powdered graphite and 3/4 of a teaspoon water. I poured it into a narrow rectangular mould about 1/4 of an inch wide by 1 1/4 inches long and embedded leads. When I removed it from the mould in the morning there were two problems. Firstly it was actually likely weaker than the clay ones. Secondly and more importantly its resistance read infinite on my multimeter. Back to the drawing board I guess. 

  • Carbon Composite first attempt

    Spockopolis09/25/2014 at 11:33 1 comment

    My first attempt at carbon composite resistors was rather simple. I mixed powdered graphite (from pencil leads) with clay, formed it into cylinders and stuck wires in the ends. They showed resistance values well into the kilohm range. I got pretty excited but soon realized a problem. They were far too brittle. they would never have the strength to allow their leads to be bent. The cover picture shows one of these early prototypes with it's resistance being measured. Ways to increase their strength are currently in the works.

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kingcloude01 wrote 07/23/2018 at 13:10 point

Use Hot glue as the final coat. It makes the resistor more durable.

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Mike wrote 03/28/2018 at 05:25 point

How about making the one with graphite and clay, and coating it with polyurethane or epoxy?

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DontStalkME wrote 04/18/2017 at 23:07 point

For low value resistor: wire wound

For slightly higher value: pencil on paper

more: nichrome wire - but kind of defeats the purpose of making your own.

Try long(ish) pieces of wire separated by only a piece of tissue paper and soaked in oil. Or oil mixed with carbon.

You can try the rust and the carbon again, but try a higher surface area / more of it. More surface area is like resistor in parallel = more conductivity. Try mixing both rust and carbon 50/50. Soak or spray some paper with glue and spread over the paper. Lay metal foil in long parallel strips across the stuff and test.

You could try making a colloidal suspension of metal (see diy colloidal silver - but use copper or aluminum). Varying the concentration would vary resistance. If it works you could try mixing with oil and boiling off the water (water evaporates so it would not make a good ong-term use resistor. Never tried it;may just end up with metal film over oil.

Caveat: more surface area of conductors = more capacitance.

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mlatu wrote 02/08/2015 at 18:45 point

I thought about what to write since it sounds like a nice project but also like you are doing it a bit head over heels, so here is a website with physical properties of various materials:

good luck.

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