Introduction: Variable Resistor

Picture of Variable Resistor

A variable resistor that is practicle for less than 100 ohms with +/- 1 ohm of accuracy.

Step 1:

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It's pretty simple, break off the .5 lead. The length shown initially provided about 8 ohms. Anyways after you've chosen a length, take a knife and scrap away the .5 lead for awhile. I think mine was about .2 or .3. Click the pencil like 1 or 2 more times, (so the lead is still strong) and coil your wire around it. I used about 3 coils. Then do it again, and put the coils on either side of the lead. Solder both joints and test your ohms.

Step 2: Adjustments

Picture of Adjustments

Slide the contacts till you get in the ballpark of what you want. If you require more accurate ohms, slide the leads till the resistor shows fewer ohms than you want. Then scrape it the rest of the way.

This lil guy is exactly between 0.9 and 1.0 ohms.

Step 3: Seal It Up

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Then seal with hot glue and your done!

Comments

esromneb (author)2006-11-02

I am sorry if you feel like I wasted the glue. If you look you can see I cut it down to size. Another option for this stage might be epoxy.

pyrorower (author)esromneb2009-12-14

If anything you could just use a more precise application of the glue or use electrical tape. It's no big deal though...

The Stumph (author)2008-06-19

are you taken the lead out of a woodend #2 pencil ?Or what? im new at this

esromneb (author)The Stumph2008-06-23

I used "mechanical lead" the kind that goes in plastic pencils. You can find it at any rite aid or stores where they sell school stuff.

This is a picture of what the packages look like:

http://www.usschoolsupply.com/category/Mechanical_Lead_Refill

TheMadScientist (author)esromneb2008-08-27

rite aid, for me, means you live in california, because that's the only place i've seen those. up here, say a walgreens, or walmart, or a K-mart (wisconsin). for all practical purposes, they're the same thing.

esromneb (author)TheMadScientist2008-08-27

Very good observation I wonder if 'The Stumph' figured it out? Another comment about this project: in hindsight these resistors only work for low/medium current applications. I haven't tested this out, but if they get really warm to hot they might change values. A little warm should be just fine.

drewdoog (author)2008-02-26

very neat tutorial

lemonie (author)2007-01-16

I used to make graphite light-bulbs, they burned through pretty quickly, but fun while they lasted. You can scrape pencil-graphite quite thin (with a knife) without it breaking.

komp001 (author)2006-12-14

you can also make hi-ohm-resistors by simply drawing a thick line on paper (with a graphite pencil). I made a resistor with a few hundred k-ohms. use paperclips as terminals. capacitors can be made of two sheets of aluminium-coated paper (chewing gum is wrapped with it) roll up very tight.

esromneb (author)komp0012006-12-14

Alright, then I guess I will have to demonstrate both. Any ideas on how to seal the paper resistor? I guess I should also post a leyden jar ;)

komp001 (author)esromneb2006-12-15

take some candle wax, or hairspray or nail polish or paint

esromneb (author)2006-07-05

I tried winding the resistor out of the wire shown in the picture, I couldn't get any ohms out of any lengh I tried...

ElFantastic0 (author)2006-06-28

i've done this for makeshift resistors too you have to watch out, the leads use a binder which will carbonize (read: burns up) if the resistor gets too hot then your values change but most resistors change in value after you burn them up. you can also use slip-plate (graphite paint) to make resistors. or you can use water and CuSo4. i prefer to just wind them out of wire.

nitroburn (author)2006-05-10

Hot Glue + Hot Resistor = remelted glue all on the inside of your projects and a possible fire hazard. Use something NON-FLAMMABLE on the outside.

godsdog (author)2006-05-10

That's pretty sweet. I bet you can pump the watts through these and with precision as accurate as your fluke, you can't beat the price. Where did you source the lead?

andorphin (author)godsdog2006-05-10

I think he is using pencil graphite.

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