Saturday, May 20, 2006

resist, V for victory.

Can you 'create' your own resistors? Sure thing, and not difficult. Here is how to do it: Draw a line on a piece of paper with a soft pencil, HB or 2HB will do fine. Make the line thick and about 2 inches (5cm) long. With your multimeter, measure the ohm's value of this line by putting a probe on each side of the line, make sure the probes are touching the carbon from the pencil. The value would probably be around the 800K to 1.5M depending on your thickness of the line and what type of pencil lead is used. If you double the line the resistance will drop considerably, if you erase some of it (length-wise obviously!) the resistance will increase. You can also use carbon with silicon glue and when it dries measure the resistance, or gypsum with carbon mixed, etc. The reason for mentioning these homebrew resistors is that this method was used in World War II to fix equipment when no spare parts were available. My father, who was with the Dutch resistance during WWII, at that time made repairs like this on many occasion.



k2h said...

that is fascinating, but if you have a meter to measure your creation, I find it hard to believe you don't have at least SOME junk laying around to salvage from.

so...... how do you hook to your carbon paper drawing? solder won't do it. oh wait.. let me guess. I GLUE my wire to the resistor. thats getting a little far fetched.

Dan said...

glue would probaly work, but my question is what kinda current density can you put through it... a lot of discrete resistors are carbon, but not a lot of flamable stuff in close proximity. Now, we just drop the line through an nwell when we need a resistor (or maybe draw a long poly line), but nwells vary less with temperature.