Let's Make Robots!

Hacking a Resistor to 100.00% accuracy

Tunes a resistor to the value that "You" want

Which 10KΩ Resistor would you choose :-

Well to tell the truth its the same one ..... just the one below has been Tweaked !

The Trick is to file the body of the resistor (beneath the outer shell _ into the carbon/metal) using a needle file (or cosmetic/nail file).

Most common resistors are made from Carbon/Metal film or metal oxide, by file_ing the Carbon/Metal away the resistance can be tuned to whatever value you want.

 

Minimal damage....

Basic rule :- The resistance increases with file_ing.

Resistance = Length of resistor / cross section Area x (substance conductivity)

 

The Bare facts ........ the shell removed reveals how the manufactures also mill/file the surface to trim (did i dig out an industrial hush-hush)

Caution :-

Resister values are are quoted @20°C ..... and fluctuations of the resistance can occur due to external environment.

If you make excessive deep cuts then the power rating of the resistor will also suffer.....

Do not adjust the Resistor on live equipment....... (risk of shock)

 

Uses :-

How many times have you hacked a servo to continuous servo and added the two resistors to replace the potentiometer...... only to find that when you send a center (1500) command to the servo ....it creeps....creeps...creeps albeit slowly but it nerves the heck out of you.... and you have to put software jigs to stop the motor from creeping......well look no further just get the file out and tune away........(leaving your code perfect)

Or.... your trim pot is just to coarse to balance a circuit ..... place a cheaper resistor in and file it too suit......

....enjoy ...... comments and likes are appreciated........... other ideas/uses even more soo...

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Thanks for all the good support ......i was staggered by the thumbs up......

Follow Up :- after one week the resister reads the exact same value i trimmed  it too :-)   without even sealing the wound with lacquer ....

Another feather in the cap for LMR.
...if you're one of the kids who suggested this to them ;-)

I tipped them off.

Seemed like a perfect thing to share there.  I hope you don't mind :)

I am glad others can profit from such a simple tip. I stand tall with the really good comments that were passed there too..... :o)

It also annoyed a few 'so called' engineers too......

Nice trick Gareth. Unfortunately it won't completely solve the continuous servo problem because the servo's circuitry is sensitive to temperature.

But..but.... both resitors will change at same rate (i assume original "pot" forms part of a bridge circuit) so i calculate temparature fluctuations will have no effect.......

...... prove me wrong and i will eat your poster "live" in Germany.......

Yes the resistors will change value proportionally. Same as they do if they are not perfectly adjusted. As Maus points of it is the other circuitry that is the problem. While resistors tend to increase in resistance with temperature, transistors tend to conduct better. Since a rise in temperature causes most materials to expand, capacitors will also change value slightly. Another problem is that the components do not change in temperature uniformly as some components get hotter than others. In some cases a low power component may heat up as a result of close proximity to a high power component. Do you want soy or tomato sauce with that banner?