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Touching a circuit makes it work better?!

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srobertjames

New Member
I find that quite often putting my fingers near or on a circuit makes it work better. I thought that this was my imagination until I read about it somewhere else... How does that work? I understand that the body has capicitance, but, why does bringing a capacitor near a circuit make it less noisy and more stable?
 

EN0

Member
First it depends on what circuit; it won't work for every kind of circuit you come across. Second, your body does just that; induces capacitance on a circuit to some extent. Remember that caps restrict AC which will then mitigate any noise near an amplifier (such as a class-A transistor amp).

Austin
 

Sceadwian

Banned
Depends completely on the circuit in question. In the case of some simple radios it's simply the fact that a human being makes a decent antenna at modest frequencies.
 
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srobertjames

New Member
So, how can I add that type of capacitance without standing there? Through in some 100pf caps to GND at random places? Doesn't sound right... but, can I artificially duplicate the same cleaning effect?
 

EN0

Member
So, how can I add that type of capacitance without standing there? Through in some 100pf caps to GND at random places? Doesn't sound right... but, can I artificially duplicate the same cleaning effect?

Yes, you most certainly can. Typically, you can just add a capacitor on the input to ground of a circuit and also on the output to ground for good filtering. The capacitance range can vary, but you might try something like
1µF to begin with.

Austin
 

Sceadwian

Banned
I'm not sure how you can say that ElectroNerdy, we don't even have the foggiest clue what circuit he's talking about... You're guessing at best.
 

colin55

Well-Known Member
You have entirely omitted the fact that your body has resistance.
We used to fix TV's with our fingers.
Collapsed vertical could be found by trying your fingers across the high value resistors until the raster jumped up and sound problems (open capacitors) could be found by feeling across each capacitor.
 

Sceadwian

Banned
Those must have been some high value resistor colin, skin resistance is anywhere from a couple meg to a few k depending on the person and how damp the skin is.
 
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