Capacitor trimmer or use a POT

metron9

My son plays guitar and wants me to do a mod on one of them. The mod calls for a 4 way switch to switch between 4 different capacitors rangeing from 33pf to 330pf.

Could I use two 10-180pf capacitor trimpots in parallel with 2 knobs to get a 20 to 360 pf range? one knob from 20 to 190 then the other would increase another 160 (20 to 180)

or

Could I use a 450pf cap and a Potentiometer to vary the amount of leakage from the cap to create a much more variable capacitor range?

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Think outside the BOX!

LoopyByteloose

I think you would have to ask yourself which device [noparse][[/noparse]the variable capacitor or the variable resistor] will work better on stage and be more durable.
Seems to me that the 'capacitor trimpots' cannnot attach to knobs. So one might have to fool with a screwdriver to adjust them.

I suspect the original design considered all this and decided that the 4-way switch was more reliable. If you want more selection, a 10-way or 16-way switch [noparse][[/noparse]the thumb wheel variety] might be easier during actual performance.

You would have to run some trials to find the right design for you.

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"If you want more fiber, eat the package.· Not enough?· Eat the manual."········

···················· Tropical regards,····· G. Herzog [noparse][[/noparse]·黃鶴 ]·in Taiwan

Post Edited (Kramer) : 7/6/2006 1:57:41 PM GMT

Bruce Bates

metron9 -

For the moment, I'm just going to refer to this device as a "black box". What were you hoping the output of the black box would be:

Pos 1· Pos 2· Pos 3· Pos 4

33 pf 133 pf 233 pf 330 pf

or some other set of values? Those above are just evenly spaced between your endpoints of 33 pf and 330 pf.

Regards.

Bruce Bates

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PJAllen

I think that dinky trim-pots trimmer caps are going to change value, they're very irritating that way, a real head-ache.

Post Edited (PJ Allen) : 7/6/2006 1:21:01 PM GMT

metron9

The original design has one flaw, it has a big pop or click when the caps are switched

That is why I am wondering if for example a WAW pedal could be used as a variable resistor to bleed power from a larger cap making a variable capacitor. I don't know how the bleed resistor would affect the rest of the circuit and I have not explored the math as to what values are necessary.

Thinking about that to get some very weird sounds (Outside the box here) one could one simply hook up a wire connected to your body as a variable capacitor? These things are running on 9V batterys so no danger of shocks.

Yes the dinky trimpots I looked at on digikey are about 6 bucks and dont have knobs however it looks like a sturdy brass or metal turning post that a knob could be attached.

A quote from another site

Somebody said...
The "peeling" effect can be demonstrated with a roll of plastic adhesive tape. Peel a few inches of tape off the roll and hold it near the circuit. The LED will show that the tape is strongly electrified. Now use the sensor to test the tape dispenser. You will discover that the roll of tape has an opposite polarity compared to the strip of tape. This illustrates that "static" electrification does not require friction, it only requires intimate large-area contact between dissimilar materials.

Perhaps one can make a capacitor from dissimilar materials and slide them over each other to create the capacitance needed for this specific range?

Additional thoughts brain notions far fetched unconventional thoughts? - Outside the box of course.....

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Think outside the BOX!

Post Edited (metron9) : 7/6/2006 1:24:04 PM GMT

PJAllen

body capacitance and weird sounds -- ever heard, or heard·of, a Theremin?· The thing about them was repeatability, but weird sounds for sure.· Maybe you're trying to make a Guitaremin.