potentiometer question

[felix jones]

hello. i'm new to effects building, placing my first orders now, and have a quick question.

for some of the effects i'm gonna build in this first batch, the bill of materials says to use something like a '10k trim pot'. what i'm wondering is...what is that? it seems from the schematics that those are pots that won't be externally adjustable, just set and forget inside the box. if so, any advice on good ones to get? if i'm wrong, what am i not understanding?

also, what about dual gang pots? i'm guessing to adjust two values at once? if so, what's an example of when this would be needed?

thanks for taking the time to read and help.

can't wait to actually get building.


alex

[Thomas P.]

Your right, a trimmer is a pot soldered onto the board and it is normally adjusted with a screwdriver. The only important thing for you is to know the grid of the trimmer used in the layout and buy one with the same.

A dual-gang pot is actually a stereo-pot.

Regards,
tomboy

[Mike Burgundy]

a trimpot is a set-and-forget type potentiometer, often used for things like bias settings. They don't have shafts usually, and mount directly to the pcb. Should look something like this:

or

Dual gang pots are basically two pots mounted on the same shaft. If you turn the shaft both potentiometers change in value simultaneously. The Univibe uses one in it's oscillator, f'rinstance.
hih

[felix jones]

The only important thing for you is to know the grid of the trimmer used in the layout and buy one with the same.

how do i know that? do i just have to get the right shape, or do i have to measure what size it needs to be on a printout of the circuit board?

speaking of which...anybody got suggestions for what program is good for printing pcb layouts from .gif files? i just tried with irfanview, but the size is way off.

again, thanks for any help anyone can provide.


alex

[Mike Burgundy]

if you haven't designed the PCB you'll have to measure. There's all kinds of different shapes and sizes, which might cause trouble with fitting it to the board. I kinow Farnell has datasheets up, Mouser probably does as well.