Is there a difference between a trim pot and a regular potentiometer?  Whats a trimpot?

A trimpot is just a miniature pot (usually adjusted by a screwdriver) for where you only want to adjust it rarely. There is no electronic difference.

yes.  A trimpot is a small PCB mounted pot that is only adjustable by using a screwdriver (or "tweaker")  It is designed to be set and left.  Usually put in where you need to fine tune a filter or an oscillator etc.  It has small voltage/current ratings compared to a normal pot.

Thanks for clearin that up guys.

I use them on my perfs because they're cheaper than pots.

QuoteI use them on my perfs because they're cheaper than pots.

I hear you. I do this too when I need to wire up a 3 band tone control and I don't have the pots onhand.

I bought some trimmers from SB a while back but they have 3 legs on them. When using the first and second leg, they never fit in the board spacing that I'm using. Am I buying the wrong ones (I think the ones I bought were Kemet or Bournes) or is it just a coincidence they don't fit into my current projects?

If you're just using it as a variable resistor (i.e. only two connections) you can bend the third lead back or just cut it off. (Make sure you don't cut off the wiper lead by mistake!)

The distinction between pot and trimpot can become fuzzy sometimes.

There are trimpots that are clearly only adjustable by means of small slot-head adjusting devices like screwdrivers or those plastic TV adjustment tools you can get (nice to be poking nonconductive plastic in there when some of the things you can touch can kill you).

Then there are trimpots with thumbwheels or manipulable shafts that are intended for possibly more frequent adjustment.  These can be horizontal or vertical.

In some cases, the manipulable shaft is long enough that manufacturers have either stuck a knob on the end of it or simply made it tweakable from the outside without a knob.  For example, the Fulltone Distortion Pro has a number of trimpots with longer shafts accessible from the outside for custom tweaking the tone.  Neither the Z-Vex Seek-Wah or Ooh-Wah would likely have room to fit as many controls in a 1590B as they do unless they used long-shaft trimpots instead of pots.  Part of how Rocktek and Rogue effects can be so cheap (and maybe Soundtank and Danelectro, but I haven't looked at them closely enough) is by using long-shaft trimpots with knobs.

Though you can use trimpots as if they were pots, it bears noting that many trimpots are not designed around the idea of constant use/adjustment and so may not hold up all that well if one attempts to do so.  On the other hand, you can always buy just about anything in better and lesser quality and I imagine some manufacturers who plan around needing externally accessible trimpots for their product make a point of buying the best they can for their anticipated pricepoint.

For the DIY-er, though, one of the most essential elements of the word "trimpot" is that when you see it on a schematic, it can mean:
a) one less knob to buy or hole to drill for that project
b) something that can eventually become mis-set and needs vigilance (or a gob of adhesive)
c) something that may well be adaptable to a panel-mount control but doesn't need to be
d) something that may well be replaceable by a fixed component once an ideal setting is identified

Quote from: 1wahfreakI bought some trimmers from SB a while back but they have 3 legs on them. When using the first and second leg, they never fit in the board spacing that I'm using. Am I buying the wrong ones ?

....this is common. there seems to be a "standard" trimpot footprint that doesn't fit 'standard' hole spacing.

To me, aside from size and how you adjust them, the main difference between the two is how easily they can be adjusted. Pots are usually an externally mounted component that are meant to be adjusted by the user. Trimpots are generally something that get adjusted once while tuning a circuit, and then you don't mess with it anymore.

The other difference is that pots usually can handle more current and higher voltages than a little trimpot can.

[quote="Paul Perry (Frostwave....this is common. there seems to be a "standard" trimpot footprint that doesn't fit 'standard' hole spacing.[/quote]

There are essentially 2 standard trimpot footprints, just in case you want to know...

The first is with all three pins in line, wiper in the middle, each 100 mils (2.54 mm) from the next.

The second is with the three pins making a triangle, with the wiper (middle) pin making the apex.  The base of the triangle is 200 mils wide (or 5.08 mm; this means that pins 1 and 3 are this far from eachother).  From the center of the base, the wiper pin is located 100 mils perpendicular... this footprint is similar to the first one, except the middle pin is just moved out 100 mils... okay... diagram...

O = pin

First:  O   O   O        Second:          O
O      O

Well forget that, the diagram failed miserably... you get the idea I'm sure.