From schematics to perfboards

[Hemmel]

Hi guys. I thought I knew how to read a schematic, but when it comes to transferring to breadboard my connections are often wrong.
Now I want to try to solder stuff on a perfboard and boxing everything up, and I feel there are a few things I need get straight.

My biggest concern is with pots.
I figured convention is that with the shaft pointing towards me, lugs pointing down, the lugs are numbered 1 2 3. Or called CCW, CT and CW (I think).

Now if I look at these pots :



A : Ground to lug 1, arrow on lug 2 and top on lug 3. Right ?
B : This is where I'm a bit puzzled. My first thought was to short lugs 1 and 2 with whatever's on the right, and connect what's on the left to lug 3. But I saw a layout recently showing that I could connect left to lug 3 and right to lug 2, leaving lug 1 not connected.

What's the logic in this ? Is my first thought wrong for pot B ?

[nocentelli]

In example B (where the pot is used as a variable resistor instead of a potential divider as in example A), there is no functional difference between connecting lug 3 and lug 2 only, and connecting lug 3 and lug 2+1 shorted together:
Both arrangements give a variable resistance from zero ohms to the pot value between lugs 3 and 2. Here, lug 1 is conventionally tied to lug 2 as protection against the variable resistor going open circuit if the wiper (lug 2) breaks contact with the resistive wafer inside the pot. All of your other suppositions are correct.

I didn't manage to regularly hook up pots correctly until I grasped the way pots actually work. I find it best to think of them as TWO variable resistors, one between lug 1 and 2, and another between lug 2 and 3. The resistance between lug 1 and 2 increases as you turn the pot clockwise, from zero ohms-ish to the pot value; Simultaneously, the resistance between lugs 2 and 3 decreases from the pot value to zero. The rate of change is determined by the taper, linear means the change is even, and half-way/12 o'clock on a linear 100k pot gives 50k between lugs 1 and 2 and 50k between lug 2 and 3. Hope this helps.

[LucifersTrip]

yes, connecting 2 lugs together is a failsafe so the circuit won't be "open" if the pot dies.

regarding lug orientation, unfortunately, there is really no consistency in schematics. the vol pots are easy since you know which is grounded. with tone & other pots, ususally the worst case scenario is you wire in reverse and just have to flip 1 & 3.

[Hemmel]

(...) ususally the worst case scenario is you wire in reverse and just have to flip 1 & 3.

This is what happens to me 98% of the time. It was 100% a few months ago. I guess I'm learning