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how to read the lugs of a pot?

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  • how to read the lugs of a pot?

    If you read from the top (shaft up) is lug #1 on the left? I cant find a standard?

  • #2
    I've never thought of pots as having #1, 2 and 3 terminals. The terminals are called counterclockwise end, clockwise end and wiper.
    "Enzo, I see that you replied parasitic oscillations. Is that a hypothesis? Or is that your amazing metal band I should check out?"

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    • #3
      Most schematic programs have this need to give numbers to the terminals on pots, resistors, capacitors, transistors and just about any other component you can name. Even a turret used as a test point gets a pin number of 1. This is necessary so the program can generate a "netlist" that will be used to layout a printed circuit board. Great care must be used when generating symbol and footprint libraries or things won't be connected correctly. A common mistake goes like this: A resistor has two "pins", 1 and 2. An EE fresh out of college can't find the symbol for a pot so he modifies the resistor symbol by adding the wiper and calls it pin 3. He hands the schematic off the a drafter for PCB layout. That person finds in a Bourns data book that terminals are numbered 1, 2, 3 so he uses that for the footprint in the PCB layout. Trouble is, Bourns calls the wiper pin #2. When the circuit boards come back, the pot isn't connected right... Ha Ha. The same thing happends with transistors. Pin 1: Emitter, Pin 2: Base, Pin 3: Collector. Makes perfect sense doesn't it ???
      WARNING! Musical Instrument amplifiers contain lethal voltages and can retain them even when unplugged. Refer service to qualified personnel.
      REMEMBER: Everybody knows that smokin' ain't allowed in school !

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      • #4
        What they said. There is no 1-2-3 on a pot. The numbers are only there for the convenience of whoever drew the schematic.

        The lesson is you should just learn what the terminals do - it isn't cosmic. Then when you read the schematic for something, you see the wiper rather than terminal 2.

        Likewise, I don;t like the terms left and right terminals. (middle is still OK to me) Left and right how? Legs up? Legs down? from the shaft side? from the rear?
        Education is what you're left with after you have forgotten what you have learned.

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        • #5
          Originally posted by loudthud View Post
          A common mistake goes like this...
          When the circuit boards come back, the pot isn't connected right... Ha Ha.
          It's happened to us all I just did the schematic capture for a large board that had a couple of right-angled USB connectors on it. Partway through, we decided we had to change them to vertical mounting ones. I just changed the part codes and sent the revised netlist off to our layout guy, not realising that the vertical ones also had a different pinout, so I should also have swapped those 1, 2, 3 and 4s around in some way. The first I realised was when plugging in a USB mouse shorted out the power supply.

          On the bright side, it was only one of a bunch of mistakes on that board, so it's going to need redone anyway.
          "Enzo, I see that you replied parasitic oscillations. Is that a hypothesis? Or is that your amazing metal band I should check out?"

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          • #6
            Originally posted by Enzo View Post
            What they said. There is no 1-2-3 on a pot. The numbers are only there for the convenience of whoever drew the schematic.

            The lesson is you should just learn what the terminals do - it isn't cosmic. Then when you read the schematic for something, you see the wiper rather than terminal 2.

            Likewise, I don;t like the terms left and right terminals. (middle is still OK to me) Left and right how? Legs up? Legs down? from the shaft side? from the rear?

            I agree exactly. When I draw a schematic for MY use I number the pots and a few other things to make assembly easier. I like multi can caps and i number those lugs 1 to 5 or 6, it works for me.

            But enzo is rigth many of these things have no real standardized numbering system.
            DIY Links

            Tolex Tutorial
            http://www.guitarkitbuilder.com/cont...lifier-cabinet

            Chassis:
            http://www.guitarkitbuilder.com/cont...lifier-chassis

            Turret board:
            http://www.guitarkitbuilder.com/cont...d-construction

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