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Switch Types (3pdt, dpdt...)

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  • Switch Types (3pdt, dpdt...)

    What is the difference between switch types? Especially the difference between switches that on the surface look identical (3pdt & dpdt).

    Thanks.

  • #2
    3PDT and DPDT do not look the same. The 3P has three more terminals than the DP.

    Actually there is a basic discussion on Wiki. Scan down a little for a chart on types.

    http://en.wikipedia.org/wiki/Switch

    The names describe the switches. The simplest switch is the basic on-off switch - the two terminals are connected together or they are not. The knife switch is an easily visualized example.



    Here there are two terminals on the ends, then there is a metal bar acting as a lever, it pivots from the left. This is the same kind of switch you see in Frankenstein and other mad scientist labs in movies. The bar is netal so it conducts. Swing the lever down and it toches teh right terminal, thus connecting the two together.

    We call the moving thing a pole, and when you "throw" the switch over to the other terminal it completes a circuit. We call the stationary terminal a throw. SO this switch is a Single Pole, SIngle Throw switch - SPST.

    Now we can add another terminal on the far end



    Now our pole piece can be thrown either direction, and so connecting the center to one end or the other. We now still have a single pole, but it now has two throws, one on each end. This is a SIngle Pole, double throw switch - SPDT. One pole, two throws.

    This can be used to select one path or another for the center terminal. of course you could leave one end unconnected and use it the same as a SPST.

    That is how they work. Now we can pair two of these side by side, and have the two moving poles controlled by the same handle. They are connected together mechanically, but the two switches are still electrically separate.



    This is the same as before except there are two of them. FLip the insulated handle and they both work together. We now have a double throw switch. In this image the switches are double throw, this is the common double pole, double throw switch, DPDT, but it could also leave the throws off one end to make it single throw - SPDT. This DPDT is what is inside the stomp switch on your effect pedal. Your switch has two rows of three terminals, and they correspond to the terminals on this large knife switch.

    A 3PDT switch is just the same but with a third switch section added beside the other two. SOmewhere around here I have some large toggle switches that are 4PDT. They were used in some Mesa or maybe Seymour DUncan amp as a switch to select between triode and pentode or some such. 4PDT is the same as two DPDT side by side with the levers connected - it has four rows of three terminals each.

    It helps to understand what is happening inside the switch.
    Education is what you're left with after you have forgotten what you have learned.

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    • #3
      Wow, thanks. That helps a lot.

      Comment


      • #4
        Better yet, go read "The Technology of Bypass Switching" at GEOFEX.
        Amazing!! Who would ever have guessed that someone who villified the evil rich people would begin happily accepting their millions in speaking fees!

        Oh, wait! That sounds familiar, somehow.

        Comment


        • #5
          I should have assumed you'd have some material on it.
          Education is what you're left with after you have forgotten what you have learned.

          Comment


          • #6
            Gee, I'd like to get a little credit too. If you go here www.1728.com/project2.htm, you can read my own explanation of switches. It's certainly not Wikipedia or GEOFEX but then again what is?

            wolf

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            • #7
              Originally posted by wolf1728 View Post
              Gee, I'd like to get a little credit too.
              OK. I award you one credit.
              Amazing!! Who would ever have guessed that someone who villified the evil rich people would begin happily accepting their millions in speaking fees!

              Oh, wait! That sounds familiar, somehow.

              Comment


              • #8
                Well, the only reason I wanted credit is that 2 of the posted graphics were being "hotlinked" with no clickable link back to the site from where they originated - mine.

                Some folks get really upset when they have had their graphics "hotlinked".
                When it is a message board, it's not that much of a problem for me. Heck, this is what the Internet is all about - one gigantic database / message board / website, with everyone making their contributions.

                What I really hate is somebody "borrowing" graphics for their own websites and sometimes they have the nerve to "hotlink" those.
                Anyway, this seems to be a good electronics message board and I just thought I'd say hello.

                Comment


                • #9
                  I see. Were those the two with "1728.com" in the picture?

                  The stuff I put on GEO is copied so much and in so many places that it's changed my perception of human nature. I'm convinced that a certain percentage of humanity is composed of congenital thieves.

                  My text and graphics are regularly stolen, and often modified to remove the identifying information that I put in. I've had to threaten lawsuits, and even had my friend the IP law attorney send letters a couple of times. That's been enough in all cases so far.
                  Amazing!! Who would ever have guessed that someone who villified the evil rich people would begin happily accepting their millions in speaking fees!

                  Oh, wait! That sounds familiar, somehow.

                  Comment


                  • #10
                    Originally posted by R.G. View Post
                    The stuff I put on GEO is copied so much and in so many places that it's changed my perception of human nature. I'm convinced that a certain percentage of humanity is composed of congenital thieves.
                    I have to chuckle when I see a copied image somewhere and right in the
                    image it is clearly stated that the author prohibits doing so. Seen that here
                    a couple of times.

                    Paul P

                    Comment


                    • #11
                      You are right, from now on I will attribute any images I copy for posting and/or provide a link.

                      Never thought of it as stealing, since the sources are in the links, I'm not profiting, and not claiming it as my own. But you did the work that I don't have to, so yes you deserve credit.

                      ALL I do usually is Google something like "electrical switch terminology" and see what pops up.
                      Education is what you're left with after you have forgotten what you have learned.

                      Comment


                      • #12
                        Well thanks for the explanation Enzo. I don't know if anyone has visited my website, but it is about more than just knife switches.

                        I've got 6 pages on guitar rewiring starting here:
                        www.1728.com/guitar.htm

                        The switch explanations are here:
                        www.1728.com/project2.htm

                        And written just for the heck of it is a band name generator:
                        www.1728.com/bandname.htm
                        It gets about 500 "hits" per day and is really popular on message boards with everybody trying to "top" the last posting. I don't know if anyone really wants to name their band "Deserted Oyster Dominion" but it's just fun to see the nutty names it generates.

                        R.G. oh I've had my graphics and calculators stolen. Several times, somebody has stolen something from my website, like an algebra calcuator and they are too darned lazy even to change the example problem.
                        Usually when I find something that was obviously stolen, I'll get in touch with their webhost. In a day or so, that website disappears.
                        As I've said, using the graphics for a message board is generally okay with me, because after a while the topic dies down and moves on elsewhere.

                        Comment


                        • #13
                          Hotlinking is, err, a hot potato. If you're not an Internet nerd, it's hard to see how there could be anything wrong with it. But in practice people get mad about it.

                          I think the fundamental reasoning is that it uses up the originator's web hosting bandwidth, which they have to pay for, without inflating their internet ego in return. They lose money, they don't get hits to their site. In practice you can get away with it on a message board if you include a link such as "I hotlinked these pictures from http://www.1728.com/ "

                          Of course, there's more to it than that. You could easily get round the above objection by downloading the image and reposting it on this forum. But if you do that, it now counts as theft of intellectual property and the original author will get even madder if he finds out...

                          BTW the band name generator is always good for a laugh
                          "Enzo, I see that you replied parasitic oscillations. Is that a hypothesis? Or is that your amazing metal band I should check out?"

                          Comment


                          • #14
                            And wolf, yours was one of the first google hits, reflective of your exposure I would assume. I will also try to look farther to find commercial images in the future. I am sure Carling or whoever won't mind, and certainly retailers will be Ok with what amounts to a plug. Try to limit the use of private web sites then.

                            REgarding your site, we are always happy to see more tutorial resources.
                            Education is what you're left with after you have forgotten what you have learned.

                            Comment


                            • #15
                              and I shall now rename my band "Forklift Gravy"

                              actually make that "Screaming Clown Hammer" you just can't buy quality like that
                              Suburbanite
                              Member
                              Last edited by Suburbanite; 07-01-2008, 11:32 AM.

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