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I am trying to include a DC jack on one of my PCBs. I am just setting up the footprints now, and I am not quite sure which pin is which. What do the symbols on the drawing mean?

I have included a snap of the schematic below, it has been taken directly from the datasheet.

DC jack schematic

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Pin 3 is the center pin, pin one connects to the barrel and pin 2 is used to detect if there is a plug inserted. The lower left drawing shows the physical pins looking at the bottom side.

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It's a visual representation of how the socket works.

  • Pin 3 represents the pin that mates with the center of the plug (typically V+)
  • Pin 1 is the sprung contact that connects to the outside of the plug (typically Gnd)
  • Pin 2 contacts to Pin 1 (Gnd) but breaks contact when the plug is inserted (as the Pin 1 contact springs away)
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While this is resurrected due to Endolith's retagging, I want to clarify the reason that Pin 2 connects to the shield of the jack, but only when there's no plug inserted. You can do one of three things to wire this correctly:

  1. Only connect to pin 1.
  2. Connect pins 1 and 2 together.
  3. Connect pin 1 to your circuit's ground node, and connect pin 2 to another power connector (Black binding post for a banana jack, or battery ground terminal, for example.) Then, you can connect pin 3 to a red binding post or battery positive terminal, and have 2 power supplies without worrying about output contention.

Method 3 is the reason that these plugs are designed the way they are.

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    \$\begingroup\$ Situation 3 is for the case when you have a circuit that can run off of battery power or a plug in (wall wart) style source right? Pin 2 is connected to pin 1 when power source is not plugged in so the battery can use pin 2 as ground. When the plug is inserted the battery is disconnected from ground so only the plug is providing power. Is that correct? \$\endgroup\$ – thomas.cloud Aug 30 '13 at 14:30
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I generally connect pins 1 and 2 together.

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    \$\begingroup\$ Doesn't answer the question at all! (Yet oddly had 2 upvotes) \$\endgroup\$ – Federico Russo May 7 '12 at 15:19
  • \$\begingroup\$ Why doesn't it answer the question? It's in addition to the other answers, as it's often done. One other person mentioned it, after I did. \$\endgroup\$ – Leon Heller May 7 '12 at 17:36

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