Core Electronics Forum

2.1mm 12v DC Barrel Jack: Query about connections

As stated above, I have a 2.1mm barrel jack designed for a breadboard. The jack has 3 pins which insert into the main part of the breadboard (Not power rails). The datasheet does not state where my wires need to go to connect positive or earth/negative. I assume it requires connections because it does not fit into the power rails.


0900766b81582446.pdf (528.1 KB)

Hi Kiennan,

Correct me if I’m wrong here, but I don’t think that the jack you’ve listed would be a good fit for a breadboard, more a PCB or hand-wiring, as the legs seem too thick to go into a breadboard.

A better choice would probably be this breadboard-compatible jack

Just triple check that you’re using a plug with a 2.1mm hole before you buy this jack though

One pin will be connected to the centre pin of the connector, one to the barrel contactor, and the third to the barrel/any other metal parts on the jack.

The most common wiring is with the centre pin positive, and the other two pins negative or ground, but there are devices that use a centre pin negative, so it’ll depend on your supply.

The datasheet I uploaded is from a different jack I was looking at, sorry I got confused. The one you have linked is the one I have bought.

The datasheet shows pin 1 as the centre pin, pin 2 as the barrrel and pin 3 connected to the barrel when the plug is not inserted. Pin1 is on the centreline furthest from the plug, pin 2 on the centreline nearest the plug, and pin 3 off to the side. Which is positive or negative depends on how the plug is wired.

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I just need to know which pins are positive, negative and earth/ground. This goes into a breadboard and the jack plugs into a DC 12v power pack.

The short answer is it’s whatever you want it to be :slight_smile: Have a look on your power supply - you’ll see a little symbol indicating whether it’s centre positive or centre negative.

Then either read the datasheet or use a multimeter to check whcih pin is which and wire it accordingly.

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