SparkFun Forums

[JulianV]

I'm using the DC Barrel Power Jack on a project but can't find what these connectors mean. Which is positive and which negative?

[Ross Robotics]

Top pin is V+, bottom 2 pins are GND.

[JulianV]

Thanks codelink.

By the way... in the future, when I need to figure this out for another component, any pointers on where to look? I've clicked and double clicked everything to try to get to a place where the schematic meets the actual PCB pads to see if I could figure out what traces go where but couldn't find any.

[Ross Robotics]

You could use Google. Search dc jack pinout.

[JulianV]

No, I get it. I'm not trying to be lazy here. I did Google it and saw many schematics with a similar jack. All I wanted was to know was how *this* particular part (in *this* particular eagle library) was wired.

[Ross Robotics]

All dc jack symbols are very similar. The fat pin from the left is always positive. It represents the physical center pin on the jack. The pin that looks like a triangle on the symbol, represents the sprung physical pin that connects to the metal on the outside of the physical plug. If you think about how a dc jack looks if it was cut in half, the symbol looks just like that.

[n1ist]

Careful - there are some wallwarts out there that have the center pin negative (and of course, some that have AC output). You need to check what you plan to plug into that power connector to determine the polarity.

The fat line in the schematic symbol represents the center pin. The bent line on the bottom represents the sleeve connection. The middle line represents a switch contact. When the plug is removed, the middle and bottom pins are connected. When the plug is inserted, the middle line is not connected to anything. That's often used to switch between battery (connected to the switched contact) and external power, or for phone jacks, between internal speaker and headphones.

/mike