2 pin header polarity

[microbug]

Hi,
I'm designing a pcb for my own linear power supply. It uses header connections for the supply input and output. The header connector sockets have a square and a round hole (see attached) - which one is ground and which is V+? I have wired it so that the square is ground for now, but it's very easy to change.
Thanks!

[8086]

If you're asking if there's a standard, I don't think there is.

There is a de-facto standard that the square pad is pin 1, but none that I know of that dictates whether it should be positive or not.

I would suggest you just add polarity markings to your silkscreen for reference.

[microbug]

OK, I suspected there wasn't a standard after seeing different orientations on Google Images, but just wanted to make sure. Thanks.

[glatocha]

I also don't know if there is any standard, but I have two boards that (I think) are using same connectors for power supply.
The boards are from Microchip and Xilinx so maybe following them would not be bad.
I can check how they are connected later today.

[Farley]

I think that most PCB patterns for electrolytic capacitors use square pads for the positive lead.

[Rufus]

OK, I suspected there wasn't a standard after seeing different orientations on Google Images, but just wanted to make sure. Thanks.

They are general purpose 2 pin connectors with no standard use and so no standard pin allocation.

If the alternative is tossing a coin then I would make the square pad +ve. A square pad (if there is one) universally indicates pin 1. On a schematic I would by default put pin 1 at the top and it is pretty universal to draw schematics with +ve supply rails at the top.

[Fsck]

Hate to point out the obvious but the square one has a + in the middle of it.

[glatocha]

 
It is the orientation point of an object in Eagle. You have is also next to the CAP

[digsys]

I ALWAYS make the pin that has the most Cu area, the GND or 0V. For connectors, caps, LEDs etc
I know you can add copper, but that's not the same thing.

[mikes]

An argument for pin 1 being ground is if you had multiple voltages - you would always need ground, so start with that on 1, and put other voltages as you work upward.

One handy trick is to use a 3 pin connector. Center pin is V, outer pins are ground. That does two things - it can be plugged in either way without reversing the voltage, and you can wire a ground to one outer pin and shield to the other. For compatibility with that, on a 2 pin connector, pin 1 would be still be ground.

[glatocha]

I also don't know if there is any standard, but I have two boards that (I think) are using same connectors for power supply.
The boards are from Microchip and Xilinx so maybe following them would not be bad.
I can check how they are connected later today.

So I checked. On Xilinx board there is a different connector.
On Microchip board connector is same like yours. And the square pin no 1 is used as a +V.

[Short Circuit]

G.Round 

[KJDS]

Best practice poka yoke suggests:-

Make sure that if something can be put in place it will work whichever way round it is put in. Therefore use three pins with the outer two as ground.

If the above isn't possible make sure it can only be fitted one way round and that the correct way is obvious, therefore use a polarized connector.

[glatocha]

This is the polarized connector what he is using. It can be only one way.

[mikes]

This is the polarized connector what he is using. It can be only one way.

It's not clear where you came up with that, he simply said "header connector." Basic headers aren't polarized, although some connectors like the Molex KK series are.

[8086]

It's not clear where you came up with that,

The silkscreen. He is right, the footprint is for a polarised connector. Looks like Molex KK.

[mikes]

It's not clear where you came up with that,

The silkscreen. He is right, the footprint is for a polarised connector. Looks like Molex KK.

That's an assumption, he may have simply chosen an Eagle part which has 2 0.1" pads. It's not like the silkscreen forces you to stuff a particular part.

[8086]

It's not clear where you came up with that,

The silkscreen. He is right, the footprint is for a polarised connector. Looks like Molex KK.

That's an assumption, he may have simply chosen an Eagle part which has 2 0.1" pads. It's not like the silkscreen forces you to stuff a particular part.

I am answering your question regarding where it came from. The footprint is for a molex KK connector.

[hlavac]

For 2 wire connectors where polarity matters and connections have to be easy and quick I have used 3-pin connectors wired as one wire middle pin, second the side pins.
It does not matter which side you plug it in.