2 pin header polarity - Page 1
Forum section: electronics / beginners

author: microbug
author_rank: Frequent Contributor
timestamp: May 13, 2013, 05:51:06 pm
content: 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!

author: 8086
author_rank: Super Contributor
timestamp: May 13, 2013, 05:55:29 pm
content: 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.

author: microbug
author_rank: Frequent Contributor
timestamp: May 13, 2013, 05:56:25 pm
content: OK, I suspected there wasn't a standard after seeing different orientations on Google Images, but just wanted to make sure. Thanks.

author: glatocha
author_rank: Regular Contributor
timestamp: May 14, 2013, 01:06:49 am
content: 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.

author: Farley
author_rank: Regular Contributor
timestamp: May 14, 2013, 02:27:05 am
content: I think that most PCB patterns for electrolytic capacitors use square pads for the positive lead.

author: Rufus
author_rank: Super Contributor
timestamp: May 14, 2013, 02:52:39 am
content: Quote from: microbug on May 13, 2013, 05:56:25 pmThey 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.

author: Fsck
author_rank: Super Contributor
timestamp: May 14, 2013, 03:23:09 am
content: Hate to point out the obvious but the square one has a + in the middle of it.

author: glatocha
author_rank: Regular Contributor
timestamp: May 14, 2013, 03:26:14 am
content: It is the orientation point of an object in Eagle. You have is also next to the CAP

author: digsys
author_rank: Unknown
timestamp: May 14, 2013, 03:31:14 am
content: I ALWAYS make the pin that has the most Cu area, the GND or 0V. For connectors, caps, LEDs etcI know you can add copper, but that's not the same thing.

author: mikes
author_rank: Regular Contributor
timestamp: May 14, 2013, 08:13:11 pm
content: 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.

author: glatocha
author_rank: Regular Contributor
timestamp: May 14, 2013, 08:40:29 pm
content: Quote from: glatocha on May 14, 2013, 01:06:49 amSo 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.

author: Short Circuit
author_rank: Frequent Contributor
timestamp: May 14, 2013, 09:24:39 pm
content: G.Round

author: KJDS
author_rank: Super Contributor
timestamp: May 14, 2013, 10:32:56 pm
content: 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.

author: glatocha
author_rank: Regular Contributor
timestamp: May 14, 2013, 11:25:52 pm
content: This is the polarized connector what he is using. It can be only one way.

author: mikes
author_rank: Regular Contributor
timestamp: May 14, 2013, 11:51:31 pm
content: Quote from: glatocha on May 14, 2013, 11:25:52 pmIt'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.

author: 8086
author_rank: Super Contributor
timestamp: May 14, 2013, 11:52:45 pm
content: Quote from: mikes on May 14, 2013, 11:51:31 pmThe silkscreen. He is right, the footprint is for a polarised connector. Looks like Molex KK.

author: mikes
author_rank: Regular Contributor
timestamp: May 15, 2013, 12:13:10 am
content: Quote from: 8086 on May 14, 2013, 11:52:45 pmThat'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.

author: 8086
author_rank: Super Contributor
timestamp: May 15, 2013, 12:28:02 am
content: Quote from: mikes on May 15, 2013, 12:13:10 amI am answering your question regarding where it came from. The footprint is for a molex KK connector.

author: hlavac
author_rank: Frequent Contributor
timestamp: May 15, 2013, 11:42:57 am
content: 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.