Marking the correct orientation of pin header plugs

[JamesF]

On my circuit board for my dew controller I have a (large number of) pin headers for plugs that go to switches, leds, sensors etc.  It struck me the other day that it would perhaps be sensible to mark them all so it's easy to identify the orientation of the plugs.

The best idea I've come up with so far is to decide on given edges of the board ("top" and "left", say, as determined by the screen printing) being reference points, and put a blob of paint on the side of the plug that should be towards those edges.

Anyone have any other methods they use?

James

[pete_l]

Two suggestions. First is to add extra superfluous pins so that each header is a different size. That way they can't get mixed up.
Second is to cut off a given pin on each header and to fill in the corresponding socket on its connector. That makes it physically impossible to connect them the wrong way round.

Alternatively bring all the connections to one single large pin strip and use a keyed connector and a ribbon cable.

[Dr_Ju_ju]

There are also 'keyed' header connectors which will also define connection orientation etc. e.g. https://gct.co/board-to-board-connector  https://uk.rs-online.com/web/c/connectors/pcb-connectors/pcb-headers/