Component mounting pins and ground

Other Hardware General Electronics
1

I’m using a RKJXV122400R ThumbPointer™ / joysitck.
As well as 10 “electrical” pins (3 for each of the two pots and 2 pairs for the push button), there are 4 mouting pins which form part of the metal casing.
Is it good practice or a bad idea to ground the all/any of the mounting pins?

I’m designing a PCB and using two of the mounting pins as a jumper would be an easy way to eliminate a ground island. (KiCAD makes provision for this in the schematic window, so I’m guessing that, at the very least, sometimes it’s not a REALLY bad idea.)

2

YES IT IS!
You do not want current flowing through the metal casing.

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3

OK ... when you put it like that … :rofl:
Just to clarify - in the circuit I’m looking at, it would only be joining Gnd to Gnd. And even then, it would just be ensuring that both Gnd pins on a Nano Every were connected to the Gnd fill. Otherwise, one would be floating.

4

Then you need to re-layout the board, so you can connect all grounds via traces or pours.

You should first try to connect all grounds with the appropriate sized traces. If you can't, then the pour won't be able to do it either.

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5

Are the Nano's ground pins not connected internally? I was under the impression they were.

I'm sure there are good reasosn in certain circumstances to connect both pins to ground, but when I've breadboard circuits with just one connected, I've not observed any issues. (FWIW I'm just in the realms of switches on Din pins and driving MOSFETS as switches on outputs.)

6

I agree with @jim-p , using the case of a component as a conductor is a bad idea. By all means connect all 4 case pins, but connect them to a ground plane that is otherwise complete without the joystick. You are correct to think you should not have ground islands.

Of course they are, how could they be otherwise? If they were not connected then at least some of them would not be ground.

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7

Yes but all GND pins should be conneced to ground. That way you don't have all your ground current flowing out of just one pin.

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8

While they are all "ground" you dont know what is the internal resistance or current carrying capacity of the conection between them.
As @jim-p says, ideally connect any/all grounds on the controller to a ground plane - and maybe run analog, digital and power grounds seperately, as explained here.

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