Aluminum case, isolatation of jacks/connectors needed?

Using Arduino General Electronics
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I've got a project where I want to use an aluminum case.

In this case, I will add some TNC jacks (e.g. for GPS, GSM), some other connectors, and a power jack (24V DC 0.5A, powered by a battery)

So my question is:
The outside of the connectors is electrically connected by the aluminum case,
is this...

  • a problem concerning safety (I don't think so but I want to be on the safe side)?
  • a general problem (antennas not working or something like that)?

power_jack.png
power_jack.png780×502 144 KB

tnc jack.jpg

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I’m guessing if you plugged both of these into a plastic or wooden case and touched the exposed metal parts that you would not get a shock, so probably safe...but no harm in adding some simple insulation washers anyway just to be sure...even cut from heavy duty plastic bags (freezer bags work well).

Not sure about performance issues...

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The outside of the connectors is electrically connected by the aluminum case,
is this...

Yes they are designed to do this. It is only a problem if you wire things to the ground connectors other than ground, then they will short out. Unless you have over 50V in the circuit there is no risk of electric schocks.

The act of mounting an RF device in a screened box might upset the output impedance matching but it is unlikely.

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I just use the "unisolated" jacks for GPS / GSM and I assume that those are only connecting ground to their outer part.

I just made a small test with aluminum box and a GPS + a GSM antenna, everything works fine :slight_smile:

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and I assume that those are only connecting ground to their outer part.

This is electronics, never assume. It is easy enough to check with a DVM.

6

If you have the metal case, use it to your advantage to help shield noise.

7

RF connectors are normally grounded to the case. Audio or sensor signals are more likely to require isolation
to avoid ground-loop noise injection.

You can ground the power input too, unless you have a need for a star-ground system due to sensitive low
voltage signals, but even then you can use the incoming power connector as the star point.

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Grumpy_Mike:
This is electronics, never assume. It is easy enough to check with a DVM.

Yeah, you are right, I checked it and it is as expected.

MarkT:
...You can ground the power input too...

Do you mean that if I want to I can connect the ground wire from my power connector to the metal case?
Is there any advantage if I do this?

MarkT:
sensitive low voltage signals

Is GPS or GSM a "sensitive low voltage signal"?

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