How should I show that a standard connector is used for non-standard purpose?

I recently started doing hardware projects with Arduino. Those projects involve custom-made enclosures to hide (and protect) the actual components. Those enclosures should have plugs in order to be able to connect the components.

If this is too abstract, here's a concrete example. One case contains the transformer, an Arduino, a resistor and a bunch of wires needed to power a LED strip. The LED strip itself is assembled with another case which hides its wiring. Two cases should then be connected together for the LED strip to work.

My idea was to use ordinary 3.5 mm TRS or TRRS connectors where tiny cables (22 AWG) are largely enough, and XLR connectors where I need thick 14 AWG cables. The benefit of using those standard connectors is that there is a broad range of cables, and that connectors are easy to find as well. Another benefit is that I already have a lot of 3.5 mm cables and a few XLR cables at home.

This causes, however, a problem. Since those connectors are familiar to everyone (well, XLR is a bit less), and since those connectors are used by many other devices, it is easy to make a mistake and plug something which is not expected to be plugged: for instance connect an audio recorder to an XLR intended to be used for a LED strip, or connect a headset to where one would expect a device which monitors the temperature in the room.

There are, potentially, two risks:

  • I myself, by inadvertence, connect the wrong thing.
  • Someone who either comes to my home or, for some unknown reason, acquires a device I created (they are made for my own personal usage, not for sale), tries to connect the wrong thing.

When the wrong thing is connected, the worst thing which could happen is that it will damage either the thing (very likely in the case of a 3.5 mm connector) or the electrical components I've used in my devices (very likely in the case of a XLR if using 12 V or more), and possibly start a fire.

How should I proceed in order to avoid those two risks (given that having custom connectors is obviously the best thing to do, but as I explained, it is not an option here)?

From the UX perspective, should I put specific labels? Use specific colors? Something else?