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I have to realize some sliding contact between a board and another one. The moving board has a fixed rail, and it can move horizontally.

I want to transfer power from the bottom board to the top one. To do that, I thought of making some copper brushes attached to conductive screws reaching the top PCB.

This actually works. However, I am currently ripping apart Dupont cables to find the bare copper wires.

I tried to buy a row of bare copper wire. I went with AWG 42 or around that, but it is not flexible: the brush remains bent when flexed, so it is not "elastic" (as it would be, for instance, the brushing part of a toothbrush).

Which AWG/copper type should I select to have more elastic capability? Should I go for enameled wire or bare wire? Is there any reasonable alternative for planar sliding contact that does not require lubrication, i.e. carbon brushes?

Edit: of course I meant AWG, thanks for editing. Also, involved power is max 1A at 9V. Movements is reduced, we are speaking mostly of continuous movement of 20/30 seconds, then the board stops in another nominal positive until next adjustment

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    \$\begingroup\$ You mean AWG? Not AVG? You consistently use AVG though. \$\endgroup\$
    – DKNguyen
    Commented May 16, 2023 at 22:48
  • \$\begingroup\$ What about bent copper strips, sort of like leaf springs? You should also probably use brass rather than copper. \$\endgroup\$
    – DKNguyen
    Commented May 16, 2023 at 22:53
  • \$\begingroup\$ What current and voltage is involved? \$\endgroup\$ Commented May 17, 2023 at 0:44
  • \$\begingroup\$ Some carbon brushes like those used in motors or power tools? \$\endgroup\$
    – SteveSh
    Commented May 17, 2023 at 0:52
  • \$\begingroup\$ Moves once in a while? Or continuously? One is more difficult than the other. \$\endgroup\$ Commented May 17, 2023 at 5:22

2 Answers 2

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Copper has no fatigue limit, that means all movement accumulates metal fatigue. It is not suitable for making springs, and will eventually crack.

For proper brushes, you can use actual brushes and brush holders. These are made of graphite and have a steel spring behind them. Spring steel is pretty good at being springy within steel's fatigue limit (so it does not fatigue), and it will last indefinitely.

You can also try putting a copper or brass contact on a hinge, and add a steel spring of some kind to make it push downward. The hinge and spring will take care of deflection and the copper won't bend, so that will minimize fatigue.

If you need to lubricate the moving track to reduce wear, try dry graphite "paint" such as Slip-Plate, EZ-Slide, etc. This is a silver bullet for many lubrication situations where stickiness is not desired, such as garage doors. But it also conducts electricity!

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Copper is not going to work well. You need to use a springy material, like phosphor bronze or carbon steel. you can buy spring contacts.

Metal on metal contact is going to require lubrication especially if it's carrying power.

Carbon as you suggest is probably a better choice, because carbon is a lubricant. Carbon brushes intended for electric motors, and automotive alternators are readily available and not too expensive but you'll need to arrange a guide mechanism and possibly grind the face flat.

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