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Pushbutton Question Answered

I have been taking apart Gameboys and keyboards. These devices have buttons or keys that you push to play a note. When I take it apart, I dont see pushbotton switches like id expect. Instead I see a rubber form with a little black dot on it, and when you press it, the black dot touches a black surface on a PCB. Anyone know how this works?

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steveastrouk
steveastrouk

Best Answer 10 years ago

Yes, the dot is conductive rubber. it makes a circuit with the inter-digitated traces on the PCB.

Steve

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frollard
frollard

10 years ago

Agreed with steve -- conductive rubber. My old NES pads had graphite pads on bare copper (hence they wore out so fast).

Nowadays they're painted with that black conductive paint to prevent corrosion on the metal pads.

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crocboy
crocboy

10 years ago

So if i wanted to replace those switches with pushbuttons I would have to follow the traces back to a solder point and connect a switch there?

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steveastrouk
steveastrouk

Answer 10 years ago

No,look carefully at the board and solder from one set of fingers to the other via your switch.

Steve

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crocboy
crocboy

Answer 10 years ago

Ok I have it figured out now. Thanks everybody!

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Kiteman
Kiteman

10 years ago

Is the black surface on the pcb at all flexible?

It might be a membrane switch.

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crocboy
crocboy

Answer 10 years ago

No its not flexible it seems to be some sort of paint? And on the keyboard there is two of them, they both have to be pressed in order to play a note. Any ideas?

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Kiteman
Kiteman

Answer 10 years ago

In that case they are patches of something conductive, and touching them together completes the circuit.

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crocboy
crocboy

Answer 10 years ago

Well I thought the same thing until i found that the two black dots that have to touch the patches arent connected in any way. They are isolated by rubber. So I am baffled at this point.

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Kiteman
Kiteman

Answer 10 years ago

See Steve's comment: conductive rubber.