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Hiding a momentary push button.

Destriarch

Nov 26, 2016
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I'm working on a silly little project and I need it to operate off a single momentary push button. I'm working with a very simple circuit driving a microcontroller, a LED and a speaker to produce light and sound. It's basically a movie prop replica. Anyway, the issue I'm having is that the device in question would normally have no visible button, so I'm looking at options to make the activation button either invisible or discrete.

Ideas I've considered:

1) Wiring directly to the casing and using the user's body to complete the circuit. (It's only 6v DC)
... Is this feasible? It's by far my favourite option if it can be done safely but I don't know the practicalities - like how far removed from each other the upper and lower terminal need to be to ensure that the connection is solid, for example.

2) Hiding the button behind a button that lies flush with the casing
Another good option, but this would require the button to be quite short in height - the device is a cylinder approximately 12mm in diameter and, although I can easily produce custom fixings to keep the switch in place, I am unsure what component I can get that will fit in the space available with a firm enough fixing to attach the faux case segment that will hide it. A good comparison is to look at a 4LR44 battery - that's what I'm using to power it, so that's how much space there is internally.

3) Some other option.
I've looked into a few other options - capacitive touch controls are too expensive and may be too complex, for example - but if anyone can think of any other ideas I'd be grateful.

Does anyone have any tips on this?
 
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Minder

Apr 24, 2015
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One self designed method could be to use some very thin shim tin, there is a source from an empty cola can, although these are usually aluminum and could be tricky to make contact with a wire conductor.
But if the shim were placed inside the cylinder in an arc that just barely makes contact with the interior wall, and a hole drilled just above it in the cylinder wall, or even if the wall is soft enough to depress slightly with a small pressure, it could be made to make contact with the inner shim.
This is if the outer is metallic and can be made a conductor.
This would definitely requires some experimentation!
M.
 

BobK

Jan 5, 2010
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Another possibility is a photo detector behind a small hole. Block the hole to trigger the button. This, of course, works only if it would normally see some light when in operation.

Bob
 

Destriarch

Nov 26, 2016
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Nov 26, 2016
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Hmm not sure about the tin can solution. It sounds likely to cause a short circuit and drain the battery. I'm also hoping the shell won't be too flexible as I'm using steel, albeit only 2mm thick. I might do some light experimentation with some metal cutlery and a coke can out of curiosity.

The photo sensor solution is an interesting one but suffers from the major issue that it would cause the device you go off in your pocket. It would also be constantly on at night, which is not advantageous for a light emitting device. Thanks for the responses though, it's all interesting and I am still quite rusty when it comes to electronics!

Any other ideas, anyone? It's good to have options.
 

Bluejets

Oct 5, 2014
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I'd say Bob's idea x 2 ...
one option there would be to supply ir light and use an ir led, blocking the transfer for switching.

One could also consider a hall effect switch but then there is either the need to carry a magnet or/ have the magnet attached to the back of the hall effect and carry or introduce a metal plate somehow.
 
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