Hey everybody,

I am working on a project right now and i need to use silicon rubber buttons similar to the ones found on remote controls. I am not sure exactly how they work. Is the button grounded when not pressed? if so how is this done? I need to feed the output from 8 buttons into a microcontroller, so the state of all the buttons have to be either high or low.

Thanks,
Ragnork83

 

Silicon rubber buttons have a bead of carbon underneath that makes contact with two electrodes underneath and connects them together. That means that the button will act as a normally open switch that will close when pressed.

Since you are using a microcontroller, they normally read pin states by pulling the pins high and waiting for an event to pull them low, that means that all you have to do is make sure that one of the electrodes below the silicon button is connected to whatever pin you want in the microcontroller, and the other one to ground, changing the pin's state from 1 to 0 when the button is pressed.

 

ok, that sounds easy enough. I think that i would need it the other way around though. If i pull the pins high, it will drain my battery when the device is not in use. I probably should have mentioned that the device is battery powered and needs to be as compact as possible. I have attached some rough diagrams. Does it look like im on the right track here


Thanks for the help,

Ragnork83.

 

Hello:

Here is an excellent article about pull up vs pull down issues.

In my experience, inputs are pulled hi and activated low ("not" logic).

http://www.ganssle.com/articles/aresist.htm

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