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Electronics => Electronics => Topic started by: MaltiK on October 03, 2008, 08:25:22 PM

Title: What is this called? (underside of a button)?
Post by: MaltiK on October 03, 2008, 08:25:22 PM

Like underneath buttons in an electronic, there is a small silver plate or something, and so when the button is pressed, it works, what is this silver thing called? these are in the underside of a remote control

I also want to know how I solder wire to this so that I can use a microcontorller to trigger it?

(http://i99.photobucket.com/albums/l303/_Corrupt_/Photo0158.jpg)

the silvery thing next to the button i took off

Title: Re: What is this called? (underside of a button)?
Post by: szhang on October 03, 2008, 10:58:25 PM

I don't know the name, but I think its just a gap in the copper trace, and the conductive material on the bottom of the button completes the circuit.  I could be wrong, but I think it's just a push botton switch.

Title: Re: What is this called? (underside of a button)?
Post by: paulstreats on October 04, 2008, 04:29:52 AM

The pad on the circuit board is made up of 2 traces and not 1. When the metal on the underside of the pushbutton hits them, it joins the traces together and makes a circuit. Nothing needs connecting to the actual button, both of the connections are underneath it waiting to be joined.


(http://www.uk-robotics.co.uk/misc/psw.jpg)

Title: Re: What is this called? (underside of a button)?
Post by: MaltiK on October 04, 2008, 05:30:16 AM

SO then, how do I solder a wire to it to be controlled with a microcontroller via highs and lows? on Picaxe28

So should I just solder a wire that overlaps both traces? And connect it to my Microcontroller?

Title: Re: What is this called? (underside of a button)?
Post by: izua on October 04, 2008, 07:14:32 AM

No dude, you'll short it.
The idea is that the user creates the short, and the MCU detects it. So, solder each trace to a MCU pin, make one pin output, and one pin input (with a pullup). Sink on the output pin (set to low), and check on the input. If the input is 1, pullup is on, you'll read 1, no button pressed. If the input is 0, there is a short between the two pins, because the user pressed the button.

Title: Re: What is this called? (underside of a button)?
Post by: MaltiK on October 04, 2008, 10:16:42 AM

what about specifically? for instance on this boarD:

http://www.radioshack.com/product/index.jsp?productId=2102855 (http://www.radioshack.com/product/index.jsp?productId=2102855)

Title: Re: What is this called? (underside of a button)?
Post by: izua on October 04, 2008, 12:51:39 PM

what about it? what are you trying to achieve, simulating a button press on that board?

Title: Re: What is this called? (underside of a button)?
Post by: MaltiK on October 04, 2008, 03:05:57 PM

exactly!

Title: Re: What is this called? (underside of a button)?
Post by: izua on October 05, 2008, 12:03:48 AM

Well then, use a small relay, or a solid state switch - fet, bjt - this will be harder, since you will have to detect which pin sources and which pin sinks between those two traces - so you can put the transistor correctly.

Title: Re: What is this called? (underside of a button)?
Post by: MaltiK on October 05, 2008, 06:07:21 AM

OK I got it to work, for future reference, I followed the line on the board from the membrane to the right where it ends in a small test point (a contact point used by the manufacturer for testing the board), and i soldered on a resistor lead, and this was connected to the output of my Picaxe, success!! thanks for the help guys