Description: A basic 12 button keypad for user input. The buttons are setup in a matrix format. This allows a microcontroller to ‘scan’ the 7 output pins to see which of the 12 buttons is being pressed.
Check the examples below for correct pin-outs and such.
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Look at the diagram of the PCB, see the black traces? They are conductive paint (or something) and on mine at least, they don’t conduct. I was able to fix it by cutting off the melted plastic that keeps the case closed, carefully sanding off the black stuff until the underlying pads at each end were exposed, and then soldering fine wire between the three pairs of pads. While you are in there, gently sand the exposed metal where the keys are supposed to press down, or half the keys will need to be pressed REALLY hard to register. Put it all back together and apply superglue where the melted plastic was on the back of the case. NOW it works like it should have out-of-the-box.
Sorry for all the extra trouble. These should work better out of the box. If you get one that gives you trouble, please let us know. https://www.sparkfun.com/returns
If you can figure out how to keep it from coming apart, you’ll be golden. For a few dollars though, not bad. Mentioned before but put headers on it so you won’t need to resolder it and maybe some hot glue on the back to help the little rivet like posts hold it together.
For the price it works okay, its still a conductive pad type of keypad, no frank, satisfying click when you press a button and most of them need to be pressed quite a bit to get a decent reading. I found that some of the buttons had over 50 and even up to 100 ohm of resistance on the line even when pressed, so take that into account if, say, you use a voltage divider in front of some pins and are expecting a precise reading.
So far, works like a beauty. However, this DOES NOT have headers pre-soldered. I would recommend products/115 or 553.
I used this for a custom number sign. Worked fine. Word of caution do not use a cold soldering iron on this as it will fry the traces. :)
Like someone else said, these buttons work by pushing down a connection on some electrical paint on the circuit. Just pushing the buttons is inadequate.
You must mash the buttons deep into the next dimension to get a clean reading (or in my case, any reading).
Once I soldered some pins and figured out how to hook it up properly to my PIC18F4550 it worked great! Solid little keypad.