12 Key Matrix Encoded Keypad Question

[jstevenperry]

Does anybody have a good circuit diagram for how to hook up a matrix encoded keypad. It doesn't have to be 12 key, that's just what I have. If, say, you have one for a 16 key, I can extrapolate. I am trying to get this sucker breadboarded and it's driving me crazy. I's appreciate any help.

Just for fun, what I'm trying to do is hook this keypad up in such a way that when I press a particular button on the keypad, a corresponding LED lights up. But it's not working, and I think that I've just got the wrong picture in my head (I'm not working from a schematic, just from what I think I know about how these suckers operate...they're just a matrix of switches, right?)...

Here's a picture of what I've got so far, just to give you an idea of what I'm going for. Any help would be appreciated. Thanks.

View attachment 38192

 

[ante1]

Hi,

This is how it looks inside, hope it helps!

View attachment 38195

 

[jstevenperry]

Thanks, Ante. Then combine the output pins on the keypad with some AND gate logic and I should have it, right?

 

[ante1]

Yes, there are chips made for this job!

 

[jstevenperry]

They're electromechanical, and work just like the picture Ante posted (except the pic he posted was for a 16 key, but conceptually no big diff...a 4x4 matrix versus a 3x4).

The problem I'm having now is my AND gates (to produce a signal that corresponds to the exact switch in the matrix that was pressed) are doing weird things. I've posted that to a new topic, so not to pollute this topic. To me, the question I had regarding the 12 Key Matrix encoded keypad has been answered.

Thanks to all for your replies!