Can't get DIY keypad to work

Bursar · Post by **Bursar** » Mon Dec 23, 2002 4:38 pm

I've been struggling all day trying to build a DIY keypad for my LK204 25 WBV LCD.

I knocked up a sheet of paper with 5 strips of tin foil on, and connected each strip to a column pin.

I then had a second sheet of paper with some holes cut in it to act as the insulation layer.

Finally there was a 3rd sheet of paper with another 5 strips of foil on, and they connected to the row pins.

Whenever I shorted a connection, I got the same keypress regardless of where on the row (or column) I press. So all of column 1 would give me an input of E for instance. Column 2 would give me a J. (I can't remember the exact keypresses, but you get the idea).

This is driving me completely mad. I've posted over at Bit-Tech, and they've given me a little advice, but I think essentially what I have built *should* work. I'm not very good at this electronics stuff, so it could be that I've missed something very very obvious.

Any pointers to what this could be would be gratefully appreciated.

Post by **Henry** » Mon Dec 23, 2002 11:35 pm

You have to make sure a row and a column get shorted together, not 2 of the same...

Bursar · Post by **Bursar** » Tue Dec 24, 2002 4:27 am

Upon further investigation, it seems as if a single sheet of paper isn't enough to act as insulation, and may have been causing a couple of keys to short at the same time.

Once I beefed it up a bit more, it seemed to work.

Talk about always checking the obvious things first...