Hello, I know there are a plethora of topics about interfacing an old phone's keypad to arduino, but the the keypad I am using doesn't appear to be working the same way!
The wire colors from the keypad are: Black, White, Brown, Red, Red-Green, Green, Orange
Most posts about this talk about finding the pin pairs that complete the circuit between row and column such as:
etc
However, the keypad I have does NOT produce such results. When I used the tone mode on my multimeter when the circuit is complete, I tried every pair and only on Red to Red-Green pair did it produce a tone, which was constant unless ANY key was pressed which stopped the tone.
Then I did another round of each pair testing the resistance. This yielded more complicated results, most pairings produced a constant reading which differed in value but wasn't affected by any key presses. Pairing any wire with the Red wire produced a constant reading which went to zero when ANY key was pressed. Some other pairings produced the same result as that except not with every color like Red did. Some pairings produced no reading.
Does anyone have any clarity on this? Almost every resource I am finding talks about having column/row pairs that complete the circuit but it does not seem to be the case for this keypad! thanks for any advice!
Thanks for the responses! I'll try and figure out how to interface the button connections with the arduino. Haven't quite wrapped my head around it yet, but as an initial question do you think I'm better off bypassing (if it's even possible/easier) the MK5087 and the other circuitry and try to just interface the pins coming straight from the keypad with some kind of pairings similar to the other row/column posts? thanks
You can use the keypad by itself, but the contacts probably have fairly high resistance.
The buttons press a rubberized carbon disk onto the naked, E-shaped PCB sections, so you might find 10K to 100K Ohms resistance between keypad leads, when a button is pushed. Let us know what you measure.
If the PCB button contact traces are oxidized, it might help to clean them with a rubber pencil eraser.
Ok just finding pairs off the keypad itself seems to be working! It's measuring about 33-40ohms so far for the pairings! Many thanks for the help, it sounds like I can just send the appropriate pins directly in the arduino GPIOs and do the logic programmically then?
That should work well. The contact resistance is lower than I expected (based on experience with a similar keypad from a calculator). Did you clean the PCB pads?
Nope I just went for it as is! Was pretty clean inside though. Well I guess I was wrong and this keypad worked just like others when I bypassed the other components.. hopefully this could help someone in a similar situation! Thanks all!
