tracing out membrane buttons
some of you may remember awhile back I was asking about VFD's and such to make a lathe variable speed. Long story short I did it by gutting a treadmill and using the motor and control boards.
Everything works fine, however I want to add my own push buttons in place of the membrane buttons and totally get rid of the treadmill console board.
There are a total of 15 buttons that do various functions and 8 wires that go into a ribbon cable that was plugged into the control board. I have unplugged the ribbon cable and replaced the 8 wires with 8 leads (just some CAT5 cable I had laying around.
Here's where I am confused. In order to get something to work I have to touch three leads together, not two. So I figured that's weird but I went with it and one by one I found three lead combinations that worked for each function. So I figured I had all the buttons figured out and what wire combination I needed to get that function to work.
I thought great I'm good to go and can put in my push buttons I'll just have two leads on one side of the button and one on the other. WRONG!
I for the life of me can not figure it out. For example if I have something like orange, orange/white, and green be my start button and I wire it to one button it works fine, but if I add another button and it's something like orange, brown, and green/white it goes haywire and starts another function randomly, or it does nothing at all.
I've tried to trace it from the membrane switch console itself just following the green lines, but I can't seem to get it right.
Can anyone shed some light on this for me? I've never dealt with membrane switches before, why does it need three leads? Shouldn't it just be "power" and "switch leg"? What the heck is the third one and how do I deal with it so I can add just normal push buttons????