Hack old vending machine touch pad to control LED lights

Question

I am converting an old vending machine into a box you can sit in and i wanted to hack the vending machine touch pad to be able to change the lighting patterns of LED strips i want to mount inside the box. the touch pad has 21 buttons, and a 12 pin attachment. (i attached a photo of it). I am a newbie at electronics and it was hard to even find a place to ask a question like this. Any help will be appreciated. 
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genebren · Answer

Mike,

These switches are usually connected as a matrix of rows and columns, with the switches connected between them. Like this:

Using an ohm meter, connected between a column and a row, press the switches until you see a low ohm reading. Just guessing from the image of the pad/connector, that the three pins towards the right might be the columns and 7 or the 8 pins to the left might be the rows.

Hopefully this will help you get started.

Good Luck!

Gene

dougw · Answer

No power needed - the resistance meter has its own power. It is not a good idea to measure resistance with power on the controller as it can overload the meter.

beacon_dave · Answer

I recall lorrainbow demonstrating working out a keypad matrix in one of her videos: #badass Woman Project Entry - Lorraine Underwood May be of interest.

genebren · Answer

Mike, This switch pad will most likely connect to a controller of some sort. You are not likely to find a controller that will directly interface to this switch pad and control the lights in the exact way that you would like. I would think that something like an Arduino would make an excellent starting point. The controller will read the switches and according to a program, take appropriate actions based on the program that you write. There are many great examples on Ardunio based projects on this site that you can look at to get an idea of what might be involved. Using an ohmmeter ( https://www.newark.com/velleman-sa/dvm850bl/compact-dmm-with-backlit-display/dp/88C3438 for example) you can map out the rows and columns of the matrix and determine where in the matrix each switch is connected. This will necessary so you can program the Ardunio how to determine which switch is being pressed, and how to respond to that switch press. To do this, start by attaching on lead of the meter to one of the pins on the connector (I would try on of the pins to the right of the connector). Attach the other to another pin (one of the pins to the left of the connector). The meter should read a high resistance (open). Now start pressing buttons until the meter reads a low resistance (switch closed). Write down the two pins and the button that was found to make a connection. Now, change the lead on the left side of the connector to another pin (still on the left side) and repeat the process. After finding seven switches, change the other lead (on the right side of the connector to another pin). It is not going to be some magical, plug and play experience. You will need to put a lot of pieces together in order to make your creation come to life. But in the end, you will have learn a lot and also have a very unique creation of your own making. Have fun, good luck and never stop asking questions or learning new things. Gene

Hack old vending machine touch pad to control LED lights

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