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Practical question about circuits and stuff.

  1. Dec 31, 2005 #1
    Practical question about circuits and stuff. :D

    Maybe this is the wrong forum.. but I'm trying to do something... (Might be silly, but oh well..)
    I have this dance dance revolution (DDR) pad-- for those of you who don't know, it's that arcade game which everyone plays at arcades and stuff-- for the playstation...
    I want to use it on a PC... but I can't afford buying a USB->PSX convertor (Shipping prices to Kuwait are pretty high :()
    So... I thought of something... buying a USB keyboard, opening it up, and making a parallel circuit such that when I press one of the arrows on the DDR pad that it "maps" to a key on the keyboard-- i.e. I'd solder one wire onto one side of the key I want to map the arrow to on the keyboard, and another one on the other side, and those would be soldered "accordingly" onto the DDR pad-- however it works..

    Now, I opened up the DDR pad to see this:
    The pics are:
    1.JPG -> the bottom side of the pad....... (opened up-- circuit)
    2.JPG -> Me pulling that bottom-side circuit up to show the soft stuff which, has under it, the top-side circuit which the pad itself comes in contact with..
    3.JPG -> The pad itself-- for those interested.
    4.JPG -> Me showing the top side of the bottom circuit... I'm guessing the top circuit behind the soft stuff is pressed down and somehow "completes" the circuit so that the button is pressed? But I'm really not sure...

    I'm now utterly confused and would like to know if someone can give me some pointers on a possible way to set this up so that I can press a button that would be "mapped" to a key on a keyboard the way I explained above....

    I'm sorry if this is in the wrong forum, but I thought electronic engineers would have a very strong foundation in these commercial products and might be able to help me out with this... (And might be able to explain to me how these work :) )

    I hope someone can help me out...

    THANKS for any replies!
  2. jcsd
  3. Dec 31, 2005 #2
    I didn't spend alot of time looking at the pictures. I would expect that the pad has a gridwork with column and rows. The keyboard is most likely the same way. There is not likely a pair of wires for each key or even a single wire for each key which is connected to a common wire when the key is pressed. Think of a spreadsheet. Each cell is connected to a column and row. Cells share rows, and cells share columns. But each cell is uniqe in the pair that it is connected to. I'm not saying that you can't do it. I'm saying that it is probably a little different than you expected.
  4. Dec 31, 2005 #3
    I thought a keyboard was really a switch... where if you press a button what it does is complete the circuit?
  5. Dec 31, 2005 #4


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    Science Advisor
    Homework Helper

    You may want to read up on computer keyboards and how they interface to other components. Here is a primer to get you started. It illustrates an example showing how to interface a PC keyboard to a single chip microcontroller (68HC705J1A)
  6. Jan 1, 2006 #5
    I never said it wasn't a switch pseudo. It just doesn't complete the circuit in the conventional way like I posted earlier.
  7. Jan 2, 2006 #6


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    Staff: Mentor

    You're on the right track. As mentioned already (and probably covered in the keyboard primer link), keypads use a row/column organization. Pressing a key or stepping on the dance pad completes a connection between a row and a column, and the scanning circuit detects this connection as it energizes each column in turn and looks to see if any row is energized. I'm using the term energized loosely of course -- the typical circuit would raise a column to something like 5V, and look at the voltages on each of the rows to see if any button is pressed. There are also diodes included in the row/column connections to allow the scanning to be able to detect multiple buttons being pressed at the same time without introducing phantom button presses.

    So your task simplifies to figuring out how to map the row/columns of the dance pad into a subsection of the keyboard row/column circuit. You should be able to just wire the limited number of row/columns of the dance pad in parallel with a couple of the row/columns of the keyboard. If you can watch the scanning signals with an oscilloscope, that will give you a good idea of how to make the connections. Have fun!
  8. Jan 4, 2006 #7
    The dance pad and many keyboards are both film contact switches. I've repaired a ton of keyboards with conductive trace paint. If you look at the connection to the console it should have 6 or eight wires/pins. if you build a cable that adapts the console plug to a ps2 keyboard plug it should be a start. The actual pinout might need to be adjusted , a free keyboard analysing program should clear up which pad press is what key.
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