DIN scan matrix

[jwillans]

As part of the organ I am buildng, I have aquired a bank of 16 illuminated rocker tab switches which come mounted on a single PCB.  Tracing the PCB to the connecting socket it seems that they are arranged as a scan matrix of 4 * 4.  Is there an approach to using a scan matrix of this type with the DIN modules?

Thanks,

James

[jimhenry]

Look at these two example projects:

http://www.ucapps.de/mios/sm_example1_v2.zip

http://www.ucapps.de/mios/sm_example2_v1.zip

The scan matrix approach has not been used many people so you'll be somewhat on your own in pursuing this. For 16 switches, I'd be seriously tempted to cut traces and just wire each switch individually. Not elegant but less work on the Midibox end.

[jwillans]

JimHenry - Thanks for your continued advise, I guessed that this would be the best solution.  Excuse the naive question but, if I was to break the traces on the PCB using a knife, how would I go about adding a new terminal to that trace that I can interface to?  Is there a well documented approach to doing this?

Thanks,

James

[jimhenry]

I have never seen documentation of how to rework a PCB, sometimes called "cut and jumper." The basic idea is to make two cuts across the PCB trace, perhaps an 1/8" apart and remove the trace between. Sometimes a soldering iron will release the cut trace. Leave enough trace that you can lay a wire flat against the trace and solder it to the trace. If done well the solder should "hug" the shape of the wire rather than being a big blob. Mechanically support the wire somehow, perhaps a dab of hot glue. Find an old PCB and practice before attacking useful boards.