A position sensitive midi drum pad

Step 5 Soldering the piezos

The next thing is to solder up the piezos. You want to use quite thin wire for the actual connection, then solder this to the thicker shielded cable that takes the signal to the arduino. The smaller disc on top of the piezo is ground, and the larger one underneath is the positive. Ideally, solder the shield of the cable to the piezo's earth and the inner core to the positive.

If you get to the end of the project and find that you have the polarities wrong, don't panic! The current firmware on the arduino only deals with absolute values not positive and negative, so it shouldn't make too much difference.

Once this is done, use epoxy to glue a small metal disc (e.g. a 1 pence coin) to the top of each piezo to provide a bit of clearance above the wires and make a solid contact with the bottom of the aluminium sheet. Make sure the disc, and the glue you use, are only on the top, inner disc of the piezo's ground electrode, not touching the outer disc.