Small Piezo Buzzers

The Chip on Blob board, From left to right, on the top:

1. Ground, unconnected
2. V+
3. Green Led (Off when Logic High) (1kΩ resistor to PNP Base)
4. Yellow Led (Off when Logic High)(1kΩ resistor to PNP Base)
5. Red Led (Off when Logic High) (1kΩ resistor to PNP Base)
6. Regulated Ground
7. Unknown, Connected to Pin 8 with a resistor, probably a mode select or delay based on the resistance.
8. See 7.

The capacitors are bypass 0.1uf capacitors, simply to filter out some noise on the power supply, standard value on nearly everything.

The Transistors are PNP transistors. Collector to the LED/Resistor/Ground, Emitter to V+. They are on when the base is logic low (ground), and off when the base is logic high (v+).

To use it with an arduino, you would simply remove the CoB board, connect a digital/pwm pin to 3, 4 and 5, as well as connecting the ground of the board and the arduino together. Since you would have it in output only, there isn't any issue with the V+ voltage level.

As the piezo's have very high output impedance, I would use a amplifier/buffer-stage as close to the pick up as possible. That way you reduce the pickup of (electrostatic) noise and it is much easier to mix the signals without one interfering the other. Once you have amplified the piezo signals to somewhere near regular line levels (1Vtt), you can use potmeters in the order of 10k for a passive resistive mixer and use a regular line input for further amplification.