A Circuit with a Speaker

Materials needed:

Any circuit with a speaker (i.e., an audio output device with more frequency
range than a simple buzzer) is suitable for this packet, e.g.
this speaker circuit that uses a transistor as an
amplifier, or the circuit below which uses a MOSFET:

Notes:

  1. The smaller resistor (1kΩ) goes between the digital I/O pin on the Arduino and the Gate of the MOSFET.
    The larger resistor goes between the Gate and GND.

  2. Do not turn on the battery pack until/unless you have made all the connections
    and verified them.

  3. Be careful to get the polarity of the Zener diode right as indicated in the figure.