Daniel C. Harris  

Orchestra is a project where I created a portable wireless speaker that is able to play notes over a range of frequencies. Wireless packets were sent by a separate microcontroller (ATmega32U4), which specified the exact frequency and duration of each note. 

 

In order to generate smooth notes, the square waves from the microcontroller were passed through both a low pass and high pass filter to create a sine wave. The frequency, which corresponds to the pitch of the note was regulated using duty cycle. To control the volume of the speaker, a potentiometer was used along with an op-amp - the output voltage was directly proportional to how loud the speaker was. Two 9.0 V alkaline batteries were used to power the device. The video below illustrates the speaker in operation.