This week I wanted to focus on using circuits to drive speakers, which I'll need to do in my final project. I built Neil's hello.speaker.45 board and drove an 8 ohm speaker from the lab inventory. I found this sound kind of grating and set out to write a code to make more pleasant sounds.
usage in final projectI used a speaker-drivng circuit in my final project in a fairly simple way; I have a detailed plan to use it in a more complex way but haven't actualized it yet. The final music box's speaker output is driven by a surface-mount N-channel MOSFET whose gate is driven by the pitch output pin of the ATtiny44. In a device with pitch and volume controls, the pitch output is structured similarly but the pin's output is also connected to the drain of a MOSFET that is connected at its gate to the volume-output pin. As the duty cycle of the square wave output on the volume-output pin decreases, more of the pitch output is pulled to this second MOSFET and the resultant output wave is high for less time.
A first draft of my ftheremin board with a separate board for driving the speaker, based on Neil's hello.speaker board.