The same circuit is used for both the talking computer and total conversion beam props. The nine buttons on the right are only needed for the talking computer. If building the total conversion beam, those (and the associated wires) can be omitted.
The circuit requires 5 or 6 ground connections (depending on prop), but the Feather M4 board only has 4 ground points (3 in the small power rails at the end opposite the USB port, 1 near the reset button).
Therefore, you’ll need to feed two wires through a couple of the ground points to make everything fit. You can see this in a couple spots in the diagram below.
To make this easier to assemble into the prop, several of these parts will have connectors installed, not shown here. We’ll detail those (and correct wire lengths) on the following pages. Consider this just a schematic.
That’s a bit of a visual tangle, so here’s a summary of the individual connections:
PAM8302 Amplifier to Feather M4
- GND to GND
- VIN to 3V
- A+ to A0
- A– to GND (use GND on amplifier)
Speaker to Amplifier
The mini oval speaker is connected to the audio out pins of the PAM8302 amplifier.
- Positive (red wire) to ⊕
- Negative (black wire) to ⊖
- Center pin to GND
- Either one of the two outer pins to En (enable)
- The other outer pin is not connected
Push Button (trigger)
The button has no specific polarity. One pin goes to Feather GND, the other to Feather pin A1.
- Anode (longer leg) to A2
- Cathode (shorter leg) to GND
- Pin 1 to GND
- Pin 2 to A3
- Pin 3 to 3V
Mechanical Key Switches (“Talking Computer” only)
Each switch has two pins and no specific polarity. One pin of every switch goes to Feather GND (these can be chained switch-to-switch, as we’ll show on a later page). The other pin of each switch is connected to a different point on the Feather M4:
Since this prop is just a noise-maker and not an actual keyboard where we need to type real things, any switch can go to any of the above pins, whatever you find easiest when soldering. If you want to tie a specific sound to a specific key, that can be easily changed in the code.
The diagram below provides a visual reference for wiring of the components. This diagram was created using the software package Fritzing.
Use Adafruit's Fritzing parts library to create circuit diagrams for your projects. Download the library or just grab individual parts. Get the library and parts from GitHub - Adafruit Fritzing Parts.