DIY Switches for Assistive Tech – Big Button Audio Sound Box
In this guide you'll learn how to build an Audio Sound Box using Circuit Playground Express and CircuitPython. This device can play back short audio clips and features a really big arcade button that lights up when you press it. It’s a pretty simple project but it’s very useful for the assistive tech community. Similar products are actually quite pricey so a DIY solution can be cost effective, and of course this is customizable!
Prerequisite Guides
If your new to electronics and the Adafruit Circuit Playground Express, I suggest you walk through the following guides to get the basics. The Circuit Python guide will walk you through setting it up.
Electronic Components
The Circuit Playground Express, massive arcade button, PAM8302 amplifier and speaker are the main electronic components used in this project.
Hardware and Supplies
Just a few screws, stickers and wires.
1 x
JST Extension
Male to Female JST-PH Battery Extension Cable 500mm
1 x
Solder Wire
Solder Spool - 1/4 lb SAC305 RoHS lead-free / 0.031" rosin-core - 0.25 lb / 100 g
Cool Tools!
These help make the project a smooth building experience. You don't need them all of them, but I recommend them.
1 x
Spudger
Double Sided Prying Tool
1 x
Wire Strippers
Hakko Professsional Quality 20-30 AWG Wire Strippers - CSP-30-1
Circuit Diagram
This provides a visual reference for wiring of the components. They aren't true to scale, just meant to be used as reference.
- VOUT from CPX to VIN on PAM8302
- GND from CPX to GND on PAM8302
- A0 from CPX to Pot
- Pot to GND on CPX
- Pot to A+ on PAM8302
- A- from PAM8302 to GND on PAM8302
- Button to GND on CPX
- Button to A4 on CPX
- Speaker to -+audio output on PAM8302
- TRS to GND and A4 on CPX
- Battery to Pot / JST Extension
Fritzing Diagram
The circuit diagram was assembled in the Fritzing software. All of the components are contained in the source so they can be reused to make new projects. Download and modify the circuit diagram.
Setup Adafruit Circuit Playground Express for CircuitPython
We'll need to get our board setup so we can run CircuitPython code. First thing we'll need to do is connect the board to your computer with a microUSB cable. Then double-click on the reset button to put it in "UF2" boot-loader mode. The NeoPixels will turn green. The board will then show up as a USB storage device on your computer named "CPLAYBOOT".
Follow the guide below to setup the firmware, once complete, come back here and proceed.
Download Adafruit CircuitPython Library Bundle
In order to run the code, we'll need to download some libraries. The download linked below will contain all the libraries available for Circuit Python. To run the code for this project, we only need a few. Unzip the downloaded file and look for the following libraries.
Required Libraries
- Adafruit Neopixel – neopixel.mpy
- Adafruit HID – adafruit_hid
- Adafruit Circuit Playground – adafruit_circuitplayground
Install Circuit Python Libraries
Now that we have all of the libraries and know which ones this project needs, we'll need to copy them onto the Circuit Playground Express USB drive (which will be named CIRCUITPY after flashing the firmware). In the CIRCUITPY drive, create a new folder and name it "lib". Then, copy the libraries to that "lib" folder. The lib folder should contain neopixel.mpy, adafruit_hid and adafruit_circuitplayground .
Upload Code
OK, now it's time to upload the code for this project onto the CIRCUITPY drive. Create a new text document using a text app. Then, copy the code below and paste it into that newly created text document. Save that text document to the CIRCUITPY drive and name it "main.py". Once saved, the code will automatically run and will start working.
Editing Code
You'll want to use the Mu python editor to modify the code. Mu is a simple code editor that works with the Adafruit CircuitPython boards. It's written in Python and works on Windows, MacOS, Linux and Raspberry Pi. The serial console is built right in so you get immediate feedback from your board's serial output! See the guide below to for download and setup instructions.
import board
from digitalio import DigitalInOut, Direction, Pull
from adafruit_circuitplayground.express import cpx
import audioio
from adafruit_hid.mouse import Mouse
import neopixel
import time
# Audio file name
# By default we'll use a friendly sample of Adabot
# https://www.youtube.com/watch?v=exlRjDKHGRg
AUDIOFILE = "electrons.wav"
# What pad our button is connected to:
button = DigitalInOut(board.A4)
button.direction = Direction.INPUT
button.pull = Pull.UP
# From 0 to 1.0 - adjust as desired!
cpx.pixels.brightness = 0.5
# also be a 'mouse' if desired (requires being plugged into the tablet/computer)
mouse = Mouse()
#NeoPixel stuff
pixels = neopixel.NeoPixel(board.NEOPIXEL, 10, brightness=1)
def simpleCircle(wait):
PURPLE = (0x10, 0, 0x10)
BLACK = (0, 0, 0)
for i in range(len(pixels)):
pixels[i] = PURPLE
time.sleep(wait)
for i in range(len(pixels)):
pixels[i] = BLACK
time.sleep(wait)
while True:
if not button.value:
# uncomment this line if you want it to click!
# mouse.click(Mouse.LEFT_BUTTON
audio = audioio.AudioOut(board.SPEAKER, open(AUDIOFILE, "rb"))
audio.play()
while audio.playing:
simpleCircle(.05)
pass # wait for audio to finish
# wait for button to be released
while not button.value:
time.sleep(0.1)
import board
from digitalio import DigitalInOut, Direction, Pull
from adafruit_circuitplayground.express import cpx
import audioio
from adafruit_hid.mouse import Mouse
import neopixel
import time
# Audio file name
# By default we'll use a friendly sample of Adabot
# https://www.youtube.com/watch?v=exlRjDKHGRg
AUDIOFILE = "electrons.wav"
# What pad our button is connected to:
button = DigitalInOut(board.A4)
button.direction = Direction.INPUT
button.pull = Pull.UP
# From 0 to 1.0 - adjust as desired!
cpx.pixels.brightness = 0.5
# also be a 'mouse' if desired (requires being plugged into the tablet/computer)
mouse = Mouse()
#NeoPixel stuff
pixels = neopixel.NeoPixel(board.NEOPIXEL, 10, brightness=1)
def simpleCircle(wait):
PURPLE = (0x10, 0, 0x10)
BLACK = (0, 0, 0)
for i in range(len(pixels)):
pixels[i] = PURPLE
time.sleep(wait)
for i in range(len(pixels)):
pixels[i] = BLACK
time.sleep(wait)
while True:
if not button.value:
# uncomment this line if you want it to click!
# mouse.click(Mouse.LEFT_BUTTON
audio = audioio.AudioOut(board.SPEAKER, open(AUDIOFILE, "rb"))
audio.play()
while audio.playing:
simpleCircle(.05)
pass # wait for audio to finish
# wait for button to be released
while not button.value:
time.sleep(0.1)
Audio Files
If you'd like to create your own sounds, they will need to be a certain file format. You can use this Adafruit Guide or online converters to encode your audio files. You can download our audio sample for reference and to quickly test and get started. The format of the sound file should be:
- .Wav File format – 16-bit integer (Little Endian)
- Mono, 22.050 kHz
What If I Don't Have A 3D Printer?
Not to worry! You can use a 3D printing service such as 3DHubs or MakeXYZ to have a local 3D printer operator 3D print and ship you parts to you. This is a great way to get your parts 3D printed by local makers. You could also try checking out your local Library or search for a Maker Space.
3D Printed Parts
All of the parts are 3D printed with FDM type 3D printers using various colored filaments. All of the parts are separated into pieces to make 3D printing easier. Assembly is pretty easy and straight forward. Use the links below to download the STLs files.
Slice Settings
These parts have been tested and 3D printed on an Ultimaker 2+ and 3 using PLA filament. The parts were sliced using CURA 3.x with the following slice settings.
- 220C extruder temp
- 65c bed temp
- 0.2 layer height
- 0.38 line width
- 2 Wall Line Count – 0.4 nozzle
- 20% infill
- 50mm/s print speed
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Enclosure Design
To house all of the electronics I designed a parametric box using Autodesk Fusion 360. Most of the components will be paneled mounted or secured to built in standoffs with machine screws. |
Design Source Files
The camera body assembly was designed in Fusion 360. This can be downloaded in different formats like STEP, SAT and more. Electronic components like the PAM8302, Circuit Playground Express, potentiometer and speaker can be extracted from the Fusion 360 Archive.
Disassembling Arcade Button
We'll need to take apart the arcade button in order to embed the CPX. The button is designed to be disassembled so it should be fairly straight forward. We'll start by removing the micro switch from the button assembly.
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Remove Micro Switch
Grasp onto the outer button housing and micro switch. Firmly twist the micro switch counter clockwise – It should make a click. Then, pull out the body of the micro switch away from the stem. The micro switch should have the LED housing intact. |
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Remove Threaded Ring
Unscrew the threaded ring from the stem of the button housing. The outer button housing should loosely pull out from the stem. |
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Separate Button Housing
Pinch the two white colored tips on the end of the button stem while pushing them into the stem – The white housing should lift up out of the black housing. Separate the two and set side the compression spring. |
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Spudger Action
Pry open the dome from the button housing using a spudger or tool with a slim shim edge to get in between the two. Firmly gasp onto the dome while conducting the prying action. |
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Micro Switch Teardown
Pull back the taller black colored clip from the red side of the micro switch. Rotate the micro switch until it comes loose from the black colored housing. Pull out the LED housing and two metal terminals from the black housing. |
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Pre-drill Planning
We need to pass wires through the white colored housing so we'll need to drill some holes. We can use the holes from the outer housing as reference for marking where the holes need to be. |
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Marking Holes
Place the white colored button housing into the main container. Flip the assembly over and use a sharpie marker to fill the holes. |
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Slotted Holes
Note the orientation of the legs on the white housing, this ought to be in the correct position to allow proper actuation. The two parts have some give so they can move slightly – you'll want to fill as much space available to create slotted holes. |
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Marked Holes
Remove the white housing from the container to the marked slotted holes. These don't have to by fully filled, just enough to get a good reference for drilling. |
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Drill Holes
Now it's time to make drill holes! Your choice of tool, a rotary tool like a Dremel or an impact drill will be suffice. To prevent drilling holes into our tabletop, we place a scrap piece of wood under the white housing. This will catch the drill bit when it pokes through the housing. |
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Drilled Holes
Drilling plastic for too long can cause the material to over heat and melt leaving behind welded chips. I used a pointed sanding bit to grind away material while smoothing out the edges. |
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Test Fitting
Reinstall the housing to see if the holes line up – Be sure to orient the actuator legs in the correct positions. These holes should allow enough space for wires to pass through. |
Wiring Check Point
Now is a great time to double check all of the component to ensure everything is wired up correctly. If any wire lengths need to adjusted or need additional pieces of heat shrink tubing, now is the time to get those setup.
