The NeoMatrix Mk I circuit is diagrammed above. You can refer to this while connecting the components during assembly.
Begin assembly by affixing components to the inside of the front panel, starting with the keypad.
The NeoSegment modules will also be assembled from the inside of the front panel, however, they require a bit of preparation first.
We'll use nylon hex standoffs to mount the Adafruit Metro board to the inside of the front panel.
- Place four medium nylon M2.5 screws into the front panel from the outside/front facing in
- Screw the four stand offs to the screws from the inside of the front panel
- Use the four short M2.5 screws to screw the Metro in place on the hex stand offs
The two potentiometers will be mounted from the inside of the front panel and screwed into place with their included hex nuts.
- Remove the small metal keying tab from each potentiometer with a pair of pliers, so that they can be mounted flush to the panel without adding a keying registration hole. One reason this works is that the soft wood allows the part to still bite in from the compression of the nut alone. If you use acrylic, you may want to also cut a keying tab registration hole to prevent the potentiometers from spinning, since acrylic does not compress
- Mount the potentiometers from the back side of the front panel as shown
- Screw the washers and nuts into place from the top
- Turn the potentiometer shafts to the far left and then place the knobs on them with the indicator at the lower left position. Check that this positioning is symmetrical when the knob is turned to the far right
You'll attach the piezo buzzer to the back panel next.
- Put the piezo into the pre-cut hole from the inside of the back panel
- Insert the two long M2.5 nylon screws from the outside, then screw on the nuts from the inside
Next, you'll connect the pushbutton and the USB jack to the two side panels.
Wiring Everything Together
Now that everything is assembled, we need to wire all of the parts together. We'll start with the keypad.
The keypad matrix uses eight wires to send data to the Metro, which we'll set up in software for pins 2-9. We'll create a custom cable to make this set of connections.
Low Profile Interconnects
Connecting the electronics is fairly straightforward, however, in order to keep a low profile in a small enclosure, we will need to make 90 degree angle connector cables.
A nice, more permanent alternative is to solder the wires directly to the Metro. If you choose this path, start of with the Metro that comes with no headers.
The other end of the wires can be pressed directly onto the phone keypad pins as shown, with a piece of heat shrink tubing over each one to prevent any shorts.
Connect the cable to the Metro as shown.
Just like any NeoPixel-based project, we'll need to connect power, ground, and data lines from the Metro to the display.
- Snip off two two-pin section of 90 degree jumper pins
- Strip off a brown jumper wire from the pack and fit and solder one end to the "left side" of the short lead of a 90 degree jumper pin as shown
- Cover the connection with heat shrink tubing
- Strip off a red and black wire from the pack and fit and solder one end of each to the other two-pin 90 degree jumper, with red on the "left" and black on the "right" as shown in the second image here
- Insulate the connections with heat shrink tubing
- Connect the brown jumper pair to pins 12 and 13 on the Metro. Pin 12 will be the data line for the Metro, while we'll use pin 13 later for the pushbutton's internal LED
- Connect the red/black jumper pair to 5V and GND on the Metro
Slide and heat some heat shrink tubing over the the other ends of these three wires. Then connect them to the NeoSegment's interconnect as shown here. Be sure to follow the image closely for wiring order.
- Connect the piezo's red and black wires to two lengths of jumper wires by sliding the piezo wire ends into the connectors and soldering them
- Cover the connections with heat shrink tubing
- Slide another piece of heat shrink tubing over each wire, then connect, solder and insulate each wire to a 90 degree header pin as we have before
- Plug the black wire into GND on the Metro, and plug the red wire into A1
Now, plug the ground wires into GND on the Metro, the power wires into 3.3V, and then the two center wiper wires into their respective pins, A2 and A3.
The pushbutton has four contacts -- two for the switch and two for the LED. Connect the switch contacts to GND and pin 11, and the LED contacts to GND and pin 13, as shown in the wiring diagram.
The final connection to wire is the USB port, which is the easiest!
Closing the Case
You can add glue to the side and bottom connections to the faceplate if you like, but just the tight fit and compression force of the four screws is enough to hold the case together nicely.
Last updated on Dec 01, 2017
Published on Nov 27, 2017
Time to add the software!