At this point, you'll have 6 LED matrices that will press fit onto the frame, and an assembled QT Py + power circuit, like shown below:

The plan is to connect 4 matrices together to form one long matrix display that will wrap around all 4 sides of the cube. Then, we'll have one matrix be the "top" matrix and another one will be the "bottom" matrix, each separately connected to the QT Py as separate displays. 

Use some kapton tape to cover about 40% of the circle pads of the matrix. This will ensure that we can press-fit the matrices flush into the 3d printed frame.

 

Tin these pads with some solder, and verify that the area under the kapton tape did not get solder on it. A tiny bit is ok, as long as the tape is still mostly flat.

Cut about 10cm of 4 different colored wires, and solder a different color onto each pad. Stick to these colors to help you chain the 4 matrices properly. These are the colors used here:

  • White for CIN/COUT
  • Yellow for DIN/DOUT
  • Black for GND
  • Red for 5V

Use the flush cutters to cut off any excess wires that might be over the taped area. Again, doing this will ensure that the matrix will sit flush in the 3D printed frame.

Do the above steps for all 4 matrices, and make sure to connect the matrices to each other via the correct pad connections as follows:

  • CIN to COUT
  • DIN to DOUT
  • GND to GND
  • 5V to 5V

You can optionally choose to braid the wires together for a cleaner look. When you've chained 4 matrices together, it should look something like this:

Take one more matrix, and solder the same colors of wires to each pad, using the same kapton tape technique discussed above.

This will be the bottom matrix.

Now it's time to connect the CIN and DIN wires of the "side panels" and the bottom matrix into the QT Py. Solder the wires as follows:

  • Side panels CIN (white) to A2
  • Side panels DIN (yellow) to A3
  • Bottom matrix CIN (white) to A4
  • Bottom matrix DIN (yellow) to A5

Afterwards, connect about 10 cm of white wire to A0 and connect the same length of yellow wire to A1. Do not connect these wires to anything yet, these will connect to the "top" matrix later.

Combine both the GND (black) and 5V (red) wires for the side panels and the bottom matrix as shown, we'll solder these next.

The QT Py has castellated edges, meaning that it's actually possible to solder on the edge of the board. We'll take advantage of this -- solder the combined red 5V wires of both the side panels and bottom matrix to the 5V edge of the pin, and then do the same for the black GND wires. 

And then cut separate pieces of 10 cm each of red and black wires, and solder to the edge of the castellated pads on the charger add-on. These two wires will be connected to the "top" matrix later on.

Now, you'll have all 4 side panels and the bottom matrix connected to the QT Py. You'll also have these 4 wires sticking out of the QT Py which will connect to the top matrix later. 

Before we can connect these wires to the top matrix, we'll need to first put some heat shrink around the QT Py to protect it while inside the cube

Measure some heat shrink (about 3/4" width) to roughly match the height of the QT Py. When heat is applied, the width will shrink but the height will barely change.

Thread the loose wires, the battery, and the switch through the heat shrink, and then position the heat shrink around the QT Py. 

At this point, you can now attach the top matrix to the loose wires, using the same kapton tape technique we used for the other matrices.

Then, take the LIS3DH accelerometer board and measure some heat shrink (about 1/4" width) to match the height of the board.

Attach the STEMMA QT wires between the QT Py and the sensor board.

Arrange the wires on the QT Py such that they are not on top of the two onboard buttons. Use a hot air gun set to about 110C and carefully apply heat to shrink the heat shrink wrap. 

Now your electronics are well protected and ready to be stuffed into a tiny cube!

At this point, you'll be ready to upload some code onto the QT Py to test that everything is connected properly. The entire assembly should look similar to this:

This guide was first published on Sep 07, 2022. It was last updated on Apr 20, 2024.

This page (Solder and assemble LEDs) was last updated on Mar 08, 2024.

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