In this project we're using 32 DotStar LEDs but you can optionally use more or less – It's up to you! However, the stick was designed for 32 LEDs. Either way, it's good idea to count multiple times and cut once.
Plan The Cut
It's a good idea to think about how you're going to cut the strip. The DotStar LEDs are very close to each other and it's easy to accidentally cut the pads too short. I suggest using a flush diagonal cutters to make flush cuts. The ends of LED strips may have wires and hotglued ends already on them, so it may be necessary to remove them. Another option is to have a "sacrificial pixel" like mentioned in Beck's Guide.
It's important to be aware of the signal direction. The arrows on the strip depict the flow and direction of the data. The wires coming from the Adafruit Feather going to the DotSar strip this way [Feather]→[LED Strip]
If you'd like to make the wand have LEDs on both sides, you can cut another strip with the same pixel count. This is optional, so you can choose how many pixels you want. We won't be needing the protective sheathing, so you can remove them from the strips.
The pads on the DotStar strips are fairly small, so it's best to use a fine tipped soldering iron. Add a tiny bit of solder to the pads, this will make it easier to attach wires to them.
Wires for Strip
Now it's time to make some wires! Each strip needs four wires to connect to the Adafruit Feather. If you'd like to use two strips, you'll need to make two sets of wires. These will need to be long, about 150mm in length (or the length of the handle). Use pieces of heat shrink tubing to keep the wires bundled together.
Since these are stranded wire, it's a good idea to tin them. Using wire strippers, remove a bit of insulation from the tips of each wire and then add a bit of solder. You can use different colored wires to help tell the connections apart.
Connect Wires to Strip
Be sure to double check the data flow before soldering the wires to the pads! Solder each wire to the pads on the DotStar strip. Use common colors like red for voltage, blue for ground, etc.
If you're using two strips, you'll need to wire those up. I used a few pieces of heat shrink tubing to keep the wires bundled together. Both have similar wire lengths and colors to keep it consistent.
Now it's time to connect the strips to the Feather! Connect the voltage power wire from the strip to one of the available 3V pins. Connect ground from the strip to one of the available ground pins. Then, clock input to SCK and data input to MO. Remember, these are not labeled on the high density strip, so you'll have to reference the circuit diagram to get the right connections.
Wiring up two strips gets a little cluttered because you'll need to share the SCK and MO pins with two wires. However, the Adafruit Feather has several power and ground pins, yay!
And here's the final circuit wired up. At this point you should have the Adafruit Feather M0 Express setup and the code already uploaded to the board. You should be able to test out the strips and power the circuit on with the slide switch. If it's all good, then proceed to the assembly.