9

Smart backpack with wireless charging pocket

FORGE

SEW THE POCKET IN PLACE

Now that we’ve made all the individual pieces, we’re

ready to attach the pocket and charger straps to the

bag. Start by pinning the strap in place on the inside

of the bag. Test the fit by slipping the charger into

the strap. Adjust the pins so that the charger is held

tightly against the bag and doesn’t slide around. Using

a backstitch, hand-sew the elastic in place from the

outside of the bag. These stitches will be covered by

the phone pocket and won’t show when we’re done.

Pin the phone pocket in place on the outside of the

bag. Slide your phone into the pocket facing forward.

To check the placement of the pocket, slip the charger

into its strap, with the charging coil facing the phone.

If your phone starts charging, you’re ready to sew

your pocket in place! Otherwise, adjust the placement

of the pocket so that the back of your phone aligns

properly with the inductive coil area on the charger.

Remove the charger, and hand-sew the pocket

in place with a backstitch ½ cm from the edge. This

seam will be visible, so take your time for even,

straight stitches. Your phone should fit into the pocket

snugly, and align with the charger when it’s in place.

If everything lines up properly, it’s time to move on to

the NeoPixels!

INSTALL THE LIGHT STRIP

We need to make a hole for the wires to pass through

to the inside of the pocket, where the Trinket will be

located. Hold the NeoPixels in place on the front of the

bag, making sure the wires are on the same side of the

bag as the charger. Mark the placement of the wires

on the pocket flap, then set the NeoPixel strip aside.

Use a hot soldering iron to make the hole, and widen it

enough so that all three wires will fit through. Feed the

wires through to the inside of the pocket.

For added weather-proofing, you can spray the

front of the casing with a hydrophobic coating, like

Scotchgard. Glue the casing in place with a strong,

flexible glue, like E-6000. Hold the strip in place with

clips or clothes-pegs while the glue dries. When the

glue is dry, solder the wires to the Trinket: connect

positive on the NeoPixels to USB on the Trinket,

negative to GND, and data in to pin 0.

PROGRAM THE TRINKET

Next, we’ll program the Trinket M0 to animate the

NeoPixel strip whenever it is on. Powering the Trinket

from the charger means that the strip will act as a

status bar, letting you know that the charger is on. The

following code will make the strip slowly pulse in bright

blue, and since the Trinket is easy to access,

Below

Keep fraying elastic

at bay with a

brief melting

Left

Like many things,

sewing is quicker

with power tools, but

still possible by hand