9

Smart backpack with wireless charging pocket

FORGE

Finally, let’s set the upper limit to 255. If the

strength value is ever larger than 255, we’ll have it

reset to 250 and flip the direction value to start going

in the other direction:

elif strength >= (255):

strength = 250

direction = -direction

That’s it for the code! Save the file to your Trinket

M0, and watch your NeoPixel strip pulse. To change

the speed of the pulsing, adjust the time.sleep value,

or change the direction value. When you are happy

with your animation, move on to installing the Trinket.

For troubleshooting help and more tutorials about

programming the Trinket M0 with Circuit Python, check

out hsmag.cc/zucqvz. Here’s the full code listing:

import time

import board

import neopixel

numpix = 34 # Number of NeoPixels

pixpin = board.D0 # NeoPixels pin

strip = neopixel.NeoPixel(pixpin, numpix,

brightness=.5, auto_write=False)

strength = 0 # blue intensity

direction = 10 # direction of intensity

while True:

BLUE = (0, 0, strength)

strip.fill(BLUE)

strip.show()

time.sleep(0.03)

strength += direction

if strength <= 0:

strength = 10

direction = -direction

elif strength >= (255):

strength = 250

direction = -direction

INSTALL THE TRINKET

We’re almost done! All that is left is to securely

attach the Trinket near the charger. Sew the Trinket

in place through the four mounting holes located

in the corners of the board. Use a short mini USB

cable to connect the Trinket M0 to the charger, and

turn the charger on. If your NeoPixel strip lights up

and pulses in blue, you’re done! If not, check your

connections, and make sure your charger is charged.

Also, check that your phone charges when inserted

into its pocket.

WEAR IT!

You’re now ready to take your smart backpack out

for a spin! Turn the charger on for visibility while

out and about at night, and slip your phone into its

pocket whenever you need some juice. There are a

few more pins available on the Trinket M0, so you

can keep adding functionality to your backpack. An

accelerometer could help the lights pulse in time

with your steps, a GPS module could change the

colour based on your speed, or speakers could...

well, we will leave it up to you. However you

decide to use this project, be sure to let us know

at [email protected]!

Above

USB power banks

can power a wide

variety of things, and

don’t need soldering

Below

With everything in place, you’re good to go out and wear your

power-bank bag with pride