Compass Hat

I made a silly hat that tells you which way is North.  It tells the people around you where it is via LEDs, and it tells you via a discretely concealed buzzer.  I’ve been remiss in posting a writeup about it, but here goes:



It’s all up over at bitbucket.  The math is kinda wrong, it’s a work in progress 🙂 You’ll also need this hmc6352 library.


I was going to draw up a diagram of how it’s all put together, but the pinouts are the most important so I’ll just list them.  While it was finicky as soft circuits tend to be, it’s pretty simple.

On the LilyPad:

Pin 3 – buzzer board (no polarity, and the other side goes to ground)
Pin 8 – pin 12 on the shift register / proto board
Pin 11 – pin 14 on the shift register / proto board
Pin 12 – pin 11 on the shift register / proto board
Pin a4 – SCL pin on the compass
Pin a5 – SDA pin on the compass

Power on the compass needs to be wired up as well, either directly to the power supply or to the pins on the LilyPad.

On the proto board with the shift register and LED resistors, pins 1-7 and 15 go to LEDs, 8 and 13 go to ground / negative on the LilyPad, and 10 and 16 go to power. 9 is unused, which is good because even the large proto board is filled right up with the resistors 🙂

I soldered the shift register directly onto the board, soldered on the resistors, then cut the leads around the resistors and the pins of the shift register.  It was honestly the most annoying and time-consuming part of the whole process.  I made a bunch of mistakes and had to jumper some connections which I’d erroneously cut.

I tried using conductive thread to wire the shift register to the LilyPad, and it didn’t work.  The slight resistance from the thread was enough to throw off the timing in the shift register.  I also used wire for the power connection.  There’s a common ground running between all the LEDs, which I connected up with the buzzer on the front side of the hat as well.

The LEDs themselves have their pins bent into a little loop, which is sewn in with the conductive thread. I’ve found this configuration to be quite stable.  Remember that there’s a flat side on the plastic of the LED package – that’s negative!

Here’s a photo of all the components except for the power supply:

compass hat parts

Check out the awesome wiring job on the compass 🙂

That pretty much sums it up as far as how to reproduce this project.  Feel free to comment with any questions, clarifications, whatever!

Some more photos:

compass hat!

lilypad and shift register on the compass hat

3 thoughts on “Compass Hat

  1. Awesome! I’ve been meaning to make one of these, or at very least, a Sensebridge, for Aaron, who would really benefit from having a sixth directional sense about him!

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