rtclauss / 3dcompass

3D compass education demonstration.

3D Compass

Bill of Materials

• (1) Arduino UNO (I used a Red board from SparkFun) $19.95/ea
• (1) NeoPixel Ring - 16 Element $9.95/ea
• (1) NeoPixil Ring - 24 Element $19.95/ea
• (1) 1000uF Capacitor - 6.3V or higher $0.35/ea
• (1) HMC5883L Magnetometer $9.95/ea
• (10) Brass Heat-Set Insert 4-40 $11.48/pk. 100
• 0.1" Header Pins
• Hook-up wire (solid)
• 300-500 Ohm Resistor (1/8 watt)
• Nylon 4-40 Screws (1/2 - 1" length)

Tools Required

• Hobby Knife
• Drill
• Drill Bit 7/64"
• Soldering Iron/Solder
• Flat-head screwdriver
• Hot Glue Gun/Glue
• USB mini cable

Mechanical Assembly Instructions

3D Printing Brackets

• Print 1 top and 1 bottom bracket. 60% infill and a raft are recommended.
• Using a soldering iron, insert the heat-set thread inserts. Eight in bottom plate, 4 in riser posts, 4 in Arduino mounts. Two in top plate for magnetometer mounts. Demonstration Video

Assemble Top Plate

• Attach the magnetometer with 4-40 nylon screws. Shear the excess length flush with the bottom of the plate using a hobby knife. Be careful to not break the superstructure on the printed part.
• Place the capacitor into the cut-out and secure with a drop of hot glue.
• Solder ~5 cm of wire onto the data in line on the 16-element ring.
• Place the 16-element NeoPixel ring into the vertical ring holder. Thread the data-in line through the hole in the bracket. This ensures that data-in, V+, and GND are all accessable. Secure with a drop of hot-glue.
• Place the 24-element NeoPixel ring onto the riser posts. Line up the data-out pad to be near the data-in line on the smaller ring. The LED should be directly above the mounting post. Secure with hot-glue on each post.

Assemble Bottom Plate

• Secure the Arduino RedBoard to the base plate with 4-40 nylon screws. Shear the excess length flush with the bottom of the plate using a hobby knife.

Attaching the Plates

• Using the 4-40 nylon screws, attach the top and bottom plates. Shear the excess length flush with the bottom of the plate using a hobby knife. You may prefer to do the wiring with the screws out for easy access, but it shouldn't be too much of a problem.

Wiring Instructions

• See photos on how to make this easier with header.

• Trim and solder the data-in wire on the vertical ring to the data-out pad on the 24-element ring.
• Connect the data-in pad on the 24-element horizontal ring to pin 13 on the Arduino. The resistor goes in-line here as well. You can use 0.1" header to make this easier to assemble and troubleshoot.
• Connect a ground pad from the 24-element horizontal ring to a ground pad on the 16-element vertical ring.
• Connect the second ground pad on the 16-element vertical ring to the ground size of the capacitor (marked with -- on the case).
• Connect the ground side of the capacitor to GND on the Arduino. Header can make this easier.
• Connect the power pads of both rings to the positive side of the capacitor.
• Connect the positive side of the capacitor to +5VDC on the Arduino.
• Connect the GND, SDA, and SCL pins of the magnetometer to GND, SDA, and SCL on the Arduino.
• Connect the power pin of the magnetometer to the +3.3VDC pin on the Arduino.

Programming

• Install the NeoPixel, Adafruit Sensor, and Magnetometer libraries. For help, see the library tutorial.
• Connect the Arduino to your computer and upload the code in the Arduino/Vector_Display directory (see the Arduino guide) if you need help uploading programs to the Arduino.
• Play with parameters such as brightness and grading to create your own display!
• The #define DECLINATION directive adjusts the compass headings for your current location. You can look up this value at (CIRES)[http://geomag.org/models/wmm-declination.html] but you need to convert the DMS to radians.

Activity Ideas

You can learn a lot from your new compass/magnetometer! In addition to learning about the electronics and hardware, you can learn about magnetic fields and the Earth's geodynamo. Below are a few links to get you started and some ideas. Please contribute any experiments or activities that you develop!

• Learn how magnetometer calibration works (Freescale App Note)
• Measure the diurnal variation in Earth's magnetic field
• See how good of a metal detector you built
• Detect the movement of metal objects like a desk drawer