In order to convert readings from the HMC5883L, we need to check out the datasheet. On page 4, this diagram illustrates that the x and y outputs represent the sides of a triangle. By taking the arctan of the ratio of these two outputs (arctan(y/x)), we are left with a heading angle with respect to North.
This table illustrates the cardinal directions of different headings:
Magnetic declination represents the difference between the Earth's magnetic north pole and true geographic north. Your magnetic declination will vary depending on your geographic location.
- Visit this website to find your current magnetic declination.
- Your result will be in the format degrees° minutes' as shown below:
Geographic minutes represent a fraction of a degree in the same way that minutes represent a fraction of an hour. So, -8°26' represents -8 and 26/60 degrees or -8.433333 degrees. It is possible to have a positive or negative declination.
- Now that you have found your magnetic declination, we need to insert it into the code.
- First, download the zip archive provided in the software section.
- Then, replace the number after the equals sign with your magnetic declination on line 38 of minecraft.ino using your preferred IDE or text editor:
float magneticDeclination = -8.433333333333333; // Find yours here: http://www.magnetic-declination.com/
- If this is your first time using TinyCircuits products, please refer to the TinyZero Setup Tutorial or the TinyScreen+ Setup Tutorial to configure the Arduino IDE correctly.
- Open minecraft.ino in the Arduino IDE if you haven't already done so in step 2.
- Make sure that you have the correct port selected. The correct port number will vary, but your processor should appear to the right:
- Then, upload the code!
- Now, your TinyScreen+ is a portable compass!
Here are 3 useful usage tips:
- For the most accurate readings keep the TinyScreen+ parallel to the ground as we chose not to consider the z axis in our calculations.
- The red line points in the direction of the true North Pole if you have assigned the correct declination angle for your location.
- Readings can be distorted by nearby metal objects, magnets, or electronics.
As always, if you have any questions or feedback, feel free to email us at firstname.lastname@example.org. We would love to hear any ideas for improvement or new projects you were inspired to work on!
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Thanks for making with us!!