Compass is device used for navigation and orientation, and consists of a magnetic needle that is mounted on a pivot and is free to rotate horizontally. The needle aligns itself with the Earth's magnetic field, and scale under her typically has four cardinal directions marked on it: North, East, South, and West.
In addition to these four main directions, many compasses also have additional markings indicating the degrees or fractions of a circle.
The device presented in the video represents an electronic version of the Compass, where the position of the needle is indicated by group of a three light-emitting diodes.
There is also an Oled display in the middle of the device, which shows the angle relative to the North Pole. In this case the resolution is greater than one degree, while in the case of LEDs the resolution is 6 degrees when moving one diode. When the red diode coincides with the top of the arrow and the value of the angle on the Oled display is about 0 and 360 degrees, then this side is North, opposite to it is South, and East and West are located at an angle of 90 degrees.
The device is relatively simple to build and consists of several components:
- Arduino Nano microcontroller
- HMC5883L compass module
- Led ring with 60 adressable RGB Leds type WS2812B
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The Arduino code is simple as it uses libraries for the Led ring as well as the Compass module. The only modification is conditioned by the fact that we need to enter the declination angle for the specific area for a more accurate result, which we can find it at:
http://magnetic-declination.com/
We also have to calibrate the sensor using the calibration code provided in the library, and input the resulting values into the code in line:
compass.setOffset(27, 200);// Set calibration offset. See HMC5883L_calibration.ino
At the beginning, let me emphasize that the instrument is very sensitive to local magnetic fields and massive metal objects in its surroundings, so the results of this video may deviate to a certain extent. First we need to place the compass in a horizontal position and then turn it on. After the initial logo, a group of 3 LEDs appears on the screen, the two surrounding ones are Green, and the middle one, which represents the direction, is Red.
By equating the arrow with the Red Led we get the direction of the North pole. By rotating the compass around its own axis the OLED display shows the angle between north and the tip of the arrow at the given moment. So the Red LED always points North.
In my case I use a box with a oled display from one of my previous projects, and Led ring is mounted in a situable case made of 3D Printer, and below is the .STL file for 3D printing.
/* Start of Code */
#include <SPI.h>
#include <Wire.h>
#include "FastLED.h"
#include <HMC5883L.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SH1106.h>
#define OLED_RESET 4
#define SCREEN_ADDRESS 0x3C
Adafruit_SH1106 display(OLED_RESET);
#define NUM_LEDS 60 // Number of LEDs on Ring
#define DATA_PIN_RING 3 // Pin 3 connected to RGB Ring
CRGB leds_RING[NUM_LEDS];
HMC5883L compass;
int fixedHeadingDegrees; // Used to store Heading value
void setup()
{
Serial.begin(9600);
Wire.begin();
FastLED.addLeds<NEOPIXEL,DATA_PIN_RING>(leds_RING, NUM_LEDS);
display.begin(SH1106_SWITCHCAPVCC, SCREEN_ADDRESS);
display.clearDisplay();
display.setTextSize(2);
display.setTextColor(WHITE);
display.setCursor(22,10);
display.println("mircemk");// Print text
display.setCursor(22,40);
display.println("COMPASS");
display.display();
delay(2000);
// Set measurement range
compass.setRange(HMC5883L_RANGE_1_3GA);
// Set measurement mode
compass.setMeasurementMode(HMC5883L_CONTINOUS);
// Set data rate
compass.setDataRate(HMC5883L_DATARATE_30HZ);
// Set number of samples averaged
compass.setSamples(HMC5883L_SAMPLES_8);
// Set calibration offset. See HMC5883L_calibration.ino
compass.setOffset(27, 200);
}
void loop()
{
Vector norm = compass.readNormalize();
// Calculate heading
float heading = atan2(norm.YAxis, norm.XAxis);
// Set declination angle on your location and fix heading
// You can find your declination on: http://magnetic-declination.com/
// (+) Positive or (-) for negative
// For Montreal,QC declination angle is -14'35W (negative)
// Formula: (deg + (min / 60.0)) / (180 / M_PI);
float declinationAngle = (5.0 + (3.0 / 60.0)) / (180 / M_PI); //for Ohrid
heading -= declinationAngle;
// Correct for heading < 0deg and heading > 360deg
if (heading < 0)
{
heading += 2 * PI;
}
if (heading > 2 * PI)
{
heading -= 2 * PI;
}
// Convert to degrees
float headingDegrees = heading * 180/M_PI;
// To Fix rotation speed of HMC5883L Compass module
if (headingDegrees >= 1 && headingDegrees < 240)
{
fixedHeadingDegrees = map (headingDegrees * 100, 0, 239 * 100, 0, 179 * 100) /100.00;
}
else {
if (headingDegrees >= 240)
{
fixedHeadingDegrees = map (headingDegrees * 100, 240 * 100, 360 * 100, 180 * 100, 360 * 100) /100.00;
}
}
int headvalue = fixedHeadingDegrees/4.88;
int ledtoheading = map(headvalue, 0, 59, 59, 0);
Serial.print("Angle:");
Serial.print(headingDegrees);
Serial.println();
display.clearDisplay();
display.setTextSize(3);
display.setTextColor(WHITE);
display.setCursor(20,10);
display.println("Angle");
display.setCursor(10,40);
display.println(headingDegrees);
display.display();
FastLED.clear();
if (ledtoheading == 0){
leds_RING[59] = CRGB::Red;
leds_RING[0] = CRGB::Green;
leds_RING[58] = CRGB::Green;
}
else {
if (ledtoheading == 59){
leds_RING[0] = CRGB::Red;
leds_RING[59] = CRGB::Green;
leds_RING[1] = CRGB::Green;
}
else {
leds_RING[ledtoheading] = CRGB::Red;
leds_RING[ledtoheading+1] = CRGB::Green;
leds_RING[ledtoheading-1] = CRGB::Green;
}
}
FastLED.setBrightness(50);
FastLED.show();
delay(100);
}
/* End of Code */
Ring.zip 
