Qmc5883l points towards another compass problem

Projects Programming
1

Hello...
I am working on a university graduation project as i am making a bracelet for parent and child to protect the child from abduction or getting lost or something so some of the features is to display an arrow on a TFT display to point towards the child direction in order to make the parent know the location of the child so i am using two compass sensor (qmc5883l) one on parent bracelet and the other on the child bracelet but i don't know how to calibrate both of them in order to make an arrow that points towards the child direction
For example for further explanation:
In this photo although child compass (on the left) is on the left according to the parent compass (on the right) the arrow points towards (east) which is incorrect according to the parent compass

IMG-20250124-WA0011
IMG-20250124-WA0011960×1280 110 KB

So what should i do in order to solve this problem..

And thanks for your time.

1 Like
2

The QMC5883L is a magnetometer.

If the magnetometer sensor is properly calibrated, and used as an electronic compass, the compass will point toward magnetic North.

That could be the North magnetic pole of the Earth, or a pole of a nearby magnet.

2 Likes
3

Consider a different sensor. Do a bit of research on 'fox hunt' an exercise used by amateur radio operators.

1 Like
4

I ll look into it

5

Ahhh i see but i tried to use the coordinates of the two compass to make this arrow direction but i failed or still missing something

6

What coordinates?

For help, please read and follow the directions in the "How to get the best out of this forum" post, linked at the beginning of every forum category.

7

That's what's had me scratching my head from the beginning.

8

Sorry for being unclear i am new at this...
At first i tried to get the compass coordinates in x,y,z for both compass meter and tried to use them to know the direction of the child compass according to the parent compass ...
I hope you understand my point.

9

Please read post #6 again, and follow the instructions.

10

That's the part that still completely puzzles me.

A magnetometer does not give you coordinates. It's not a GPS or even an IMU. It just measures magnetic field strength.

How do you propose to go from magnetic field strength to a position in space? And even if you could, how do you propose to transmit those coordinates from one unit to the other?

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