Driveway Alarm / Vehicle detection

[Tris]

After extensive googling i found others who had successfully used a HMC5883 magnetometer/compass to detect metal vehicles - AKA cars.

The use cases are around car parking (detect when car space is free) and car counting (counting number of cars that use a road).

I would really like to use this HMC5883 sensor to detect a car moving past the sensor, to act as a cheap driveway alarm.

I am hoping to use a battery powered node for this, and i think a big induction is too power hungry loop and i would like to avoid digging and placing a sensors in the road.

Existing driveway alarms seem to use a (magnetic field change?) probe to detect a car, but i cant find just the probe available, and kits are quite expensive and defeat the point of MySensors - DIY!!
The HMC5883 solution would be low power and i could maybe get away with the sensor/node beside the road and not underneath it.

I discovered this: https://gitlab.com/ColoradoSchoolOfMines/parking_sensor/commit/cca7b040654297fd06bc806e0ca8cef844f8d456
which works - serial prints CAR in or CAR OUT when a car moves past the sensor.
I tried to blend the above sketch with a MySensors sketch (and failed) - the gitlab code is way over my head and i think it uses memory that MYS also uses....

Has anyone played with the HMC5883 for a similar purpose?

@fleinze can you please share your code from your "Fun with magnetometer / digital compass sensors" post?

Anyone else interested in this car detection idea?

[hek]

Interesting idea!

[Mrlynx]

Maybe you could use an ultrasonic distance sensor to detect if anything is in its measuring range?

[enlo]

If you did not yet buy that chip: According to SparkFun, that sensor is retired. But they do suggest alternatives.
I am not sure if that's SparkFuns definition or Honeywell