MA780 Magnet Presence Detection with noise

Motor Drivers/Sensors
1

So I have to use the MA780 Sensor for a project and it needs to detect if my little weak magnet of 5mT is present. I am limited to having power for around 250ms and during this time, it needs to determine if there is a magnet present or not.

At the moment I am just using the variance to determine if the magnet is there. But sometimes even with no magnet, the variance is low as if the magnet is present.

Are there any other methods or tricks I could use to get some informatoin of the Z-axis?

2

Hello Uwe,

Unfortunately, there are no other methods to detect the magnet presence with MA780, besides the one you are already using. To check if there are any other possible solutions, can you please share more details about your application?

  • Do you just need to detect the magnet or are you also using the angle measurement?
  • Do you need the low power features provided by MA780?
  • Is the sensor on-axis or off-axis?

Best regards,

Carmine

3

Hello Carmine,

So the variance does work but out of 100 Hall sensors with FW9 and 100 samples, there are usually around 10 sensors that doesn’t show enough noise when its away from a magnet. Is there a reason why this could be the case? Some are really noisy right when I remove the maget, which is perfect!

  • I am using your MA780 for angle measurements since its fast and low powered, but it would open more doors for us if it could also detect if the magnet has fallen off which would then trigger some alarm in the system.
  • I would say I’d rather have the Z-axis function over low power features.
  • Its on-axis but the magnet is rather small, it has around 5mT and it does work and we are able to compensate the nonlinearity.

Do you have a contact in Germany that I could reach out to?

Best regards,
Uwe Wong

4

Hello Uwe,

The amount of noise in absence of a magnet is related to the residual offset of the Hall devices. This offset varies from part to part, and parts with a higher offset will show less noise.

I will send you a PM with the contact details.

Best Regards,

Carmine