drv425: magnet detection

HS FAE Germany

Part Number: DRV425
Other Parts Discussed in Thread: DRV425, DRV425EVM

Hello,
I have the DRV425 EVM and tested it with a magnet. I got see a voltage at Vout when I move the magnet. Is it also possible to detect a static (reposing) magnet with the DRV425?

Regards, Holger

over 8 years ago

0 Javier Contreras4 over 8 years ago

TI__Mastermind 33780 points

Holger,

Yes you can measure a magnetic field from a static magnet. The question is how far way is it and how strong is the magnet. We have a calculator on the DRV5023 product page for . Your Rshunt will determine your resolution and the range, but the maximum range you can have is 2mT. You can use our DRV425 System Parameter Calculator to help determine Rshunt based on your requirements.

You also need to be concerned with the direction of the magnetic field. The DRV425 has a field sensitivity in only one axis. If the field is normal to that sensitivity you will not read an output change.

Please let me know if you have any further questions or you have other concerns.

0 HS FAE Germany over 8 years ago in reply to Javier Contreras4

TI__Mastermind 32680 points

Hello,how can you do this with the DRV425 EVM. If I didn't move the magnet the voltage at pin Vout goes down to 0V.

Regards, Holger

0 HS FAE Germany over 8 years ago in reply to HS FAE Germany

TI__Mastermind 32680 points

any answer?

0 Javier Contreras4 over 8 years ago in reply to HS FAE Germany

TI__Mastermind 33780 points

Hello HS WG-FAE,

Are you sure you are not saturating the DRV425 with the magnet. The DRV425 can only measure up to 2mT. The calculator I mentioned before can help with this. Also to verify this is the case remove the magnet from the DRV425EVM and the Vout should go near 2.5V ± 0.35V due to the earths magnetic field.

I will explain the ±0.35V. I am assuming you still have the R1 (Rshunt) at 100Ω. If you see the DRV425 System Parameter Calculator you will see that you will get 4880 V/T. Assuming the earth filed is ±70µT, I just calculate 4880V/T * 70µT = 0.35V.

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drv425: magnet detection