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Hall sensor (DRV5023)

Willie de Kort77
Prodigy 80 points
Other Parts Discussed in Thread: DRV5023

Dear all,

I do have two questions about these Hall sensors:

1) Is the DRV5023 aible to sense a current floating in a cupper pcb-trace below of it?
The current is a DCC signal (kind of PWM), an example can be seen at <http://www.modeltrainbuilder.com/DCC-operation.html>

What I want is detection of the current, which can be in the range of 20mA (lost carriage) till 2A (heavy loaded train).
The detection signal should be galvanic seperated from this DCC-signal, thats why I gues this DRV5023 can do the job???

2) Is the DRV aible to detect a small magnet?
The DRV will be build in the road, where the moving car will be controlled by a small magnet on the steering-axle. The magnet is 'following' the magnet-band. This band will be removed for a small part where the sensor is positioned. Looks like <forum.miniatur-wunderland.de/.../2377_Sensor_9366_1.jpg>. For the small magnet at the steering-axle an example can be <www.miniatuura.nl/.../Magneetband-fig11.jpg>

I hope it is clear what I mean. If not, just ask.

regards,
Willie

  • 0
    TI__Guru** 114905 points
    Hi Willie,

    Our experts have been notified and should reply soon.
  • 0
    TI__Mastermind 20985 points
    Hi Willie, welcome to the forum.

    Hall effect switches like the DRV5023 usually aren't suitable for measuring current. To give some idea, a long wire carrying 2A produces 0.4mT at a distance of 1mm. 0.4mT is much lower than the threshold of the DRV5023. For measuring only 20mA to 2A, shunt sense resistors are often used. TI has amplifiers for this that start with part number "INA".

    Small magnets can definitely be used. The flux density produced at a given distance depends on the size of the magnet. K&J has a useful magnetic flux density calculator on their website: www.kjmagnetics.com/calculator.asp

    Best regards,
    RE
  • 0 in reply to RE
    Prodigy 80 points
    The idea for detecting the current is that the sensor is galvanic isolated from the DCC-circuit.
    The range of 20mA till 2A is necessary because a lost carriage at the track have to be detected, as well as a heavy loaded train with 2 locomotives.
    It is not necessary to measure the current, only detect if a current is floating or not. The track at the PCB is straight, but can be looped for a double strength in field. Or even a small coil from wire(s) over the sensor.
    If we have to design a shunt sense resistor circuit, we have to add some galvanic isolators. This will result in a much bigger space needed at the PCB.
    Is there another sensor possible doing this job?
  • 0 in reply to Willie de Kort77
    TI__Mastermind 20985 points

    Do you only need to distinguish between 20mA versus 2A (2 levels), or do you also need to know if 0mA, 50mA, 100mA, 1A, etc is present?  What resolution do you want?

  • 0 in reply to RE
    Prodigy 80 points
    Hi Mastermind,

    In the beginning we would like to know the value of the current in every section, but we will measure that value in a common line.

    For detecting the rolling stock (carriage, locomotive or train) we only need to know if a current is present or not.

    For reason that the rail will always have a leaking conduction (sand, glue, dust, etc) we have found in the early days that a current till - let's say - 20mA is free track. Values above 20mA means there is something on the track. A people-carriage with LED-lightning will have a current of this value, a cargo-car will have a resistor.
  • 0 in reply to Willie de Kort77
    TI__Mastermind 20985 points
    I think it will be difficult to distinguish tens of milliamps using Hall sensors.

    Best regards,
    RE