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Sensor to detect clockwise and anticlockwise and convert signal to a 4-20mA value

David Hawthorn
Prodigy 10 points
Other Parts Discussed in Thread: DRV5053

Good morning Technical

I have a hydraulic motor mounted on a horizontal plate with an output shaft that has a bevel gear. The other end of the shaft protrudes from the non-drive end of the hydraulic motor enough to get a sensor to count or measure. The bevel gear meshes into another gear at right angles, with a larger diameter bevel gear and this shaft rotates to open and close a valve. The ratio is never 1.1 and can vary on every application. I would like to be able to display the position of the valve on a digital display showing the % open from 0-100. I was looking at a pulse (inductive sensor) to analog converter to enable the 4-20mA to be scaled, however when the valve shaft travels in the opposite direction the converter wouldn't know. I wondered if I could insert a magnet into the shaft and when the shaft went clockwise, a sensor would detect a north pole and when it went anticlockwise, a south pole. I am looking for a solution that requires 12 or 24VDc supply.  I require a solution for ten systems, but this will increase.

  • 0
    TI__Mastermind 21340 points

    David,

    Thanks for reaching out on E2E.  For this application, you will likely be best served using a linear Hall-effect sensor in order to get angle measurements from the rotating magnet.  If using a latch or a switch, you could only detect two states.

    For the VCC range you have specified, our only suitable device is DRV5053, which accepts from 2.7-38 V.

    The output of this device will be centered about 1V and will vary linearly with the input magnetic field with the output ranging from 0-2V.  The maximum output current of this device is 2.3 mA, so you would likely need to add a buffer amplifier with a higher output current range to reach your 4-20 mA current drive.  

    By itself, a single sensor would be able to detect up to 180 degrees of rotation if placed carefully with the magnet. The goal here would be to position the midpoint of the magnet rotation such that it is at the 0 crossing (1V on the output).  There should be unique output voltages ranging from +/- 90 degrees rotation. 

    To extend this to 360 degrees, a second sensor could be installed 90 degrees out of phase.  This would create sine and cosine outputs which could be used for arctangent calculations.

    Thanks,

    Scott