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Sensor for detecting a rotating pulley

Paul Wolfert1
Prodigy 20 points
Other Parts Discussed in Thread: DRV5015, DRV5012, DRV5013, DRV5011, LDC0851, LDC1612

One of the tools in DMOS6 uses a belt and pulley system with a motor attached to one end and a output pulley attached to the other. Currently we have no means of detecting if a belt has failed, the only feedback we have is a tachometer on the motor.

I've been tasked with finding a solution that can verify if the output pulley is spinning, exact speed is not necessary, just push a high voltage signal if it is rotating and a low signal if it is not. 

My background is in mechanical engineering so if you could give me some pointers on what would be a good solution, let me know or shoot me an email for more details!

Paul

  • 0
    TI__Mastermind 21135 points
    Hello Paul,

    From your description, it looks like a simplified rotary encoding method would work nicely for you.

    Here is a link to a document on rotary encoding: www.ti.com/.../sboa200.pdf

    As an overview, you would put a magnet (usually a multipole magnet) on the pulley directly, and put a Hall effect latch device (DRV5011, DRV5012, DRV5013, or DRV5015) near the magnet/pulley setup, which will output a square wave when the pulley is rotating. If the output stays high or low too long then you would know that the pulley has stopped rotating. Since you probably don't care about which direction the pulley is rotating, you probably only need one sensor.
  • 0 in reply to Mitch M
    TI__Prodigy 20 points

    Ideally we would not want to physically modify the pulley since this makes getting spare parts more difficult. I've read up a bit more on the inductive sensors and something that caught my eye are gear tooth sensors which use a stationary permanent magnet on the sensor side to induce a magnetic field in a ferromagnetic gear and a hall effect sensor to watch as the field changes from the tooth geometry passing by. 

    It doesn't look like TI has a fully integrated solution for something like this, in your opinion would this be something worth exploring or just find an off the shelf solution? 

  • 0 in reply to Paul Wolfert1
    TI__Mastermind 21135 points
    Hello Paul,

    The reason we don't have an integrated application to do this with a Hall sensor and a stationary magnet is because TI actually has inductive sensors as well. If the pulley is made out of a ferromagnetic material, then you can use our inductive sensors without the need for a stationary permanent magnet.

    I will pass this thread over to the inductive sensing team to assist you further on how to do this and what parts might be useful.
  • 0 in reply to Paul Wolfert1
    TI__Mastermind 23810 points
    Paul,

    The LDC0851 has a switch type output that can be used for event counting. Here is an event counting reference design:

    www.ti.com/.../TIDA-00851-LDC0851

    Depending on the mechanical design of the pulley, it might be more reliable to read out the raw data and post-process. The LDC1612 is a good part to look at for this function.