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detecting shaft rotation

Discussion in 'General Electronics Discussion' started by stormin norman, Jan 24, 2016.

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  1. stormin norman

    stormin norman

    Dec 1, 2011
    I'd like a simple & inexpensive method of detecting when a shaft is rotating . This needs to trigger a relay that in turns turns an indicator light on. I have access to the shaft end...but need a method to read and convert this for my indicator light.
    Last edited by a moderator: Jan 24, 2016
  2. HellasTechn


    Apr 14, 2013
    Can you attach something on the shaft ?

    If yes then you could attach a small magnet and then install a magnetic switch close to it. The switch could then be connected to a power supply and a relay.
  3. Alec_t


    Jul 7, 2015
    You could put a paint mark on the shaft end and detect it optically.
  4. Minder


    Apr 24, 2015
    I have used the stated methods, the problem with the magnet, it can unbalance the motor rotor if the rpm is high.
    There is the retro-reflective means or the slotted opto, which entails a shutter mounted to the shaft, all these methods though will cause indication if using in a simple manner when the shaft sensor stops under the reading device.
    In this case you could use a 555 in a watchdog timer sense.
    IOW as soon as the pulses stop, the relay picks up.
    HellasTechn likes this.
  5. AnalogKid


    Jun 10, 2015
    I've done a lot of motor and fan sensing. There are about 19 ways to do this, so more data is required to get to a good solution for your application.
    Shaft speed in rpm or rps
    Shaft diameter
    Environment (wet, humid, dry, dusty, medical, food processing, etc.)
    Output signal (transistor switch to GND, opto isolator, email message, etc.)
    Power available to run the detector (AC/DC, volts, amps)
    Distance the signal has to travel
    Minimum detection time - how soon do you have to know that the shaft is moving (1 rev, 0.1 rev, 5 seconds, etc.)
    Minimum release time - how soon do you have to know that the shaft is stopped

    HellasTechn and hevans1944 like this.
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