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electric roller shutter: powering 'up' and 'down' simultaneously

Discussion in 'General Electronics Chat' started by g2c, Jun 13, 2018.

  1. g2c

    g2c Member

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    Hello,

    I was wondering how are these motors protected in case of simultaneous up and down branching error. Can someone help?

    Thanks in advance
     
  2. gophert

    gophert Active Member

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    Usually, there is only one motor in roller shades. An "H-Bridge" circuit allows a dc motor to be run clockwise and counterclockwise. If your device truly has two motors, simple logic circuits can prevent both from turning at the same time, or programming logic if it is controlled by a microcontroller.
     
  3. g2c

    g2c Member

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    Thanks dear, By 'these' I meant of such stores.

    So, If I understood well, the motor is a dc one with some kind of rectifier and the commend is as in Wikipedia: the current can flow through the motor in both directions but then, what protection is provided if the user wires both 'up' and 'down'?

    error A
    motor common - phase #1
    motor up - phase #2
    motor down - phase #2

    Error b (I guess that in this case, no current flows at all?)
    motor common - left open
    motor up - phase #1
    motor down - phase #2
     
  4. dave miyares

    Dave New Member

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  5. crutschow

    crutschow Well-Known Member Most Helpful Member

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    A motor in a bridge circuit has only two leads.
    The direction of the current through the leads determines the motor rotation direction.
     
  6. g2c

    g2c Member

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    rolling shutter motors has 3 leads
     
  7. crutschow

    crutschow Well-Known Member Most Helpful Member

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    Then you would need some sort of interlock logic to prevent both directions from being energized at once.

    Why are you concerned about this?
     
  8. dave miyares

    Dave New Member

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  9. g2c

    g2c Member

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    Thanks. I would simply like to know what protection is built into the shutter motors. I think that there should be such a protection simply because there can be wiring mistakes even by a professional so there ought to be tolerance for such faults. And that even prolonged erroneous wiring should not be destructive.
     
  10. Pommie

    Pommie Well-Known Member Most Helpful Member

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    Without more information it's all guess work. Allthough unlikely, the three wires could indicate a brushless dc motor.

    Mike.
     
  11. crutschow

    crutschow Well-Known Member Most Helpful Member

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    T
    That's not normally done.
    It's not feasible to protect against all possible wiring errors.
    If here's a wiring error in making the device than there are unavoidable (and possibly catastrophic) consequences.
    But things like connectors are normally keyed so they can't be connected incorrectly and wires are often color-coded to minimize wiring mistakes.
     
  12. alec_t

    alec_t Well-Known Member Most Helpful Member

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    If you tried driving a motor in both directions simultaneously, the likely result would be that the motor wouldn't budge, or the motor or its supply would instantly burn out or operate a trip; so either way the shutter wouldn't move.
     
  13. ronsimpson

    ronsimpson Well-Known Member Most Helpful Member

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    Because I have not seen a 3 lead motor it is hard to know what is happening. I need to know more about how the motor is used. Where are these three wires going?

    In the shutters I have played with; pushing up and down results in noting.
    I think the power supply is current limited. If the motor stalls out the supply will reduce the voltage to a small voltage to save the motor.
    ---edited---
    We need a picture of the motor. Some think it is a DC small motor and some think it a three phase 220V monster. So what we say is based on what size of motor we think it is.
     
    Last edited: Jun 14, 2018
  14. rjenkinsgb

    rjenkinsgb Member

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    From the ones I've seen, industrial roller shutters are usually either three phase for larger ones or single phase capacitor-run motors for small ones.

    The three phase type swap two phases between open and close; both directions being made at the same time shorts the supply - they usually have mechanically and electrically interlocked contactors to prevent that.
    eg. https://qph.fs.quoracdn.net/main-qimg-fbfcc48098b1dda9c8cfce53ee4f47bf

    https://www.picclickimg.com/00/s/MT...tactor-10HP-220V-Electrical-Mechanical-_1.jpg

    This is a typical diagram for the single phase type - complete with a limit switch in series with each "live" direction feed. (Found on stack exchange rather than me re-drawing it).
    https://i.stack.imgur.com/CWgp0.png

    If both lives are fed at the same time, the motor will just get hot rather than running. Hopefully there is a circuit breaker to protect it!

    The ones I've seen like this have a centre-off rocker switch so only one direction can be active at a time. The larger ones can have two separate buttons, which activate the contactors.
     

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