Cbus after a power flick !

Discussion in 'C-Bus Wired Hardware' started by Charlie Crackle, Aug 14, 2007.

  1. Charlie Crackle

    Charlie Crackle

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    Can some one please tell me why cbus cannot recover from a power flick

    By "power flick" I mean a very quick power outage. The sort that would make all the sodium street lights go out and then recharge..

    No cbus commands can be sent on the network...


    Looking at the DIN dimmers/relays unit lights are green Cbus light is green and flashing. all channels are off.

    1 dimmer has NO unit light and NO cbus light.
    turn this circuit off then on and this dimmer springs to life
    Cbus lights stop flashing and all works....

    Do dimmers have some sort of internal protection system that requires the power to be turned off then on ??

    Why does the failure of this unit bring cbus to it knees ? (there is not a Cbus power supply problem plenty from other units, this unit is not the clock and is not supplying burden)

    why did it only effect this unit and not the others ??

    Charles
     
    Charlie Crackle, Aug 14, 2007
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  2. Charlie Crackle

    ashleigh Moderator

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    Charlie

    ALL electronical thingumies will have this kind of behaviour in brownout conditions.

    I suggest you try flicking the power off and on again quickly on your CD player, DVD player, TV, or whatever. There is a very high chance that they won't recover properly under some circumstances as well.

    A full power outage causes all the internal voltages to drop to 0, and when power comes back the makers of the integrated circuits design them so that they start normally and run in accordance with their spec.

    A brownout, on the other hand, causes internal voltages to fall (to something - who knows what though, it depends on the design). Sometimes the devices can get into weird operating states that are not documented by their makers (and if the voltage continues to fall to 0 then nobody knows or cares about this) - if the voltages then rise again though they don't always go back to normal.

    We go to some trouble to try and detect these kind of conditions using things like power supervisory ICs, thresholded reset detector circuits and what not. Even these are not always perfect, sometimes in some circumstances you end up in a condition known to the technical types as "**** happens". :(
     
    ashleigh, Aug 14, 2007
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  3. Charlie Crackle

    Charlie Crackle

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    I was trying to think of a way to at least trip the emergency lighting when this happens

    In this example the emergency lighting did not turn on as the power came back on and all the light were off and could not be turned back on as C-BUS had locked up.

    It was PITCH BLACK !!!


    I remember there used to be a module that watched the cbus and if problems then shorted the "ALL channels ON pair (green)"

    1) I cannot find this module any more... Not in the trade price catalogue or the current cbus catalogue... is it a special ??

    2) Would it work in this case ?? if the dimmer is in the "S*** happen state" does shorting out "All channels on pair" still work ??

    I was thinking a better idea would be to drive a relay that turned off the power to the "Emergency lighting circuits"

    I assume this module could do this. are the contact dry on the Green/Green-white pair on this module ?

    Charles
     
    Charlie Crackle, Aug 16, 2007
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  4. Charlie Crackle

    PSC

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    Hi Charlie,

    No module required, simply short the green pair for all 'ON' and brown pair for all 'OFF'.
     
    PSC, Aug 16, 2007
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  5. Charlie Crackle

    znelbok

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    I think I read that one of the Pro series units had an emergency lighting trigger for when the power was out. I dont know if it would work on a bus crash though.

    The idea of a watch dog on the c-bus network is not a bad one. You could trigger an alarm and bring on emergency lighting. Even though some lights may still be on after a c-bus crash (and by crash I include the above mentioned scenario, and all other times the network is down), it would fail into a safe condition.

    PSC - shorting them is what you do, but how do you achieve it - through a change over relay that is always on?

    Mick
     
    znelbok, Aug 16, 2007
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  6. Charlie Crackle

    ashleigh Moderator

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    Charlie

    The network monitor module is a special. It was built for one very special site with a large number of units that made it worth doing.

    It comes with some SERIOUS restrictions on network wiring and topology, that's why its a special rather than a general release product.

    Basically, if you don't design the install for it, then retrofitting afterwards would not work in about 9 out of 10 sites.

    All if does, in the end, is to short those remote overrides in the cables as you suggest - it just has some specific monitor conditions under which it does this.

    There is still electronics and software in between the bits of wire and the dimmer / relay loads, so if those have gone ga-ga for some reason then the possible operation of the overrides may still be compromised.
     
    ashleigh, Aug 16, 2007
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  7. Charlie Crackle

    PSC

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    Hi Mick,

    All you need is a standard toggle switch.
     
    PSC, Aug 17, 2007
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