DIN Dimmer Question

Discussion in 'C-Bus Wired Hardware' started by Roti, Jul 9, 2012.

  1. Roti

    Roti

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    Hi.

    Do the standard (non architectural high power) DIN dimmers have different dimming curves? If so, are they selectable or identifiable/readable in any way?

    I note the documentation says a bit about the electronics adapting to the load, but could not find much detail. I have noted before when attaching LED fixtures to a test rig that they behaved differently after re-powering up the system. I assumed the dimmer adapted according to what the "perceived load" type was.

    I have a house where the C-bus was powered up after the ground floor had all lights fitted, but the top floor lights weren't, and the dimmers on the top floor are behaving weirdly - like on a different dimming curve, won't go below about half brightness.

    I thought maybe the sparkies had used different transformer types for the low voltage halogens, but the same thing happens with a few 240V incandescents as well.

    If the dimmers do adapt to load then maybe I should just cut the power completely and restart all the C-Bus gear ?
     
    Roti, Jul 9, 2012
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  2. Roti

    Newman

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    The DIN Leading Edge dimmers do not have selectable dimmer curves. They use an approximation of linearisation of the RMS power delivered to the lamps. For incandescent lamps it gives a reasonably linear change in perceived light level vs the C-Bus group level.
    The DIN Leading Edge dimmers do not have any intelligent sort of adapting ability for different load types.
    This can certainly happen with newer load types. Things like some LED loads or dimmable CFL's may not meet the minimum load requirement for the dimmer channel and it may appear not to dim to off.
    This is pretty much impossible. Either the dimmer will dim incandescent loads properly or it won't dim them at all. About the only things I can think of here may be that the dimmer is struggling to properly detect the zero-crossing due to mis-wired neutrals. Remember that the power supply to both ends of the dimmer needs to be on the same phase. It's also possible that C-Bus comms is unreliable and the network is trying to correct itself, which is stopping the dimming part-way.
     
    Newman, Jul 9, 2012
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  3. Roti

    Roti

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    Thanks for the info.

    I'll look into this. C-Bus comms seem fine. The house has 3-phase power, and of all the possibilities I think it's the only plausible explanation.

    Identical incandescent 240V circuits are definitely not dimming in the same way on different circuits. One one floor, both LV halogens (iron core transformers) and 240V incandescents dim normally. On another floor, both will only go down to about 50%.
     
    Roti, Jul 10, 2012
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  4. Roti

    NickD Moderator

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    The only other thing I can think of is that a minimum level may have been set.

    Nick
     
    NickD, Jul 10, 2012
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  5. Roti

    Roti

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    Minimum levels are all set to 0.

    A quick check shows that of the 7 x 8 channel dimmers:

    All the loads attached to dimmers 4 to 7 work fine (LVH & incandescent).
    All loads attached to dimmers 1 to 3 don't dim properly (LVH & incandescent).

    I guess that supports to mis-wired neutrals hypothesis.

    I'll give that a look and get back next week.
     
    Roti, Jul 10, 2012
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  6. Roti

    Roti

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    Got the phases sorted (control and load supplies to each unit on same phase) and now everything works fine.

    Thanks for the advice !
     
    Roti, Jul 26, 2012
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