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Thread: Fluorescent tube and qld

  1. #1
    Automated Home Sr Member
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    Default Fluorescent tube and qld

    Hi guys,

    An odd question, but I have a 5a socket wired to one of the channels on a qld. I'd like to connect a floor lamp with a tube in it to the socket. If I don't dim the qld (ie only use 0%and 100%) can I connect the lamp or will inrush currents et al fry the dimming circuit.

    I know I'm being lazy, but it will be a real pain to find another relay channel in node 0.

    Thanks, Peter.

  2. #2
    Automated Home Legend chris_j_hunter's Avatar
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    we use our QLDs with dimmer dimmable CFLs, so maybe that could be an option ?

    Chris
    Last edited by chris_j_hunter; 29th October 2014 at 11:04 AM.

  3. #3
    Automated Home Legend Karam's Avatar
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    If you use a non dimmable fluorescent then you may get different symptoms. For small CFL type lamps you may find that the lamp will not switch off but flicker at 0% - the reason probably being the leakage current through the QLD filter capacitor is high enough to ignite it. Between 0 and 100% dimming relies on rapid switching at non zero voltage points of the mains cycle so the capacitor is a necessary part of a filter circuit to reduce the consequent switching noise. In principle you could 'disconnect' the capacitor if all you want to do is operate in on/off mode but you'd need to be happy to open up your QLD and have a soldering iron handy.. not that I want to encourage this..

    A large fluorescent may have a different symptom whereby the leakage is not sufficient to ignite it but at 100% there can be flicker due to the way that Triacs in the dimmer are triggered (not held constantly on). However the latter is under firmware control and in fact we have different variants of this (to deal with vaggaries of dimmable LEDs) so it would probably be possible to resolve that one by firmware.

    As Chris suggests the other option is use a dimmable CFL. These are designed to take into account the way that dimmers work. I suppose then you'd also be able to dim the light - though from my experience the range is not great with these.

  4. #4
    Automated Home Sr Member
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    Thanks Karam,

    Happy to report that I've got no problems with the standard QLD. Just for info it's a 5ft tube (I'm guessing it's a T8 as it's about 15 years old...)

    Peter

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