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Thread: LED dimmer ...

  1. #1
    Automated Home Legend chris_j_hunter's Avatar
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    Default LED dimmer ...

    a spot of banter over on UK_Selfbuild led to the following device for making an LED driver with dimming (for lighting - cupboard, room, whatever - not indicators) :

    http://datasheets.maxim-ic.com/en/ds...8-MAX1698A.pdf

    http://datasheets.maxim-ic.com/en/ds/MAX1698EVKIT.pdf

    the trick being to substitute a link to an Idratek QAO module output for the potentiometer that's shown connected to the REF/ADJ pins ... not sure quite how to do that yet (more homework required), but thought I'd mention this because LED dimming is not easy to come by !
    Last edited by chris_j_hunter; 30th April 2009 at 01:30 PM.

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    Moderator toscal's Avatar
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    Actually there is possibly a better device on the market. Simpler to wire up and can either be controlled via a potentiometer or via a 0 to 10v signal or via PWM.
    http://www.recom-power.com/pdf/Innoline-2008/RCD-24.pdf

    I've just ordered one to play with.
    So will let you know how I get on.
    IF YOU CAN'T FIX IT WITH A HAMMER, YOU'VE GOT AN ELECTRICAL PROBLEM.
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    Automated Home Legend chris_j_hunter's Avatar
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    well done, look forward to hearing how you get on ... we're looking to drive LEDs around the house, ideally with one controller to lots of lamps - most of which will likely be strips, eg:

    http://www.tlc-direct.co.uk/Products/FL4205WH.html

    which are a bit expensive at the moment, but we'd hope to be able to use something of the sort to give halo effects around various things, to provide lighting for shelves & displays, for reading lights, for under-bed lights, and so-on - the idea being that it would be good with such things to keep not too far off what will inevitably be variable ambient light levels (daylight & artificial), and so help keep the mood, avoid glare, etc ...
    Last edited by chris_j_hunter; 30th April 2009 at 04:04 PM.

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    Moderator toscal's Avatar
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    How about some of these, they come in 1m lengths. Are very flexible and may possibly work out cheaper than the 30cm strips. We also do special under cabinet lighting. If you PM me I can email you the details. All work from 12DC. We also do other types of rigid and flexible led lighting.
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    Last edited by toscal; 30th April 2009 at 04:34 PM.
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    Automated Home Legend Paul_B's Avatar
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    I've ecommended these guys before but once again they ae always my first stop fo anything LED elated:

    http://www.ultraleds.co.uk/

    How about something like this:

    http://www.ultraleds.co.uk/self-adhe...en-p-2017.html


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    Automated Home Legend chris_j_hunter's Avatar
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    interesting - still frighteningly expensive, though, and the dimmer seems to be by push-button only ... they also say 0-100%, which always makes me wonder !

    hopefully, prices will come down ... suspect we'll be provisioning rather than installing, for the moment !

  7. #7
    Moderator toscal's Avatar
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    Thats very expensive. We do something very similar cheaper.
    IF YOU CAN'T FIX IT WITH A HAMMER, YOU'VE GOT AN ELECTRICAL PROBLEM.
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    Automated Home Legend Karam's Avatar
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    Quote Originally Posted by chris_j_hunter View Post
    the trick being to substitute a link to an Idratek QAO module output for the potentiometer that's shown connected to the REF/ADJ pins ... not sure quite how to do that yet (more homework required), but thought I'd mention this because LED dimming is not easy to come by !
    Chris,

    As far as I can see it is controlled by a voltage value (0-1.25V I think) so perhaps just a voltage divider on the QAO output could do the job. But toscal's Innoline suggestion looks more practical. Haven't looked at costs.

    Or perhaps there is some hinting going on here

  9. #9
    Automated Home Legend chris_j_hunter's Avatar
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    Karam -

    voltage-divider ... was wondering about grounding strategies, since the LEDs would be on separate power-supplies to the QAO ?

    0-1.25V - looks that to me, too, max' control to max' brightness, and the Recom looks to be 0-4.5V, max' to min' ...

    hinting - could-be !

    Maxim or Recom obviously depends on costs, but it would be easy to believe the latter could work-out best ...

    dedicated module or satellite (to a QAO), possibly making use of the spare pair in the Cat-5e cable (?)

    wonder if PWM would actually be better than analogue ?

    either way, LEDs would seem to be here to stay, so dimmers for them would be good, able to operate on groups of lamps !

    Chris
    Last edited by chris_j_hunter; 1st May 2009 at 08:23 AM. Reason: spelling & afterthought

  10. #10
    Moderator toscal's Avatar
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    We about to get a test LED dimmer. (should be arriving early July). This will be for 12V LED lighting, and will have a 0 to 10V input so control via some home automation systems should be possible. It will have a local dimming control and a separate on off switch. Once we get the prototype and have it up and running I will post here with pics etc. It should look similar to a standard mains dimmer.
    IF YOU CAN'T FIX IT WITH A HAMMER, YOU'VE GOT AN ELECTRICAL PROBLEM.
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