DIN Rail Dimmer (8 x 1A) - with Dimmable LEDs ?

Discussion in 'C-Bus Wired Hardware' started by theboyg, Nov 11, 2007.

  1. theboyg

    theboyg

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    theboyg, Nov 11, 2007
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  2. theboyg

    wanricky

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    very interesting...I mean the LEDs. Since the LED is dimmable and must be used with magnetic transformers, there is, on paper, nothing wrong to use it with a leading edge dimmer such as the D1As.

    (Of course, with minimium leakage current when dimmer is at zero percent, the LED may still lights up slightly even if it doesn't flicker. Also, something funny may happen at low brightness, when the consumption is very low....not because of the dimmer but the new LED, so I am very interested in knowing the result if you tried them. I think it is better to email the LED manufacturer about their dimming performance with common brand's advance electronic dimmers.)
     
    wanricky, Nov 12, 2007
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  3. theboyg

    amberelectrics

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    Cant see what makes you think these are dimmable LED's?

    They are simply replacement units for MR16 package lamps.

    The main reason I doubt they are dimmable is because LED's are dimmed using a pulse width modulation technique, this would require the unit to internally have circuitry to maintain a fixed voltage with variable pulse in direct relation to the input voltage, clearly this would give issues at very low voltages as the input may well be under the required voltage for the circuitry to operate.

    There is nothing in the document that would suggest these would dim at all.

    If using with a CBus dimmer, treat as per flourescent without the need for PFC.
     
    amberelectrics, Nov 12, 2007
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  4. theboyg

    NickD Moderator

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    Perhaps it was the bit on the datasheet that he posted that says "Dimmable"? ;)

    Seriously though... whilst PWM is generally considered the best way to control LED lighting, it's not the *only* way. LEDs have a more or less fixed voltage drop and you vary the current to vary the brightness. Phase control is still a means to varying the average current in a resistive load, even if not the most efficient means.

    Nick
     
    Last edited by a moderator: Nov 12, 2007
    NickD, Nov 12, 2007
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  5. theboyg

    amberelectrics

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    LOL, well hush my mouth, I totally missed the one line in the features list that states it is dimmable :)

    I am presuming that PWM is the preferred method as all the LED dimmable stuff I fit, either in single or RGB format uses PWM control to achieve dim control. I have done it others ways back in the dim and distant days of my electronic engineering but PWM has always been the preferred and more dependable method.

    If these do operate correctly as dimmable units then thats very interesting indeedy.
     
    amberelectrics, Nov 13, 2007
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  6. theboyg

    KERRAW

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    GU10 LED lights

    I have a number of GU10 lighting bars in my office and found that it was impossible to use the 8 x 1A dimmer units with them. There is sufficient current leakage to ensure that they are always on slightly and that the dimmer function does not actually do very much.

    The only way round this is to ensure that there is at least one ordinary light in the circuit as this takes all the leakage and ensures all the lights do switch off. I then just use them as on / of switches.

    The advantage I do find is that the heat in the room is so much less and that power consumption is signficantly less (less than 1W each).

    Gus
     
    KERRAW, Dec 9, 2007
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  7. theboyg

    znelbok

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    There is another way to do it. Run a dimmer in series with a relay channel (output of dimmer channel into voltage free relay). Switch the relay channel on when you want to light them up and off when not needed. This will stop the leakage from lighting them up. The dimmer will obviously be used only for ramping the light level when the relay channel is on.

    Mick
     
    znelbok, Dec 9, 2007
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  8. theboyg

    wanricky

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    just remind me a question, will it affect the electronic dimmer channel such as C-Bus if we constantly switch on/off the load side using Relay or traditional switches?
     
    wanricky, Dec 10, 2007
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  9. theboyg

    damian.flynn

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    Hi,

    I am installing the light fixtures for a new house build at the moment, and the only purchase I have remaining is the MR16/GU10 type lights for the Kitchen and Hallway. I was originally going to run Low Voltage Diclorics; but firgured that now maybe a good time to go with LED.

    However - most of the LEDs i have located either are non-dimmable, or run at 6000+k colour temps and look very 'blue'

    With lots of 8 Channel Diimers installed, and 3 core cable home ran for each circuit, I now have a dellimma of whats the correct purchase.

    Can i impose on your experience on how you would do this? do i consider a dali gateway [no idea how this works], or is there a smarter way to integrate all these into my CBUS system.

    thanks so much for your feedback

    kind regards from Ireland
    Damian
     
    damian.flynn, Jan 21, 2008
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  10. theboyg

    JohnC

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    If it was me, I'd use 12V halogen. Preferably 20W or 35W IRC type, as they are 30% more efficient than the standard halogens. DO NOT use GU10, they are rubbish and you will curse the day you decided to install them rather than doing it properly.

    The efficiency of cheap LEDs is about the same as a IRC lamp. But instead of 35W of light, you might get 1 or 2W... so you gotta use a LOT more of them to get the same light level. This makes them expensive.

    The colour of cheap LEDs is pretty dreadful, and due to batching (or lack thereof) there is wide variation between individual LEDs. Good quality LEDs will have much better colour, but all LEDs will shift towards blue as the yellow phosphor coating deteriorates... at end of rated life they are a very dim, pure-blue LED ;)

    Quality LED modules from reputable suppliers usually use Dali or 0-10V control protocol for dimming, and then PWM (pulse width modulation) on the output side to drive the LEDs. This is the best way to ensure the LEDs lasts and is driven properly, but it's not a "retrofit" solution - you have to run the separate control wires out to the loads.

    And you really should have the drivers out near the lamps... remember that LEDs run on a nominal 3V, so the output wiring needs to be kept short to avoid voltage drop. To light a normal room, 200W worth of LEDs is pulling 66 AMPS on the output of the drivers! :eek:
     
    JohnC, Feb 6, 2008
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  11. theboyg

    damian.flynn

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    Thank you for your reply, I have being reading up on the IRC Halogen's - I am now looking to see if i can install the 230-12V transformer in the pannel close to the CBUS dimmers, and use the cable already pulled to drive the lamps in the celing. I dont think its economical to install a transformer Per Halogen.

    -d
     
    damian.flynn, Feb 7, 2008
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  12. theboyg

    NickD Moderator

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    It's pretty much the norm to install a transformer per halogen here in Australia. I suspect mainly because the additional transformers are cheaper than the additional labour to fit multiple lamps per transformer. A good quality LV lighting transformer *retails* for less than A$20, so it's not that expensive.

    That said, it's not the most efficient solution... 2 x 35W lamps on a 70W transformer or 3 x 35W lamps on a 105W transformer is a better option.

    Also, many of the transformers state a maximum lamp cable length. Part of this is probably due to losses in the cable at high current as JohnC points out (no point in going for high efficiency lamps if you're losing your gains in the cable), although it's also possible that excessive cable length may create instability or EMC problems in some electronic transformers.

    Bottom line - the transformers are designed to be put close to the lamp.

    Nick
     
    NickD, Feb 7, 2008
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  13. theboyg

    ICS-GS

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    Dont do it!

    Damian,

    The further you put the transformers from the fittings, the more voltage drop you create. This will result in a noticable difference in the light output of each lamp. So you will get a situation where the lamp furthest from the transformer will be noticably 'duller' than the lamp that is closest to the transformer. :eek: That is unless you make sure all cabaling is EXACTALLY the same length.

    But as nick says, check the transformer specs, or check with the manufacturer, they will almost definately have a recommended maximum cable distance. They may say you can get around this by increasing the cable size to overcome the voltage drop, but the cost of upgrading the cable versus some additional transformers makes the decision pretty elementary.

    Good luck

    Grant
     
    ICS-GS, Feb 8, 2008
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  14. theboyg

    JohnC

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    Electronic transformers will have a maximum distance of about 1m to the lamp. 1.5m at the very most for some selected models.

    There truly is no better way than putting the transfomer at the light point. You just spent a lot of money on a lighting control system, don't skimp at this late stage.
     
    JohnC, Feb 11, 2008
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  15. theboyg

    samluo

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    I think not proper.usual dimming ways of LED are the PWM or voltage-change.
     
    samluo, Feb 10, 2010
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