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New to DC

Discussion in 'LOR DC' started by Robbo, Dec 23, 2010.

  1. Robbo

    Robbo Full Time Elf

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    Ok so I have decided to introduce DC to my display for my low voltage lighting and was wondering a couple things, which may be a good idea to document for future reference to people first enquiring of DC....

    first of all the lights I want to run on DC all have 8 function controllers.....and transformers, so where do I cut the wires, is it cut the controller off all together and plug into the DC board or is it after the controller?

    also how do you know how much power to supply to the board, I notice on the transformers that it has an output rating, eg 24v so does this mean that you need to supply 24V to the board or just to that channel? Assuming I can use a 24v output power supply to run this particular string can it also run a 12v set on the same board?

    your input will be much appreciated :)
     
  2. David_AVD

    David_AVD Bite my shiny metal ass!

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    LED strings can be a bit of a pain as the various brands use different voltages. I think there's a thread somewhere about how to remove the multi-function controllers and determine the correct voltage (and add resistors) for your strings.

    Most DC controllers will have one or two DC inputs. For the simplest set up, this usually means that all channels (or bank of channels) must use the same voltage lights. In reality, you can get around this by connecting the +ve wire of each string to your chosen power supply's +ve terminal and the -ve of the DC controller board to its -ve terminal.

    I think we'll need to do up a diagram and add to the wiki, as it does sound confusing! The point I'm making though, is that the DC controller does not have to use the same power source as the lights. It can (and usually does), but is doesn't have to.
     
  3. kel

    kel Dedicated Elf

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    What testing instruments are required?
     
  4. David_AVD

    David_AVD Bite my shiny metal ass!

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  5. aussiexmas

    aussiexmas Sinnamon Lights

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  6. AAH

    AAH I love blinky lights :) Community Project Designer

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    I haven't got any DC controllers yet but as I'm starting to look at going LED with all new lights I'm starting to think that I should investigate DC. I had a look at LOR site and that didn't help me much. I'm currently using 7 out of 8 of my CTB16PC AC controllers which I love.
    For anyone out there that's willing to give a DC novice some advise I'd love to hear the pro's and con's of what LOR have to offer.

    Alan/AAH
    Eaglehawk,Vic
     
  7. Beacy

    Beacy It's so much better on the dark side

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    Welcome, this is a great place to learn all you need to go to DC next year, they're a great bunch that are more than happy to help you up the learning curve with all the technical issues and questions you will have drop into chat sometime.
     
  8. darkeyrie

    darkeyrie Light-O-Rama User

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    Alan,

    Having started out with DC I can say that it is certainly the cheaper and safer way to go compared to running 240V AC everywhere.

    As to where to start, that depends on what LED lights you source. I have seen some retailers (the specialty Christmas ones) selling monochromatic 24V DC LED strings in a range of colours. Those are the best way to go in my opinion if you are starting out. In Adelaide, Starlight Christmas Warehouse has some, and I am sure there are others in the other cities too.

    You can also do what I did the first year I went LED and get some of the cheap strings from the major retailers (Big-W, K-Mart etc) but those almost certainly will need modification. It is rare to find them without multi-function controllers (which you will need to bypass) and often the strings are cheap and nasty to the extent they may not have current limiting resistors in the strings. (A good example was the K-Mart 252 LED sets - available for the past couple of years - which have no resistors in the strings and only have something inside the controller which you want to bypass). The current limiting resistors are important as over-driving LEDs with excessive current shortens their lifespan (considerably as I found after destroying a string of yellows before I got my meter in series to figure out how much current they were trying to draw).

    The other catch with LEDs is that each different colour has a different required voltage per LED to get them to light up. The red and yellows for example need only ~1.5v across them at 20mA, while the greens, blues etc need up to ~3V at 20mA. Adapting the K-Mart strings with their 12 LEDs per sub segment to be single colour strings was tricky as to make whole green and blue strings I ended up feeding one control bank with 36V DC, while the red and yellows were fed with 24V DC.

    The LOR controllers can at least have a different feed voltage per 8 channels - so I have one board with 8 channels on 24V and the other 8 on 36V.

    The links elsewhere in this thread give you tips on the Big-W LEDs.

    My tip however, to save you a load of pain and time, if you are starting out with LEDs, source LED strings that are 24V DC, single colour, have the current limiting resistors in them and ideally are cut-able in segments. They are around and are not too expensive (although more costly than the department store ones), but what you spend in $$ you will make up for in a reduction in time needed to be spent modifying them to make them work. That time can then be put into building more decorations :)

    Regards,
    Grant VK5GR
     
  9. AAH

    AAH I love blinky lights :) Community Project Designer

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    LEDs aren't really an issue to me. I'm an electronics tech and have already modded up some multifunction 240V leds into non-multi 24VAC strings for my 2010 lights. With the exception of some incandescent 240V ropes I have everything running off 24VAC with large torroidal transformers mounted in LOR plastic enclosures back to back with my ctb16pc's. This provides me with the power I need for the lights and allows me to have nodes all over the 1/3 acre'ish area that I decorate. This minimises on the use of kilometres of extension leads.
    My main interest in DC is the possibility of reducing the number of controllers needed when I add maybe another 100 channels for 2011 with some RGB led channels.
    I'm also wondering if full wave rectified AC from the torroidal transformers I'm using for my AC can be used to power the DC channels on a DC LOR.

    I don't know if the link will work but the following points to an old LOR forum post explaining my current setup.

    http://groups.google.com/group/aussie-lor-users/browse_thread/thread/30a0d23498bac86d/6323d9a8fcdd862c?lnk=gst&q=240v#6323d9a8fcdd862c
     
  10. darkeyrie

    darkeyrie Light-O-Rama User

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    OK, thanks for the link - yes it worked and now I remember your setup from when I read about it previously. I must admit to have been curious in the past as to whether the AC controllers would run on a 24V AC feed instead of 240V. Great to see that someone has tried it (more ideas now for recycling my old 240V controllers when I finally get rid of the 240V lights).

    As for the DC boards giving you a gain, I am not sure that they will other than I think the new QC versions are cheaper than their AC cousins. The channel count is still the same (16 per board) so the $/channel is still around the $5/ch mark (not including freight). DC however is easier driving LEDs as of course they are inherently a DC device.

    The DC boards I also think need a filtered DC supply. Raw full wave rectified AC without regulation I think will crash the controller micro as the boards are not designed to run on unfiltered DC from memory. This is why you see most people talking about using the switchmode power supplies when they discuss driving those boards. Might be worth a question to LightORamaDan on the LOR forum if no one else can offer any insight into this? (I personally have only ever run them on filtered switchmode supplies).
     
  11. AussiePhil

    AussiePhil Dedicated Elf Administrator

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    AAH

    I too would recommend using dedicated Switched Mode Power Supplies (SMPS) for all your DC boards. It's the way i went when I made the switch two years ago.

    Cheers
    Phil
     

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