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Advice on Electrics Please

Discussion in 'Power Supplies' started by BigKev, Dec 29, 2012.

  1. BigKev

    BigKev New Elf

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    Hi All

    I’m a complete newbie at this and no doubt this will be the first of many questions to come in my search for knowledge that will hopefully enable me to progress my thoughts to practical application.

    Unfortunately the electrics are my weak (very weak) point as I know almost nothing about the theory of electricity so that is where I would like some initial advice.

    I’ve tried to start at the beginning and get my head around the impact of a Christmas Light Display on my household power setup. Not so much the cost of usage but rather the hardware requirements, ie do I need the electric company to run 220,000 volt power line to my house so I can do this?

    So I’ve made some broad assumptions as a starting point which whilst not completely accurate will at least give me a rough idea of what will be required power supply wise.

    Anyway I’ve drawn up an initial design concept and calculated it will require 262 metres of LED string to light it up. Assuming a 5 volt DC system and the LED’s draw 0.3 watts each and are spaced at 10cm. That will give me 2,620 LEDs at a total of 157.2amps if my understanding of the ACL 101 Manual is correct.

    I know that the next step will be to work out how many channels, controllers and DC power supplies, etc. I’ll need but as indicated I first want to understand what the primary power source will be/look like.

    If I’ve got it right so far then I now need some guidance, please, as I don’t understand how the 5VDC current requirement (157.2amps) relates to the 240V primary power source. I know, in terms of 240V power, that you can’t draw 157.2amps from a 10amp wall socket but does the diagram at the bottom of page 41 in the ACL manual mean that 157.2amps at 5VDC represents a 3.275amp draw on the 240V primary power source.

    If that’s the case then it seems to me, theoretically at least, that one 10amp wall socket would adequately supply my power requirements. Conversely if I am the poor misguided sole that I think I probably am and 157.2amps is 157.2amps then I assume I would need to spread the load across more than 16 wall sockets and different circuits, etc.

    As I’m doing this a zillion more questions spring to mind but I’ll leave those for another time. If I can get my head round this bit then I think a lot of the other stuff will fall into place and will also give me an idea if the CFO will approve the likely budget.

    I only hope I have explained myself reasonably clearly and that someone out there can point me in the right direction.

    Thanks
    Kevin
     
  2. AAH

    AAH I love blinky lights :) Community Project Designer

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    Hi Kev
    That question is a pretty easy one. 157.2Amps at 5V equals 786 Watts. Power equals volts times current. So to get the power at 240V you need to divide the power by the volts. 786/240=3.275 Amps. In reality power supplies are typically about 85% efficient so that 3.25Amps would be about 3.85Amps which is well under what you can run off a power point. It's about the same sort of power as an average microwave.
     
  3. battle79

    battle79 Full Time Elf

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    What he said. :)
    Reality (IE the layout of your yard will determine if one PSU is practical or if it is better to run 2.
    With 5V you suffer from volt drop and will have to check the table in the 101 manual for how big you cable to feed each string will need to be. This is where you decide if it's cheaper to buy bigger cable or a second PSU.

    Cheers,
    Rowan

    P.S. Had a thought, if your talking pixels, they are often 0.3W per color, just something to be aware of)
     
  4. ecbailey

    ecbailey Full Time Elf

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    Are you certain that the LEDs are running at 0.3w each? That seems a fair bit, however I guess this is 5v. Have you considered using something at a higher voltage (I use 24v AC/31v DC), this would reduce the need to be concerned with voltage drop and also would significantly reduce the amperage you are dealing with.


    Also, most controllers (LOR/AVD) can handle voltages up to around 50V-60V, but can only manage a limited amperage (say 2A per channel).
     
  5. AAH

    AAH I love blinky lights :) Community Project Designer

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    I assumed (which I do too much) that being 5V they were going to be pixels rather than led strings or strips.
     
  6. OP
    OP
    BigKev

    BigKev New Elf

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    Hi and many thanks to those very powerful beings who have answered my query. Seems I won't be needing that 220,000V line after all, which is a bit of a relief.

    The info I provided was largely hypothetical for the purposes acquiring some important knowledge regarding primary power requirements. Now that I understand that bit I can continue with some more serious and detailed research and planning with a view to establishing things like which voltage, contollers, PSU's, software, etc. to use.

    I'm sure that will involve many more questions to you folk and at the end of the day the final outcome will, no doubt, be driven by the almighty dollar. First job however is to spend a few hours detailing out my design concept so that I can quantify the individual elements to get a handle on channel/controller requirements.

    Thanks again and best regards
    Kevin
     

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