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How many Strings can I run

Discussion in 'Power Supplies' started by ando1961, Jan 23, 2015.

  1. ando1961

    ando1961 New Elf

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    Newbie question

    How many of these type of strings can I run from a single 250w 50a 5v power supply

    Input voltage:.............DC5v;
    Power:.......................7.2watt/meter, 36watt/roll;
    LED resource:.............WS2812B led(5050 SMD RGB LED with built-in improved version of ws2811 ic)
    Q'ty of LED: ...............30leds/meter, 150leds/roll, each LED is separately controlled
    IC Type: .....................improved version ws2811 IC(built inside the 5050 smd rgb led)
    Q'ty of IC: ..................30IC/meter (1 IC drives 1 led chip);
    Pixels:......... 30/meter;
    Pitch: .........................33.3mm(1000/32);
    Grey scale: ................256;
     
  2. multicast

    multicast Senior Elf Generous Elf

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    easy answer is about 4 rolls
     
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    ando1961

    ando1961 New Elf

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    Thanks for this so if I had a 30amp one only about 2 ??

    Just one question. I calculated that the amp for a single string was 7.2 and that I could get at least 5 strings. Did I do something incorrect in my calculation?
     
  4. bpj1980

    bpj1980 Full Time Elf

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    Hey Ando you should never run a psu at 100% i always try to aim for 70-80%max, other guys here will explain it a little better
     
  5. lizardking

    lizardking IT IS STILL ALL BENS FAULT

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    hi Ando welcome to ACL mate the comment about not running your PSU's at 100% is correct by running your PSU at 80 % you will increase the life of your psu and reduce the amount of heat produced , HEAT + ELECTRONICS = failures better to run a bigger PSU or run two to make sure you dont lose your display at a critical time
     
  6. AAH

    AAH I love blinky lights :) Community Project Designer

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    Not only should you be wary of loading a power supply to full load but a 50A supply isn't necessarily a 50A supply. Meanwell in particular and probably other manufacturers as well make a generic package size like their 320W supplies and use the 320 as part on the nomenclature but not all of the supplies pump out 320W. I created a topic at http://auschristmaslighting.com/forums/index.php?topic=6431.msg57259#msg57259 that includes a table from a Meanwell spec sheet.

    As a generic way of working out how many pixels you can put on a power supply. Find out the current of the supply for example 50A. Multiply that by 0.8 to give a maximum load of 80%. From that 40A divide it by 0.06 to give a total number of pixels. In this example it would be about 667 pixels. 0.06 is based on pixels using approximately 20mA (0.02A) per colour or 60mA (0.06A) per pixel.
     
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    ando1961

    ando1961 New Elf

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    Thank you to all for your very helpful responses and links. I really apprecaite all your assistance.

    Ando
     
  8. mararunr

    mararunr Here to learn! (and share)

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    One other point is whether your are running the strings end to end or each string starting directly from the psu. For 5v, the rule of thumb is generally only 50 pixels directly from the power source before you have to do power injection. So you can't actually run the number of strings mentioned end to end directly from one output of the psu without doing additional work. Hope this helps.
     
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    ando1961

    ando1961 New Elf

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    Mark,
    Thanks for this. these are LED sealed (in tubing)strips at 150 pixels per run, I would be injecting into the end of the run. Would this be sufficient or do I have to into the tubing to get sufficient power? So far I only have one strip that would be this length the others will be 90 - 120 LEDS. I only have a small house frontage.
     
  10. mararunr

    mararunr Here to learn! (and share)

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    Honestly, the best thing to do is try (in your garage or shop or wherever you tinker) and see what happens. I've only used square and bullet nodes in the past and this past week I just got my first "strip" pixels from Ray last week. The rule of thumb was based on individual pixels versus strip. As far as I know you won't hurt anything if you test and find the run without power (lights will just run odd colors or no color at all). Sorry. I hope to know more about strips as the year goes on.
     
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    ando1961

    ando1961 New Elf

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    Mark,

    Thanks for this. I will be doing testing of the strips and pixels. I just ordered a load from Ray today so these all will arrive in the next couple of weeks. Pixels, several types of strips, and pixel modules. Several power supplies, 1 set of meteors, and a bucket load of pigtails.

    Les
     
  12. Eastwood16G

    Eastwood16G Full Time Elf

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    I'd add a couple of extras. I would not run anything at 80%, but I'm an electrical engineer, notorious with the accountants and politicians for 'gold-plating'. I'd always use 50% or much less.

    Unless you are running a 100% white display for extended periods then their 80% should be a good approximation of my 50%.

    If you are running a PSU in an Aussie summer, packaging them without forced air then you must significantly de-rate your supplies.

    And buy spare PSUs for peace of mind. If your budget is AliExpress you don't want to be paying JayCar prices in a crisis because one failed.

    The most frequent problem I have with Chinese supplies is the 110v/220v switch being reversed. The biggest problem with all supplies not just xMas lights is electrolytic caps. They fail with heat, high duty cycle, age and shoddy manufacture.

    Long story short buy twice as many PSUs.

    R
     
  13. Benschristmaslights

    Benschristmaslights Dedicated Elf Global Moderator Generous Elf

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    well for the last 4 years I have been using rays psu and running most close to 80% and have only had 1 fail and due to having a spare I was back up and running in 30 mins.

    as stated fans are a must IMHO.
     
  14. Eastwood16G

    Eastwood16G Full Time Elf

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    Peace of mind.
     
  15. Fing

    Fing Full Time Elf Generous Elf

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    Does anyone run multiple supplies and diode auctioneer them for redundancy?


    Cheers
    Fing
     

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