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Yet another power question....

Discussion in 'Power Supplies' started by Baf05, Sep 12, 2018.

  1. Baf05

    Baf05 Full Time Elf

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    Power, injection, fuses, amps, watts, I have long found this part of the hobby very, very confusing.

    But I am determined to learn, I still find amps and watts way over my head but I guess I will get there...

    ...todays question is more about current draw (I think) through a fuse....

    When I built my mega tree I followed Ruprects instructions, pretty much to the letter, even buying the same 600w meanwell power supply. I its run pretty well for 3 years just of that one power supply (which I did blow up this year and have 2 new 600w arriving today..... ). The tree has 8 injection, fuses (15amp no reasoning behind this and that's way to big I know, I think 10amp would suffice, and I think the wire would cope. but again no actual reasoning behind that thought). These branch out into 4 injection points each, so effectively each fuse is responsible for just 176 12v pixels.

    However, I think, with the way its put together, if a fuse blows, rather than one section of the tree going out, (or I guess all the tree, depending on which fuse blows) the load will be passed to the next fuse, presumably blowing it, because its now overloaded, and then the same thing happens again, until all 8 fuses are blown....

    I think I need to be cutting power at some point to isolate each fuse from the others.

    SOOOO.... I am updating my 5v arches.... 100pixels per arch. I have used 3pin pigtails for the power ground and data in, and out, however on the out pigtail I have not connected the power wire. For power at both ends I have 2pin pigtails connected to both power and ground. The I can run my injection back to a fuse (one 5 amp fuse per prop in this case) and if one fuse blows its isolated from the other props!

    I am still unsure how to work out what size fuse to use, I know that's linked to the wire size, but still doesn't help decide what fuse to use....

    Does all this sound right. (hope that all my some kind of sense)
     
  2. scamper

    scamper Senior Elf

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    Yep you are right. There is one thing you can do to help the power and that is to run a wire from the start of the arch to the end (same wire) and effectively run it back still having it separated from the next.
    The way to work out your fuse is to look at it as protection (which is exactly what it is meant to be) You need to know the size of the wires ie the current capacity and the max handling capacity of all other items, ie boards, supplies whatever is in line and make the fuses slightly smaller.
    So for instance, if the board can handle and output of 15amps, the wire you are using is 10amps, then the fuse must be equal or less than the value of the lowest item. So in this case 10amps or less.
    A fuse is designed to blow at the value written on it, but a wire will keep supplying power but just get hotter and eventually burn etc.
    Check to make sure that the total load of pixels does not go over what you are fusing. so 100 pixels are rated at 60ma (full white) which is 6amps. so no problem there.
    You could conceivably double that if you ran them at lower brightness, as brightness in led's is directly related to current draw.
     
  3. OP
    OP
    Baf05

    Baf05 Full Time Elf

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    SO how do you know the rating of your wire? for injection I run 16awg speaker wire,
     
  4. fasteddy

    fasteddy I have C.L.A.P Global Moderator Generous Elf

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    There are current ratings for cable sizes in the ACL 101 manual, or these can be found on the internet
    The voltage drop of a cable is determined by Ohms law with the load current (amps) Voltage (Volts) and length of cable (resistance) all playing a part in the correct cable selection
     
  5. OP
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    Baf05

    Baf05 Full Time Elf

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    I get that? but its my understanding that not all wire is created equal :(
     
  6. scamper

    scamper Senior Elf

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    you will find it will be close enough. The main problems are the quality of copper, in it has been tinned etc. But in general terms if it says it is 16awg it should be close enough as all of your planning is based on theoretical values anyway.
     
  7. videoman3857

    videoman3857 Full Time Elf

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    Make sure you use multi stranded copper wire.
    Stay away from from single strand and copper tinned aluminium wire.
     

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