Powering my light show

Discussion in '101 Display Basics' started by Cptmick, May 10, 2017.

  1. Cptmick

    Cptmick New Elf

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    Hi guys I've been playing around with my lights and i'm hitting problems with Powering a few hundred pixels.
    at the moment I've got a 220w PSU from an old PC with a bit of tire wire (about and inch long) running from alligator clipped to a bit of old thick car amplifier wire(approx 5mm) clipped to a banana plug wallplate directly to a string of 100 ws2811 pixels form ray wu this draws 5.55 amp when all pixels are on white and runs fine . but when i double the pixel load same setup just two strings of 100 at the banana plugs. ( the ground wire is all 0.12mm).

    My question is with that amp draw of just 2 strings how do I power a few hundred lights ( with out risking fire and move that much amp draw from the garage to the front yard and around (approx 20m - 30m.

    i feel like I'm missing something, any help would be appreciated.

    also what power supply is suitable or should use a few PC PSU?
     
  2. ezellner

    ezellner New Elf

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    If I understand correctly, your ground wire may be too small. Ground and power should be the same since the current runs in both.
     
  3. David_AVD

    David_AVD Good news, everyone!

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    As a rough guide, cable is good for about 10 Amps per 1 square mm of wire. For example, 0.75mm (cross section area) cable is good for 7.5 Amps.

    Also, using computer power supplies for Christmas lights can be hit and miss. Better to use a proper single output voltage supply.

    Ideally you should also split the high current power supply output and run through fuses to feed your various light sets.
     
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  4. fasteddy

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

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    You will also have to consider power injection and cable size as voltage drop will be an issue if you are looking at 20 to 30 meter runs especially with 5VDC.
    You may need to take a look at the ACL101 lighting manual for reference to connecting multiple strings and dealing with power injection and voltage drop
    https://auschristmaslighting.com/threads/auschristmaslighting-101-manual.1889/
     
  5. scamper

    scamper Senior Elf

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    I concur. The ground wire must be the same size as the positive, as power does a full circuit, in one side out the other.
    Also when you go to the next set of strings, you will start to get voltage drop through the strings that will require power injection.
     
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  6. David_AVD

    David_AVD Good news, everyone!

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    And just to clarify my earlier post, fuses should over ever go in line with the positive wire, never the negative (ground) wire.
     
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  7. videoman3857

    videoman3857 Full Time Elf

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    Interesting comments about wire sizing here.
    I am from the irrigation industry and we have rules of thumb for wiring up irrigation control valves - all be it 24 volt ac with a high inrush current but still nowhere the current draw that some of the blinky things can draw.
    Our rule of thumb is for gaining greater run distances to which we would normally increase the sizing of both wires,
    There are times where the load does not warrant the need or the expense of the size increase of both wires, in which in this case, one would increase the
    common (-ve in irrigation) without increasing size of the control wire (+ve) Ergo a system could operate well on a 1.5 mm2 common and a 1mm2 active.

    I am only running Dumb RGB pixel and found that one display worked fine, but connecting two caused a power drop off because of the distance and the load .
    Rather than beef up the wires or running a power injection point I changed the set up. Instead of running the lights in series I opted to run them parallel.
    - Basically run the power to the middle of that display. They all worked fine.
    Not having any Smart Pixels in my set up (time will tell) I am wondering if the same can be done with them, or does that muck up the data to the "smart Stuff" in the lights ? Can a universe of lights be run in parallel or must they be run in a series ?
     
  8. fasteddy

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

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    You can run power parallel and you can run power from the middle of two strips or strings as long as the cable used can cope with the current and distance needs for the load but your data will still need to be fed into the start of the string or strip
    But if you are wanting to run data parallel then this is where is can become an issue because for every time you split the signal the signal strength is weakened and also if you have long parallel runs then you can cause issues with data reflection in the cable causing bad results with flickering lights especially if the cables are not the same length. Also if you split the signal then effectively all you are doing is repeating that signal and not keeping them separately controlled as each parallel run will see the same data
     
  9. scamper

    scamper Senior Elf

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    What you say about the size of -ve being larger would to me indicate that you are as you say running a common ground. Therefore each solenoid only draws x current and are wired up individually and the ground or return wire is wired parallel meaning if more than 1 solenoid is on, it has to cope with the return current. So that would make sense.
    Here we are talking about each string, however if you were to run a common ground wire and control the strings separately then again you would need a ground wire that could handle the TOTAL return current.
    By applying power to the middle of the 2 strings, you are effectively power injecting, as the voltage drop occurs a lot because of the wire gauge of the led strings themselves not just the current draw of the led's
     
  10. videoman3857

    videoman3857 Full Time Elf

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    Whoa. Smart Blinky things are a little more complicated than the dumb ones and solenoid valves :p
    Wiring is pretty close and is logical. I didn't know about data reflection etc.
    For the moment - its the dumb stuff for me.
     
  11. OP
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    Cptmick

    Cptmick New Elf

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    thanks for the advise i will definitely help
     
  12. OP
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    Cptmick

    Cptmick New Elf

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    I do have one of these i got off ebay last year, when I started playing with lights. My only concern with using it, Is from what I can tell you just run a wire from the mains in the wall into the device. I'm not exactly comfortable with having just a 240v (death lama) lying around. I know its just about the same having a pc supply, but with the pc one has a proper insulated connector for the 240v, via the jug lead. That's my only real concern with using them as I'm a bit of a newbie to the whole power thing. also the pc PSU shuts down if it detects a short
     
    Last edited: May 22, 2017
  13. David_AVD

    David_AVD Good news, everyone!

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    A PC power supply may also supply a lot of current into too thin cable without shutting down.

    I do take your point about the mains wiring of course.
     
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  14. scamper

    scamper Senior Elf

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    If you are in a rental house, by law you should have a safety switch which "should" protect you if you accidentally touch anything. If it is your own house, then I suggest you get a safety switch installed and circuit breakers if you have the old fuses. It is worth the investment just for peace of mind.
    It still may hurt if you touch the mains, but you have a better chance of surviving :)
     
  15. David_AVD

    David_AVD Good news, everyone!

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    Never rely of an RCD (safety switch). Nothing will protect you if you get yourself between live and neutral. :(
     
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