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Thread: Power supply and controller for 15 metre LED strip

  1. #1
    Unenlightened
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    Default Power supply and controller for 15 metre LED strip

    Hi all,

    I've got 15 metres of 12V 6 Pin LED strip. They're in 5 metre rolls.

    I wanted it all to be 1 length so it goes are round my ceiling, but it's come with 3 power supplies, 1 power supply does power 10 metres but it's noticeably dimmer than with just 5 metres. 15 metres it'll barely be lit.

    I'm also using a Gledopto pro controller and I expect this would also struggle with power 15 metres of LED.

    Ideally I wanted to connect all 15 metres together as 1 piece and use one controller and one power supply to power it all.

    Is there anything capable?

    Thanks for any help.

    Wayne

  2. #2
    Flashaholic
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    Default Re: Power supply and controller for 15 metre LED strip

    Could you give more product/technical detail on the LED strips? Are they white or RGB? How much current per strip? Also detail on the 12v power supplies (current capacity). Problem with strips like these is if you connect enough of them in series, resistance in the power traces adds up and can dim ones further out. They may just not be meant to connect three in series. It could also overtax the power supply if not sufficiently rated for the setup. Dave

  3. #3
    *Flashaholic* Lynx_Arc's Avatar
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    Default Re: Power supply and controller for 15 metre LED strip

    You have several problems here.
    1)3 sets of light and 3 power supplies means to go to 1 strip that is 3x as long you still need 3x the power of 1 power supply
    2)The reason each set works with the power supply is that the wiring is designed that way. The facts are wires do have resistance to them that over the length of wire the voltage will drop. Larger wires incur less voltage drop while smaller wires incur MORE voltage drop. In a 5M strip you have 1X voltage drop but in 3x 5M strips you have 3X voltage drop. Adding power supplies won't stop the voltage drop you have to either increase the wire size in the strips or raise the voltage and the LEDs and resistor setup likely cannot manage too much of an increase in voltage as the ones farthest from power may be lit up fine by raising the voltage but those closer could fry.

    My advice is to either use the separate supplies and run larger wire from them to EACH strip that is far away or get a 3X power supply and do the same. Simply put you need to get power to EACH strip separate of any voltage drop of another strip. If they designed these strips with larger wire you could possibly chain them together but they used marginal sized wire/foil in the strips to save a penny here and there.
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  4. #4

    Default Re: Power supply and controller for 15 metre LED strip

    With three strips, 15 meter total, you can have success running equal lengths of wire to each end of the 15 meter length. No guarantees, but can be easier than trying to wire into the middle in two spots. You will need a larger supply of course.

  5. #5
    *Flashaholic* Lynx_Arc's Avatar
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    Default Re: Power supply and controller for 15 metre LED strip

    Quote Originally Posted by JustAnOldFashionedLEDGuy View Post
    With three strips, 15 meter total, you can have success running equal lengths of wire to each end of the 15 meter length. No guarantees, but can be easier than trying to wire into the middle in two spots. You will need a larger supply of course.
    That would leave LEDs in the middle probably dimmer than desired it is better to like you say wire in two spots at both ends of the middle 5M strip paralleling all 3 supplies to those two points it may have the ends of the 15M strips a little dimmer perhaps.
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  6. #6

    Default Re: Power supply and controller for 15 metre LED strip

    Quote Originally Posted by Lynx_Arc View Post
    That would leave LEDs in the middle probably dimmer than desired it is better to like you say wire in two spots at both ends of the middle 5M strip paralleling all 3 supplies to those two points it may have the ends of the 15M strips a little dimmer perhaps.

    The resistance to the middle, 7.5 meters in, will be the same as 7.5/2 meters = 3.75 meters, as you are supplying from both ends. Hence the center of a 15 meter length supplied at both ends, will be brighter than the end of a 5 meter length supplied at only one end.

  7. #7
    *Flashaholic* Lynx_Arc's Avatar
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    Default Re: Power supply and controller for 15 metre LED strip

    Quote Originally Posted by JustAnOldFashionedLEDGuy View Post
    The resistance to the middle, 7.5 meters in, will be the same as 7.5/2 meters = 3.75 meters, as you are supplying from both ends. Hence the center of a 15 meter length supplied at both ends, will be brighter than the end of a 5 meter length supplied at only one end.
    No, because you fail to consider that the drop is equal from both ends to the middle so at the 5 meter spot you will already have some drop and an additional drop another 2.5 meters from each end to reach the middle LEDs in the middle strip. Now the drop will not be anywhere near as noticeable as feeding it from one end. If you could wire all 3 supplies together in parallel and feed the two end strips from both ends where they connect to the middle strip that would probably work better as the most the power would have to travel through the strips is then 5 meters instead of 7.5 meters to light all the LEDs in it and likely the middle strip would be a little brighter than the two ends and instead of having to travel 5 meters to get all the LEDs lit the power only needs to travel 2.5 meters from either power connection.
    Last edited by Lynx_Arc; 03-10-2021 at 02:42 PM.
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  8. #8
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    Default Re: Power supply and controller for 15 metre LED strip

    Quote Originally Posted by Lynx_Arc View Post
    No, because you fail to consider that the drop is equal from both ends to the middle so at the 5 meter spot you will already have some drop and an additional drop another 2.5 meters from each end to reach the middle LEDs in the middle strip. Now the drop will not be anywhere near as noticeable as feeding it from one end. If you could wire all 3 supplies together in parallel and feed the two end strips from both ends where they connect to the middle strip that would probably work better as the most the power would have to travel through the strips is then 5 meters instead of 7.5 meters to light all the LEDs in it and likely the middle strip would be a little brighter than the two ends and instead of having to travel 5 meters to get all the LEDs lit the power only needs to travel 2.5 meters from either power connection.
    Most cheap switching power supplies are not designed to work in parallel. There is no good mechanism for load-sharing unless something
    implemented externally, which is hardly worth the bother.

    Dave

  9. #9
    *Flashaholic* Lynx_Arc's Avatar
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    Default Re: Power supply and controller for 15 metre LED strip

    Quote Originally Posted by Dave_H View Post
    Most cheap switching power supplies are not designed to work in parallel. There is no good mechanism for load-sharing unless something
    implemented externally, which is hardly worth the bother.

    Dave
    That is something I didn't know thanks for revealing that. He was talking however of a single power supply solution which would work.
    I think the best and cheapest solution is to get something like 18-20 gauge wire and using it to extend power leads for the 3 supplies to each power their own strip separately instead of buying 1 larger supply to handle all 3 strips. It would entail more wire and finding a place to mount more power supplies.
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  10. #10

    Default Re: Power supply and controller for 15 metre LED strip

    Quote Originally Posted by Lynx_Arc View Post
    No, because you fail to consider that the drop is equal from both ends to the middle so at the 5 meter spot you will already have some drop and an additional drop another 2.5 meters from each end to reach the middle LEDs in the middle strip. Now the drop will not be anywhere near as noticeable as feeding it from one end. .

    NO, because you fail to consider ohms law. I explained it to you. Sorry, but you just way wrong here and misleading the op. Do the math please.

  11. #11

    Default Re: Power supply and controller for 15 metre LED strip

    Quote Originally Posted by Dave_H View Post
    Most cheap switching power supplies are not designed to work in parallel. There is no good mechanism for load-sharing unless something
    implemented externally, which is hardly worth the bother.

    Dave

    Bingo. If you try to parallel them, depending on how much internal resistance they have, one could be in overload, while another has barely any load.

    *OP* ---> Since your supplies are rated to driver 10 meters, just use two of them, connected at opposite ends of the 15 meters combined string as I suggested above. The resistance of the 15 meters of string will be more than enough to ensure effective load sharing.

  12. #12
    *Flashaholic* Lynx_Arc's Avatar
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    Default Re: Power supply and controller for 15 metre LED strip

    Quote Originally Posted by JustAnOldFashionedLEDGuy View Post
    NO, because you fail to consider ohms law. I explained it to you. Sorry, but you just way wrong here and misleading the op. Do the math please.
    Actually I know ohms law. What the problem is, is the strips themselves designed to carry 3x the current across the first strip to the second strip and 2x the current across the second strip and not have a substantial voltage drop due to loss in the wiring itself on the way.
    You see larger wires when you both need to run wiring longer distances and when additional loads are put on the wiring to accommodate higher power and reduce voltage drop and power loss and heating in the wiring. Wiring designed for 0.5A current that is suddenly required to carry 1.5A of current may end up going from a manageable unnoticeable drop in voltage to a noticeable drop. LEDs can be more sensitive to voltage drop even shifting color tint in some cases. Now if you parallel the strips by running wires to EACH strip separately and use a 1.5A supply then the problem vanishes. He was considering daisy chaining or running power from both ends to the middle. I said you may see it darker in the middle due to having 7.5M to drop voltage in wiring plus 50% more current on the wires themselves in the strips.
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  13. #13
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    Default Re: Power supply and controller for 15 metre LED strip

    Some of these solutions such as driving the long strip from both ends, sound unwieldy.

    Perhaps each short strip could be beefed up with additional power/ground wires running between each end, then connected in series and driven from one end. This is analogous (but not completely) to 3-wire Christmas light strings which pass two wires through to the end, for cascading.

    The OP has not come back with detail on strips or power supplies so things may just keep going around. I would just look for long strips designed to do the job.

    Dave

  14. #14

    Default Re: Power supply and controller for 15 metre LED strip

    If you could wire all 3 supplies together in parallel and feed the two end strips from both ends where they connect to the middle strip that would probably work better as the most the power would have to travel through the strips is then 5 meters instead of 7.5 meters to light all the LEDs in it and likely the middle strip would be a little brighter than the two ends and instead of having to travel 5 meters to get all the LEDs lit the power only needs to travel 2.5 meters from either power connection.

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