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Thread: Led help please

  1. #1

    Default Led help please

    Hi everyone,I have 6 solar lights that don't work anymore and wanting to rebuild them. My plains are to add leds to them and wire them all together with one DC power supply. I have no idea though on what is needed and what way to do it.
    Here are my questions of what I want to use.
    1>>Do they need to be wired in Series or Parallel Circuits so they will all have the same brightness.
    2>>Will I need to use resistors on each light and if so what size would I need.
    3>>What size power supply would I need to run them all. I have 2 power supply's,a 12VDC 1000mA and 12VDC 25A. Also have more.


    Thanks for the help!!

  2. #2

    Default Re: Led help please

    Yes and No and Yes etc.
    There is a lot of ways to do what you want but the first thing you need to do is get a good idea of the light output you want from them and what type of light is in there as sometimes changing LEDs to something not physically identical ends up changing the light output pattern and can even reduce the light output using the same amount of emitter light. As for the LED you show to the right with 5050 LEDs I bought one of them off Ebay that showed the 5050s and advertised them but I got one big COB panel instead of it. I'm not totally sure of the longevity of some of these premade 12v setups especially the COB ones that without proper heatsinking can slowly fry the LEDs and in the summer time the heat will be even more an issue in some places where it is in the 90s and 100s when it starts to get darker.
    I can't tell you how big of a power supply needed without you testing the LED(s) but I will say with 6 lamps you will need to wire them in parallel unless you have an 18V or higher DC power supply. With the 1A transformer you will get about 150-175ma or so per LED if they are about equal in resistance load one issue however is the wiring you use can add additional resistance load that may slightly affect the output of the lights farther and farther away if you use too small a gauge of wire. Most likely your LED modules will have series LEDs with possible resistors to adjust the voltage down to within limits so at 12v 150ma that is about 1.8watts and 5050s are probably about 80 lumens/watt with losses you may get 100 lumens of light out per fixture which most likely is more than the solar light setup gives.
    One other things that can be a problem is if using a power brick, many of them aren't regulated and "float" without a load way above the listed voltage so if you measure the output with a meter with no load you may find it at 15-18, even 20v output. This can be a problem if the voltage doesn't drop under a load that isn't close to the current listed on it and could possibly damage LEDs. A 25A power supply is probably way overkill unless you want a lot more output depending on how much output you may need 3-5A perhaps.
    One other thing to consider is these 12v spotlight LED bulbs for ceiling enclosed lighting I don't recall exactly what they are called but the advantage of them is they can be sourced locally I think in most places vs taking a chance on ebay to get something that will both work up to expectations and hold up over time instead of quickly burning up.
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  3. #3

    Default Re: Led help please

    Thanks for the help,think I have it figured out.

  4. #4
    Flashaholic
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    Default Re: Led help please

    Quote Originally Posted by lightnut57 View Post
    Thanks for the help,think I have it figured out.
    First, if you haven't already, I recommend opening them up to check condition, and perhaps
    why they stopped working, Have the batteries given up? What type and number of battery is
    used. Check their voltage. If they are low, that may not mean bad, just not charged.

    I've opened up a wide variety of lights, and powering runs the gamut from single NiCd or NiMH
    cell with boost converter, to three series cells (direct drive), to single rechargeable Lithium
    Iron Phosphate cell or even Lithium-ion (18650).

    Water often leaks in over time, corroding battery terminals, battery ends, switches, even LEDs
    themselves. You'll want to check each light to verify mod will be worth it.

    I'll guess that your lights are big enough to use multiple cells and LEDs but internal details
    matter. Wiring in series means a failed light is likely to take out the others (unless it fails "short").
    For parallel connection you likely need well below 12v, probably 1.25v to 3.75v, so a 5v adapter
    might be more suitable.

    Your 25A supply looks like massive overkill.

    Dave

    I notice that the LEDs you want to use are rated for 12v, in that case parallel wiring is the only
    way with 12v supply. Looks like you may want to bypass whatever circuitry/battery is in there?
    Last edited by Dave_H; 10-06-2019 at 11:09 AM.

  5. #5
    Flashaholic
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    Default Re: Led help please

    Appears the LED panels likely use sets of 3 in series, with 5 sets paralleled. It is not clear if
    the board has current-limiting on-board, probably not. Don't connect directly to 12v supply at first,
    at risk of a meltdown. LEDs need current-limiting which will not come from a regular 12v adapter,
    which is not specifically designed as a LED driver. One in the image looks like the former. Check on
    voltmeter under no load. Switching type adapters are regulated, iron transformer types usually not so could
    go up under light load.

    To test board try connecting to a regulated 12v supply through a 22 ohm 1W or higher resistor. That
    would give roughly 30mA per LED (150mA total). See how it looks. Higher current/brightness may be
    possible, keeping in mind that LEDs can get warm/hot depending on power, heatsinking it any, and
    ambient temperature (especially enclosed). Temperature too high can shorten life.

    When you open the solar lamp, check how LED board would mount and how light gets distributed; see if you're
    happy with one before modding the lot.

    Dave

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