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DIY LED - maybe others can learn from my expensive mistake

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  • DIY LED - maybe others can learn from my expensive mistake

    I've done DIY LED for 3 tanks so far. Getting a bit of a dab hand.

    Tonight I blew up around $100 worth of LED. For the benefit of others, here's how I did it.

    After painstakingly soldering 6 x Cree xp-g in series, I poked the bare-wired output from my 700ma meanwell supply to the contacts to test them. It sparked. Nothing lit up.

    I checked the output with my multimeter, floating at 48 vdc as expected. Assuming that I'd bodged a soldering joint (my eyes aren't what they used to be), I put that strip to one-side and did the same thing to another two circuits, each of them with 4 x Cree Royal blue in series. Each time, when I pushed the wires against the contacts, I was reward with a nice juicy spark - and instant death to the LED (didn't figure that bit out until later).

    Finally freaked, I carefully used screw terminals to my remaining LED circuit - all works perfectly.

    The death-toll stands at 6 x Cree XP-G and 8 x Cree Royal blue. The last circuit of 6 x Cree XP-G was the one where I'd learned my lesson. If you examine the LED lense with a loop, you can clearly see carbonisation at the junction on the royal blue. The XP-G look fine but buzz out as a dead short.

    This is my first time using Meanwell supplies. I can only assume that they get nasty if you splatter the connections and emit something horrid.

    I'm soak-testing my remaining 18 x Cree XP-G - they're fine. It HAD to be the dry jointing on start up.

    You have been warned...

    don

  • #2
    so your LED's blew, cos one of the joints wasnt soldered properly ?

    i know with the meanwell, if it puts out more current than your leds can handle your meant to adjust it with the pot first.

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    • #3
      Originally posted by dcm View Post
      I poked the bare-wired output from my 700ma meanwell supply to the contacts to test them.
      That's probably what did the damage.
      The driver isn't designed to be run without a load. My guess is that you got a nice capacitor discharge or inductor backlash from the driver, as it was all charged up with nowhere to go.

      Sorry to hear about the damage . Thanks for sharing though.

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      • #4
        am i reading what you wrote correctly ... you ran 6x cree led's off 48volt ??

        the led's are rated at 3.2 volt max at 700mA.... 48 / 6 = 8 volt ...

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        • #5
          Originally posted by mtwalkert28 View Post
          am i reading what you wrote correctly ... you ran 6x cree led's off 48volt ??

          the led's are rated at 3.2 volt max at 700mA.... 48 / 6 = 8 volt ...
          It's a constant current supply so it was only 48v with no load - it will drop down once the LEDs are connected (or at least it would if the LEDs weren't a short circuit). My best guess aligns with Vim's opinion. It was probably a capacitor discharge or inductor backlash from an unloaded constant current supply suddenly exposed to load.

          If I'd thought it through, I could have seen that coming...

          Oh well, hopefully somebody else will learn from my mistake.


          don

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          • #6
            thanks for posting don.

            So basically the driver should just be connected (soldered) to the LED circuit before turning the power on? And what blew it was having the power on on the driver before connecting it whilst live?
            nothing to see here

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            • #7
              Thanks for the tip Don. I'm not too far from rigging up 3x 50W emitters so I'll heed your advice. Basically you've given the capacitor within the driver an expensive current path to earth - ouch!! $$$
              Live your life like no-one's watching!

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              • #8
                Originally posted by johnno View Post
                thanks for posting don.

                So basically the driver should just be connected (soldered) to the LED circuit before turning the power on? And what blew it was having the power on on the driver before connecting it whilst live?
                Yes. I've replaced the LED but this time, used a terminal block to screw the LEDs to the supply before switch on. All the circuits are fine and I've soak-tested the LEDs for hours off the same power supply.

                It HAD to be letting the supply float before attached the load and having a cap charge up.

                So, those Meanwell supplies have Mean streak. I've used other constant current supplies and never had that issue.


                don

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                • #9
                  There are many peoples who like to make up a lot of mistake and never go for the recovery of this mistake though and you can even learn from the big assignments review to check other website status of rating so you wont be able to make a mistake though and make a great decision which can help you out for learning and better understanding.

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