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Mort Bay connectable leds

Discussion in 'Lights - Store Bought and Home Made' started by Daemon, Oct 11, 2011.

  1. Daemon

    Daemon Apprentice Elf

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    Hi guys


    I bought 4 sets of connectable end to end 120 pc leds which are distributed/produced by Mort bay of Australia.


    They are 12 metres long and I intend to chop them up into 4 metre sections for my display.


    Nowhere on the box do they state what voltage they are and they do not come with a transformer, they simply state that they are low voltage.
    They have a dc plug on one end and a dc socket on the other. They say they are for use with Mort bay No 1991 adapter set but I cannot find any info on google about that either.


    There are 9 bulbs in a series so I am thinking perhaps they are 12v?


    Does anyone have any experience with these lights at all?
     
  2. David_AVD

    David_AVD Bite my shiny metal ass!

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    9 LEDs in series would be approx 24V. The LED Vf ("forward voltage") varies between about 1.6V and 4V depending on the colour, hence it's hard to say without examining the string and doing some measurements.

    You have to be careful with multi-colour LED strings as they use the various LED Vf ratings to arrive at a certain overall voltage. If you start changing LEDs around to make single colour sections from them, you'll end up with some sections blowing and others not even lighting up!
     
  3. AAH

    AAH I love blinky lights :) Community Project Designer

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    Judging by http://www.truelocal.com.au/business/mort-bay-traders-pty-ltd/balmain it looks a lot like they are backyard importers. If they truly are 9 leds per segment then it would just about have to be over 30VDC to turn on the LEDs fully. I'm pretty sure that you are going to have to suck it and see but I would think that the lights would more likely be 24V or 36V rather than 12V.
     
  4. TimW

    TimW Full Time Elf

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    I think you're onto something there... Its the peak voltage that matters for LED.

    Say you had a 24Vac wall wart powering your off the shelf strings.... If you full wave rectified them, what would the peak voltage be? Around 33.9 v

    I'm guessing that the manufacturers took their 24VAC multifunction controllers and simply came up with a led string to fit...

    Same story for the BIGW led strings...
     
  5. OP
    OP
    Daemon

    Daemon Apprentice Elf

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    Sorry for the late reply. I keep forgetting to select notify on my post to receive email notifications.
    I was thinking 9 leds at 1.3v each perhaps but you are correct about the 30+v.I tried 12v, no lights. I tried 24v, no lights.
    I didn't have a 36v dc power supply so I made a bridge rectifier out of diodes and measured 33.4v at the outputs and I connected them and they lit beautifully and then the leds started to sizzle and pop out one by one.


    It seems strange they didn't even dimly light at 24v but popped at 33v.


    Do I need to go somewhere in between?
     
  6. AAH

    AAH I love blinky lights :) Community Project Designer

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    The 33.4V is possibly something pretty close to an RMS voltage depending on the meter used which would give a peak voltage of around 47V (33x1.41). This is a pretty huge step up from 24V. The fact that they went from no on to cooking suggests to me that there may not be resistors in series with the leds though :(
     
  7. OP
    OP
    Daemon

    Daemon Apprentice Elf

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    There doesn't seem to be any resistors in the series at all, so how do you suggest I find the correct psu with an appropriate peak voltage?
    I only have a multimeter to test with.
     
  8. aussiexmas

    aussiexmas Sinnamon Lights

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    Hi Daemon

    I used to use the setup discussed in this topic http://auschristmaslighting.com/forums/index.php/topic,46.msg225.html#msg225 to test LED voltage requirements and the currents drawn. I had a couple of different voltage power supplies and built a resistor box from which I could measure the string voltage together with the string current by measuring the voltage drop across the resistors in series with the LED string.

    This year I bought a variable voltage / current DC supply which reads the voltage and total current directly. http://www.ebay.com.au/itm/Linear-Adjustable-Variable-DC-Power-Supply-30V-5A-Digital-Power-Supply-PS305D-/360396453994?pt=AU_Components&hash=item53e94d786a This has made life so much simpler.

    Regards Geoff
     
  9. David_AVD

    David_AVD Bite my shiny metal ass!

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  10. OP
    OP
    Daemon

    Daemon Apprentice Elf

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    Hopefully I will win Lotto on the weekend and then I will be buying one of those too!
     
  11. OP
    OP
    Daemon

    Daemon Apprentice Elf

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    Actually reconsidering, it seems there have been plenty of occasions when one of these may have been great to have.


    Do you have any recommendations of what to look out for?


    I will probably look for a 30v 5 A also, perhaps from Aliexpress.
     
  12. David_AVD

    David_AVD Bite my shiny metal ass!

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    Mine was only $95 delivered, but is only 3 Amps. The 5 Amp one Geoff linked to is $120 delivered.

    I was quite happy with the cheaper unit though as I only wanted it for testing smaller items. 3 Amps is still a lot for most LED testing applications.

    If I want more than that (testing lots of pixels), I'd probably use a dedicated 320W Mean Well power supply.
     
  13. OP
    OP
    Daemon

    Daemon Apprentice Elf

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    They only deliver to Australia so I will check if they will deliver to NZ and look at that one also.
     
  14. David_AVD

    David_AVD Bite my shiny metal ass!

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    I think the 3A version like mine are on AliExpress for the same price. I bought from eBay as it was Chinese holidays and I didn't want to wait. Might be worth doing a search.
     
  15. OP
    OP
    Daemon

    Daemon Apprentice Elf

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    $92 US which is around the same with free shipping.
    It states it is 220v so hopefully comes with a proper insulated plug.


    What does this mean Atten APS3003Si One Way Number Reveal CCCV Regulated Power Supply


    I assume it is the same thing, looks similar.
     

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