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Deals Direct Christmas Tree (Pop-Up 1.8m Pre-Lit)

Discussion in 'Lights - Store Bought and Home Made' started by David_AVD, Oct 10, 2012.

  1. David_AVD

    David_AVD Bite my shiny metal ass!

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    I bought a couple of these from Deals Direct as I wanted a simple lit tree to go on either side of my front door.

    [​IMG]
    The supplied plugpack is 24V AC. Looks like the rectifier is inside the in-line on/off switch. I haven't tried running the tree from DC yet to see if it's in the 24V - 30V range like other light sets.

    The tree arrived in a flat box about 60cm x 60cm x 8cm. Assembly is quick as the lights are already on it. You just need to click the base and pole together and attach the supplied baubles if desired.
     
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    David_AVD

    David_AVD Bite my shiny metal ass!

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    OK, just had a better play with this item and found that the in-line button is actually a steady/flash selector, not on/off as I first assumed.

    Powering the tree using a DC power supply set to 29V gave the same light level as the supplied 24V AC plugpack. At 29V DC, the set draws approx 120mA (3.5W).

    I did increase the voltage to 31V, but don't think this would be good long term as the current drawn increased to 200mA (6.2W) and the LEDs looked overly bright.

    When powered fro DC, the flashing function doesn't work; the LEDs stay on. This is likely due to the tiny controller (in the switch housing) needing the AC power to derive the timing used for the flashing function.
     
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    David_AVD

    David_AVD Bite my shiny metal ass!

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    So that I can use these LED trees with the same (30V DC) power supply as my Big W strings, I had to do a simple modification. I also wanted these trees to be plug compatible with the other Big W string based items I have, so used the 3 pin plug from a dead string of lights.

    First I cut off and discarded the controller / switch box from the Deals Direct tree. I then soldered the common +ve wire of the Big W plug to the +ve of the Deals Direct string. (I had already used a 30V power supply to determine which wire was +ve on the tree's string)

    Next I soldered a 22 Ohm, 1 Watt resistor inline with the -ve of the string and the channel 1 wire of the Big W plug. (Plug pinout is in the ACL wiki) The channel 2 wire was cut back a little shorter as it's not used here.

    [​IMG]

    After a quick test (to make sure it worked!), I slipped the pieces of heatshrink over the connections and resistor and shrank it down being careful not to overheat the shrink or wires.

    [​IMG]

    So, how did I come up with that resistor value? I actually wound up the power supply to where it indicated the string was drawing 120mA (approx 12mA per LED) and noted the voltage (27.3V in this case). That meant I had to drop approx 2.7 Volts across the resistor.

    Using Ohms Law, that calculated to 22 Ohms (2.7V / 0.12A). The wattage dissipated by the resistor is about 0.3W (2.7V x 0.12A), so I selected a 1W type as that will handle the 0.3W continuously and is also mechanically sturdier than a 0.5W type.
     

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