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Assembling the Trees

ntewinkel
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Assembly of the trees has begun.

As you might recall from my previous post, I picked up some LED Christmas tree kits from AliExpress, with "some assembly required"...

image

 

So far I've only had enough time for one side of one tree. I assembled the base so I could prop up the tree half to be able to give it a quick test:

image

 

Unfortunately, it turns out that the green LEDs are MUCH brighter than the red and yellow ones.

There are 3 different resistor values being used for the different colours, but I wonder if the included LEDs were a different rating than the others, as no matter which resistor value I use for it, it's still too bright. For a $4 kit, it's quite possible that parts are swapped in with whatever is available cheaply.

I did follow a youtube example to make sure I got the resistors in the right place, but I should have tested this before assembly!

 

Here I did some tests to determine which resistor value would be best for each colour:

image

 

The kit comes with 3 values for the LEDs: 330 ohm, 1k, and 2k. So I tried a few ways to balance out the brightness.

Turns out the yellow is fine with 1k. The red seems correct with the 330 ohm resistor that was originally assigned to the green ones. But the 2k resistor in the kit is not enough for the green LEDs - I ended up bumping up to a 10k in the test above, and that looks much more balanced.

 

I'll probably just try to clip the two wrong resistors off the board, and surface solder the new ones in place there.

 

One thing that surprised me is that the 3 LED sets seem to depend on each other for the flashing effect - trying to test light just one string before the others were assembled didn't work.

 

-Nico

 

Previous Post:

Connected Christmas Trees

 

Next Posts:

Finally! Two Trees Assembled

Two Trees by a Tree

Connecting the Tree to the Internet

Motion Sensor on Wemos

Trees! one with motion sickness...

Motion Sensor Issues, continued

The Connected Trees are Working!

Merry Boxes - A Project Within a Project

Connected Christmas Trees - Finished!

  • in reply to ntewinkel

    I just stuck the switch in and didn't even look.

     

    resistors.

    The 10k base drive is meant to saturate the transistor (ie collector to emitter voltage 0.5 or less), but even if it achieves it, the design with the LED's in parallel not the best method.

    Each LED will have a slightly different forward voltage .... they should be in series.

    image

     

    This is how we drove the ones in Project X, and there was a difference in brightness between colours.

    Note the 1k base series resitor and this was a picaxe micro, so I suspect dropping the 10k might help.

     

    I'll check tomorrow and see if I do do some pcb surgery.

     

    Mark

  • in reply to mcb1

    It's clearly been a long week... I thought that url was just for the schematic, but it's the complete instructions!

     

    One thing of note, which I screwed up on both trees, is that the on/off push button can be turned 180 degrees. In my case up is on, down is off. oh well. so maybe test that before installing it.

     

    -Nico

  • in reply to ntewinkel

    ps, that video also shows a bit of the instructions, which lists which resistors go where... although I found the order to be wrong for my kit.

    I used:

    330 for red (A.R2, B.R4)

    1k for yellow (A.R4, B.R6)

    and 2k for green (A.R6, B.R2)

     

    10k ones were marked on the PCBs: A.R1, R3, R5, R7 (I replaced R7 with something like 680 ohm for my flashing LED), and B.R1, R3, R5

     

    Long arm of LED ( + ) goes to the square pads.

     

    For PCB A (with notch at top and R7 resistor),

    Red = D1 - D6

    Yellow = D7 - D12

    Green = D13 - D18

     

    For PCB B (with notch at bottom),

    Green = D1 - D6

    Red = D7 - D12

    Yellow = D13 - D18

     

    And my kit included a red LED for the very top spot, but I chose to use a flashing RGB LED instead.

     

    Hope that helps!

     

    Cheers,

    -Nico

  • in reply to mcb1

    Mine didn't have instructions either, but I found this YouTube video: https://www.youtube.com/watch?v=lBWJVutPsCY

     

    I found A is the one that has the notch at the top, and includes R7 (for the top LED)

     

    That schematic is helpful, thanks for sharing that image

    I wonder if the 10K resistors R1, R3, R5 can be tuned so that all LEDs have similar intensities and flash time. (I found using 10k for the green lights resistor made it the right intensity but kept them on too long).

     

    -Nico

  • Mine arrived today.

    No instructions .... however reading the feedback has this link. http://attach01.oss-us-west-1.aliyuncs.com/IC/DIY-Manual/7213.pdf

     

     

    snip of the cct is

    image

    which explains why you need the LED string in place to make it flash.

     

     

    Mine have both boards marked as CTR-30B but clearly one should be A as it different.

     

    Mark