How do addresses on SK6812 144 LED pixel strips work? Can it be cut in half and doubled up?

Sabers
1

Hi,

I’m looking to create a short ~20" blade with an SK6812 LED pixel strip. The bundle I bought on TCSS came with two strips, but I only need to double up the halves of one strip (approximately 72 LEDs) to form a 19" blade. I know I can cut/trim the strip safely, but if I double up and wire both halves (in the right direction from the “start” of the strip), will the “2nd half” work properly? Is it just counting resistors or something? Or is it going to be missing a control board at the start of the “2nd half” strip?

Thank you

2

The end of a pixel strip is not special. If you cut a pixel strip somewhere, each part becomes a complete (but shorter) pixel strip. Each pixel is it’s own self-contained part.

So yes, you can cut a strip in half and hook them up in parallel.

You can also just fold it over and make it a zig-zag blade which lets you send different data to the pixels on one side than the pixels on the other side. Either will work, but obviously the zig-zag version requires a little extra programming.

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3

Ah very cool, ty!

4

Just to clarify how a zigzag blade works, I can fold over a single LED strip and when turning on the blade, it’ll light both the first and last LEDs together and then work in to the middle of the strip (from both sides simultaneously) for a regular lighting effect?

What extra programming other than enabling it in the config generator is required?

I saw a YouTube video where it was a very unsteady blade effect (https://youtu.be/M48WyZmvVBU?si=WPiRYyFszEsZKh3E) and I don’t really want that for this blade although it does look cool.

Ty

5

I just finished making a 22" zig-zag blade using the new 5mm COB strips with 160 led/m. I used two strips folded over one-another, with the data OUT from the first strip soldered to the data IN on the second strip. Power wires for both strips soldered directly to the PCB. I glued the strips to a 6mm 3d printed square dowel. Counting the pixels on each strip was tricky and is important to get the lighting to work properly–it was further complicated because I had to clip off one of the LEDs because I melted off a pad (the 5mm strip has very tiny pads and I’m relearning my soldering skills)–and because the second strip was longer because it went over top of the first strip (note if you do this, beware of the contacts at the seems between LEDs).

Here are my changes to make it work:

BladeConfig blades[] = {
 { 0,  
    SubBlade(0, 84, WS281XBladePtr<345, bladePin, Color8::GRB, PowerPINS<bladePowerPin2, bladePowerPin3> >()), //main blade
    SubBladeReverse(85, 169, NULL), //stripe 2 a little short
    SubBlade(170, 256, NULL), //stripe 3 a little longer due to hump
    SubBladeReverse(257, 343, NULL), //stripe 4 same as 3
    WS281XBladePtr<15, blade2Pin, Color8::GRB, PowerPINS<bladePowerPin4, bladePowerPin5> >(), //buttons
   CONFIGARRAY(presets) },
};

This config needs five blade styles for each preset, here is an example (with using functions I created from FETT263’s website):

{ "SATELE SHAN-GRANDMASTER;common", "tracks/SentinelShan.wav",
    StylePtr<ControlMainRotoscope>("0,32896,0"), //Green,  HyperResponsive Rotoscope Prequels
    StylePtr<MainRotoscope>("0,32896,0"),
    StylePtr<MainRotoscope>("0,32896,0"),
    StylePtr<MainRotoscope>("0,32896,0"),
    StylePtr<MainStatic>("65535,0,0"), //Red 
    "satele/shan"},

I followed Profezzorn’s video on his zig-zag blade.

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6

Thanks! Do you have a link to the video? I tried googling it but couldn’t find it.

7

The video is actually TCSS, but it’s linked from the Proffie site under Profezzorn’s zigzag blade.
Here’s the link.
Quad-strip zig-zag blade (hubbe.net)

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Basically, you need to use subbbladereverse for every other strip in your zigzag blade, then increase NUM_BLADES by 1 and set up one style for each of the strips. The configuration generator does this for you, assuming your blade just has two strips. The other examples in this thread are quad-strip zig-zag (zigzagzigzag?) blades.

For most styles, zigzag blades look very similar to a regular blade, but unstable and fire blades generally look better with a zigzag configuration.

The video linked is a general “how to put a blade together” video, it’s not specific to zig-zag blades.

One more thing: After you fold the strip over, you’ll want to solder power wires to both ends of the strip to avoid voltage losses as much as possible.

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