Hello Folks! This post is sort of an introduction, and also includes what's in the title...
My name is Mark and I have been building sabers since 2009. I took a break from the hobby in 2015 for some other projects and am finally back. I cannot tell you how excited I was to see both Neopixels and Smoothswing...wow!
Anyways, I am working on a new saber and was not super happy with the available Neopixel strips. If you go with the "Skinny Mini" 3535 strips you sacrifice some brightness for evenness. On the other hand the 5050 strips are brighter, but harder to diffuse. I saw KR-Saber's new hard-PCB
strip and was inspired to try something similar.
I have made some progress on the design and wanted to share it here to see if anyone has suggestions or tips. I'll keep this thread updated with progress.
Here are some renderings of a proof-of-concept model (parallel data lines not shown):Specs:
- Width: 6.9 mm
- Thickness 3.3 mm
- Density ~144 LED/m
- Total Cost: $30
So you get smaller width/height than skinny strips and the same pixel density, all with 5050 Neopixels instead of 3535.
In order to drive the LED's with a single set of voltage rails, you have to flip the LEDS on one side of the strip 180-degrees...basically an upside-down mirror image. This, however, causes the data line of one side to run from top to bottom, which is a problem. I had the idea to pull the intermediate data signal from between each LED from the serial side to drive each LED on the reversed-side. Below is a picture of the test-setup I made. Also, here is a link to a short video of it working: Driving Parallel Neopixels - for Lightsaber - YouTube
For ease of assembly I decided to use axial ceramic capacitors. No, there is not a cap per Neopixel, however having 0.1uF between each set of 2 pixels should be plenty to prevent transients. Unfortunately these capacitors are really the limiting factor of the pixel density (they are also expensive) and I am toying with the idea of using an 1806 SMD package...but durability might be a concern.Here is a materials list and cost breakdown:
TOTAL: ~$29.85....let's just say $30
- Pixels: SK6812 -> $26.99 for 500 pcs-> ~$13.5/blade
- Rails: 20 AWG 99.9% copper wire -> $6.99 for 22 ft -> ~$2.20/blade
- Capacitors: 0.1uF Axial Ceramic -> $6.50 for 100 pcs -> ~$9.5/blade
- Data Wire: 30 AWG Mil Spec Solid Core PTFE -> $7.98 for 20 ft -> ~$4/blade
- Heat Shrink: 8 mm OD Clear -> $4.12 for 20 ft -> ~$0.65/blade
- Time: I estimate 15-20 hrs -> whatever your time is worth to you -> ~$0/blade
So, you can build this whole blade for less than it costs to buy one 144/m strip. Of course, this may be a garbage idea/design that will break in the first few swings, which would make the low cost not so important. (Not to mention the tremendous amount of time needed to make one...
Please let me know your thoughts/suggestions/criticisms. I am not married to this design and have open ears for any pointers!UPDATE 1/15/2020
Okay, so I found some 1206 SMD capacitors (much cheaper) and changed the wire size to 18 awg (0.0403"). The new capacitors will fit between the two neopixels (like a sandwich), which allows the neopixels to theoretically have no gap between them. Of course, I left 0.5mm to give the strip some play and make room for data wires. Here are the specs with the new arrangement:
- Width: 5.77 mm
- Thickness 4.11 mm
- Density ~166 LED/m -> 322 for 35" blade
- Total Cost: $25
A few screenshots/renderings: