LED Wearables: Neopixel bowtie

Thanks Dad for modelling!

As you may have noticed, I like building LED wearables. A friend of mine thinks they are super cool, and he’s having his 2^30th birthsecond coming up (that’s about 10,5 billion seconds). Naturally this needs to be celebrated. I’m making a glowing bowtie!

This circuit is just like all other circuits I build: a Digispark microcontroller and WS2812B (Neopixel) LEDs powered over USB via powerbank. The soldering was a bit more of a technical challenge than normal though.

WS2812B has the nice feature of having exposed metal on both the up- and downside. So at the edges of the bowtie, I presolder on the underside of one strip and the upper side of the other. Then I heat the component from the top, and they melt together!

Presolder one on the upside, one side on the downside. Sandwich and heat!

The rest of the lines I solder normally with super short cables. They were so short that most of the isolation melted. I had to be very careful to ocularly inspect (==look) to make sure that the connections didn’t cross each other.

I have never burned myself as much by soldering as I did with this project.

Finding the exact right angle wasn’t easy, and would probably have been better to do with some math. Buuut… it’s Saturday night, yolo! After making the first angle connection, I soldered the Digispark MCU as I usually do, making sure that the cables had just the right length for the MCU to end up in the middle. I fastened it with an adhesive knob and tested the connectivity.

Making sure the first part worked, the next two connections is only making the same thing again. The fourth corner of the bowtie shall NOT be soldered, and I put an adhesive knob there. Then I used my friend the glue gun for extra isolation and for structural integrity of the corners.

The final assembly, from the back.

I programmed it using some Neopixel sketch I had lying on the computer, and glued an elastic band to the MCU. Now I only needed to paint everything except the LED’s black with nail varnish. 

Finished bowtie, no battery

Here’s the schemetics. Very straight forward, just a serial line of 24 pixels (9+3+9+3), connected to GND, 5V and P0 on the Digispark. There is a resistor on the data line. Pixel number 5 or 17, will not show because it’s under the strip.

Schematics for LED bowtie @emalstm

Happy hardware hacking!

Mandatory LED wearable selfie