tl;dr
Ever since I made my LED paracord usb cable I wanted to build a paracord lanyard with LED’s. I decided It was time tackle this build. Join me below to see what it took to pull it off.
Hardware
- Paracord 550
- Micro led strip
- TP4056 lipo charge board
- 350mah lipo battery
- M2.5 5mm bolts x4
What triggered me to build this lanyard was that I found a lipo that was small and still packed a punch. This lipo actually came out of a used single use e-cig/vape. It was 350mAh 13300 in size which would power the micro led strip for 7 hours on a single charge.
I have been playing around with the tp4056 lipo chargers for awhile now and I wanted to fix a few things that I didn’t like about the USB C version you can buy. I was going to start by looking at the schematic and reversing the PCB but then I found that someone had already done it in kicad HERE, It wasn’t the same because they had used a different chip in the lipo protection circuit but it was a good starting point.
The first thing I wanted to add was the 5.1k resistors to the USB C port so that I can be charged with a USB C PD charger.
Secondly the thing I wanted to do was make it easy to change the Rprog resistor shown on the schematic HERE. This will tell the tp4056 the appropriate current while charging, As it stands it will pump 1amp into the battery which is over kill for small battery and heats the tp4056 up somewhat, I changed the resistor footprint to be a 0604 hand solder-able one from the 0402 one on the board.
I also moved the charging LED’s to ether side of the USB C port to make it easy to see when your embed it into a project.
When I start laying out this board I wanted the replacement board to have the same footprints as the original board and in the same orientation so it would be easy to move the parts over. I reused the USB C port too which was a USB C 2 one.
Paracord
My plan was to take a length of paracord and remove all the inner strands then replace them with the mircoLED strip, I thought I better add some of the stands back into the cord to add some strength back into it and take some of the strain off the LED strip.
In the past I’ve made paracord lanyard’s so I thought it was going to be a piece of cake to pull off, The problem with the other lanyards was I would just tie a knot in the end to stop it coming out of the 3d printed end. I couldn’t do this because of the LED strip so I had to come up with a different idea. I could have used some zip ties like I’ve done with other projects but they take up a lot of space. I came up with the idea to 3d print a washer with the slit instead of a hole so it could be slide on and super glued in place. Then in the 3d printed lanyard it would have a recess so it wouldn’t pull put.
With the stoppers sorted I glued it all up and made sure to leave plenty of length on the LED wire strip.
3D printed case
I wanted the case to be as small as possible, The main bulk of the case came from the lipo but I also needed a switch which I had poking out the side, This let me have room on ether side of the lipo to use some M2.5 bolts to secure the lid. The wiring was super tightly packed but I took advantage of the tube shape of the lipo and hide the wires in the empty space round the top of the curve.
The custom tp4056 board would live in the lid and have the charge port points out the bottom so It wouldn’t be seen during use.
Files
kicad and freecad files – https://github.com/facelesstech/light_up_lanyard
Video
Facelesstech 
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