# 3D Printed LED Knuckle Jewelry 

## Overview

https://www.youtube.com/watch?v=Dk6rchpqhQg

![](https://cdn-learn.adafruit.com/assets/assets/000/017/573/medium800/leds_hero-kunckle-2.jpg?1403547400)

Bling out your swag with 3d printed LED knuckle jewelry. Its stylin’ to make this bright and blingy project!  
  
3d print yourself a fully assembled chain for a more casual approach. You can easily show ASCII characters or scroll messages to make custom tags.

## Prerequisite Guides

- [Introducing Trinket](https://learn.adafruit.com/introducing-trinket "Link: https://learn.adafruit.com/introducing-trinket")
- [Adafruit LED Backpacks](https://learn.adafruit.com/adafruit-led-backpack/0-54-alphanumeric)
- [Collin's Lab: Soldering](https://learn.adafruit.com/collins-lab-soldering "Link: https://learn.adafruit.com/collins-lab-soldering")

![](https://cdn-learn.adafruit.com/assets/assets/000/017/601/medium800/leds_parts.jpg?1403571397)

You'll need a few tools and parts to get this project lit up.

## Parts

- 1x [Quad Alphanumeric Display](https://www.adafruit.com/search?q=quad+alpha)
- 1x [Trinket 5V micro-controller](https://www.adafruit.com/product/1501)
- 1x [~100mAh Lithium Polymer Battery](https://www.adafruit.com/product/1570 "Link: https://www.adafruit.com/product/1570")

## Tools & Supplies

- 1x [Wire Wrap Spool](https://www.adafruit.com/product/1446) or other thin wire (3 separate colors are best!)
- 1x [Slide Switch](https://www.adafruit.com/product/805)
- 1x [JST Extension Cable](https://www.adafruit.com/product/1131 "Link: https://www.adafruit.com/product/1131")
- [Soldering Iron](https://www.adafruit.com/product/1204 "Link: https://www.adafruit.com/product/1204")
- [Solder](https://www.adafruit.com/products/734 "Link: https://www.adafruit.com/products/734")
- [Heat Shrink Pack](https://www.adafruit.com/product/344 "Link: https://www.adafruit.com/product/344")

# 3D Printed LED Knuckle Jewelry 

## 3D Printing

## Filament
This design was printed on a [Printrbot](https://www.adafruit.com/product/1760) in transparent yellow PLA filament. The tolerances are optimized for PLA, but should print well in ABS. [Edit STLs](http://www.123dapp.com/Project/LED-Knuckles/2499760)
[Download STLs](http://www.thingiverse.com/thing:372777/#files)
Easily switch out the design to either a chain necklace or knuckles, just swap out the lid of the enclosure!

![](https://cdn-learn.adafruit.com/assets/assets/000/017/589/medium800/leds_3d-parts.jpg?1403548224)

 **knuckle.stl**  
Measure your middle and ring finger for a nice fit around your fist. The clips that hold onto the lid will require supports.  
  
**knuckleBox.stl**  
Print with the face down, the slide switch hole will require supports.  
  
**knuckleBoxLID.stl**  
This lid connects to the knuckleBox.stl via the knuckle-lidClip.stl  
  
**knuckle-lidclip.stl**  
Insert into the knuckleBoxLID.stl and slide the connected parts into the knuckle.stl clips.   
[Download Chain](http://www.thingiverse.com/thing:28405)
![](https://cdn-learn.adafruit.com/assets/assets/000/017/596/medium800/leds_chain-hero.jpg?1403565184)

# 3D Printed LED Knuckle Jewelry 

## Circuit Diagram

![](https://cdn-learn.adafruit.com/assets/assets/000/017/597/medium800/leds_circuit-diagram.jpg?1403567438)

The illustration above is a reference of the wire connections. The slide switch adapter allows the circuit to be easily turned on.

- **Vi2c** pin to 3V or 5V pin (depending on which trinket you use) 
- **VCC** pin to **Trinket BAT+** pin  
- **SDA** to **Trinket #0**  
- **SCL** to **Trinket #2**
- GND to GND

# 3D Printed LED Knuckle Jewelry 

## Code

Get more code examples on our github: [Adafruit-LED-Backpack-Library](https://github.com/adafruit/Adafruit-LED-Backpack-Library/tree/master/examples)

```auto
#include <avr/power.h>
#include <TinyWireM.h>
#include "Adafruit_LEDBackpack.h"
#include "Adafruit_GFX.h"

Adafruit_AlphaNum4 alpha4 = Adafruit_AlphaNum4();

char *message = "**3D** 4 LIFE***    ";


void setup() {
  if (F_CPU == 16000000) clock_prescale_set(clock_div_1);
  alpha4.begin(0x70);  // pass in the address
  alpha4.writeDisplay();  // clear display
}

void loop() {
  // just display 4 letters
  alpha4.writeDigitAscii(0, 'H');
  alpha4.writeDigitAscii(1, 'A');
  alpha4.writeDigitAscii(2, 'C');
  alpha4.writeDigitAscii(3, 'K');
  alpha4.writeDisplay();
  delay(1000); // hold for 1 second

  // scroll the message above!
  for (uint8_t i=0; i<strlen(message)-4; i++) {
    alpha4.writeDigitAscii(0, message[i]);
    alpha4.writeDigitAscii(1, message[i+1]);
    alpha4.writeDigitAscii(2, message[i+2]);
    alpha4.writeDigitAscii(3, message[i+3]);
    alpha4.writeDisplay();
    delay(500);
  }
}
```

# 3D Printed LED Knuckle Jewelry 

## Assembly

![](https://cdn-learn.adafruit.com/assets/assets/000/017/574/medium800/leds_add_dis_backpack.jpg?1403547436)

## Assemble 14-Segment LED
The Quad Alphanumeric Display comes with a backpack that you will need to solder together. Follow the [guide to complete this assembly](https://learn.adafruit.com/adafruit-led-backpack/0-54-alphanumeric "Link: https://learn.adafruit.com/adafruit-led-backpack/0-54-alphanumeric"). ![](https://cdn-learn.adafruit.com/assets/assets/000/017/577/medium800/leds_dis_backpack.jpg?1403547778)

## Soldering Assistant
Use a [third-helping hand](https://www.adafruit.com/product/291) and [Panavise](https://www.adafruit.com/products/151) to assist you while you solder. ![](https://cdn-learn.adafruit.com/assets/assets/000/017/576/medium800/leds_quad-pin-clip.jpg?1403547752)

## Clip Pins
The access pins can cause the circuit to be too large to fit into the enclosure so you'll need to trim these. Use [flush diagonal cutters](https://www.adafruit.com/product/152 "Link: https://www.adafruit.com/product/152") to clip off the pins from the back. ![](https://cdn-learn.adafruit.com/assets/assets/000/017/586/medium800/leds_alphaquad-wires.jpg?1403548142)

## Wire Connections
Measure and cut 4 strands of wire wrap to about 20mm in length. Solder these wires to SCL, SDA, GND, VCC and Vi2c pins on the 14-segment LED Backpack. ![](https://cdn-learn.adafruit.com/assets/assets/000/017/578/medium800/leds_slide-switch-soldering.jpg?1403547830)

## Slide Switch
Build an on and off switch by measuring a JST Extension cable and splicing the positive wire between the slide switch. We'll need it to be as small as possible, so cut off the pin and solder the wires to the small nub that's left over.  
![](https://cdn-learn.adafruit.com/assets/assets/000/017/580/medium800/leds_slide-switch.jpg?1403547931)

## Heat Shrink
Use heat shrink tubing to secure the spliced ground wire connections. These little slide switch come in handy in many projects, so it's a great idea to make extra! ![](https://cdn-learn.adafruit.com/assets/assets/000/017/579/medium800/leds_trinket-back.jpg?1403547902)

## Solder JST connetor to Trinket
You'll need to solder on a female JST connector to the back of Trinket . This will connect to the male JST connector of the slide switch. ![](https://cdn-learn.adafruit.com/assets/assets/000/017/581/medium800/leds_trinket_wire_prep.jpg?1403547967)

## Wire Trinket
Use a panovise jr. or third-helping hand to secure the backpack in place. Lay the trinket over the backpack and thread the wires through the corresponding pins. ![](https://cdn-learn.adafruit.com/assets/assets/000/017/594/medium800/leds_trinket-soldered2.jpg?1403564942)

## Solder Connections
Ensure the wires are long enough so that the Trinket has enough room to plug a USB cable in for reprogramming.  
  
Solder wires as listed below:  
**#0** to **SDA**  
**#2** to **SCL**  
**VCC** to **VBat**  
**Vi2c** to **5v / 3v** ![](https://cdn-learn.adafruit.com/assets/assets/000/017/583/medium800/leds_add-display.jpg?1403548067)

## Install into Enclosure
Plug in the slide switch circuit, align and carefully slide the completed circuit into **knuckleBox.stl**. Once the 7-segment display fits through the opening, grip the edges the pull the rest the the circuit. ![](https://cdn-learn.adafruit.com/assets/assets/000/017/592/medium800/leds_push-matrix-in-box.jpg?1403564761)

## Fit into place
If the tolerance is too tight, use an x-acto knife to enlarge the opening. ![](https://cdn-learn.adafruit.com/assets/assets/000/017/584/medium800/leds_slide-switch-in-box.jpg?1403548097)

## Install Slide Switch
Position the slide switch into the the opening and push it through. ![](https://cdn-learn.adafruit.com/assets/assets/000/017/585/medium800/leds_circuit-in-box.jpg?1403548113)

## Adjust Wires in Enclosure
Curve the JST extension around the inside of **knuckleBox.stl**. ![](https://cdn-learn.adafruit.com/assets/assets/000/017/587/medium800/leds_add-batery.jpg?1403548157)

## Install Battery
Plug in the 110mAh battery. Curve the wire to fit it inside the box. ![](https://cdn-learn.adafruit.com/assets/assets/000/017/598/medium800/leds_lid-pieces.jpg?1403568663)

## Prepare Enclosure Lid
Position the **knuckle-lidClip.stl** over the **knuckleBoxLID.stl** part.![](https://cdn-learn.adafruit.com/assets/assets/000/017/599/medium800/leds_lid-clip.jpg?1403568679)

## Secure Lid
Snap in **knuckle-lidClip.stl** into **knuckleBoxLID.stl**.![](https://cdn-learn.adafruit.com/assets/assets/000/017/588/medium800/leds_knuckle-side.jpg?1403548191)

## Install Knuckles
Slide the **knuckle-lidClip.stl** nub in between the clips on **knuckle.stl.** ![](https://cdn-learn.adafruit.com/assets/assets/000/017/591/medium800/leds_hero-kunckle-2.jpg?1403556169)

## Right-side Up
The rings should have a comfortable fit, not too tight or loose. Ensure the parts are positioned with the 7-segment display facing the correct orientation. ![](https://cdn-learn.adafruit.com/assets/assets/000/017/593/medium800/leds_lids.jpg?1403564885)

## Chain Customizer App
Included is a chain that prints fully assembled in place. The **knuckle-lidHoop.stl** part was created by the [chain generator customizer app](http://www.thingiverse.com/thing:28405) available on thingiverse.![](https://cdn-learn.adafruit.com/assets/assets/000/017/595/medium800/leds_chain-hero.jpg?1403565155)

## Wear it!
Show of your bling bling in your latest music video and be sure to share it with us! 
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