If you want a very small and glittering finalkey you have to work with the tiniest components ever.
Lets see how this is done for the Green Miracle.
During the process you have several chances to brick your arduino.
Be careful and patient and you will succeed.

Green Miracle : a glittering FinalKey with a flat form factor

FinalKey : Green Miracle, almost done

Parts used (almost all used in Red Heart, besides the gemstones and glitter)

FinalKey Green Miracle, parts used
  1. arduino micro pro
  2. brass rod, 1mm thick, about 12 cm long
  3. 24LC512 EEPROM
  4. 2 x 4,7 kOhm
  5. 2 acrylic poles used as light pipes
  6. aluminium foil (less than a square cm)
  7. red smd led (finalkey led)
  8. green smd led (power led)
  9. 2 x smd resistor (160-220 Ohm for red, 220 to 500 Ohm for green, both set led current)
  10. One red or one transparent gemstone, flat (1-2 mm thick), 6 to 10 mm diameter ( to cover red finalkey led and make it even more shiny)
  11. One green or one transparent gemstone for power led (flat, 1-2 mm thick)
  12. large pushbutton (finalkey button)
  13. 2 single strips of a stripboardboard (to set up red finalkey led and green power led)

Additional Stuff


Technical Problem: 2 leds at the bottom.

I wanted to get a small form factor and a large shiny red finalkey light. Input and output  led are at the bottom of this design (opposite to finalkey button). As with the red heart design light will be sent to surface by small acrylic parts. The general design will follow the Red Heart design. But the green miracle will be thinner than Red Heart.


Check functionality after each step is done! If you discover any serious error after step 8 you have nice brick :(

1. FinalKey basic setup
    program arduino -> see dusteds setup,
    Glue and solder eeprom to arduino board
    Glue and solder big pushbutton to arduino board
    solder 2 x 4.7 kOhm to arduino board,    
2. Bend brass rod and glue it around the arduino board.
3. Prepare two thin mini strip-boards.
4. Prepare finalkey-led and power-led each with a mini circuit board.
5. Glue stripboards to arduino board and solder them.
6. Glue gemstones on LEDs.
7. Glue 2 acrylic strips as light pipes onto green and yello led of arduino micro board.
8. Cover your creation in repair glue.
9. Sand it, color it, varnish it.

2. bend brass rod and glue it around the arduino micro pro board :

FinalKey : Green Miracle, back with brass rod


Brass rod/wire, 1mm thick
Brass rod (1mm) is easy to bend and strong enogh to make a proper handle. Thinner brass rod is too soft. Thicker brass rod is very hard to bend. Aluminium is too soft. Anything with  plain iron will rust. High quality steel is too hard. Silver is too soft. Go for gold alloy, used for tooth crown, if you have the money. Its even shinier than brass ;-)
dremel or sand the edges of arduino pro to get "round" soft edges at the usb side of the board
It is close to impossible to bend the rod to a 90° angle. Its always a bit round at the edge. As you will want a close fit you have to get rid of the sharp edges at the usb port side of the circuit board.
This is not a problem on the other side (not usb ...). There is no 90 degree angle for the brass rod.
cut about 12 cm from a brass rod of 1mm diameter
Do this first because its handy to have an extra part to handle the arduino in all steps following. Dont use anthing thinner, because its too fragile then. Dont use anything thicker as 1 mm as it will be very hard to bend.
bend 3-5 mm as tight and close to 90 degrees for the usb side as possible
If you sanded the edges properly, the rod will have a tight fit which is essitial for handling the board afterwards. These bended parts of the rod take the load for any drag on the opposite side. If you dont have tthem the glue at the sides of the board has to take the load alone. This is not prefereable.
bend it to a curve on the other side with a distance of 1-2 cm from the board
If you need a large curved rod to even put your finger through it, make it larger. I only want it to hang an a hook or to attach it to a key ring.
bend it as tight and close to 90 degrees as possible for the other edge close to usb. Cut off  the part which does not fit :).
see 2.2
Its no problem if the rod just slightly touches the usb port as it is grounded. But the rod should not move away from the board because the bent part is too long. Remember : a tight fit is the goal.
make sure to have a flat construction that fits exactly around the circuit board
If your construction is not flat you will not be able to glue it around the circuit board. Instead you will be ruining your fingers, the circuit board, your clothes and anything close to your handling area in the attempt to get it done.
glue it around the board and let it cure. Make sure that it does not touch any wires/conducting parts.
I always use a strong 24 hour curing 2 component glue to make sure that i get a strong and durable connection. Dont use super glue or any stuff which goes hard like a crystal after curing. Its not very usefull for parts with large gaps. And dont use anything soft like regular paper glue. It will not even hold the circuit board alone if bad luck hits you. Hot glue might be an alternative if you have a gluegun with a very fine tip. Otherwise you will find glue all over the place. And its not as strong as i want the bonding to be.

With the rod attached you now have a good handle for the steps following.

3. Prepare two thin mini strip-boards

stripboards, top

1) Get some junk stripboard with 5 to 7 holes (1)
2) Sand it down until you have only a very thin film on the copper line left. (2),
    Dont sand down the copper, only the opposite!
    Make sure to leave a thin film of isolating material on the copper.
    If you sand it up to the copper you will have a nice chance to create a short.
3) Cut off two lines  and cut these in half. (3). Thats the middle where the led will sit.
4) Cut off the small parts until you have 2 straight lines at soldering position.
5) Cut one of the pieces into half again where the resistor will sit.

4. prepare finalkey-led with a mini circuit board

Arrange your copper parts with small gaps of about 1 mm up to 2 mm in a line and solder your parts.
thin copper line with parts
This line will fit onto the arduino micro pro board.
Any stripboard with 2.54 mm distance between holes will do it. Otherwise you have to recalculate length. Anyway, only one hole has to fit exactly : GND. The other end will be connected by a wire, so there does not have to be an exact match of holes at the ends of our mini-led-board with the arduino board.
Cut off any overhanging copper.
Make sure that you have nice gaps below your components :
Side View : 1 -red LED board , 2- green LED board, R - Resistor
              leds on thin stripboard, side view
The two gaps are the mounting places for  resistor and led. The resistor has to have a minimum of 160 Ohm.
A red LED needs about 1.8 Volt at 20 mA. As we are running our finalkey from usb port, 5 Volt will kill it without a resistor taking the voltage up to 5 Volt.
R=U/I -> R= 3.2Volt / 0.02 mA -> R=160. Depending on your LED and its brighness you can go up to several hundred Ohm and it will still be bright. Nowaday LEDs might blind you if you run them with maximum allowed current. I used a 180 Ohm resistor which protects the red led and still allows enough current to make it shine bright. The green LED is not as bright as the red one. I just want a faint glow for power. 
Test your boards with 5 Volts and mark the working polarity on your boards
Test green
              LED, working ok

5. Glue stripboards to arduino board and solder them.

Glue your boards to your arduino board between resistors and usb port.
Mini stripboards with LEDs glued to
As we need some space for the gemstones, the red LED goes to the middle and the green LED goes close to usb port

Solder mini striboards
Mini LED stripboards soldered to
                arduino board, top view
Make sure to leave a gap between your wires and arduino board (1):
Mini LED-stripboards soldered to
                arduino, side view

Test your board. If you want to be on the safe side just use 5 Volts on arduinos usb-port
If this works :  -> no smoking components, no LED burnout
->but a short blink for red and constant light from green LED/power-LED then :

Test it on your pc-usb-port with FinalKey software running
(arduino drivers and putty on WinX or dusteds JAVA-Gui on any OS or Terminal on Linux)

6. Glue gemstones on LEDs.


Prepare red Gemstone : scratch a square from the reflecting back
red gemstone, preparation
1: top view                        2 : bottom view with scratched square

Most cheap gemstones have a refleting back. If you glue this on your LED no light will shine through. So you better scratch some stuff off where your LED will sit.
The FinalKey LED should be the most prominent part to watch. Its the brightest LED and the biggest source of light.
Prepare green gemstone :
Cut off a rectangle from a round gemstone.
Scratch off a square in the middle of the back-reflector.
gren gemstone, preparation
3 : Top view,    4 : after cutting, scratching     5 : bottom view
The power-LED is used just to make sure everything is connected proberly. The LED just gives a faint glow and has a small footprint.
Adjust this to your needs and your surroundings.
Glue gemstones on LEDs : red on red, green on green ...
Use fast curing two component glue. If possible fill all gaps between gemstones and arduino board.
finalkey board with gemstones
If your glue needs a long time to cure you have to fix the gemstones on the LEDs. Otherwise they tend to wander to a place where you dont want them to stay. Fixing these parts is a pain. So you better use fast curing glue (3-5 Minutes is ok with me waiting and keeping stuff in place).
You should be able to see the leds. If you cant see them you forgot to scratch the back-reflector ... rip off gemstones before glue is hardening.
Dont move until glue is cured :-).

7. glue two acrylic poles as light pipes onto green and yellow led of arduino micro board

FinalKey with
        acrylic pole as mirror on io-led

arduino pro micro with one of the two lightpipes mounted :
1 : acrylic pole sends light from led to surface, works as light pipe.
2: aluminium foil mirrors light into your light pipe.

Cut some acrylic of a thin sheet 1x1mm up to 2x2mm, 1cm long
This tiny pole will act as a light pipe and guide light from an led to the surface of your FinalKey. The smaller its cross section is the better it will work. See your old physics book at : total internal reflection. The bigger your cross section gets the more light will escape.
Cut one end at an angle of about 45°
This end will act as a mirror. It will sit exactly above the led.
If you want to make it perfect, polish all sides. The smoother the surface the more light will stay inside your light pipe.
Glue a small square of aluminium foil onto the 45 angle part (see image at 2).
Or put a long strip of foil on the upper part of your light pipe. Dont cover the whole pipe because you are most likely creating a short when you glue this on your board.
This is the mirror ... it will reflect light from the LED into your light pipe.
Glue your mirror on top of the led
Put the aluminium exactly above the led. If you miss the LED most of its light will escape.
If you want even more light put some more aluminium on top of your pipe and at its side. Dont put anything below. Chances are high that you short some contacts and brick your arduino. If you put aluminium on the sides be carefull to only cover the upper part and dont come close to the bottom -> avoid short circuits on arduino!
Mount another light pipe on top of the second LED.
Cover both with aluminium foil without any contact to components on your board.
finalkey board with two mounted
                acrylic light pipes on IO-LEDS

Let it cure

8. Cover your creation in repair glue.

If everything is cured, cover your creation with repair glue. Dont cover your gemstones. The stuff i used cures in about 8 to 10 minutes.

After this time there is about an hour to cut off stuff easily without damaging the main construction. After about an hour you cant cut it, you have to sand or dremel it.  So use your time carefully. Its best to make a test before using repair glue on your board.

finalkey covered in repair glue, raw

finalkey board backside, covered with repair glue,

9. Sand it, color it, varnish it.

9.1 Sand it down to the properties you prefer

finalkey, backside, sanded step 1
sand it down until you get a glimpse of the eeprom
finalkey, back,
        sanded step 2
sand it until you just remove the eeprom text. If go down even more you might ruin the eeprom chip!


Frontside sanded but not polished :
finalkey, front,
        sanded part 2

Start polishing now. Use a silikon polisher, very fine sanding paper or whatever is appropriate for your repair glue. Be careful not to scratch your gemstones. You can do it on purpose to get another look. If you dont like your scratched gemstone you can cover it with transparent varnish. It will not be as shiny as the original but can come close.

Coloring :

To be on the safe side put a cover on top of the switch first. Cut some plastic sheet and glue it to the edge of the button. Be careful not to come close to the button itself. With my button i used the outer black square to put glue on. As you can see fom the green speckles on this part of the button i didnt wait for it to cure. So some green particles were glued there too. If you use some soft glue these particles can be removed easily. Always keep the usb connector down while using glitter. If you dont you will mess up the usb port. You can cover this too if you want to. If you are carefull you dont need to cover it.

If you go for a shiny glitter-look put some clear varnish on your FinalKey first and sprinkle the glittering stuff on the wet surface. Repeat this until all parts you want to color are covered. Let it cure before you apply another layer otherwise you will just smear and uncover parts which you considered done. The glittering stuff will give a rough surface. Put some more layers of clear varnish on top until you have the look and feel you want.
And again : LET IT CURE before going for another layer. Failed speckles of glitter can be scratched of easily if you use common nail varnish. For a tougher surface use spar varnish used for boats or use resin.

 Almost done :

FinalKey : Green Miracle almost done

The closeup shows some minor speckles which you will not notice with the naked eye.

Enjoy !

              (thunderchild), logo

Design and hardware extensions used for
Red Heart, Alien Artefact and Green Miracle :
tc (thunderchild), Nov 2014

All praise and credit for FinalKey hardware and software go to dusted.