Red Heart : a shiny finalkey with a small form factor

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 x strips acrylic, 1 to 2 mm diameter and 10 mm length ( to send light from green and yellow led to surface)
6. tinfoil (1 square cm  will give you lots of reflectors to direct light from led to surface)
   
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 heart shaped 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 white/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)

• 2 component glue, curing fast/5 Minutes (to hold small stuff in place)
• 2 component glue, curing a long time/24 hours, very stable (to attach the brassrod to arduino)
• repair glue, 2 component ( to build the body/cover of Red Heart)
• some drops of red tint/tinting paste or red varnish if you use clear top coat (18), not needed if you use red nail varnish
  
• nail top coat (clear or red) or anything which sticks to repair glue and protects it without ruining it.

Tools

• soldering iron with fine tip for smd parts
• tin-solder for smd parts
  
• 3d hand to hold arduino and parts
  
• tweezers to handle smd parts (or a vacuum pickup)
  
• pliers to cut and hold stuff
• small saw to cut one line of stripboard (or use a dremel)
  
• sanding paper
  
• rasp/file or dremel
• gloves to protect you from epoxy glue, tint paste and varnish
• protection against dust from sanding or dremeling stuff (copper and any kind of epoxy are dangerous!)
  
• vacuum cleaner and cleaning tissue to clean up the mess afterwards
  

Steps

1. finalkey basic setup

       program finalkey software or -> see dusteds setup,
       solder eeprom to arduino board
       solder big pushbutton to arduino board
       solder 2 x 4.7 kOhm,
      

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

Step	What	Why
2.0	Cut about 12 cm from a brass rod of 1mm diameter. Make it longer if you want to hold with your finger.	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 ;-)
2.1	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.
2.2	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.
2.3	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.
2.4	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. If you bend it just a little too much inwards it will cling to your board by itself (see image in the left). Gluing will be easy then. If you don't have a tight fit, you will have a hard time fixing the rod when you try to glue it to arduino.
2.5	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. A simple test : lift your arduino board wihout touching the rod. If the rod sticks to the board without moving you are ready to go for the glue.
2.6	Glue it around the board and let it cure. Make sure that it does not touch any wires/conducting parts. You will have a nice handle now for all the steps following.	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. If you dont attach this handle all coloring and varnishing actions will be a pain. And you can't put your key on a chain or necklace.

3. prepare finalkey-led and power-led with a mini circuit board

Step	What	Why
3.0	Cut off a single line stripboard, seven holes long.	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 : +5V. 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.
3.1	Cut the copper line at 2 holes, one exactly in the middle, thats where the led goes.	The two cuts are the mounting places for a resistor and the led. The resistor has to have a minimum of 160 Ohm. Red LEDs 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=U/I=160. Depending on your LED and its brighness you can go up to several hundred Ohm and it will still be bright. Nowadays LEDs might blind you if you run them with maximum allowed current.
3.2	Solder resistor and led over cuts, test it at 5 Volts ! Resolder if necessary. Kathode (GND) goes to Pin 10 of arduino for your FinlKey LED.	I used a 180 Ohm resistor which protects the red led and still allows enough current to make it shine bright. Dont connect it to arduino yet. NO GLUE, NO SOLDERING to arduino. You have to glue fiber optics to red power led first. This is located to some extent below the finalkey led stripboard. See image 4.4. Attention reset button users : If you want a reset button you better solder the resistor to the right and cut off 2 holes from the stripboard on the left. You will need this space for the reset button
3.3	Build another one with a green LED for power-LED. Anode goes to +5V/VCC. Kathode/GND goes to GND.
3.4	Test both strips before soldering them onto your arduino.  Available connectors on your arduino board :

4. Glue LED-stripboards to arduino mini pro and connect them.

Led-stripboards soldered, side-view. The image is taken from the Green Miracle. Stripboards are sanded to a minimum. If you dont sand them the stripboards will raise LEDs and gemstones.
Make sure not to short anything by leaving a clear gap between arduino board and your wires (1).

5. Glue gemstone on red FinalKey LED and power-LED and let it cure.

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

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

Nr.	What	Why
6.0	Cut some acrylic of a thin sheet 1x1mm up to 2x2mm, 1cm long (see image above)	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.
6.1	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.
6.2	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.
6.3	Glue your mirror on top of the led (see below, 6.4, and the image above)	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!
6.4	Mount another light pipe on top of the second LED. Cover both with aluminium foil without any contact to components on your board.	Its ok to have too long light pipes. They will be cut off after you covered your board with repair glue. If you have too short light pipes it will be a pain to find them afterwards. The repair glue will be in line with the button edge. In the picture on the left i had to remove about 1 to 2mm.
6.5	Let it cure

7. Cover your creation in repair glue. (See green miracle)

8. Sand it, color it, varnish it.

If you know your repair glue you can just cut off stuff while its curing. Sanding should be done only when its really cured after about a day. Start with medium grade sanding paper (180). This works for almost 90% of your work. Only at the very end you might use very fine grades (400).
If you dont want to color and varnish it try to get a very smooth surface. It will not collect any dirt then.
If you varnish it, you dont have to be very picky about a smooth surface. Small screatches will be filled and cleared by the varnish.

Color and Varnish:

To be on the safe side put a cover on top of the switch first. Cut some plastic sheet and glue it to the edges of the button. Be careful not to come close to the button itself.  If you use some soft glue then varnish and color stains can be removed easily by removing the plastic. Always keep the usb connector down. If you dont you might mess up the usb port. You can cover this too if you want to. If you are carefull you dont need to cover it.

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