Step 2: Building the controller
Tools and materials
Soldering iron- A good quality soldering iron is a must. I received an Aoyue 2900 soldering station a couple years ago for Christmas and it's been great. You won't believe the difference once you start using a good soldering iron.
I also use a small tip for soldering small surface mount components-
Wire cutters/wire strippers- Small flush cutters are the best. If you don't have wire strippers or cutters then these will work well-
Tweezers- Get some small tweezers to work with surface mount components. Here's an inexpensive set-http://sra-solder.com/product.php/6409/79
Magnifiers- Being able to see what you're working on makes a world of difference.
Multimeter- Most any multimeter will work. You don't need to spend big $$$. I personally own a Wavetek Meterman 16XL and it's great. If you don't already own a multimeter and are really getting into hobby electronics then this meter will probably do everything you could ever want-
Servo board PCB-
Arduino Pro Mini- http://www.sparkfun.com/products/9220
USB mini-B connector- http://www.sparkfun.com/products/587
capacitors- 2 ea 1210 package 1uF SMD ceramic capacitors
resistor- 1ea 1206 package 1K Ohm SMD resistor
LED- 1 ea 1206 package SMD LED
JST connector- 1 ea
MAX1555 IC- 1 ea
Straight break away header pins - 2ea 40 pin row
These come in really handy so it's always good to get extras to have on hand
Female break away header pins- 2 ea 40 hole row
These also are super handy to have around
Single cell LiPo battery- 1ea (you can use any capacity you like.)
USB mini-B cable- 1 ea
Odds are you've already got one but if you don't here you go-
Assembling the servo board
The first thing to do is build the charging circuit. I usually start with the smallest components first. I've found the easiest way to solder SMD parts is to get a tiny bit of solder on your soldering tip and touch it to one of the component pads on the PCB. Then hold the component in place using tweezers and heat up the pad and component pin- this allows you to get the part attached to the board so you can check its alignment for the rest of the pads. Then simply solder each of the remaining pads. There is a great series of SMD soldering tutorials here- http://www.sparkfun.com/tutorials/36
Begin by soldering on the MAX1555 IC (labeled U1) -this can only go on one way. Next comes the LED- make sure to check the polarity as it is labeled on the PCB (the LED cathode is connected to one end of R1.) Then solder resistor R1 followed by the capacitors C1 and C2. These can be soldered on either direction. Next comes the mini USB connector- this one is a bit tricky as the pins are positioned nearly underneath the connector. Now solder on the JST connector. Make sure to double check your soldering job for these connectors as they receive a fair bit of mechanical stress.
Now test your charging circuit. Plug in a USB cable and check the voltage at the JST battery connector. It should read about 4.2-4.3V. Now connect the LiPo battery. If everything is OK the small LED should turn on, indicating the battery is charging. Disconnect the battery.
Now solder on the pins to connect the Pro Mini board. This is done by soldering on the break away straight header pins. First insert the long pin ends into the PCB, flip the board over and solder them in place. Double check your solder joints. Now flip the board over and place the Pro Mini board in place on top of the exposed pins and solder all the pins in place. Next solder the remaining straight pins into place in the digital out positions and the 3.3v port along the bottom of the board.
To finish the board solder all the female headers in place. The best way I've found to cut the female headers is to remove a pin where you want to make a cut- just yank the pin out the bottom using a pair of pliers. Then take wire cutters and cut through the opening left by the pin. Now take a file (or sandpaper) and smooth out the cut edge.
Make sure your board is getting power by plugging a USB cable into the mini USB port on the controller board. The red LED on the Arduino Pro Mini should light up.
That's it- your controller is ready to go!