Installing the Circuit Board
The next step is to install the circuit board.
The hardest part of this project is making the circuit board. We get ourboards professionally printed up. We’ve managed to build boards out of blank breadboards and copper tape, but it’s a pain. You could also etch the board yourself; it’s a fairly simple design, so it might not be that difficult.
Schematics, board designs, and microcontroller code are all available for free on our Google Code page.
Right now, there are two main revisions of circuit boards in print. The easy way to tell is that the older board has legible silkscreening where the VCC, SCL, SDA, and GND wires to the Wii connect, while the newer board’s silkscreen is very hard to read. The older board is also dated January 2010, while the newer is March 2010. There are a few caveats for each that bear mentioning.
- On the January board, the blank little boxes next to the USB jack are for the Zener diodes – install these so that the black band is on the side closer to the chip, as seen here:
- You’ll wind up with some extra regular diodes, and an extra big black diode on the January boards – you can install the black diode into the VCC hole in the Wii connector so that the band is near the board – this helps prevent damage if the board is plugged into the Wii and the USB jack at the same time, which you shouldn’t do.
- On the March board, that big black diode goes in the diode slot next to where the Wii wires come in. Also, the silkscreen that says 20K should be filled with the 10K resistors included.
When putting the board together, we usually go for installing the shortest components first. This allows you to flip the board over and solder it while it rests on the table, and the components won’t fall out so much, making it look a bit neater.
Resistors
Start by bending the leads as sharply as you can, it will make them fit in the board more smoothly:
There are two types of resistors we’ve shipped with the kits – 68 Ohm resistors and 10K ohm resistors. The 68 ohm ones have a blue stripe, and are packed loose, so they’re easy to identify. Now put all the resistors in the spaces marked 10K or 68 like so:
Next, carefully flip the board over so none of the resistors fall out, and solder them to the board. We don’t have any pictures of soldering, but just hold the iron against to the holes you’re trying to solder, and add some solder in there. There’s a great soldering tutorial on SparkFun, as part of their great electronics tutorial, so check that all out!
Once you’ve got everything soldered, go ahead and clip off the excess wire leads – this is a kinda cramped board, so you’ll want the freedom when you start putting in other parts. You can buy some nippers, which I need to get around to doing, but I’ve just been using a pair of toenail clippers (also, they’re great for stripping wire – just hold a finger in between the lever and the body for a little bit more control) like so:
Capacitors
Next is the capacitors – just like the resistors, put them through the holes, then solder and clip them. Again, we’ve got 2 flavors of capacitors, and again, they’re marked by electricians, so they’re not totally obvious. The 27 pF ones are thankfully marked “27″, so they go in the 27pF spaces, but the other .1 uF ones are small, yellow, and are marked “104″ in tiny text – they go into the Dcpl spaces, since they are decoupling capacitors (this means they help reduce noise from the chip’s power consumption, since the chip actually draws it’s power in big spikes every clock cycle). So the capacitors go here:
Diodes
Next, the diodes. These pictures are a bit confusing, unfortunately, since we used to have 2 package styles for our regular diodes – the orange glass and the black plastic. To avoid confusion, we’ve now moved to exclusively the orange glass ones, since we also added a special diode in the new boards. Added on top of this, there are two 3.6 volt Zener diodes loose in the kits that help the USB communication.
We’ll start with the Zener Diodes – they go into the small boxes near the
Diodes need to be installed in the proper direction – diodes act like one-way gates for current. Each diode has a band of black or silver on it that is closest to the cathode (the end that goes to ground), and it corresponds to the marking on the silkscreen. In this picture, the Zener diodes have been installed incorrectly – the bands should go to the side closest to the chip, so watch out.
In this picture, the zener diodes are installed CORRECTLY -
Everything Else
Next, since it’s short, we’ll install the crystal oscillator – it’s that little metal oval thing. It doesn’t matter which way this guy is inserted.
Next, go ahead and install the chip mount – you can take off the actual chip if you’re concerned about heat damage from the soldering. However, make sure that the notch in the chip/chip mount corresponds to the graphic on the board – otherwise things won’t work at all.
Next, the actual USB plug. It’s probably already kinda installed, since we ship them in the boards to protect the pins on the bottom from getting bent. Still, go ahead and crimp the gull wings on it into the holes like so:
Once that’s all soldered together, get some wire and install the button included with your kit. We’re only using the “Plus” button right now – it’s the start button, and is used for programming the different modes of the guitar, and to reprogram the firmware via USB, so it’s pretty important. The other button, “Minus”, is just used to activate Star Power in the games, so feel free to figure out a way to trigger that that’s cooler than just a button!
Solder some wire leads to the button, then solder those wires to the “+” hole and any of the holes marked “GND”
Finally, just solder the pick into the “pick” hole. One recommendation we have is to add in some sort of header-pin connection so that if you yank the pick cord, it comes off of that connection rather than ripping out of the PCB. We’ll probably include that in future kits, so if you want a header pin and a connector, just e-mail us and we’ll drop you one in the mail!
Installing the PCB into the Guitar
- If not already open, take off the cover of the cavity you’re putting the circuit board in.
- Position the PCB so that it can be reached by all the wires/connectors from the other steps, and that the cover will close fully with the circuit board installed.
- Mark out where the mounting screws will go in the body, then remove the PCB
- Drill out thin shallow hole for the screws to go into
- Drill a hole in the cover for the pick’s wire and the connector to go out of.
- Insert the pick wire, wires coming through any holes, and the button into the guitar body.
- Solder or connect the connections from the other parts to the PCB
- Replace the PCB and screw in.
- Replace the cover.
Congratulations! You’re now ready to rock out.
