This instructable will show you how to build the OpenChord.org V1 external, a device that lets you use a real guitar to play Guitar Hero/Rock Band/Frets on Fire.
We love playing Rock Band, Guitar Hero, and Frets on Fire. However, we also know that we'll never learn how to play guitar by pressing buttons on a plastic controller. That's why we've made the V1. Using the V1, you can practice real notes and chords with a real guitar, and the hardware translates those fingerings into button presses in the game. While you're still not going to become amazing at guitar, it can help you develop muscle memory and work on chord transitions while having a bunch of fun!
For more information, please visit www.OpenChord.org.
Step 1: Materials
For this project, you'll need the following:
- A metal-stringed guitar (the strings must be conductive, so nylon-stringed guitars won't work)
- 12 flanged plastic spacers: 0.375" x 0.12" OD (McMaster-Carr part # 91145A118)
- 6 flanged plastic spacers: 0.25" x 0.17" OD (McMaster-Carr part # 91145A143)
- Copper tape (with conductive adhesive) (McMaster-Carr part # 76555A641)
- Cable to connect to your system (Wiimote cable, USB cord)
Electronics - All can be ordered from DigiKey, except the circuit board
- Circuit board (this can be made from a blank breadboard and copper tape)
- 6 normal diodes
- 2 3v6 zener diodes
- 1 Atmel ATMega168 microcontroller
- 1 16 mHz external clock
- 11 Resistors - 10K Ohm
- 2 Resistors - 68 Ohm
- 1 Capacitor - 0.1mF
- 2 Normally open push-button switches
- Small foam
- Small box
- Optional: Pin headers
- Optional: Pin receptacles
- Optional: Jumpers
- Soldering Iron and solder
- Wire strippers
Step 2: Insulating the Strings - Part 1
The OpenChord V1 works by sending a small electric charge through the strings and the frets. If a string is touching a fret, then a circuit is completed, and a microcontroller processes this information and outputs the appropriate controller signal. Therefore, in order to work properly, the strings must be electrically isolated from each other.
Unfortunately, the metal bridge on a guitar will connect all the strings together. This is where the plastic spacers come in.
To start with, take off the plastic cover on the back of the guitar that hides where the strings come through. Then completely take off the strings on the guitar. On the back of the guitar, you'll see where the balls on the strings rest. We'll be putting the wide plastic inserts in those holes so they keep the little ball part of the string from touching the metal.
Now slide one of the wide, short inserts onto each string so that the flange side touches the ball.
Thread the string back through the guitar, but not through the little moveable metal part on the front of the guitar (the saddle). Make sure that the flange seats at the top of the hole properly.
Step 3: Insulating the Strings - Part 2
Now it's time to insulate the place where the strings touch the bridge on the front of the guitar. If any of the strings got pushed through the saddle, take them out of the saddle.
With each string, thread one of the thin, long inserts down each string so that the flange part is further away from the guitar. This first set of inserts will go into the hole directly on the face of the guitar. It helps to rotate the saddles 90 degrees so you can access underneath them easier. It might take a bit of jiggling around, since the faceplate on the bridge might not be perfectly lined up with the holes the strings are coming through, but get the first set of the inserts flush with the faceplate of the bridge.
Next, thread the strings through the saddles. Add another thin insert to each string; this insert will rest between the saddle and the string so that the string doesn't touch that part of the bridge.
For the sake of the next step, leave the strings loose; we'll need to access the fretboard.
Step 4: Wire the Frets
Next, we need to add wires to the fretboard. For this, we'll actually be laying copper tape over each of the frets and running that up the neck, so that the actual circuitry can be clipped onto the head of the guitar somewhere.
First, measure and cut out 5 long L-shaped pieces of copper tape. They should ideally be just as thick as needed to completely cover each fret, and the other leg should be long enough to reach from the fret to the head of the guitar.
Now take one of the 'L's and peel off the tape's backing and carefully apply it to the first fret, wrapping it around the guitar so the other end of the L runs along the neck of the guitar about 1 cm away from the fretboard. Make sure there is at least 0.5 cm of clearance between the track on the head and any hardware on the head so you'll have room to clip the other hardware there later.
Next, attach the other 4 'L's to the next 4 frets, being careful to leave an even amount of space between them. You'll want to put them fairly wide apart, since when you prepare the box to clip onto it, you'll want that extra room.
Step 5: Assemble the Electronics
Now comes the hard part - circuit assembly.
Circuit board plans and electrical schematics can be found here-
Meanwhile the code for the microcontroller can be found here:
I've had success building the circuit board by applying copper tape to a blank breadboard and then cutting out traces, but if you've done anything with PCB etching, that's most likely the best way to go.
Populate the board according to the schematic. All resistors are 10K ohm, except the 2 68 Ohm resistors that are marked on the silkscreen.
Where the image of the board says Connectors, you can either solder straight pins there, or just solder long pieces of wire. Where the board says 'Strings', solder 6 long wires in - these wires will go outside of the enclosure and attach to the strings at the tuning pegs, so make sure they're long enough. You'll attach the two buttons via small wires, since these buttons will be attached to the case. Finally, you'll need to attach one really long wire to the pick pin, that wire will go to the guitar pick, so it needs to be long enough to comfortably reach the bridge of the guitar.
If you're planning on attaching a Wii controller, instead of a USB plug, attach the cord from a Nunchuk directly to the place where the USB plug is supposed to go, then use the jumper on the board to route the SDL/SCA signals to the appropriate pins on the ATMega168.
As far as the code goes, you'll need some way to get the code onto the microcontroller - Atmel makes a wide variety of programmers, as does Adafruit industries. I recommend both, since their products are compatible with Atmel's AVR Studio software, which makes programming things a snap. The code was also written in AVR Studio, so it is most easily viewed and organized that way.
Step 6: Modify the Enclosure
Now you'll need to put that circuitry somewhere. In whatever enclosure you choose, though, it will need to fit flush on the back of your guitar where those copper traces went.
In order for the circuit to contact the tape on the guitar's neck, we're going to add copper tape contacts to the outside of the box that will line up with the tracks on the guitar.
This part is hard to describe, but look at the picture and it will make sense...
First, you need to position the enclosure on the neck and mark where would be a good spot for those contacts. Then, cut 5 strips of copper tape wide enough to serve as reliable contacts and long enough to reach around the edges of the box and reach inside. Finally, cut a thin piece of foam that is wide enough to cross all 5 contacts. These strips are going to be laid parallel to each other along the outside of the box and over the foam so that when the box is pressed to the guitar head, the foam presses the tape against the traces on the neck. Apply the tape so that it also goes into the inside of the box.
Now that the contacts are installed, cut 5 small strips of wire and solder these to the section of the contacts that reach inside the box. Then solder the other ends to the circuit board.
Finally, insert the circuit board into the enclosure, mark out holes for the buttons and outgoing wires and cut those out.
Step 7: Make a Pick
The last real step is to make a conductive pick. Strip off a bit of the long wire headed to the pick pin. Cut a thin strip of copper tape and use it to tape the stripped bit of wire to the bottom of the pick. If you want to make sure the connection is good, or if your tape doesn't have conductive adhesive, put a little bit of solder between the top of the tape and the wire. Then wrap the bottom of the pick with copper tape.
Step 8: Assemble and Play
Now add the circuit board and buttons into the enclosure. You can now clip the box onto the guitar, and attach the string wires to each of the strings by wrapping them around the strings or pushing them through the holes in the tuning pegs.
You'll also need to make a pick -
You should be all set! If you made the USB version, you can plug it into a PC and open up the Game Controllers menu in Windows and see how your new controller works.
The current firmware supports 3 operation modes :
Fret Mode: Use the first 5 frets on the guitar as the buttons on a normal guitar controller
Note Mode: Custom map up to 6 guitar notes to each color button, allowing you to practice individual guitar notes
Chord Mode: Custom map chords to color buttons, so you can use your favorite guitar game to practice chord transitions.
For more information about how to play the guitar and how the guitar works, please visit www.OpenChord.org! Thanks for reading.