view and display the signals (Figure J). Verify that the signals displayed correspond to the contraction of your forearm muscles by moving your wrist and pinching each of your Index, Middle, Ring, and Little fingers.
6. ROCK OUT. Once you’ve tested the individual compo- nents, it’s time to put it all together to check out your Air Guitar Hero chops. Disconnect your laptop from the wall sup- ply. Ensure that the EMG electrodes are well attached to your forearm (too much electrode gel on the adhesive can make them fall off). Open MiniVIE and select your input hard- ware device. Use the Signal Viewer to verify that the muscle signals are at rest when you’re at rest; you should only see EMG activ- ity when you’re actively pinching your fingers. Select the LDA classifier and choose Index, Middle, Ring, and No Movement, initially for beginner mode. Train each of these classes using the Simple Trainer interface. Verify that your accuracy is at least 80% or higher. Start your Wii console and select a song to play using the guitar controller, then select AGH from the Presentation drop-down and run it. In the default configuration, you don’t have to use the Strum button. Just press your fingers when it’s time to play the note, and it will be played with a strum added (Figure K). That’s it! Now you can play Guitar Hero simply by making muscle contractions and thinking about playing the desired note (Figure L). And after you become a Rock God, you can modify your Wiimote — see our WiiEMG hack at
makezine.com/go/wiiemg — to play games like Wii Sports Tennis or Mario Kart ; We’d like to thank Jonathan Kuniholm, founder of
openprosthetics.org and Duke University doctoral candidate, and Jacob Vogelstein of the Johns Hopkins University Applied Physics Laboratory for their help creating and testing the first Air Guitar Hero system back in 2007. J KL Robert Armiger is an engineer at the Johns Hopkins University Applied Physics Lab working on the Revolutionizing Prosthet- ics Project. He completed his master’s in biomechanical engineering at Johns Hopkins and his B.S. at Virginia Tech. Carol Reiley is a surgical roboticist completing her doctorate at Johns Hopkins and running Tinkerbelle Labs. See video of Air Guitar Hero in action at
makeprojects.com/v/29.
51 Follow us @make
