Here are some amazing photos of a robotic guitar playing invention. Very cool.
Presenting: The Crazy J- guitar playing machine
The Crazy J is made up of mechanical parts, electronic components and software control.
The mechanical parts can be seen in the picture above and include a fingering module (on the left) and a plucking module (on the right).
Here is a close up of the plucker:
Here is a close up of the teflon picks that actually contact the strings, and the solenoids (top, pink and blue wires) that power them, via the pluck rod linkages (middle).
The fingering on the guitar is actuated by solenoids also (below), which connect to levers (above).
The "fingertips" that press the strings to the neck are seen close-up here, the springs that return the fingertips after a note is played are also visible:
This next picture shows the banks of solenoids that actuate the fingertips and the springs, which serve to damp the slapping of the solenoids (held by two nuts on threaded rod).
The control part of the Crazy J is a Motorola HC11 Micro-Controller. The output ports B and C of the HC11 connect directly to the Control Board shown below (ribbon cable on left of board). The control signal is sent through adressable latches (column of black chips) and then to the Power Boards (3 ribbon cables on right of board). Each signal line has an LED connected in parallel with it, so that the LED lights up when a signal is sent (yellow, green, red bulbs). This helps in debugging.
One of the two Power Boards for the fingering solenoids can be seen below. The blue potentiometers allow for adjustability and fine tuning of the power sent to each solenoid. The transistors see a lot of current and are therefore connected to heat sinks (metal bars in back). The connection to the solenoids is made via a 15 pin connector (back right of board).
The Power Board for the plucking solenoids is very similar to the fingering board. One difference is in the connection to switches, which act as hard stops for the plucker (brown connector with cable coming out, in middle of board, behind blue potentiometers).
The switches can be seen in this end-view of the Crazy J (small black tops touching levers between solenoid connections).
The positioning of the Power Boards in the black box below the guitar can be better seen in this picture:
The MIDI signal that comes into the HC11 connects in the right connector on the top end of the box, shown below. The power cord plugs in to the left of the MIDI cable, and the other end is plugged into any AC wall jack. The metal grate on the right covers the cooling fan.
And here is one more picture of the entire Crazy J.