Non-Theremin projects
Mini-LCD Oscilloscope
Original design of the 18F2550 PIC-based core is from Steve at Semifluid.com.
Audio band, portable LCD scope.
Non a REAL oscilloscope, but a sometimes useful tool for project development (and a great gadget!).
I took Steve's design and improvised the circuit of the voltage divider, X10 amplifier, and input protection (see diagram). Multi holed prototype board, no PCB.
Apart from the the display and the PIC, all components (and the enclosure too) are from the junkbox. The apparently weird values of the resistors are those required for the decade divider. Can be scavenged from a wrecked Digital Multimeter, as I did.
NOTES:
-I didn't take into account the (not infinite) input impedance of the PIC. A second opamp working as a buffer would have made this a better job.
-If the wiring PIC-LCD is longer than a few centimeters, the latter may show erratic behavior. After a few trials, I found that a .01 cap across the supply leads of the LCD's edge connector was the solution (in my case).
Wiring the instrument...