This is a quick project sketch, building on a conversation with Josh Burker. It’s a reference, not a tutorial.
— Josh Burker (@joshburker) March 4, 2014
Need #PicoBoard help. Want to measure resistance along a piece of copper wire as it is touched in various places w/a finger. cont.
— Josh Burker (@joshburker) March 6, 2014
This is probably possible using the MakeyMakey’s analog input ports, but the Picoboard’s resistance sensors are a better and more direct choice.
This was my first prototype. Apologies for the sideways video.
One “string” prototype for Josh Burker 18kOhm resistors in series for the resistance port from PicoBoard. #… https://t.co/2rmBDewCni
— Andrew Carle (@tieandjeans) March 7, 2014
This just uses a few resistors in series along a span of copper tape. After checking that the values were distinct enough, I had the Scratch instrument play the resistance value as the note. This is probably a bad plan for actual music. :)
Josh asked for a string that could be fingered to change pitch, while the “bow” played in the same place.
This is random wire, wrapped around popsicle sticks at either end of the cardboard tube and taped in place. The kinks and bends in the wire are no good, but the concept is sound.
I attached one clip form the Picoboard to the bow, and one to the copper tape + resistor strand. The key is that the wire/string doesn’t touch the copper tape at all. If you touch the bow to the string, you don’t complete the circuit.
In order to get any reading (ie, resistance less than 100 in Scratch), you need to pinch the string to the resistor+tape.
You need a multimeter for this. The Adafruit Circuit Playground app would also be a helpful, between checking resistor codes and calculating the voltageOut.
— Andrew Carle (@tieandjeans) March 10, 2014
Making this into a stable instrument is hard work. What voltage range can the PicoBoard sense? How do those values map to Scratch’s 0-100? How do those 0-100 values turn into pitch? What size resistor makes a good step? How many “frets” can you fit on the neck of your instrument? How close together do you fit the strings? Does fingering a chord produce a clean combination of tones or something else? Do you keep the fingers on your chord-ing hand electrically isolated? Does the bow need to be isolated?
Those aren’t facts to discover, but choices that will shape design. You could give that framework to 50 kids and wind up with an orchestra of different instruments.