Recently, we have been wanting to become more familiar with an interesting technology from MIT called So, in typical Learning Studio style, we hauled a wide variety of materials (switches, motors, art supplies, found objects, etc.) onto a central table, and started playing around.
What caught my (Luigi) attention immediately was an old rotary telephone dial. It had a wonderful tactile feedback to its action, and a hint of nostalgia that appealed to me. So I set out to figure out how this entirely mechanical analog device actually manages to count!
This was possible thanks to a Scratch sensor board: this is an input device with a button, a light sensor, a sound sensor, a resistance slider, and four resistance input jacks. Scratch can monitor and detect changes in the sensors, so using the resistance sensors I set out to figure it out. I found that there are two sets of wires that come out of the rotary dial. One set is connected to a switch that is normally closed at rest (call it A), and the other to a switch that is normally open (call that one B). What happens is that as you start spinning the dial, switch B closes, and stays closed until the dial returns to resting position. Meanwhile, switch A stays closed while the dial is moving counterclockwise (toward the stop), and the moment you let go and it starts to spin back toward resting, switch B opens and closes once for each "click" of the dial. So I wrote a simple program to count the number of clicks for each number dialed.
Next, I decided that the dial would be used as an input device to enter people's date of birth, and so a simple fortune telling device started to take shape. I called it "Telephortunes". It's become much more complicated (and cool) than that since then, so stay tuned for the evolution of this project...