Many of us grew up using chalkboards in school. Chalkboards are not too expensive but digitizing the information you write on them is not convenient. String2String is a fun project that shows how to digitally encode writing on a Chalkboard using strings. As you can see in the below video, String2String digitizes what you write on the chalkboard:
The developers have used strings, pulleys, ultrasonic distance sensing, a radio transmitter, and some filtering algorithms to pull this off. Here is how String2String works:
The algorithm works by computing the difference between the position of each weight in the current and calibration position, effectively allowing us to accurately measure the distance of the chalk-holder from each pulley. This gives us an approximation of each of the three sides of the string, string, top of board triangle. From there, by applying the law of cosines, we can convert the position of the chalk-holder to x,y coordinates.
Using a wireless radio transmitter attached to a button, writing is only digitized when the button is pressed. A second button exists to erase the current state of the board.
The project is certainly intriguing and not too expensive to pull off. You can find out all about it on GitHub.