Have you ever used a Hall Effect sensor?
The hall effect sensor is a sort of magnetic sensor that can detect the strength and direction of a magnetic field created by a permanent magnet or an electromagnet, with its output proportional to the measured magnetic field’s strength.
However, it turns that information into an electric signal that can be utilized for a variety of purposes, including position sensing, keyboard switching, proximity sensing, speed detection, current sensing applications, anti-lock braking systems, magnetometers, DC motors, disk drives, etc.
For the second project, he made an Electronic Pantograph. It is a device for copying lines on a flat surface using parallel rods pivoted at set points.
By adjusting where the rods have pivoted the scale of the copied lines can be altered.
He made an Electronic Pantograph that only need two rods and recorded the position electronically.
The recorded positions can then be used to electronically draw the copied lines at any scale.