Proximity Sensors

Measuring difference in position, aka distance between two points

• Stud Sensors
• Sonar Sensors
• Optical Ranging
• Anne Odborn says:

• "...mount small aluminum foil "flags" on a low - friction bearing (say a length of fine thread) [to the side of a fan] and photodetectors to sense the position of the foil. When the robot approaches an obstruction, the wind will be reflected back and move the foil flags."

See also:

• https://www.mdpi.com/1424-8220/16/7/961/htm A wire bend sensor+
• http://thereminvision.com/ Sensing nearby objects using the Theremin circuit.+
• http://www.mindspring.com/~sholmes/robotics/ultrasnd.htm Low cost ultrasound proximity sensor
• Quantum Research Group. QProx One chip proximity sensors.
• http://www.xs4all.nl/~jwasys/techtalk2.html Application of the Sharp GP2D02 distance sensor.
• http://www.allegromicro.com/control/prodsel1.htm - Hall effect
• http://www.rdrop.com/~marvin/parts/issue14.pdf Marvin Greens notes on adapting Stud Sensors for proximity detection.
• http://www.seattlerobotics.org/guide/infrared.html IR Proximity Detection