Digital Sensors
Digital sensors can only indicate two states, typically on and off. They produce a voltage that is either 0 or a given high value, typically 5 volts, but nothing in between.
Note that with some microcontrollers, you must wire the sensor with a pull-up resistor. For an explanation about why and how to do this, please see the Pull-Up Resistors note.
We have grouped them into categories, according to function, as listed below, but the interfaces to a microcontroller are very similar for all of them.
Buttons
Micro/Tact
Pushbutton
Momentary
Switches
Toggle
Rocker
Snap
Key
Slide
Lever
Rotary
Floormat
These are very useful for detecting when someone is standing in a particular location.
http://www.trossenrobotics.com/store/p/3508-Switch-Floor-Mat-14-Inches-x-30-Inches.aspx
Magnets
Reed
Hall Effect
These are sensors that detect the presence of a magnetic field. They are used, for instance, on bicycles to count revolutions of the wheel as the magnet passes by.
Keyboard
Most microcontrollers only have 8 or less inputs. But it is possible to get many more than that by fooling your computer into thinking it is talking to a standard keyboard when it is actually talking to your switch inputs. This works by plugging a special interface into your USB port that appears to the computer to be a standard keyboard. Your software then simply listens for KeyPress events. You could hack a USB keyboard, or you can buy a special interface here:
http://www.ultimarc.com/ipacve.html
Tutorial on how to use this with Flash: http://hci.stanford.edu/cs247/2008/tutorials/ipac/
Motion
Motion sensors detect the motion of a heated object (typically a person) in a room, typically very wide angle. Not to be confused with proximity sensors, which measure the distance of a thing from a position in a room.
http://www.makingthings.com/store/sensors/motion-sensor.html
Last modified July 6th, 2010
