1. [HW] 2015 – sensors purpose of a sensor:
convert a state or change in the physical world into an electrical signal

2. some sensible phenomena
light – smoke – sound frequency – sound level – color – flow – identity – proximity – bending – movement – position – distance – conductance – temperature – tilt – vibration – direction – gravity – heartbeat – voltage – taste – speed – magnetic field – rotation – time elapsed – current – acceleration – fluid level – touch – force – gas presence – humidity – barometric pressure – air pressure – proximity – gesture – capacity – angle – presence – orientation – balance – air pressure

3. operating principles electromechanical on/off or rotary switch
reed relay
bi-metal
resistive
temperature (ntc, ptc)
light (LDR)
pressure / force (FSR)
angle (potentiometer)
fluid level
inductive
rotation
ac current
sound (dynamic microphone)

4. operating principles (2)
optical
infrared (passive = object radiation / active = beam) IR sensor
light barrier – laser - lamp/LED - photodiode
distance – US, IR
camera, kinect
light (intensity, color)
capacitive
moist
distance / proximity
acceleration
hall effect
magnetic field, movement, distance
compass, orientation
electromechanical
pressure
flow

5. how to read the sensor: communication
simple interfaces
discrete voltage (on/off)
analog: voltage level that reflects the physical situation
time – duration – frequency
capacity (charge time, frequency)
resistance
more complex: use a protocol
asynchronous serial (RS232, RS485, USB, MIDI)
clocked serial (e.g. SPI)
I2C
1wire
CAN

6. sensor behaviour: static or dynamic
dynamic: reacts to a change in the situation only static: continuously reflects the actual situation to adapt or to be actual detecting people in a room: - infrared (burglar alarm) - camera + background substraction

7. movement: toggle, rocker- or slide switch

8. momentary /touch button

9. micro switch – well defined switching point
reed switch – requires no physical contact

11. angular movement: potentiometer

12. infrared: light barrier

13. passive infrared (pir)

14. radar

15. acceleration / gravitation

20. angular movement: gyroscope, compass

21. pressure: force sensitive resistor (FSR)

22. pressure: flex sensor

23. distance - ultrasonic

25. using a cheap ultrasound sensor

26. Fritzing example
Arduino code
smoothing with Puredata

27. distance: infrared (angle)

29. Sharp GP2Y0A21 output voltage / distance

30. distance: capacitative (proximity)

31. touch: capacitative Arduino/Processing: ‘touché’
arduino theremin
arduino cap sensor

32. touch key sensor: Atmel QT1010

33. temperature: bimetal switch

34. temperature: resistor, PTC

35. light dependent resistor (LDR)
photo transistor
light dependent resistor (LDR)

36. LDR

37. color
Taos TCS230 / TCS3200

38. color
Adafruit Flora Color Sensor w. TCS V (!?) I2C interface

39. color

40. sound: electret microphone
mic output level: max 1 mV
arduino input level: 5 V = 5000 mV

41. sound: connecting audio to Arduino
line level ( V)
microphone level (0.5mV AC)

42. sound: piezo element