1. Sensors
Sensing the real world
Sensors (v.1c)

2. Sensors Motion (Orientation/inclination )sensors Force/pressure/strain
Position
Temperature and humidity
Rotary position
Light and magnetic field sensors
Sensors (v.1c)

3. Motion (Orientation/inclination sensors
Acceleration
Gyroscope
Compass
Tilt Sensor
Sensors (v.1c)

4. Accelerometer http://en.wikipedia.org/wiki/Accelerometer
Functions:
measure acceleration in one or more directions, position can be deduced by integration.
Orientation sensing : tilt sensor
Vibration sensing
Methods:
Mass spring method ADXL78 (from Analog Device )
Air pocket method (MX2125)
Sensors (v.1c)

5. Mass spring type (output acceleration in G)
ADXL78 (from Analog Device )
Mass spring type (output acceleration in G)
Measure the capacitance to create output
Sensors (v.1c)

6. ADXL330 accelerometer for three (X,Y,Z ) directions http://www. analog
Sensors (v.1c)

7. 2D translational accelerometer MX2125 (from www.parallax.com)
Gas pocket type
When the sensor moves, the temperatures of the 4 sensors are used to evaluate the 2D accelerations
Sensors (v.1c)

8. Accelerometer demo: orientation sensing
Self-balance Robot
Sensor demo
Sensors (v.1c)

9. Accelerometer demo : Tilt sensing demo
Sensors (v.1c)

10. Gyroscopes http://en.wikipedia.org/wiki/Gyroscope
Measure rotational angle
Rate Gyroscope
measure the rate of rotation along 3-axes of X (pitch), Y (roll), and Z (yaw).
Modern implementations are using Microelectromechanical systems (MEMS) technologies.
Gyroscope
Sensors (v.1c)

11. Gyroscope to measure Rational acceleration ADXRS401 http://www. analog
FEATURES
Complete rate gyroscope on a single chip Microelectromechanical systems (MEMS)
Z-axis (yaw-rate) response
APPLICATIONS
GPS navigation systems
Image stabilization
Inertial measurement units
Platform stabilization
Sensors (v.1c)

12. Compass-- the Philips KMZ51 magnetic field sensor
50/60Hz (high) operation, a jitter of around 1.5°
Sensors (v.1c)

13. Using Gyroscope compass for virtual reality application in an iphone
Rate gyroscope demo
Using Gyroscope compass for virtual reality application in an iphone
Sensors (v.1c)

14. Application of motion sensors Self balancing robot
by Kelvin Ko
Motion sensors:
gyroscope and
accelerometer
20cm
35cm
Sensors (v.1c)

15. Complementary filter Since Combine two sensors to find output 15
Gyroscope
High frequency
Accelerometer
Low frequency
Sensors (v.1c) 15

16. Complementary filter θ=rotation angle, =filter time constant, s=laplace operator
Sensors (v.1c) 16

17. Self Balanced robot using complementary filter
Sensors (v.1c) 17

18. Tilt Sensor by OMRON http://rocky. digikey
Detect tilting 35 ~ 65 degrees in right-and-left inclination
Sensors (v.1c)

19. Force/pressure/strain
Force-sensitive resistor (FSR)
Strain gauge
Flexion
Air pressure
Sensors (v.1c)

20. Force Sensing Resistors http://www. interlinkelectronics
FSR402
Sensors (v.1c)

21. Force Sensing Resistor Demo
Sensors (v.1c)

22. Application for a walking robot
Sensors (v.1c)

23. Four sensors under the foot
Application of force sensing resistance sensors to balance a walking robot
Balancing
Floor tilled right
upper leg bend left
Floor tilled left
upper leg bend right
Neutral position
Four sensors under the foot
Sensors (v.1c)

24. Four Force sensors under the foot
Sensors (v.1c)

25. The Nao robot uses force feedback at its feet http://en. wikipedia
Sensors (v.1c)

26. Strain Gauge : Force sensors http://www. meas-spec
Piezoelectric crystal: produces a voltage that is proportional to force applied
Strain gauge: cemented on a rod. One end of the rod is fixed, force is applied to the other end. The resistance of the gauge will change with the force.
Sensors (v.1c)

27. Single element strain gauge
sensitive to temperature change. Vb
gauge
Gauge=R+R R
rod V0 R R
load
Sensors (v.1c)

28. Four-element (Wheatstone bridge) strain gauge sensor,
Four times more sensitive than single gauge system; not sensitive to temperature change.
All gauges have unstrained resistance R. t1 t2 Vb
t1=R+R
rod
b2=R-R V0 b1 b2
b1=R-R
t2=R+ R
load
Sensors (v.1c)

29. Flexion (bend) sensors
resistance:
10 KΩ (0°);
30-40 KΩ (90°)
Sensors (v.1c)

30. Felixon resistance Demo
Sensors (v.1c)

31. Air pressure sensor Measure up to 150 psi (pressure per square inch ).
Sensors (v.1c)

32. Position sensors Infra-red range sensor
Linear and Rotary position sensors
Sensors (v.1c)

33. The distance corresponds to the triangle formed.
Infra-red Range detectors by SHARP (4 to 30cm)
An emitter sends out light pulses. A small linear CCD array receives reflected light.
The distance corresponds to the triangle formed.
Sensors (v.1c)

34. IR radar using the Sharp range detector
Sensors (v.1c)

35. Position sensors, from[1]
Rotary Linear
Optical shaft encoder
Sensors (v.1c)

36. Magnetic rotary encoder (http://www. renishaw
non touch sensing
Sensors (v.1c)

37. Optical rotary encoder (http://en.wikipedia.org/wiki/Rotary_encoder)
The light received (on or off) will tell the rotation angle)
3 light receivers
Light paths
Rotation shaft
3 light emitters
Crank shaft sensor
Sensors (v.1c)

38. Temperature and humidity
Sensors (v.1c)

39. Temperature sensors LM135/235/335 features(from NS) http://www
Directly calibrated in °Kelvin
1°C initial accuracy available
Operates from 400 µA to 5 mA
Less than 1 Ohm dynamic impedance
Easily calibrated
Wide operating temperature range
200°C over range
Low cost
Sensors (v.1c)

40. Application note (connecting to an ADC e.g. ADC0820 or ADC0801)
Sensors (v.1c)

41. Capacitive Atmospheric Humidity Sensor http://rocky. digikey
BCcomponents %RH Dc
Sensors (v.1c)

42. Leaf Sensor Alerts When Plants Are Thirsty
Sensors (v.1c)

43. TSL250, TSL251, TSL252 LIGHT-TO-VOLTAGE OPTICAL SENSORS http://focus
Light-to-voltage optical sensors, each combining a photodiode and an amplifier (feedback resistor = 16 MW, 8 MW, and 2 MW respectively).
The output voltage is directly proportional to the light intensity on the photodiode.
Sensors (v.1c)

44. Cadmium Sulfoselenide (CdS) Photoconductive Photocells http://faculty
Light sensing using CdS
Sensors (v.1c)

45. Hall effect Sensors for sensing magnetic flux“B field”, see:
Sensors (v.1c)

46. Magnetic levitation Train Model
Application on Magnetic levitation 磁懸浮
Magnetic levitation Train Model
磁懸浮火車
frog levitation
Sensors (v.1c)

47. Hall effect sensors and brushless DC motors
Is it using Hall effect sensor? Don't known.
Sensors (v.1c)

48. Novel sensors Kinect http://www.ladyada.net/learn/diykinect/
Sensors (v.1c)

49. Many KINECT DIY projects
Sensors (v.1c)

50. Control systems Example: A temperature control system
Sensors (v.1c)

51. Control example: Temperature control system
computer
Digital control
circuit
Timer
Water tank
Temp.
Sensor
CPU
Sample
&
Hold
A/D
Instrum.
amp.
Pulse Width
modulation
& solid state relay
Heater
D/A
Sensors (v.1c)

52. Temperature control method 1: ON-Off (bang-bang) control (poor)
Easy to implement, bad control result -- contains overshoot undershot. Algorithm for on-off-control:
Loop forever: If (Tfrom_sensor > Treq required temperature)
then (heater off )
else (heater on).
Overshoot
Treq
Steady state error
Undershoot
Temp
On-off control result
Time
Sensors (v.1c)

53. Proportional, differential, integral
Temperature control method 2 : Proportional-integral-differential (PID) temperature control (good)
Init. (set required temperature Treq)
Loop forever{
get temperature T from sensor,
e=T - Treq
then Tw =e*G*{Kp+Kd*[d(e)/dt] +Ki*e dt }
else
} //G,Kp,Kd,Ki can be adjusted by user Tw
Proportional, differential, integral
Sensors (v.1c) Tw

54. PID block diagram http://www.controlviews.com/question12-12-03.html Kd
                                                                                                      
Figure 1 - Parallel PID block diagram Kd Kp Ki
Sensors (v.1c)

55. PID control using pulse width modulation PWM
Tw (depends on e )
Time
Fixed period and fixed number of pulses
Temperature
On-off control: oscillates and unstable
Treq
PID control result
of method 2
Time
Sensors (v.1c)

56. Summary Studied the characteristics of various sensors
and their applications
Sensors (v.1c)

57. References
[1] S.E. Derenzo, Interfacing -- A laboratory approach using the microcomputer for instrumentation, data analysis and control prentice hall.
[2] D.A. Protopapas, Microcomputer hardware design, Prentice hall
[3] CUHK_FYP report HML0602, KHW0703
[4]
[5]
Sensors (v.1c)