Chapter 2 - Sensors Actuators Microcontrollers.pptx

Transducer
a device that converts a primary form of energy into a corresponding signal with a different energy form
Primary Energy Forms: mechanical, thermal, electromagnetic, optical, chemical, etc.
take form of a sensor or an actuator
Sensor (e.g., thermometer)
a device that detects/measures a signal or stimulus
acquires information from the “real world”
Actuator (e.g., heater)
a device that generates a signal or stimulus

Four major classes of sensors:
Tactile (contact - limit switches)
Proximity & Range (non-contact)
Vision (recognition, orientation)
Miscellaneous (temp, pressure, strain)

Two types of sensors:
Analog (continuous physical quantity)
Digital (discrete physical quantity)

1. Sensors, Actuators and Microcontrollers

2. Definitions Transducer a device that converts a primary form of energy into a corresponding signal with a different energy form Primary Energy Forms : mechanical, thermal, electromagnetic, optical, chemical, etc. take form of a sensor or an actuator Sensor (e.g., thermometer) a device that detects/measures a signal or stimulus acquires information from the “real world” Actuator (e.g., heater) a device that generates a signal or stimulus real world sensor actuator intelligent feedback system

3. Sensor Systems Typically interested in electronic sensor convert desired parameter into electrically measurable signal General Electronic Sensor primary transducer : changes “real world” parameter into electrical signal secondary transducer : converts electrical signal into analog or digital values Typical Electronic Sensor System usable values real world analog signal primary transducer secondary transducer sensor sensor input signal ( measurand ) microcontroller signal processing communication sensor data analog/digital network display

4. Computer-Process Interface To implement process control, the computer must collect data from and transmit signals to the production process Components required to implement the interface: Sensors to measure continuous and discrete process variables Actuators to drive continuous and discrete process parameters Devices for ADC and DAC I/O devices for discrete data

5. Computer Process Control System Actuators Computer Controller Transformation Process Sensors DAC ADC Input Devices Output Devices Continuous and Discrete Variables Continuous and Discrete Parameters

6. Sensors Physical Medium Sensing Element Conditioning Target Handling Temperature Resistance Voltage Information Transducers Micro-sensors 10 -6 m Stimulus (s) Signal (S)

7. Transfer Function where S = output signal; s = stimulus; and f(s) = functional relationship For binary sensors: S = 1 if s > 0 and S = 0 if s < 0. The ideal functional form for an analogue measuring device is a simple proportional relationship, such as: where C = output value at a stimulus value of zero and m = constant of proportionality (sensitivity)

8. Example The output voltage of a particular thermocouple sensor is registered to be 42.3 mV at temperature 105  C. It had previously been set to emit a zero voltage at 0  C. Since an output/input relationship exists between the two temperatures, determine (1) the transfer function of the thermocouple, and (2) the temperature corresponding to a voltage output of 15.8 mV.

9. Solution 42.3 mV = 0 + m (105  C) = m (105  C) or m = 0.4 028571429   S = 0.4 (s)    15.8 mV = 0.4 (s)  15.8 / 0.4 = s  s = 39.22  C

10. Classes & Types of Sensors Four major classes of sensors: Tactile (contact - limit switches) Proximity & Range (non-contact) Vision (recognition, orientation) Miscellaneous (temp, pressure, strain) Two types of sensors: Analog (continuous physical quantity) Digital (discrete physical quantity)

11. Examples Position Limit switches ac/dc current location Potentiometers dc voltage angular / linear Resolvers ac voltage phase shift angular Encoders ac/dc current angular / linear location Incremental / Absolute Velocity Tachometer Analog dc voltage angular velocity Digital pulse frequency angular / linear velocity Temperature Capacitive Resistive Thermistors Pressure Piezo-electric Resistive

12. Examples Transducers ADCs - Analog to Digital Converters DACs - Digital to Analog Converters Frequency to Voltage Converters Voltage to Frequency Converters Analyzers Counters Timers Computers Ultra-Sonics Radar distance frequency shift Vision Systems

13. Contact and non-contact sensors Contact sensor: a sensor that requires physical contact with the stimulus. Examples: strain gauges, most temperature sensors Non-contact sensor: requires no physical contact. Examples: most optical and magnetic sensors, infrared thermometers, etc.

14. Absolute and relative sensors Absolute sensor: a sensor that reacts to a stimulus on an absolute scale: Thermistors, strain gauges, etc., (thermistor will always read the absolute temperature) Relative scale: The stimulus is sensed relative to a fixed or variable reference. Thermocouple measures the temperature difference, pressure is often measured relative to atmospheric pressure.

15. Other schemes Classification by broad area of detection Electric sensors Magnetic Electromagnetic Acoustic Chemical Optical Heat, Temperature Mechanical Radiation Biological Etc.

16. Other schemes (cont.) Classification by physical law Photoelectric Magnetoelectric Thermoelectric Photoconductive Magnitostrictive Electrostrictive Photomagnetic Thermoelastic Thermomagnetic Thermooptic Electrochermical Magnetoresistive Photoelastic Etc.

17. Other schemes (cont.) Classification by specifications Accuracy Sensitivity Stability Response time Hysteresis Frequency response Input (stimulus) range Resolution Linearity Hardness (to environmental conditions, etc.) Cost Size, weight, Construction materials Operating temperature Etc.

18. Other schemes (cont.) Classification by area of application Consumer products Military applications Infrastructure Energy Heat Manufacturing Transportation Automotive Avionic Marine Space Scientific Etc.

19. Primary Transducers Transducer A device that converts energy of one form into energy of another form. Conventional Transducers large, but generally reliable, based on older technology thermocouple: temperature difference compass (magnetic): direction Microelectronic Sensors millimeter sized, highly sensitive, less robust photodiode/phototransistor: photon energy (light) infrared detectors, proximity/intrusion alarms piezoresisitve pressure sensor: air/fluid pressure microaccelerometers : vibration, ∆ -velocity (car crash) chemical sensors: O 2 , CO 2 , Cl , Nitrates (explosives) DNA arrays: match DNA sequences

20. Actuators Hardware devices that convert a controller command signal into a change in a physical parameter The change is usually mechanical (e.g., position or velocity) An actuator is also a transducer because it changes one type of physical quantity into some alternative form An actuator is usually activated by a low-level command signal, so an amplifier may be required to provide sufficient power to drive the actuator

21. Actuators Signal Processing & Amplification Mechanism Electric Hydraulic Pneumatic Final Actuation Element Actuator Sensor Logical Signal

22. Classification of actuators Classification of actuators by type of motion Linear Rotary One-axis Two-axes Three-axes Etc.

23. Types of Actuators Electrical actuators Electric motors DC servomotors AC motors Stepper motors Solenoids Hydraulic actuators Use hydraulic fluid to amplify the controller command signal Pneumatic actuators Use compressed air as the driving force

24. Actuators Linear Action: Stroke Length Cylinders: Hydraulic High force (1000 psi, typical) Low to medium speed Leaks, noise, bulk, cost Pneumatic Medium force (100 psi, typical) High speed Noise; intermediate mess, bulk & cost Solenoids (Electromagnetic) : Low force (< 1 lbf , typical) Medium speed Quiet, clean, small, cheap Linear Slides (Electro-mechanical) Medium Force (50 – 400 lbf ) Low to medium speed Quiet, clean, medium size & cost

25. Rotary Actuators (Drives) Rotary Action (may be converted to linear): Motors Hydraulic (rotary vanes) High power Low to medium speed, medium precision Leaks, noise, bulk, cost Pneumatic (rotary vanes) Medium power High speed, low precision Noise; intermediate mess, bulk & cost Electric Low power Medium speed, high precision Quiet, clean, small, cheap

26. Electric Motors Stepper Motors DC pulses result in fixed angular motion Pairs of coils activated Lower speed (to avoid ringing) Lower power & holding torque

27. Diff. Amp. Electric Motors Servo Motors Require feedback to operate (tachometer) AC speed controlled by the frequency of the power supplied to the motor more powerful DC speed controlled by the magnitude of the voltage supplied to the motor holding torque Velocity In Feedback Tachometer Motor Shaft + –

28. Stepper motor and Servomotor

29. Motion Control Hard Automation Mechanical Cams: Shape of the cam determines motion of the follower “Reprogrammed” by changing out the cams Examples: Automatic screw machines, gun stocks Mechanical Stops: Range of motion is limited by stops “Reprogrammed” by changing the position of the stops Examples: Pneumatic “bang-bang robots” Cam Follower Piston Cylinder Stops

30. Motion Control Point to Point Starting and ending points are given, but the path between them is not controlled Advantage: simple, inexpensive controller Example: Peck drilling

31. Motion Control Continuous Path Both endpoints and the path between them are controlled Advantage: complex shape capability Example: NC contouring

32. Connecting Sensors to Microcontrollers Analog many microcontrollers have a built-in A/D 8-bit to 12-bit common many have multi-channel A/D inputs Digital serial I/O use serial I/O port, store in memory to analyze synchronous (with clock) must match byte format, stop/start bits, parity check, etc. asynchronous (no clock): more common for comm. than data must match baud rate and bit width, transmission protocol, etc. frequency encoded use timing port, measure pulse width or pulse frequency µ C signal timing memory keypad sensor sensor display instrument

33. Connecting Smart Sensors to PC/Network “ Smart sensor ” = sensor with built-in signal processing & communication e.g., combining a “dumb sensor” and a microcontroller Data Acquisition Cards (DAQ) PC card with analog and digital I/O interface through LabVIEW or user-generated code Communication Links Common for Sensors asynchronous serial comm. universal asynchronous receive and transmit (UART) 1 receive line + 1 transmit line. nodes must match baud rate & protocol RS232 Serial Port on PCs uses UART format (but at +/- 12V) can buy a chip to convert from UART to RS232 synchronous serial comm. serial peripheral interface (SPI) 1 clock + 1 bidirectional data + 1 chip select/enable I 2 C = Inter Integrated Circuit bus designed by Philips for comm. inside TVs, used in several commercial sensor systems IEEE P1451: Sensor Comm. Standard several different sensor comm. protocols for different applications

34. Sensor Calibration Sensors can exhibit non-ideal effects offset : nominal output ≠ nominal parameter value nonlinearity : output not linear with parameter changes cross parameter sensitivity : secondary output variation with, e.g., temperature Calibration = adjusting output to match parameter analog signal conditioning look-up table digital calibration T = a + bV +cV 2 , T= temperature; V=sensor voltage; a,b,c = calibration coefficients Compensation remove secondary sensitivities must have sensitivities characterized can remove with polynomial evaluation P = a + bV + cT + dVT + e V 2 , where P=pressure, T=temperature T1 T2 T3 offset linear non-linear

35. An embedded microcontroller is a chip which is a computer processor with all it’s support functions (clocking and reset), memory, and i/O built into the device. Power dist Control store Reset control Clock and timing RAM Microcontroller block diagram Microcontrollers

36. CPU Memory Peripherals 36 PC vs Microcontroller

37. Microcontroller architecture 37

38. Comparing µC with µP General-purpose microprocessors contains No RAM No ROM No I/O ports Microcontroller has CPU (microprocessor) RAM ROM I/O ports Timer ADC and other peripherals Have the advantage of versatility on the amount of RAM, ROM, and I/O ports The fixed amount of on-chip ROM, RAM, and number of I/O ports and less computing power; suitable for very specific purpose with much less cost.

39. 39 CPU General-Purpose Micro-processor RAM ROM I/O Port Timer Serial COM Port Data Bus Address Bus General-purpose microprocessor: CPU for Computers Commonly no RAM, ROM, I/O on CPU chip itself Many chips on motherboard

40. 40 RAM ROM I/O Port Timer Serial COM Port Microcontroller CPU A single-chip computer On-chip RAM, ROM, I/O ports... Example ： Motorola’s 6811, Intel’s 8051, Zilog’s Z8 and PIC 16X A single chip Microcontroller :

41. 41 Microprocessor CPU is stand-alone, RAM, ROM, I/O, timer are separate designer can decide on the amount of ROM, RAM and I/O ports. expensive versatility general-purpose High processing power High power consumption Instruction sets focus on processing-intensive operations Typically 32/64 – bit Typically deep pipeline (5-20 stages) Microcontroller CPU, RAM, ROM, I/O and timer are all on a single chip fixed amount of on-chip ROM, RAM, I/O ports for applications in which cost, power and space are critical single-purpose (control-oriented) Low processing power Low power consumption Bit-level operations Instruction sets focus on control and bit-level operations Typically 8/16 bit Typically single-cycle/two-stage pipeline Microprocessor vs. Microcontroller

42. Embedded System General Block Diagram Microcontroller (uC) sensor sensor sensor Sensor conditioning Output interfaces actuator indicator

43. Microcontroller Architectures CPU Program + Data Address Bus Data Bus Memory Von Neumann Architecture CPU Program Address Bus Data Bus Harvard Architecture Memory Data Address Bus Fetch Bus 2 n

44. Microcontroller Architectures

45. Microcontroller Architectures CISC versus RISC RISC stands for “Reduced Instruction Set Computers”. Instructions are as bare a minimum as possible to allow users to design their own operations. CISC stands for “Complex Instruction Set Computers”. Large number of instructions, each carrying out a different permutation of the same operation. MCs with Harvard architecture are called "RISC MCs". MCs with von-Neumann's architecture are called 'CISC microcontrollers'. Harvard architecture is a newer concept than von-Neumann's. In Harvard architecture, data bus and address bus are separate. Thus a greater flow of data is possible through the CPU, and of course, a greater speed of work.

46. Microcontroller Families Zilog Z8 series Arm 32 bit microcontrollers MicroChip – PIC microcontrollers Intel 8051 series The 8051 family has the largest number of diversified (multiple source) suppliers: Intel (original) Atmel Philips/ Signetics AMD Infineon (formerly Siemens) Matra Dallas Semiconductor/Maxim

47. Common Microcontrollers Atmel ARM Intel 8-bit 8XC42 MCS48 MCS51 8xC251 16-bit MCS96 MXS296 National Semiconductor COP8 Microchip 12-bit instruction PIC 14-bit instruction PIC PIC16F84 16-bit instruction PIC NEC Motorola 8-bit 68HC05 68HC08 68HC11 16-bit 68HC12 68HC16 32-bit 683xx Texas Instruments TMS370 , 16/32 bit MSP430 , 16 bit Zilog Z8 Z86E02

48. 8051 µC features Intel introduced 8051, referred as MCS-51, in 1981 The 8051 is an 8-bit processor The CPU can work on only 8 bits of data at a time 1 to 16 MHz clock The 8051 has 128 bytes of RAM 4K bytes of on-chip ROM Two timers One serial port Four I/O ports, each 8 bits wide 2 external and 3 internal interrupt sources

49. 8051 µC features 8051 instruction cycle consists of 12 clock cycles. Application should be run using slower clock speed to reduce power consumption. Dallas version of 8051 is 87C51 has EPROM as control store and CMOS device: 24Mhz 12 cycle per instruction 4Kbyte of Control stote 128 bytes of RAM 32 I/O lines Two 8/16-bit times Multiple internal and external interrupts sources Programmable serial ports Interface upto 128Kbytes of external memory

50. 8051 Block Diagram oscillator 4K Prog Memory 128 B RAM 2 16-bit timers/ counter 8051 CPU 64K bus expansion control I/O ports Serial port/ UART Frequency Reference interrupt interrupt control Ports/IO/ ADD/Data bus Tx Rx counters

51. On-Chip Facilities Overview (Original 8051) Parallel Input/Output Ports System Clock Generator Serial Port Timers Interrupt Control

52. Parallel I/O Ports Port0 latch Port1 latch Port2 latch Port3 latch Port0 Port1 Port2 Port3 Each port can be input or output Direction is set in Special Function Registers (SFR)

53. System Clock Generator Input circuit 8051 sysclk Original 8051 uses 12 sysclk cycles per “machine cycle” External crystal oscillator

54. Serial Port Universal Asynchronous Receiver-Transmitter (UART) Serial Port TX (transmit) RX (receive) Data sent and received serially BAUD rate must agree between sender and receiver (The  baud rate  is a measure of the number of bits per second that can be transmitted or received by the UART) Transmission modes selected using Special Function Register (SFR) Original 8051 had one serial port

55. Internal Timers Original 8051 has 2 timers 16 bits TH0 : TL0 Timer 0 16 bits TH1 : TL1 Timer 1 Timers increment on each system clock Timer registers (TH0, TL0, TH1, TL1) can be read or written to Timer overflow can cause “interrupts” or set SFR bits high

56. Microcontroller Memory ROM is a type of memory that does not lose its contents when the power is turned off. For this reason, ROM is also called non volatile memory. There are different types of read-only memory, such as  PROM (Programmable ROM) – Can be programmed once. Cannot be changed once you programmed it. EPROM (Erasable Programmable ROM) – Can be reprogramed by erasing the content on it – exposing to ultra-violet light. EEPROM (electrically erasable programmable ROM) - Can be reprogramed by erasing the content on it using electricity. Flash EPROM - When Flash memory's contents are erased (electrically), the entire device is erased, in contrast to EEPROM, where one can erase a desired byte.  Mask ROM - Mask ROM refers to a kind of ROM in which the contents are programmed by the IC manufacturer. In other words, it is not a user-programmable ROM. 

57. Microcontroller alternatives 58

58. IR Object Detector 59

59. Sonar Object Detector 60