Electronic Instrumentation Sensors and Actuators

Transcription

1 Electronic Instrumentation Sensors and Actuators * In this presentation definitions and examples from Wikipedia, HowStaffWorks and some other sources were used Lecturer: Dr. Samuel Kosolapov

2 Items to be defined/refreshed/discussed Volt-Ampere Characteristics Voltage and Current Sources Black Box Concept Sensors & Actuators 2

3 V-A (Volt-Ampere) Characteristics Linear V-A Characteristic: Example: Resistor: Ohm law: Line I EE will say: V-A Characteristic; But Graph is I as a function of V Line slope is G= 1/R #1 V 3

4 Nonlinear V-A Characteristic: Example: Zener diode 4

5 DC Ideal Voltage Source: definition & symbol Voltage (Amplitude) is constant (Independent on LOAD connected) The following symbol will be used for DC + Friendly name Voltage 5

6 AC (and DC) Ideal Voltage Source: definition & symbol Voltage (Amplitude) is constant (Independent on LOAD connected) The following symbol will be used as for DC as for AC. AC Amplitude Vo Or V(t) or V(s) DC Amplitude (Shift, Offset, Bias) 1Vac 0Vdc V1 Friendly name + Not always seen on printed exam 6

7 AC (and DC) Ideal Voltage Source: definition & symbol Voltage (Amplitude) is constant (Independent on LOAD connected) Multisim 11 provides a number of options Multisim 11 Signal Voltage Source AC_Voltage Peak value is used Multisim 11 Power Sources AC_Voltage RMS value is used 7

8 Ideal Voltage Source: usage Voltage (Amplitude) is constant (Independent on LOAD connected) The following EWB symbol will ALSO be used as for DC as for AC. (EWB): RMS Value sometimes specified (not so good for us) Q1. What is the voltage on the Load? A1: 1V Q2. And if Rload = 1 W? A2: 1V 8

9 Ideal Voltage Source: V-A Characteristics Voltage (Amplitude) is constant (Independent on LOAD connected) V(Rload) = V(I) = Vo = const I Line slope is INFINITY Vo = const V 9

10 Ideal Current Source: Definition & Symbol Current in the LOAD (Amplitude) is constant (Independent on LOAD connected) The following symbol will be used as for DC as for AC. (Schematics, Multisim): Peak Value specified This + Is misleading Arrow direction will be used in the node equations I1 0Adc Friendly name Amplitude Io Or I(t) or I(s) EWB Multisim 11 Misleading + is omitted 10

11 Ideal Current Source: Usage & V-A Characteristics Current in the LOAD (Amplitude) is constant (Independent on LOAD connected) I(Rload) = I(V) = Io = const I Is=Io = const Line slope is 0 V 11

12 Practical Voltage & Current sources Thevenin Model Norton Model Rs internal resistance of the Voltage (or Current) Source I S V R S S V S R S I S #1 Practical Voltage Source may be converted to the Practical Current Source (and vice versa). We ll convert Practical Voltage Source to Practical Current Source and back whenever it is convenient. 12

13 V-A Characteristics of Practical Voltage Source (Ideal Voltage Source: tg(a) = INFINITY) I Line Slope: tg(a) = 1/Rs Vs V 13

14 V-A Characteristics of Practical Current Source (Ideal Current Source: tg(a) = 0) I Is Line Slope: tg(a) = 1/Rs V 14

15 Q: Voltage or Current Source? Theoretical answer: both (because conversion can be made) Practical Answer: depending on LOAD. V if if I LOAD S R R I R LOAD VS RS R LOAD R then V LOAD LOAD LOAD R V R S S S S then: ; LOAD I S I V S LOAD R S VS R ( no dependence on no dependence on R Current Source LOAD LOAD R LOAD ) Voltage Source 15

16 Practical Voltage Source: Parameters Example: Electrochemical Battery Electrochemical Battery constant DC voltage source Minimal Set of Parameters: Vs = 1.5 V (EMF) Rs ~ 2 W : depending on sizes!!! (AA, AAA), aging: Rs grows, Rs is small Electrochemical Battery is mostly referenced as Voltage Source. Reminder: small is comparing to the LOAD Vs is constant (slowly fades during battery aging) Real battery has many properties Simple battery model Has only two parameters Other parameters: battery capacity (Ampere x Hours), weight, color, company name, price Q1. Voltmeter is connected to AA battery and shows V=1.5 V. Can one claim: the battery is good? 16

17 Voltage or Current Source: Example: Hadera Power Station AC Power Generator Sine Wave Vs = 220 V (RMS) (Peak Voltage is ~325 V) f = 50 Hz ( V, 60 Hz in USA) Rs MUST be very close to ZERO (otherwise voltage in the house will go down), mostly VOLTAGE SOURCE Q: Why sometimes brightness of the lamp is visibly changed? Simple Model of Hadera Power Station Rs ~ 0 17

18 Voltage or Current Source: Example: Laboratory DC Power Supply Laboratory (stabilized) DC power supply. Q1. Why so expensive? (~ 1000 NIS) Q2. Parameters? Q3: Why 2 (independent) departments? Q4: Why and How and for What reason EE must to restrict current at the beginning of the lab? 18

19 Practical or Ideal Voltage Source? V1 and V2 are Ideal Voltage Sources. V1=10V, V2 = 5V. Q1: Vx =? A1:. Important part of solving Electronics problem is to NEGLECT some elements of the circuit. Be careful. Think when stop neglecting. 19

20 Reminder (Deterministic) Black Box Concept Input Signal X(t) Black Box (Color of the Box is not important) Output Signal Y(t) Internal Structure & Practical Implementation (of the Black Box) is not known (or not important), but IF the same Input signal X(t) (say, sin wave) is applied to the input, THEN the same Output signal Y(t) (say, triangle wave) always appears on the output 20

21 Black Box Example: Voltage Divider Black Box Implementation A Implementation B 21

22 Black Box Example: Voltage Divider Q1: Is internal design really important here? A: Depending who is asked: EE: No. Implementation A and B behave ELECTRONICALLY the same way Mechanical Engineer: Implementation B requires more room Sales Manager: Implementation B is more expensive Quality control: More elements and connections less reliable 22

23 Reminder Black Box Concept Black Box Output Input Black Box Private cases of Black Box: Only Input (Signal) or only Output (Signal) 23

24 Black Box Example: Practical Voltage Source Black Box Output Load (Resistor) Electronically it is of no importance here what is internal design of the Ideal Voltage Source (while it is ideal ) 24

25 Reminder Mathematical Model (of the Black Box) MM is a description of the system (Black Box) using exact (mathematical!) language Practically, MM is a set of mathematical rules/equations describing SOME (but not ALL!!!) aspects of the system (Black Box) behavior. MM is a Rude Simplification of real object. Important: Non-relevant in THE current context staff is IGNORED BIG Question: Who, how and why decides what IS important and what is NOT Important: The same Black Box can be described by a different models of a different complexity level 25

26 Electrical Model & Equivalent Circuit (of the Black Box) EM: Set of electrical/electronic rules/equations EM: is Rude Simplification of real object: all non-electronics features are ignored EC: EQUIVALENT CIRCUIT: Visual presentation of the chosen math/electronic model as electrical circuit (by using standard symbols) Reminder: Real structure of the Black Box may be not known Models, Equivalent circuits are used mostly for calculations In this sense, one can replace Black Box to its equivalent circuit 26

27 Model Example: Voltage Divider V OUTPUT = V INPUT / 2 Math/Electrical Model Equivalent Circuit 27

28 Sensor: Definition Sensor: Converts SOME Energy (Signal) to ELECTRICAL Energy (Signal) Sensor in Electronics is SIGNAL SOURCE (Voltage/Current Source) To provide electric calculations: Sensor can be replaced by its BLACK BOX MODEL / Equivalent circuit Vs and/or Is and/or Rs are functions of time and some other parameters Input of sensor is some non-electrical signal, only output is drawn here 28

29 Sensors In the frames of FOURIER/LAPLACE approach Vs and Is are COMPLEX AMPLITUDES / MAGNITUDES on some frequency w or s. Any signal Vs(t) is treated as DC (Voltage/Current) source! Resistance may be complex (Zs instead of Rs). Only (complex) amplitudes are used in all intermediate calculations. Finally: Sensor (Signal Source) is characterized by: 1. Its SPECTRUM (Amplitude as function of frequency) 2. Its (equivalent / internal) resistance/impedance. 29

30 Actuator (broad definition) Actuator: Converts ELECTRICAL Energy (Signal) to SOME Energy (Signal) Actuator in Electronics is LOAD resistor (complex resistance - impedance) To provide calculations: Actuator can be replaced by its BLACK BOX MODEL / Equivalent circuit: Finally: Actuator is characterized by its (equivalent) resistance or impedance. Output of actuator is some non-electrical signal, only input is drawn here 30

31 Sensor Example: Outdated Carbon Microphone Sensor: Carbon (Granular) Resistance Microphone Carbon microphone - The oldest and simplest microphone uses carbon dust. This is the technology used in the first telephones and is still (?) used in some telephones today. The carbon dust has a thin metal or plastic diaphragm on one side. As sound waves hit the diaphragm, they compress the carbon dust, which changes its resistance. By running a current through the carbon, the changing resistance changes the amount of current that flows. Google How Telephones Work for more information. Usage & Parameters: External Battery & Resistor needed ( ~ 12 V), ( Rs ~ 100 W ). 31

32 Sensor: Usage Example Real structure Black Box Equivalent Circuit of the Carbon Microphone Real physical structure of the carbon microphone Real appearance of the carbon microphone Black Box for user Equivalent circuit of Carbon Microphone (Including Support Battery and resistor) Q: Develop Thevenin equivalent 32

33 Actuator Example Electromagnetic (Dynamic, Moving-Coil ) earphone ( R LOAD ~ 75W.. 1 kw ) 33

34 Actuator Example Electromagnetic (Dynamic, Moving Coil ) speaker ( R LOAD ~ 7 W ) 34

35 Sensor & Actuator Usage Example Simple Home Telephone System: Sensor: Carbon (Granular) Resistance Microphone (with battery!) Actuator: Electromagnetic (Dynamic) earphone PRACTICAL TELEPHONE - View from the CUSTOMER s point of view 35

36 Analog Sensor & Actuator Usage Example Simple Home Telephone System: Warning: Long distance telephone: Line (Wire) must be replaced to R LINE Attenuation (Speak in a loud voice) After replacement one can make electrical calculations External Battery is DC Battery. But starting from ~ 1920 HF Telephones were developed to prevent sniffing. Story about Stalin and Bazhanov 36

37 Sensor Example: Condenser Microphone A condenser microphone is essentially a capacitor, one plate of the capacitor moving in response to sound waves. The movement changes the capacitance of the capacitor Condenser microphones usually need a small battery to provide a voltage across the capacitor. Discuss properties in the frames of box model This is why You learn physics M And solve dull problems with capacitors Q: Can anyone write relevant equations Explaining Condenser Microphone operation? 37

38 Sensor Example. Electret Microphone Unlike other condenser microphones electret types require no polarizing voltage, but they normally contain an integrated preamplifier which does require a small amount of power An electret is a stable dielectric material with a permanently-embedded static electric charge (which, due to the high resistance and chemical stability of the material, will not decay for hundreds of years). 38

39 Standard Electret Microphone with Arduino Preamplifier is not enough!!! Envelope Detector int sensorvalue; void setup() { Serial.begin(9600); // sets the serial port to 9600 } void loop() { sensorvalue = analogread(0); // read analog input pin 0 Serial.println(sensorValue, DEC); // prints the value read delay(100); // wait 100ms for next reading } 39

40 Arduino Microphone sound sensor module Details of operation: see: KY-038 Microphone Sensor KY-037 Sensitive Microphone Sensor The only difference is KY-037 has High sensitivity 40

41 KY-038/KY-037 Microphone sound sensor module Microphone here is connected without Capacitor LM393 is a voltage comparator. When the voltage of in-phase terminal (pin 3) is higher than that of the inverting terminal (pin 2), output terminal (pin 1) will output high. Otherwise, it outputs low. First, adjust potentiometer to make the voltage for pin 2 of LM393 less than 5V. (LED2 will be OFF) When microphone detects sound output of comparator is HIGH and LED2 is ON Demonstrate with +5V and GND (without Arduino) 41

42 Arduino KY-038 Microphone sound sensor module For sound detection Module has two outputs: 1. AO, analog output, real-time output voltage signal of the microphone 2. DO, when the sound intensity reaches a certain threshold, the output is high (threshold can be adjusted by potentiometer) Connecting to the Arduino Pin + to Arduino 5+ Pin to Arduino Pin A0 to Arduino A0 (for analog program) Pin D0 to Arduino 13 (for digital program) 42

43 Arduino KY-038 Microphone sound sensor module Example code: Digital output int Led = 13 ;// define LED Interface int dpin = 3; // define D0 Sensor Interface int val = 0;// define numeric variable value void setup () { pinmode (Led, OUTPUT) ;// LED will blink pinmode (dpin, INPUT) ;// D0 of sensor } void loop () { val = digitalread(dpin); if (val == HIGH) // If the module detects a sound { digitalwrite (Led, HIGH); // LED13 on } else { digitalwrite (Led, LOW); // LED13 off } } Usage of Analog output will be demonstrated later 43

44 Arduino KY-013 Analog Temperature Sensor (NTC Thermistor) Thermistor resistance is changed with temperature Temperature range: 55 C / +125 C Accuracy: + / 0.5 C Real-life specification of thermistors will be discussed later Meanwhile, see Wikipedia for details Arduino pin analoog A0 -> module S (Signal) Arduino pin GND -> module - Arduino pin 5+ > middle pin 5V KY-013 additionally contains 10 k resistor, so that all the module operates as a plain voltage divider 44

45 Arduino KY-013 Analog Temperature Sensor (NTC Thermistor) #include <math.h> int sensorpin = A0; // select the input pin for the potentiometer double Thermistor(int RawADC) { double Temp; Temp = log( *((1024.0/rawadc 1))); Temp = 1 / ( ( ( * Temp * Temp ))* Temp ); Temp = Temp ; // Convert Kelvin to Celcius //Temp = (Temp * 9.0)/ ; // Convert Celcius to Fahrenheit return Temp; } 45

46 Arduino KY-013 Analog Temperature Sensor (NTC Thermistor) void setup() { Serial.begin(9600); } void loop() { int readval=analogread(sensorpin); double temp = Thermistor(readVal); Serial.println(temp); // display tempature //Serial.println(readVal); // display tempature delay(500); } 46

47 Arduino KY-028 Temperature sensor module Additionally has comparator. Connect to 5V and GND. Rotate potentiometer until LED2 is OFF. Then heat by fingers LED2 will be ON. Code: trivial 47

48 Arduino KY-001 Temperature sensor module Contains specialized Dallas 18B20 module. Operation includes 1-wire protocol will be discussed later 48

49 Sensor Example: Linear Temperature Sensor: LM35 (LM = National Semiconductor) Widely used in the student s projects to build digital thermometer. Black Box Model: Vsensor = 10*10-3 * T (Volt) T temperature in C 0 Only 2 out pins!!! Vs is not included!!! (Why?) 0 Vsensor Rsensor 0k 49

50 Arduino with LM35 Connection is trivial. Some calculations are needed 50

51 Arduino with LM35 int val; int temppin = 1; void setup() { Serial.begin(9600); } val = analogread(temppin); float mv = ( val/1024.0)*5000; float cel = mv/10; // float farh = (cel*9)/5 + 32; Serial.print("TEMPRATURE = "); Serial.print(cel); Serial.print("*C"); Serial.println(); delay(1000); 51

52 Sensor Example: Photo Diode Diode Non-Linear Device!!! Black-Box Model is not trivial Later Important to understand: Physics: Current is EXACTLY proportional the Light Intensity But Current is non-linear function of the Voltage (explain: photon, quantum yield) 52

53 Arduino KY-018 Photo resistor module Physical Operation and real-life parameters will be discussed later Arduino pin analoog A0 -> module S (Signal) Arduino pin GND -> module - Arduino pin 5+ > middle pin 5V KY-023 additionally contains 10 k resistor, so that all the module operates as a plain voltage divider Code is primitive 53

54 Actuator Example LED = Light Emission Diode LED (+ remote control for TV IR = Infra Red) Diode Non-Linear Device!!! Black-Box Model is not trivial Later Important to understand: Physics: Intensity is EXACTLY proportional to Current But Current is non-linear function of the Voltage 54

55 Sensor Example: MEMS accelerometer MEMS = Micro Electro Mechanical Systems Idea Design Device for amateurs Application for everyone Q1: Does EE needs Physics M to invent and design new devices? 55

56 Actuator Example MEMS Electrostatic Actuator : mirror Compact Imaging Device Model: Capacitor +? Explain how it works, why heavily heated Why do not start and stop Power when Projector was ON 56

57 Motivation Question Electronics today is mostly DIGITAL, But Sensors and Actuators in their nature are (mostly) ANALOG DEVICES! Question: How to connect these ANALOG devices to DIGITAL staff? Answer: EE must know as Analog Electronics as Digital Electronics to do that 57

58 Control Questions What have I learned? V-A characteristics Sensor and Actuator Concepts A number of real sensors and actuators examples 58

59 Literature to read 1. TBD 59