Electronic Systems Example: Thermo Warning Light

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1 Electronic Systems Example: Thermo Warning Light ENGG115 1 st Semester, 11 Dr. Kenneth KinYip Wong Course Topics High Level Today Applications Systems Digital Logic Circuits Image & Video Processing Computer & Embedded Systems Computer Network Mobile Network Combinational Logic Boolean Algebra Basic Circuit Theory Department of Electrical and Electronic Engineering Level Electrical Signals Voltage, Current Power & Energy 1st semester, 11 ENGG115 Dr. K. Wong Input Stage: Digital Systems Input Stage: Digital Systems Input Process Output Input Process Output Physical World Input Process Output Physical World Physical World Physical World, 5, 6, 7 7., 6.1, 4.8,.14, 5, 6, 7 7., 6.1, 4.8,.14 1st semester, 11 ENGG115 Dr. K. Wong 1st semester, 11 ENGG115 Dr. K. Wong 4 Analog to Digital Conversion The process of converting analog information into digital representation is referred as analog to digital conversion The circuit that performs the conversion is called an analog to digital convertor (). The reverse process is called digital to analog conversion, using a digital to analog convertor (). Today: We ll look at how to build a 1bit circuit Review of basic circuit design Extremely useful for project 1bit Recall that an converts (quantizes) an analog signal into digital representation An 1bit quantizes the analog input into a two possible comes hot VS cold analog signal is presented VS not presented input voltage is highehan certain value VS otherwise. Use a single binary bit to represent values In other word, an 1bit makes a binary decision ab the analog input. 1st semester, 11 ENGG115 Dr. K. Wong 5 1st semester, 11 ENGG115 Dr. K. Wong 6 1

1bit : logical design Essentially, an 1bit is a comparator Compares to a built in threshold Compares to a side input value An electronic implements this concept using electronic circuits 1bit (cont

2 1bit : logical design Essentially, an 1bit is a comparator Compares to a built in threshold Compares to a side input value An electronic implements this concept using electronic circuits 1bit (cont d) = 1 if > v t Threshold = 1 if > v ref v ref Comparator In the simplest case, an 1bit can be thought as a thresholding circuit, If the input voltage is highehan a builtin threshold v t, then the put is 1, otherwise the put is. In a slightly more elaborated design, an 1bit can be implemented as a comparator circuit that compares the value of the input to another reference input (v ref ). 1st semester, 11 ENGG115 Dr. K. Wong 7 1st semester, 11 ENGG115 Dr. K. Wong 8 Peeling an onion I/O Characteristics of 1bit 1 or 1 layer down v ref 1 or Note that what we have done so far was indeed gradually unveiling the inner details of an From the abstract t concept of analogtodigital it l conversion, we are moving downward to unveil more implementation details with the underlying circuits A thresholding or comparator circuit v ref time Next: What are those 1 s and s? 1st semester, 11 ENGG115 Dr. K. Wong 9 1st semester, 11 ENGG115 Dr. K. Wong 1 Implementing Logic Levels The s and 1 s in previous slides are merely symbols to represent two logical states e.g. the value 1/, high/low, on/off, true/false, hot/cold In actual circuit implementations, these s and 1 s 1s are represented by the voltage (potential) presented at the put. NOTE: There are other circuit implementations that uses current at the put node to represent s and 1 s, but we will focus in voltage here. What voltage should be used to represent 1 and what voltage to represent? Logic Families Image source: There are industrial standards on the voltage levels for representing logic levels in discrete components. Sometimes referred as I/O standards. 1st semester, 11 ENGG115 Dr. K. Wong 11 1st semester, 11 ENGG115 Dr. K. Wong 1

3 Own standard? You can have your own standard when you build your own circuit, e.g.: digital VLSI designs e.g..v,.5v, 1.5V, 1.V Your class project e.g. 1V Usually uses the maximum allowable voltage as 1, and minimum allowable voltage as Customary to label the max voltage as or V dd Minimum allowable voltage usually is volt (not ). Realistic Circuit I/O 1bit. v ref time 1st semester, 11 ENGG115 Dr. K. Wong 1 1st semester, 11 ENGG115 Dr. K. Wong 14 Real Circuits. v ref Quick Summary Quiz (1) Which one is an example of discrete quantities? Height of a person Number of fingers Area Mass time 1st semester, 11 ENGG115 Dr. K. Wong 15 1st semester, 11 ENGG115 Dr. K. Wong 16 Quick Summary Quiz () Which of these statements is false? Discrete values are easy to store, transport. Enable very powerful and complicated processing of input. Immune to a lot more interferences from inside and side of the system than an analog system. Relatively fastehan analog systems in standard circuit implementations. Quick Summary Quiz () What does logic 1 represent? 1 V.5 V 1 V All of the above 1st semester, 11 ENGG115 Dr. K. Wong 17 1st semester, 11 ENGG115 Dr. K. Wong 18

4 erature Warning Light We want to turn on a warning light if the surrounding temperature is too high We ll use a thermistoo sense temperature around the system The resistance of a thermistor changes depending on its temperature In this example, assume the resistance decreases as temperature increases 1st semester, 11 ENGG115 Dr. K. Wong 19 System Specifications Thermistor (rt): High temperature: High temp = r min = / temp = r max = Input stage: Output when temperature is high Output 1 when temperature is low Output stage: Accept 1 to turn light on Accept to turn light off Warning Light Apply 9V to turn on Apply V to turn off 1st semester, 11 ENGG115 Dr. K. Wong High Level Design Digitally controlled thermo warning light High Level Design Input Digitally controlled thermo warning light. Input Process Output Light. Input Process Output Light, 1 1,, 1 1, 1st semester, 11 ENGG115 Dr. K. Wong 1 1st semester, 11 ENGG115 Dr. K. Wong Converting R to V R?. Thermistor changes its resistance according to temperaturet But We want a change in voltage to be fed into our 1 bit One method: Use a potential divideo convert changes in R to changes in V V A Review: Potential Divider i V 1 V V B Recall that current remains the same going through resistors in series R R1 R R Q Rtotal = R1 R R and VAB = irtotal VAB 1 V1 = ir1 = R1 = VAB Rtotal R1 R R R V = ir = VAB R 1 R R R V = ir = VAB R R R 1 The potential across each series resistor is proportional to it s resistance 1st semester, 11 ENGG115 Dr. K. Wong 1st semester, 11 ENGG115 Dr. K. Wong 4 4

5 Converting R to V: Potential Div v v = Complete Input Stage v Logical 1 Through a thermistor, the change in temperature ( k) becomes a change in resistance ( ) Then, through a potential divider, changes in resistance resistance ( ) is translated into change in v. Sanity check: When is low (~Ω), v is low (~V). When is high (>> ), v is high, close to. Once the resistance of the thermistor is translated as voltage, it can feed our 1bit to convert into logical 1 and Need to pick the right value for to turn on/off at right resistance 1st semester, 11 ENGG115 Dr. K. Wong 5 1st semester, 11 ENGG115 Dr. K. Wong 6 Quick Summary Quiz (4) Which one can NOT be the threshold? 7 Picking the /resistor values v Hi r min v = = r min r max v = = r max = 4 = 8 4 Set threshold at Assume: High temp Hi = r min = / temp = r max = 1 8 1st semester, 11 ENGG115 Dr. K. Wong 8 1st semester, 11 ENGG115 Dr. K. Wong 9 Quick Summary Quiz (5) If we want the threshold at, which of these statements is correct? High Level Design Process Digitally controlled thermo warning light r min = / ; r max = r min = / ; r max =. Input Process Output Light v r min = / ; r max =, 1,,,, 1, r min = / ; r max = 4 v = 1st semester, 11 ENGG115 Dr. K. Wong 1st semester, 11 ENGG115 Dr. K. Wong 1 5

6 Digital Processing Recall that the design of any subsystem is largely dependent on the system specifications: (1) The intended function of the system () The interface specification In our example: (1) System is to turn on a light bulb when temperature is high (a) From input stage: high temp., low temp. 1 (b) From put stage: 1 turns on light bulb, turns off light bulb Therefore, we need a digital processing stage that converts a to 1, and converts a 1 to. Converts to 1, vice versa How to make a processing stage that converts zero to the value one? Many ways:. Calculate the put! = 1 in 1 1. Use a logical NOT gate (will come back to logic gates in a few weeks) in 1st semester, 11 ENGG115 Dr. K. Wong 1st semester, 11 ENGG115 Dr. K. Wong High Level Design Output Digitally controlled thermo warning light. Input Process Output, 1,,,, 1, Light Connecting to the Output Specifications (given): 1 9V Light on V Light off Do not confuse between logical 1 with 1 volt, and logical with volt. Logical values and 1 should not be used to di drive put tdirectly These internal discrete values (e.g. 18.9,, etc) must be translated into suitable analog put values Suitable V, I, R A digitalanalog convertor () converts discrete input values into analog put voltage values 1st semester, 11 ENGG115 Dr. K. Wong 4 1st semester, 11 ENGG115 Dr. K. Wong 5 Extremely Simple 1bit in in = 1? 9V IN1 IN v Output 9V when input is 1 Output V when input is Can effectively be implemented using a relay A relay switch to NO (normal open) when the input is active Otherwise it switch to NC (normal close) 1st semester, 11 ENGG115 Dr. K. Wong 6 NO com NC 9V v Final System Block Diagram v invert Straightly speaking a digital processing system Can be made far more complex by more elaborated, and digital processing Can be made far simpler by reducing the boundary between subsystems. 1st semester, 11 ENGG115 Dr. K. Wong 7 6

7 Simple version boundary breaking Simple Version Single Stage. v proc in proc v High low ~ 1 ~ (9 V) Lo high ~ 1 Hi v v invert Can we bypass all intermediate stages? 1st semester, 11 ENGG115 Dr. K. Wong 8 r lamp v r lamp v = r lamp v Caveat: resistance is not really or infinite Make sure enough current is available through lamp when is large 1st semester, 11 ENGG115 Dr. K. Wong 9 What if thermistor operates in opposite? Simple Version Single Stage?? Hi r v t v Can we bypass all intermediate stages as before? r lamp v Not working!! r lamp v = r lamp r v V t cc 1st semester, 11 ENGG115 Dr. K. Wong 4 1st semester, 11 ENGG115 Dr. K. Wong 41 Complex version The same digital processing structure is also applicable to complex processing systems For example, we can altehe brightness of the warning lamp depending on the input temperature: Higheemperature brighter lamp A multilevel will be needed to obtain input temperature at higher precision Complex Version (1) Input voltage Related to temperature v,,5,6,1,, Process invert 1st semester, 11 ENGG115 Dr. K. Wong 4 1st semester, 11 ENGG115 Dr. K. Wong 4 7

8 Complex Version () Output Voltage vs erature v = v is not linearly proportional to temperature Need digital processing to linearize it before put to the lamp Output Stage Implementation In general s are quite complicated One of many designs: in =? =? = 1? =? 1V 8V 4V V v 1st semester, 11 ENGG115 Dr. K. Wong 44 1st semester, 11 ENGG115 Dr. K. Wong 45 In conclusion All electronic/electrical systems can be divided into three main subsystems: input, process, put Analog systems manipulate analog signals through Digital systems handles digital data in process stage 1bit can be implemented using simple comparator Logical values electrical values Administrative Announcements 1st semester, 11 ENGG115 Dr. K. Wong 46 1st semester, 11 ENGG115 Dr. K. Wong 47 Administrative Announcements Labs Be on time! Yes, it was a bit tough as a first lab Next week will be (hopefully) shorter You need the skills for your project Not absolutely required to attend the lab with your group project partners You might make new friends there too! No makeup lab! If you miss your lab session with good reason, we will not grade your lab afterward Administrative Announcements Project Project will start in week 7 (Oct 1) You must have a project group by then Group size is four (4, quattro, 四 ) people You get penalized for any more or less than 4 If you have or 5 people, you get % discount on your project grade If you have people, you get 5% discount on your project grade The only reason there will be a group size not equal to 4 is when the class size is not multiple of 4. Only one (1) team will be chosen in week 7 to allow a group size of 4 We reserve the right to change the rule at will 1st semester, 11 ENGG115 Dr. K. Wong 48 1st semester, 11 ENGG115 Dr. K. Wong 49 8

Electronic Systems. Dr. Kenneth Kin-Yip Wong. ENGG st Semester, Department of Electrical and Electronic Engineering

Electronic Systems. Dr. Kenneth Kin-Yip Wong. ENGG st Semester, Department of Electrical and Electronic Engineering Electronic Systems ENGG1015 1 st Semester, 2011 Dr. Kenneth Kin-Yip Wong Department of Electrical and Electronic Engineering Introduction Today H ENGG1015: Hybrid 1 semester L Recall that ENGG1015 is about