Focus in Phys 253. Basic electronics, mechanical design Prototyping skills Independent design

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1 Focus in Phys 253 Basic electronics, mechanical design Prototyping skills Independent design PHYS 253 Introduction to Instrument Design Instructors Andre Marziali, Jon Nakane Tech Bernhard Zender TAs Matt Lam, Theo Pacson, Ryan Wicks 1 Practical problemsolving Team work Prioritization of time, team effort Estimating time, effort for technical tasks 2 Schedule First six weeks: Lecture: Tue 2:00 5:00 Henn 201 Lab: Thurs 2:00? (typically 9:30) Hebb 42 After week 6: Lab: Tue & Thurs 2:00 10pm additional days and evenings as required. Formal Labs (6 weeks) 1 Microcontrollers and digital I/O 2 Analog circuits 3 Analog input 4 PWM and Power circuits 5 Software PID control and servos (2 weeks) Machine Shop Course ALL STUDENTS take the machine shop course (10 hrs lecture) if they have not completed the 40hour shop course. 10hr course for groups of 6 held on two afternoons (M/W/F), signup during Lab 1 Design and design review (1 week) Construction (6 weeks) Individual timetrials (week 12) Wed May 11, 1pm 3pm, Henn201 (attendance required for all students) Machine Shop Intro and Safety Fri May 13, 2pm 3:30pm, Henn201 (attendance required for all students) Intro to Solidworks / OMAX waterjet cutting 3 Competition: Thurs Aug 4th, 10am Cleanup Friday Aug 5 th, 10am 3pm Final Report Friday August 12 th 4 Team Mark Competition results 25% Robot design / construction: 30% Individual timetrials: 25% Design Review 20% Lab practice and Safety Max 20% (parts hoarding, unsafe practice, messy space, etc) Individual Mark Team self evaluation: ± 10% Lab performance: ± 20% References and Other References There is no required text. Lecture notes, labs and data sheets will be posted on web page: refer to Wiring programming website (wiring.org.co) Horowitz and Hill, Sedra and Smith MIT Course Notes (link on course website) Online Component Vendors (Newark, McMaster) Logbooks necessary for labs & construction, but not marked 5 6 1

2 Ph253 final 2011: Climbing Bots! 7 8 Smart instruments Mechanical thermostat The use of microprocessors to replace mechanical systems leads to better performance higher reliability more complex behavior with a mechanically simpler instrument often lower total cost of instrument Eg #1: mechanical vs. electronic thermostats 9 Uses a bimetallic strip to sense temperature, and a mercury switch to turn heat on and off. inaccurate large temperature swings subject to perturbation by mech. damage, friction effects, dirt etc. mechanically complex (and hazardous contains mercury) 10 Electronic thermostat Uses a sensor to sense temperature, makes complex decisions using a microprocessor, and then uses a relay to turn heat on and off. accurate and stable (limited only by sensor) adjustable temperature swings, and accurate control not easily damaged, does not wear out mechanically very simple can react intelligently to large temperature swings can adjust itself based on time of day can learn behavior of house it is heating to correct heat in advance of request (can predict the future)

3 Analog inputs Digital Inputs Some terminology Vcc or V (for example 9V) Motor Outputs Ground (0V) circuit circuit circuit Vee or V (for example 9V) Referred to as Voltage or Power rails and usually not shown. (This does not violate conservation of energy) TINAH microcontroller board Lab 1 Digital Inputs Getting information INTO your microprocessor Leaving highimpedance input lines to float to unspecified voltages when disconnected is bad engineering practice inputs are almost always pulled to an internal voltage reference so they have a clearly defined state. CAREFUL WHAT YOU PULLUP THOUGH some lines are supposed to be left open or grounded: Read the data sheets. Digital input digital(7) J2 V V 47k TINAH board digital inputs Pullup up resistor Buffer U1 74LS244 OEa Ia3 Ya3 Ia2 Ya2 Ia1 Ya1 Ia0 Ya0 OEb Ib3 Ib2 Ib1 Ib0 Yb3 Yb2 Yb1 Yb0 15 Digital input schematic Pullup resistors Digital inputs A digital buffer chip, used to protect the microcontroller from high voltages, currents To microcontroller 16 Digital Inputs Touch sensor Digital Inputs Touch sensor A simple mechanical switch can be used as a collision or touch sensor V 17 switch no nc c J2 V if (digital(7)) printf ( switch closed ) else printf( switch open ) 47k U1 74LS244 OEa Ia3 Ya3 Ia2 Ya2 Ia1 Ya1 Ia0 Ya0 OEb Ib3 Yb3 Ib2 Yb2 Ib1 Yb1 Ib0 Yb0 When switch is pressed, digital input is pulled low (0 V) by the switch. When not pressed it is pulled high () by the resistors 18 3

4 Digital Inputs Touch sensor #include <phys253.h> #include <LiquidCrystal.h> #include <Servo253.h> /////////////////////////////////////// // Physics 253 Lecture 1 // 2009 May 4 /////////////////////////////////////// void setup() { while(!startbutton()) { LCD.clear(); LCD.home(); LCD.print("Welcome to 253!"); delay(0) ; LCD.clear(); LCD.home(); LCD.print("Come down to"); LCD.setCursor(0,1) ; LCD.print("pickup kits..."); delay(0) ; } } void loop() { while (!stopbutton()) { LCD.clear(); LCD.home(); if (digitalread(0)) { LCD.print("switch pressed."); } else { LCD.print("switch NOT pressed."); } delay() ; } while (!startbutton()) { LCD.clear(); LCD.home(); if (digitalread(0)) { LCD.print("object detected."); } else { LCD.print("object NOT detected."); } delay() ; } } 19 LM311 comparator open collector output Comparators and other chips are sometimes provided with Open Collector outputs for easy interfacing to digital inputs. Vcc V V LM 311 NPN Output pin When V < V, is turned on (conducting). Output pin is grounded through. When V >V, is off, and output pin floats unless externally pulled up!!!. (but cannot sink any current to ground). Remember: it takes very little charge to change the voltage of a disconnected wire! 20 LM311 comparator Tour of a data sheet Background info and application suggestions 21 DANGER LEVELS: Exceeding these voltages / currents will blow up the chip. 22 The most often used page how to hook up the chip. 23 Important operating characteristics: these numbers will tell you how the chip will behave. 24 4

5 V LM 311 J2 V 47k V NPN V How much power is dissipating when V is < V? 1) 2 mw 4) mw 2) 10 mw 5) 300 mw 3) 30 mw Some characteristics cannot be expressed with one number, so graphs are provided. 25 (A 9V battery holds ~ 500mAh) 26 V V LM311 comparator open collector Vcc output LM 311 NPN J2 V V 47k U1 74LS244 OEa Ia3 Ya3 Ia2 Ya2 Ia1 Ya1 Ia0 Ya0 OEb Ib3 Yb3 Ib2 Yb2 Ib1 Yb1 Ib0 Yb0 The best part: example circuits designed by the pros who manufactured the chip in the first place. 27 Unlike an OPamp, the 311 is NOT a source of power! You cannot drive a load with the output pin. Now, when is off, digital input J2 is pulled high by. When is on, J2 is pulled low (~ 0.1 or 0.2 V) by. Note that the LM311 and the TINAH must share ground for this to work, but DO NOT NEED TO SHARE POWER RAILS Hz square wave ( pp ) 10 Hz square wave ( pp ) Example: QRD1114 reflectance sensor A 311 B 311 C Hz square wave (3V pp ) (all 311 are powered to GND) (square wave : 0 for a,b 1 4Vforc) Which of these circuits will turn the lamp on / off at 10 Hz? 1. A 2. B 3. A and B 4. C 5. all the above

6 Example: QRD1114 reflectance sensor Discrete devices: diodes V1 V V6 V 330 QRD1114 R4 47K R3 V5 V k 40% V2 V U1A LM311 LM339 J2 V V 47k U2 74LS244 OEa Ia3 Ya3 Ia2 Ya2 Ia1 Ya1 Ia0 Ya0 OEb Ib3 Yb3 Ib2 Yb2 Ib1 Ib0 Yb1 Yb0 V = 0.7 V Treat as conductor I V 2 TINAH Board I = 0 A Treat as open circuit Typical ~ 0.7 V 31 Diagrams courtesy of: University of St. Andrews, St Andrews, Fife KY16 9SS, Scotland 32 V in = DC, V out is connected to scope only. a) V out = 5 V if = 1K b) V out = 4.3 V regardless of c) V out = 4.3 V if = 1K d) V out = 5 V if is removed e) V out = 4.3 V if is removed The following are true: 1. a 2. b,c,e Vin D1 DIODE 1k Vout Discrete devices: Transistors Transistors are semiconductor devices used to amplify a signal (e.g. small current/voltage to large current/voltage). In Phys 253, we use transistors as switches to turn on and off larger amounts of current. Two major types of transistors: 3. c,d 4. a,e MOSFETs 5. c b ~ 20 or more Diagrams courtesy of: University of St. Andrews, St Andrews, Fife KY16 9SS, Scotland 35 Diagrams courtesy of: University of St. Andrews, St Andrews, Fife KY16 9SS, Scotland 36 6

7 37 38 BJT circuit BJT circuit 3.3K V1 9V D1 LED1 3.3K NPN Typical circuit (NPN): When is closed, lamp lights up. I B = (50.7)/1k = 4.3 ma = 30 I c = (30)4.3 ma = 130 ma V BE = 0.7 V V CE = 0.3 V V2 I B 1k V BE V1 V 2N3904 I c ebc V2 I B 1k V BE V1 V 2N3904 I c Checking V BE is a quick way to test a transistor. If V BE >> 0.7 V, the transistor is dead. 41 GND 42 7

8 V1 V Typical circuit (PNP): When S2 is closed, lamp lights up. V1 V I c S2 1k V BE 2N3906 ebc V2 I B 1k V BE 2N3904 I B L2 I c GND Field Effect Transistors Gate voltage either ENHANCES or DEPLETES the conduction channel. JFET = Junction FET MOSFET = Metal Oxide Semiconductor FET MOSFETS have an insulating layer at gate so draw less current. Field Effect Transistors There are FOUR kinds of MOSFETs: Enhancement Mode: N type P type Q7 2N3906 R6 R5 V gs I d MTP3055 HUF V Q8 2N3904 V V gs Q3 IRF5305 MTP2955 I d M1 MT Current passing from source to drain now controlled by VOLTAGE at the gate (rather than by CURRENT into the base as in a BJT). 45 Increasing V gs increases I d. Depletion : Increasing V gs decreases I d 46 FET circuit

9 Enhancement: N type P type V V V V MTP305 HUF V V Q3 IRF5305 MTP2955 gds GND MTP305 HUF V V MTP305 HUF If after closing (and turning on the LED) we cut the circuit at the red line: 1. The LED will stay lit 2. The LED will go off V V MTP305 HUF GND V V For Lab #1: Design a circuit with a LM311 to interface the QRD1114 reflectance sensor to the TINAH board, with an adjustable threshold. MTP305 TINAH digital input GND Gate is floating, but lamp is still lit!!

10 Things to keep in mind for Lab 1 Bring a Lab Notebook! Common problems: Circuit (LM311) and TINAH are not connected to a common ground. The LM311 comparator output pin is not pulled up. The power rail break in the proto board is not bridged. The strobe pin of the LM311 is pulled low. The ground pin of the LM311 is not grounded. Blowing up the TINAH. Please use LM311 to interface to the frequency generator