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

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1 PHYS 253 Introduction to Instrument Design Focus in Phys 253 Basic electronics, mechanical design Prototyping skills Independent design Practical problemsolving Team work Prioritization of time, team effort Estimating time, effort for technical tasks Instructors Andre Marziali, Jon Nakane Tech Bernhard Zender TAs Matt Lam, Nick Geraedts, Allison Schaap Machine Shop Nick Lemmel Technical Support Sing Chow, Tongkai Huang 1 2 Schedule First six weeks: Lecture: Tue 2:00 4:30 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 Wed May 6, 1 2:30pm, Henn201 (B. Zender) Machine Shop Intro and Safety Intro to Solidworks / OMAX waterjet cutting Mon May 11, 12:30pm, Henn201 (R. Coope) Intro to Structural Design Design and design review (1 week) Construction (6 weeks) Individual timetrials (week 12) Competition: Thurs July 30 th, 10am Cleanup Friday July 31 st, 10am Final Report Friday August 7 th, 10am Review of past 253 robots 3 4 Team Mark Competition results 25% Robot design / construction: 30% Individual timetrials: 25% Design Review 20% Inappropriate lab practice Max 20% (parts hoarding, unsafe practice, messy space, etc) Individual Mark Team self evaluation: ± 10% Lab performance: ± 20% References There is no required text. Lecture notes, labs and data sheets will be posted on web page: Manuals (Interactive C, HandyBoard) Labs, lectures Data Sheets Other Suggested reading Horowitz and Hill, Sedra and Smith MIT Course Notes (link on course website) Catalogues (Newark, McMaster) Logbooks necessary for labs & construction, but not marked 5 6 1

2 2009 Ph253 final: Return of the RESCUE BOTS North Vancouver, 2018: All attempts to regulate access to the Grouse Grind have failed, and throngs of poorly equipped hikers now routinely walk up what has become the world s steepest singles club. As a result, the number of search and rescue operations to retrieve stranded lonely hearts has reached astronomical proportions. A new, less demanding means of recovering the hikers must be found. A new crown corporation, Rescuebots Inc, has asked for tenders to construct robots capable of autonomously searching for and rescuing hikers. You are one of many bidders on a contract to develop a prototype robot to accomplish this task. 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. Sensors Thermocouples RTD Potentiometers TC Encoders Phototransistors Reflectance Capacitive proximity Conductance Photoresistive (CdS) CCD (Video) Photomultipliers Pressure information Strain Piezo Reed switches Mechanical switch Hall effect sensor (B field) Accelerometers Tilt switch Smart instruments Microcontroller AI DI AO DO Actuators DC Motors AC motors Algorithm Servos accurate and stable (limited only by sensor) (CPU) Stepper motors Pneumatic actuators adjustable temperature swings, and accurate control Or action Hydraulic actuators not easily damaged, does not wear out Solenoids FPGA Lights mechanically very simple LEDs can react intelligently to large temperature swings Or Display (Text or video) Heaters can adjust itself based on time of day Digital logic Peltier cooler can learn behavior of house it is heating to correct heat Data link. Sonar in advance of request (can predict the future) Feedback? Data link.. 2

3 Analog inputs Digital Inputs Motor Outputs TINAH microcontroller board Some terminology Vcc or V (for example 9V) Ground (0V) circuit Vee or V (for example 9V) circuit circuit Referred to as Voltage or Power rails and usually not shown. (This does not violate conservation of energy) 15 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 47k TINAH board digital inputs Pullup resistor Buffer U1 74LS244 OEa Ia3 Ya3 Ia2 Ya2 Ia1 Ya1 Ia0 Ya0 OEb Ib3 Ib2 Ib1 Ib0 Yb3 Yb2 Yb1 Yb0 16 Digital input schematic Pullup resistors A digital buffer chip, used to protect the microcontroller from high voltages, currents To microcontroller Digital Inputs Touch sensor Digital inputs

4 Digital Inputs Touch sensor Digital Inputs Touch sensor A simple mechanical switch can be used as a collision or touch sensor switch no nc c J2 if (digital(7)) printf ( switch closed ) else printf( switch open ) 47k U1 74LS244 OEa Ia3 Ya3 Ia2 Ya2 Ia1 Ya1 Ia0 Ya0 OEb Ib3 Ib2 Ib1 Ib0 Yb3 Yb2 Yb1 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 19 #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() ; } } 20 LM311 comparator open collector output Comparators and other chips are sometimes provided with Open Collector outputs for easy interfacing to digital inputs. Vcc V LM 311 Output pin LM311 comparator Tour of a data sheet V NPN 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 Background info and application suggestions disconnected wire! LM311 comparator Example of a data sheet LM311 comparator Example of a data sheet DANGER LEVELS: Exceeding these voltages / currents will blow up the chip. 23 The most often used page how to hook up the chip. 24 4

5 LM311 comparator Example of a data sheet LM311 comparator Example of a data sheet Important operating characteristics: these numbers will tell Some characteristics cannot be expressed with one number, you how the chip will behave. so graphs are provided LM311 comparator Example of a data sheet LM311 comparator Example of a data sheet V LM 311 J2 Ω 47k V NPN How much power is dissipating when V is < V? 1) 2 mw 4) mw 2) 10 mw 5) 300 mw 3) 30 mw (A 9V battery holds ~ 500mAh) 27 The best part: example circuits designed by the pros who manufactured the chip in the first place. 28 V V LM311 comparator open collector cc output LM 311 NPN J2 U1 74LS244 OEa Ia3 Ya3 Ia2 Ya2 Ia1 Ya1 Ia0 Ya0 OEb Ib3 Ib2 Ib1 Ib0 Yb3 Yb2 Yb1 Yb0 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. 47k Unlike an OPamp, the 311 is NOT a source of power! You cannot drive a load with the output pin. 29 A C 10 Hz square wave ( pp ) Hz square wave (3V pp ) 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 B 10 Hz square wave ( pp ) 311 (all 311 are powered to GND) (square wave : 0 for a,b 1 4 V for c) 30 5

6 Example: QRD1114 reflectance sensor Example: QRD1114 reflectance sensor V1 V6 330 QRD1114 R4 47K R3 V5 k 40% V2 U1A LM311 LM339 J2 R2 47k U2 74LS244 OEa Ia3 Ya3 Ia2 Ya2 Ia1 Ya1 Ia0 Ya0 OEb Ib3 Ib2 Ib1 Ib0 Yb3 Yb2 Yb1 Yb0 Handy Board Discrete devices: diodes Diode circuit I ;V 2 V = 0.7 V Treat as conductor I = 0 A Treat as open circuit Typical ~ 0.7 V Diagrams courtesy of: University of St. Andrews, St Andrews, Fife KY16 9SS, Scotland Discrete devices: diodes V in = DC, V out is connected to scope only. Vin D1 DIODE Vout V = 0.7 V Treat as conductor Vin D1 DIODE Vout 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 3. c,d 4. a,e Diagrams courtesy of: University of St. Andrews, St Andrews, Fife KY16 9SS, Scotland c 36 6

7 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: MOSFETs 37 Diagrams courtesy of: University of St. Andrews, St Andrews, Fife KY16 9SS, Scotland 38 b ~ 20 or more Diagrams courtesy of: University of St. Andrews, St Andrews, Fife KY16 9SS, Scotland BJT circuit

8 Typical circuit (NPN): When is closed, lamp lights up. I B = (50.7)/ = 4.3 ma β= 30 I c = (30)4.3 ma = 130 ma V BE = 0.7 V V CE = 0.3 V V2 I B V BE V1 R2 2N3904 I c ebc V2 I B V BE V1 R2 2N3904 I c Checking V BE is a quick way to test a transistor. If V BE >> 0.7 V, the transistor is dead. 43 GND 44 V1 R2 Typical circuit (PNP): When S2 is closed, lamp lights up. V1 I c S2 R2 V BE 2N3906 ebc V2 I B 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 MTP3055 HUF I d Q8 2N3904 V gs Q3 MTP2955 IRF5305 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). 47 Increasing V gs increases I d. Depletion : Increasing V gs decreases I d 48 8

9 FET circuit Enhancement: N type P type MTP305 HUF Q3 IRF5305 MTP2955 gds GND MTP305 HUF 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 MTP305 HUF GND

10 For Lab #1: Design a circuit with a LM311 to interface the QRD1114 reflectance sensor to the Handy Board. MTP305 TINAH digital input GND Gate is floating, but lamp is still lit!! Common errors in Lab1 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. Bring a Lab Notebook! 57 10