Announcements • Reading assignments on the syllabus must be done BEFORE the lecture • Read Ch. 6 before next lecture • Read Ch. 4-5 before lab this week • Quiz is a way to check roll • Each lab write-up due at beginning of next lab • Someone on each team must get two motors from the Scientific Supply Store in Saunders Hall • Need cash or check
Announcements -- cont’d. • Links to professional organizations on web site • http://eng.auburn.edu/admin/ess/organizations/engorg.html • Lab sections and team assignments are on WebCT. • If not correct, send email to firstname.lastname@example.org
Lego Car PC with sound card Circuit Left Channel Right Channel DC motors Lego Car Design • Volume controls speed • Balance controls steering • Circuit converts sound wave to a drive signal
Competition • Each team designs and builds a car • Work on car done outside of class • Team must build the car with their own supplies • No supplies are provided • Lectures/Labs 1-7 provide background material for the design project • Start early on the design project! • COMPETITION – (Tentatively) Thursday, April 21, 7PM
Identify Customer Needs Establish Product Specification Define Alternative Concepts Select the Most Suitable Concept Design/Integrate Subsystems Build/Test Prototype Design/Build Production Produce Track Engineering Design Process
Engineering Design Process • Example: Mousetrap • Identify customer needs. • “I want a device that gets rid of the mice in my house.” • “I want a device that won’t hurt my toddler.” • “I want a device that won’t wake me up at night.”
Engr. Design Process (cont’d) • Establish product specification. • Device must kill the mouse. • Any moving parts must be inaccessible to toddlers. • Any poison must be inaccessible to toddlers and remain inaccessible when trap is handled. • Device must be quiet
Engr. Design Process (cont’d) • Define alternative concepts. • Spring-loaded trap is enclosed. Baffled door keeps out small fingers and muffles mechanical spring noise. • Poison is formed into a module that is affixed to a far corner of the trap away from reaching fingers. • Laser zaps mouse when optical beam shows nothing in door of trap.
Brainstorming • The brain uses two basic modes in the design process: • creative mode • critical mode • These two modes work against each other. • Brainstorming separates the two processes into different time frames.
Select the most suitable concept. Cost Design cost Material cost Assembly cost Weight Appearance Performance Safety Environmental risks Reliability Ease of use Engr. Design Process (cont’d)
Tradeoffs in Engineering Design Examples: • Cost vs. performance • Safety vs. performance • Performance vs. reliability
Engr. Design Process (cont’d) • Design the subsystems and integrate them • Break a complex system into small subsystems • Optical sensing subsystem • Decision logic • Laser subsystem • Mechanical packaging • Build and test a prototype • Build and test each subsystem • Integrate and test the subsystems
Engr. Design Process (cont’d) • Design and build production facility. • Produce and distribute. • Track product and improve.
Design for Lego Car • Specification is given. • Define alternative concepts. • Select the most suitable concept. • Bottom line is finishing time. • “Cost” is figured in by penalizing use of parts. • Car should be sturdy enough not to fly apart during race. • Car and course must pass minimal safety specs.
Design Subsystems • Car path & steering strategy • Type and number of wires connecting to amp. • Type of waveform used to power car. • Type of circuit & component values. • Vehicle mass, wheels, etc.
Further Design Steps • Build and test, then modify!!! • Production design, distribution, and tracking are not relevant to a single-shot prototype design.
Circuit Basics • Electricity flows through a circuit just like water through a pipe. • charge -- water in a pipe • current -- water flow • voltage -- pressure • resistance -- inverse of pipe diameter • capacitance -- water stored under pressure
Units • charge -- coulombs (C) • current -- amperes (A), A=C/s • voltage -- volts (V) • resistance -- ohms (), =V/A • capacitance -- farads (F), F = C/V
Circuit Elements • voltage source (e.g. battery) -- water pump with specified pressure. Units: volts (V)
Circuit Elements • resistor -- pipe with small diameter that makes water flow more difficult. Units: ohms ()
Quiz Put the following on each quiz: Name Lab Date and Time 1. (True or False) Engineering requires teamwork. 2. Which of the following is NOT one of the six main sub-areas of Electrical and Computer Engineering: a) Microelectronics, b) Electromagnetics, c) Control Systems, d) Physics, e) Power Systems