Electronics class curriculum Tom Jennings mru 27 June 2005 new Aug 2004 The goal is to teach practical design and construction of electronic circuits. Light on theory, heavy on rule-of-thumb design. Solid fluency in schematics as a thinking and documentation tool. Visualization with schematics, oscilloscope, voltmeter, built-in checkpoint LEDs. Common components, Ohm's Law and RC time constants. Schematics, schematics, schematics. [in email to Mark Allen Aug 2004: A huge thing I'd add is, thorough fluency in schematics. Not only the basic symbols, which don't seem to be too hard to master, but the "grammar" of them -- the graphical transformations you can make that for example -- turn a marked-up schematic into a clear one; redrawing schematics to make them more readable (for example, the classic full-wave diode bridge, the diamond shape you see in power supply schematics, is much clearer drawn differently); making more clear that it's really a graphical language. I think it's a really big deal. Because people aren't comfortable writing them, and using them to think, they tend to try and think of circuits in terms of physical component arrangements, which is a sure formula for disappointment. I realized this finally while trying to help out ACE students, who, stuck with often a very simple circuit, simply can't visualize the problem, they have no language. I'd look at some non-functioning breadboard, and get the demo of the problem, and ask "where's your schematic?" uniformly there was none, or it was vastly out of date because it's considered "documentation" just like it is to programmers. They miss the point of it all, which is that electronics is not that far from abstraction, you can't do without the drawing. Maybe they think it's like staring at code, staring at parts. But code is literate (even bad code).] [FIRST SECTION: begin fluency in schematics, subset abstracted components. Intro schematics in the ordinary simplistic way, input on left, power on top, etc] !!! So far covers only whiteboard only, need to add physical demo and student construction. GENERAL NOTES: big box of random components, disassembled pots and switches, air-variable caps, huge electrolytics, monster resistors, inductors, weird transistors, etc available at all times and appropriate per class. ------------------------------------------------------------ 1. Intro goals, methodology, etc to able to make functional electronic objects, PIC interfaces that stay running and are repeatable. Emphasis on schematics as a language for discussion, understanding, and documentation. basic schematics it's what gets published! MANDATORY required materials gridded pad pencils not pens fat eraser graphic symbols abstract NOT physical occasional exception mcCulloch-Pitts schematic grammar and style power top, ground bottom, in left, out right color codes (cheat chart OK) wire color conventions COMPONENTS. A few components [schematically, of course. drawn reasonably, but begin schematic transformations...] All drawn schematically. battery voltage mention current, punt switch make clear the trivial physical nature of light bulb (not LED yet!) resistor voltage divider [good opp to show abstractness of schematics] ohm's law, bare intro E at points in ckt (just) mention I potentiometer exam: what is voltage at various circuit points? use simple integer ratios (emphasize back-of-the-hand estimations, with calc backup) ------------------------------------------------------------ 2. POWER. Nothing is free, everything turns to heat. At beginning of class, set up a battery stack with LEDs and voltmeter, watch it decline during class. refer to cheat charts and series/parallel calcs demo power 9V battery, big honkin' 12V ruin some resistors ruin a pot demo need for Ohm's Law! IR temp probe watts for "small signal" can mostly ignore rule of thumb: when close to the edge of the schematic, likely need to pay attention to power! heat sinks heat-sink a resistor the problem with batteries terminal voltage vs discharge types of batteries rule of thumb: ohm's law from a mile away: 9V, 1K... two Rs in series, one burns up exam: why? exam: how to fix/prevent? rule of thumb: if heat resolved/not an issue, you can concentrate on voltages alone AC/DC, BABY. it's all the same thing, just a convenient convention for voltage that varies periodically with time. Sine vs. square (frequency domain). Will appear as "signal" in later classes. no such thing -- convenient terminology if it varies in mathematically describable way it can be measured/calced in that same way eg. sine function transformer simple power supply... intro "power supply" black box/equivelant circuit [sneaks in nicely I think] power supply vs. battery [all should EXPLICITLY have occasional bad-draw, require redraw to favored conventions] hand out schematic of power supply project describe example P.S. to pass around ------------------------------------------------------------ 3. CONSTRUCTION. Use of tools, and techniques for building physical circuits. [[[BEGIN POWER SUPPLY CONSTRUCTION AT THIS POINT???]]] breadboarding, perf board, vector board, CAD PCB dead bug easy but unreliable (breadboard) ugly but reliable (perf board) breadboard to perf/vector/PCB schematics! build power supply on perf board component selection note 7805 regulator as example of black-box -- will be covered in later class layout or dictate soldering wires physical mounting [[[SLIGHT PROBLEM/OVERLAP HERE W/BOX CONSTRUCTION]]] physicalities wire, cable, component restraints standoffs labelling fuses and grounds and safety ------------------------------------------------------------ 4. NONLINEARITY. First, the oscilloscope: the premier visualization tool, and the model for mental visual models. Thinking in the time domain (may have to mention frequency domain). it's a plotter, X vs. Y simple demo -- on whiteboard simple demo -- time vs. voltage switch resistor voltage dividers start thinking in schematics and time/voltage plots (time domain) exam: what is voltage doing at various circuit points Capacitors, and practical RC mainly. Hard to get across; few good analogies. brief mention of physics demo hand-held inductor (yuk yuk) a BROADEST range of values of any electronic component mention physicality that instrudes on abstraction: electrolytic, air, mica, plastic, ... RC time constant demo on scope! calc! rules of thumb "timer" (say > 10mS) deglitch (say < 1mS) bypass (>> 1 sec) cobble up motorboating demo? Megohms and Microfarads value bounds amps/femtoamps not practical! nomographs! demo w/lamp brightness = current *** the RC time constant thing is a fundamental visualization tool for ALL time/integration physics analogies. ------------------------------------------------------------ 5. SEMICONDUCTORS. Keep it simple! Nonlinearity is what makes electronics useful. "practical applications of quantum physics" odd constant voltage quantum thingie LED fwd drop depends on materials/color (atom energy bands) diode fwd drop depends on material (Si, Ge) transistor as diode! demo common-emitter base vs. collector current MANY DIFFERENT VIEWS -- ALL THE SAME switch amp inverter demo common-collector (aka emitter follower) cascade two common-emitter amps feedback more on this later we hate them but they're cheap! INTEGRATED CIRCUITS. Individual transistors generally suck. 555 timer will use shortly op amp logic PIC ------------------------------------------------------------ 6. PULSE GENERATOR PROJECT. Demo trivial "timer" then build the pulser, useful in later projects. make Q/RC "timer" demo built pulse generator add pulser parts to project box debug! ------------------------------------------------------------ ------------------------------------------------------------ 7. CIRCUITS. Finally, some near-practical assemblages of components, based upon SCHEMATICS DRAWN FIRST. exam: derive from 'scope output, draw schematic. THEN build... breadboard op amp demo analog computer pot input, DVM out uses as interface/level shifter logic gates nand nor flip-flop AND/OR diodes vs. transistor, demo abstraction of OR kirschoff gate! ------------------------------------------------------------ POWER BUDGETS tally up power consumption quiescent vs. active loads active dynamic loads motors RC power supply vs. battery how batteries work (power curve, etc) ------------------------------------------------------------ CYBERNETIC ROBOT. A demonstration of complex behavior derived from a simple circuit, including servo feedback. The light-seeking mobile... photocell, transistor, glue, motor schematic does not show the feedback/servo action! construct and debug ------------------------------------------------------------ INTERFACES. Switches, PICs, relays, motors, high voltage, other real-world necessities and problems. switches for logic (PICs) pull down, pull up bouncing! 9. FEEDBACK AND ADVANCED TECHNIQUES 10. WHERE TO GET STUFF. OTHER COMPONENTS connectors friendlies RCA phone db, de, etc spade lugs fastons barrier strips zillion types wraps, ties, harnesses weird components zeners fets vacuum tubes FEEDBACK REALITY. Physicality of components; where to get. ------------------------------------------------------------ ------------------------------------------------------------ ------------------------------------------------------------ ------------------------------------------------------------ Beyondeth this pointe lieth monsters, but mostly random notes. [ NEXT PHASE: USE THIS CRAP ] Intro: summarize input and output the idea that person sees a door, joystick, lever, electronics sees switch closure or pot LED SWITCH BOX leftover from LAATHC class: PIC mediating I/O with people. ----------------------------------------------------- READING OTHER PEOPLES SCHEMATICS drag out examples (post-basics) BUILDING BLOCKS getting transistor amps to do what you want setting bias points B, E R's E diodes POWER BUDGETS tally up power consumption quiescent vs. active loads active dynamic loads motors RC power supply vs. battery how batteries work (power curve, etc) other components zeners inductors FETs IGBTs ICs only three: timer op amp nand TIMER bunch of transistor junk nice driver limitations OP AMP gain block inverting, non-inverting summation (operations!) integrator sample and hold analog computer! NAND basic boolean logic inversion RS flop OK I lied, rundown on: packages go through the national catalog SUBTLETIES bypass oscillations phase errors PACKAGING! not exactly electronics... breadboard solder board boxes connectors strain relief! fuses switches power heat labelling if there's time... SERVOS this would be a major item... op amp/motor servo error voltage phase how to debug? FUN WITH ANTIQUES neon tubes selenium dynamotors selsyns -------------------------------------------------------------------- "compound" circuits: two common-E amps, etc different views: I: non-inverting E: inverting Something like that. I think if people get comfortable with reading and writing, reasonably comfortable with a few components, and can transform schematics (fluency test) and begin to be able to predict what will be on the scope from the schematic, that's most of the battle. Note at this point I think Ohm's Law could be mentioned only minimally, and in the simplest form. For all the RC and transistor junk, we can use all 10K resistors, and hand-wave it for later. With a fundamental understanding of the these critical things, the rest is "corollary". tomj > here's what comes to my mind, in no real order. > > ohms law > parallel and series circuits > capacitance > induction > voltage, current, resistance > voltage divider > magnetic fields and the use thereof (motors, solenoids, relays, > speakers, microphones) > transistors > how to switch stuff on/off (transistors, switches, relays, solid state > relays) > diodes > how to build/prototype (breadboards, soldering, printed circuit boards) > basic construction (wire, stripping wire, heat shrink, 5 minute epoxy, > hot glue, molex connectors, crimping?) > how to use a multimeter (voltage, current, continuity, resistance) > schematics > more on schematics > basic debugging? > what is an integrated circuit with example (555?) > op-amps > basic sensors (photoresistor, other examples) > scope overview > microcontroller introduction > > what do you think? things that could be left out? things that need to be > added? order of instruction? > > best, > > Mark >