Difference between revisions of "Intro to Electronics"

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=== Week 4: Oscillators — and the venerable 555 ===
 
=== Week 4: Oscillators — and the venerable 555 ===
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 +
'''Goal:''' Build a 555 circuit to blink an LED
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 +
Explanations:
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* 555 timer
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** What is it?
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** How does it work?
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*** High-level explanation, though more detail can come afterward for anyone who wants to know
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*** Modes of operation
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**** Look at [http://www.kpsec.freeuk.com/trancirc.htm#inverter the datasheet]
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**** We're interested in the astable multivibrator
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***** What does that mean?
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** What crazy things do people do with it? ([http://www.555contest.com/ All kinds of things.])
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** '''Hands-on:''' Wire one up
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*** Show output on an oscilloscope
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* LED (review)
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** Look up forward voltages
 +
*** Use a different LED this time (maybe blue!)
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** '''Hands-on:''' Figure out an appropriate current-limiting resistor
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*** Hook it up to the output of the 555
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* Potentiometer
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** What is it?
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** How do I use one?
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*** '''Hands-on:''' Measure resistances between different terminals
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*** Could have used it in Week 2 to vary regulator output voltage
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** '''Another hands-on:''' Replace one of the 555 frequency-setting resistors
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*** Change its resistance and watch what happens!
  
 
=== Week 5: Digital logic ===
 
=== Week 5: Digital logic ===
  
 
=== Week 6:  Soldering ===
 
=== Week 6:  Soldering ===

Revision as of 07:16, 20 March 2012

Concept

The idea behind this course structure is for six sessions held a week apart. In order to provide a tangible end for students to feel like they’re working toward, each week will have a project; students will be walked through building that project and completing it by the end of the session.

In that sense, each week stands alone — a project started in one week does not need a future week in order to be complete. That said, later projects will depend on the knowledge gained in previous projects, and some of them will even be based on previous projects. (For example, Week 5’s project is a Larson scanner, and it uses Week 4’s project — a typical 555-based astable multivibrator circuit — to provide its clock signal.)

The course starts with a few basic circuit components (a voltage source, a resistor and an LED) and an explanation of typical prototyping equipment (breadboard and multimeter) and builds up to include regulated power supplies, basic optoelectronics and eventually digital logic.

It does not (at least in this draft) include much in the way of detailed exploration of analog electronics; it’s intended more as an introduction to the field of hobbyist electronics as a whole and to an assortment of the basic components one might find in a variety of projects.

Suggestions are, of course, welcome, as are other potential projects to use in place of some of the ones listed here. (In particular, a good introductory op-amp project might be handy to have.) I’ve listed component prices for 25 students; my goal would be to keep the cost per student at $25 or less — preferably more in the $20 range.

Syllabus

Week 1: Getting familiar with components

Goal: Light an LED with AA batteries and an on-off switch

Explanations:

  • Breadboard
    • What is it?
    • How is it organized?
    • Why is it useful?
    • Hands-on: Here's a breadboard
  • LED
    • What is it?
    • How does it work?
      • Not at the P/N junction level
      • Current goes in, light comes out
      • Current only flows in one direction (diode!)
      • Too much current = bad
    • Hands-on: Plug one into the breadboard
  • Battery
    • What is it?
    • How does it work?
      • Roughly constant voltage source for a while
      • Discharges over time — voltage decreases
        • Definition of "dead"
      • Maybe some chemistry? Doubtful, though
    • Hands-on: Batteries (three or four AAs) in a holder
      • Plug them into the breadboard
  • Switch
    • What is it?
    • How does it work?
      • Define poles and throws
    • Hands-on: Plug one (SPST) into the breadboard
  • Resistor
    • What is it?
    • How does it work?
      • Ohm's Law
        • Units of measurement
          • Ohm
          • Ampere
          • Volt
      • Non-polarized
      • Describe color codes
        • Give resources — memorizing is a bit daunting right now, I imagine
      • Tolerances — nothing's perfect
        • What does a <math>\pm 5%</math> tolerance mean?
    • Hands-on: Pick a resistor and plug it in to the breadboard
      • Select using Ohm's Law
  • Schematic
    • What is it?
    • Symbols
      • LED
      • Battery (DC source)
      • Switch
      • Resistor
      • Ground!
        • Define ground
    • Draw one
    • Hands-on: Connect components to match
      • Moment of truth: Turn it on!

Week 2: Test equipment

Goal: Build a power supply

Explanations:

  • Multimeter
    • What is it?
    • Review units of measurement
      • Ohm
      • Ampere
      • Volt
    • Hands-on: Measure last week's LED circuit
      • Voltages at different nodes
      • Current through LED branch?
      • Resistance of current-limiting resistor
  • Voltage divider
    • What is it?
    • How does it work?
      • Ohm's Law!
      • Walk through the analysis
    • Hands-on: Build one
      • Measure no-load output voltage
  • Regulated versus unregulated power supply
    • What's the difference?
    • Hands-on: Add a load to the voltage divider
      • Measure difference in output voltage
      • Why does this happen?
        • Equivalent resistances in series and in parallel
  • Datasheet
    • What are they?
    • How can you find them?
    • Hands-on: Here's an LM317
  • Capacitor
    • What is it?
    • How does it work?
      • Polarized (electrolytic) versus non-polarized (ceramic)
      • Filter capacitors
        • Show them on the datasheet's example circuit
      • Hands-on: Build the example circuit
        • Measure input voltage over time with and without filter capacitors
          • Not sure if we'll be able to notice on the multimeter
  • Oscilloscope (if there's time)
    • What is it?
    • How does it work?
      • Time axis
      • Voltage axis
    • Hands-on: Look at regulator's output waveform
      • Vary load and see what happens!

Week 3: Optoelectronics

Goal: Build a night light (Many thanks to EMSL)

Explanations:

  • LED (review)
    • What does it take to light one?
      • Remember to limit current
    • Hands-on: Light one
      • Probably just rebuild Week 1's circuit, though you really don't even need the switch for this
  • Transistor (BJT)
    • What is it?
    • How does it work?
      • Amplifier
      • Switch — what we'll focus on for now
    • What are the different terminals?
      • Base
      • Collector
      • Emitter
    • NPN versus PNP
    • Hands-on: Use one to control the LED
  • Phototransistor
    • What is it?
    • How does it work?
      • Apply light instead of base current
    • Hands-on: Add one to our circuit to switch the other transistor
      • Should look essentially identical to the EMSL circuit, except that we'll keep a current-limiting resistor in series with the LED
  • Bonus: Start talking about digital logic
    • What is it?
    • Logic gates
      • High-level explanation
      • Names: AND, OR, NOT (maybe XOR)
      • Show examples of 7400-series ICs
    • Show a schematic of a NOT gate (for example: [1])
    • Hands-on (ish): Compare the NOT gate schematic to our night light
      • We've made one with a phototransistor!
      • Could have been done with a normal transistor, too
      • Way less useful that way

Week 4: Oscillators — and the venerable 555

Goal: Build a 555 circuit to blink an LED

Explanations:

  • 555 timer
    • What is it?
    • How does it work?
      • High-level explanation, though more detail can come afterward for anyone who wants to know
      • Modes of operation
        • Look at the datasheet
        • We're interested in the astable multivibrator
          • What does that mean?
    • What crazy things do people do with it? (All kinds of things.)
    • Hands-on: Wire one up
      • Show output on an oscilloscope
  • LED (review)
    • Look up forward voltages
      • Use a different LED this time (maybe blue!)
    • Hands-on: Figure out an appropriate current-limiting resistor
      • Hook it up to the output of the 555
  • Potentiometer
    • What is it?
    • How do I use one?
      • Hands-on: Measure resistances between different terminals
      • Could have used it in Week 2 to vary regulator output voltage
    • Another hands-on: Replace one of the 555 frequency-setting resistors
      • Change its resistance and watch what happens!

Week 5: Digital logic

Week 6: Soldering