Intro to Electronics

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 ±5% 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
    • Look up example circuits in the datasheet
• 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: this one)
  • 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

Goal: Build a Larson scanner (Schematic (more or less) from EMSL)

• Use Week 4's 555 project for the clock signal
  • Can change resistor values to EMSL values at the end to change speed
• Probably leave out the low-pass filter because of time and cost

Explanations:

• Digital logic (in general)
  • What is it?
    • Compare to analog electronics — also has cool applications
  • What can I do with it?
    • State machines
    • Multiplexers
    • Counters
  • Hands-on: Manual logic switch
    • SPST on a line with a pull-up (or pull-down) resistor
      • How does such a resistor work? What does it do?
    • Watch it on a multimeter
      • How does it differ from the SPST without the resistor?
• Decimal counter
  • What is it?
  • How does it work?
  • Hands-on: Hook one up to power
    • Use the logic switch we just built to control the counter's clock signal
    • Watch what happens — maybe connect each output pin to an LED to make it more obvious?
• 555 (review)
  • What is it?
  • What did we do with one in Week 4?
    • Astable multivibrator!
  • Hands-on: Use it as the clock signal
    • 555 output pin connects to counter clock pin
    • Use resistor values from EMSL tutorial
• OR gate
  • Review logic gates (if we got to them at the end of Week 3)
  • Why are we interested in these?
    • Plot out Larson scanner details/excitation table
  • We need four of them
  • Hands-on: Add them to the circuit
    • Watch the lights scan back and forth

Week 6: Soldering

Goal: Solder Week 5's project on a printed circuit board

Explanations:

• Solder
  • What is it?
  • How do I use it?
  • Leaded versus lead-free
  • Hands-on (ish): Here's some solder
• Soldering iron
  • What is it?
  • How do I clean and tin the tip?
  • Demo: How do I form a good solder joint?
    • Heat both terminals
    • Apply solder
  • Examples of solder joints
    • Ideal
    • Cold
    • Bridged
  • Hands-on: Solder two wires together
• Printed circuit board
  • What is it?
    • Fiberglass
    • Copper traces/pads
    • Drilled holes/plated vias
    • Silkscreened markings
  • Hands-on: Solder a component
• Assembly
  • Hands-on: Finish the board!
• Bonus: Do I need one of these? (Other ways to mount circuits)
  • Prototyping board, layout tools, etching (chemical and mechanical)

Bill of materials

Pricing assumes 25 kits with no special discounts (e.g., Adafruit hackerspace discount). Total cost — not including breadboard jumpers, multimeter, PCB and shipping for all of these things — comes out to $368.20 (or $14.73 per person).

Equipment

• Multimeter
  • Relatively inexpensive (but maybe more than we want students to spend)
  • Voltage, current, resistance, continuity
    • Diode test would be nice to have
  • Do we want people to get their own, or do we want to use the space's?
    • MAS830 ($337.50 for 25: Adafruit)
    • Does the space have enough working meters? (If not, can we convince some place to donate some more?)
• Breadboard
  • Full size x1 ($180 for 25: Adafruit)
• Battery holder
  • 4xAA x1 ($21.18 for 25: Digi-Key)
• Batteries
  • Alkaline AA x4 ($33.48 for 100-pack: Amazon)

Things we could make ourselves

• Assorted breadboard jumpers
  • We could cut these ourselves to reduce cost, assuming we have enough small solid-core wire
  • Apparently Digi-Key also sells these in packs of 150 or 200 for various lengths for $16.48
    • Beginners might be more comfortable with longer pieces of wire (e.g., these packs of 75 for $6.00 each), though — thoughts?
• Printed circuit board for Week 6
  • Do we etch or mill these ourselves? Do we have some batch PCB service (e.g., Seeed, Sparkfun) get them done?
  • First design (EAGLE files here) is 1.70 x 3.00 inches
    • BatchPCB price at that size for 25: $328.75 ($13.15 each)
    • Fusion PCB price at that size for 30: $84.70 ($2.83 each)
      • Fusion PCB price at that size for 50: $84.90 ($1.70 each)
      • Both Fusion PCB prices are with the extra fee for testing all of them (instead of half) since it'd be nice not to have to troubleshoot the boards themselves in addition to the students' work
    • Still have some room in the corner if we're interested in doing anything else with it

Components

• LEDs
  • 5mm red x10 ($19.38 for 250: Digi-Key)
    • Week 1: x1 (light)
    • Week 3: x1 (light)
    • Week 4: x1 (555 output)
    • Week 5: x10 (4017 output, later x6 for Larson scanner)
    • Week 6: x6 (Larson scanner)
  • 5mm blue x1 ($4.75 for 25: Digi-Key)
    • Week 4: x1 (555 output)
• Switches
  • SPDT slider x1 ($14.72 for 25: Digi-Key) (Note: We only need SPST, but for some reason those are several times more expensive. Not sure why that is. SPDT will take a tad more explanation, but it shouldn't be that big of a deal.)
    • Week 1: x1 (power)
    • Week 5: x1 (logic)
• Voltage regulator
  • LM317 x1 ($9.80 for 25: Digi-Key)
    • Week 2: x1 (regulator)
• Resistors
  • 220 Ω x1 ($4.23 for 250: Digi-Key)
    • Week 1: x1 (current limiting)
    • Week 2: x1 (LM317 R1)
    • Week 3: x1 (current limiting)
    • Week 5: x10 (current limiting)
    • Week 6: x6 (current limiting)
  • 360 Ω x1 ($1.38 for 25: Digi-Key)
    • Week 2: x1 (LM317 R2)
  • 1 kΩ x1 ($1.38 for 25: Digi-Key)
    • Week 3: x1 (BJT base current)
    • Week 5: x1 (pull-up or pull-down resistor)
  • 180 kΩ x2 ($1.50 for 50: Digi-Key)
    • Week 5: x2 (555 R1, 555 R2)
    • Week 6: x2 (555 R1, 555 R2)
  • 1 MΩ x1 ($1.38 for 25: Digi-Key)
    • Week 4: x1 (555 R1)
  • 2 MΩ x1 ($1.38 for 25: Digi-Key)
    • Week 4: x1 (555 R2)
  • 150 Ω x1 ($1.38 for 25: Digi-Key)
    • Week 4: x1 (current limiting)
• Capacitors
  • 0.1 µF ceramic x1 ($2.91 for 25: Digi-Key)
    • Week 2: x1 (LM317 input filter)
  • 0.22 µF ceramic x1 ($5.00 for 25: Digi-Key)
    • Week 4: x1 (555 C)
    • Week 5: x1 (555 C)
    • Week 6: x1 (555 C)
  • 0.01 µF ceramic x1 ($4.70 for 25: Digi-Key)
    • Week 4: x1 (555 filter)
    • Week 5: x1 (555 filter)
    • Week 6: x1 (555 filter)
• Potentiometer
  • 2 MΩ x1 ($15.08 for 25: Digi-Key)
    • Week 4: x1 (555 R1)
• Transistors
  • 2N3904 x1 ($6.90 for 25: Digi-Key)
    • Week 3: x1 (switch for output LED)
• Phototransistor
  • x1 ($6.75 for 25: Digi-Key)
    • Week 3: x1 (light sensor)
• 555 timer
  • NE555N x1 ($6.99 for 25: Digi-Key)
    • Week 4: x1 (oscillator)
• Decimal counter
  • 74HC4017 x1 ($17.05 for 25: Digi-Key)
    • Week 5: x1 (counter)
    • Week 6: x1 (counter)
• OR gates
  • 74HC32 x1 ($6.88 for 25: Digi-Key)
    • Week 5: x1 (count reverser)
    • Week 6: x1 (count reverser)