A 12-week electronics course where every circuit already runs

They will be able to

• Trace a complete circuit as a loop from the supply and back to it
• Wire parts into a breadboard so the strips make the connections you meant
• Explain why an LED needs a series resistor, and work out the current from the supply, the forward drop and the resistor

Exercise

Run it, then click the switch while it runs and say what the open position does to the loop. Change the resistor to 1 k, then 100 R, and write down the current you expect each time and the brightness you see. Find the value where the LED stops being visible.

Assessment idea

A wiring diagram of their own loop with the current calculated for their chosen resistor, submitted as a link to the running circuit.

Parts: breadboard, power and ground, slide switch, resistor, LED

Read more: Ohm's Law, in a Circuit You Can Run · Picking a Resistor for an LED · Series vs Parallel Circuits, Seen With LEDs · Voltage Dividers and Why They Are Bad Power Supplies

They will be able to

• Set a pin as an output and drive it high and low from code
• Use delay() and relate 500 ms in the sketch to 500 ms of simulated time
• Find the compile errors the editor reports and fix them

Exercise

Change the blink to 100 ms and confirm the speed readout still says 1.00x. Then add a second LED on another pin and try to blink it at a different rate with delay() alone. Write down why it cannot be done that way.

Assessment idea

A blink pattern written to a spec (three short, three long, three short), graded by opening the shared link and watching it run.

Parts: Arduino Uno R3, breadboard, resistor, LED

They will be able to

• Wire a button with an internal pull-up and explain why the pin reads low when pressed
• Observe contact bounce as extra edges, not as a fault in the code
• Debounce in software with millis, and say what the delay you chose costs

Exercise

Hold the button and watch the LED. Then pick the interrupt example in the board's Firmware panel, press ten times and record the count it prints; the pushbutton's contacts really bounce, so the number will be too high. Set the button's bounce property to worst and repeat, then write a millis debounce and repeat again.

Assessment idea

A table of presses against counted edges for bounce set to none, typical and worst, plus the debounce code that brings the count back to the number of presses.

Parts: ESP32-C3-DevKitM-1, pushbutton, resistor, LED, breadboard

Read more: Pull-Up Resistors and the Floating Input They Fix · Debouncing a Button: Why It Fires More Than Once · Analog vs Digital Pins, and ADC Resolution

They will be able to

• Explain what a capacitor charging through a resistor does over time
• Use f = 1.44 / ((R1 + 2 R2) C) to pick parts for a rate you want
• Trade resistance against capacitance for the same frequency and say why you would pick one

Exercise

Click the switch to change gear and count the blinks against a clock. Then choose R and C for a one second blink and for a five per second blink, build both, and measure them. Finish by opening the doorbell circuit, where the button gates the 555's reset pin instead of switching the load.

Assessment idea

Predicted against measured frequency for three different R and C pairs, with a sentence on the error. Mokxi integrates the capacitor in steps, so expect the measured rate to sit within a couple of percent of the formula rather than exactly on it.

Parts: NE555, capacitor, resistors, LED, slide switch, breadboard

Read more: The RC Time Constant, on an Oscilloscope · The 555 Astable: Timed by a Capacitor, Not a Crystal · The 555 Monostable: One Press, One Timed Pulse

They will be able to

• Fill in a truth table by driving the inputs of a real gate
• Read a DIP pinout and wire VCC and GND before anything else
• Explain why a CMOS input needs a pull-down and what an unpowered chip does

Exercise

Press the two buttons in all four combinations and fill in the table for AND, XOR and NOT. Then take one chip's VCC wire out and record what the output does. Build the same gate twice, once with the ideal gate part and once with the 74HC chip, and describe the difference.

Assessment idea

A completed truth table sheet plus one paragraph on what the real chip has that the ideal symbol does not: a supply, a threshold that follows it, a propagation delay and a high impedance state when it is off.

Parts: 74HC08, 74HC86, 74HC04, pushbuttons, resistors, LEDs, breadboard

They will be able to

• Add binary numbers by hand and name the sum and carry columns
• Derive sum = A xor B xor Cin and carry = AB + (A xor B)Cin
• Follow a signal through three chips and check each stage against the table

Exercise

Set A, B and the carry-in on the three switches and complete all eight rows of the truth table. Then draw what a second bit would need and mark where the carry goes.

Assessment idea

The eight-row table, plus a hand-drawn two-bit ripple-carry adder with the carry chain marked and the number of gates counted.

Parts: 74HC86, 74HC08, 74HC32, slide switches, resistors, LEDs, breadboard

They will be able to

• Explain what makes a flip-flop different from a gate: it holds a bit
• Wire a D flip-flop as a toggle and show that it halves the clock
• Read four LEDs as a binary number and explain the ripple delay between stages

Exercise

Set the clock to 1 Hz and write the four LEDs down as binary for sixteen steps. Then take one stage's clock from Q instead of Q-bar and record what happens to the direction.

Assessment idea

The sixteen step count sequence, plus a sentence on why the stages do not all change at the same instant and why a real design uses a synchronous counter. Worth saying in class: Mokxi powers a 74HC74 up cleared so a circuit built from toggles starts somewhere known, where a real chip powers up at random and needs a reset.

Parts: 74HC74 (two), clock, resistors, LEDs, breadboard

They will be able to

• Describe serial in, parallel out in your own words
• Name what the data, shift clock and latch clock pins each do
• Explain why the latch is pulsed once after eight bits and not after each one

Exercise

Change the pattern to a binary count from 0 to 255. Then move the latch pulse inside the bit loop and describe what the LEDs do. Finish by opening the electronic dice, where the same idea drives a seven segment display.

Assessment idea

Their own pattern function running, with a short explanation of what the latch buys and what MR and OE are tied to.

Parts: Arduino Uno R3, 74HC595, resistors, eight LEDs, breadboard

They will be able to

• Define duty cycle and work out the average of a square wave
• Tell hardware PWM from software PWM and say which pin gives which
• Predict what an RC low-pass filter does to a 1 kHz square wave

Exercise

Watch the two branches: one LED sees the raw chopping, the other sees it through a filter. Change the brightness table to a straight ramp and say why it looks as though it rushes the top end. Change the filter capacitor and describe the effect.

Assessment idea

A short write-up of duty cycle against perceived brightness, comparing the Uno's hardware PWM on timer 1 at 490 Hz with the ESP32-C3 example's software PWM at 1 kHz.

Parts: ESP32-C3-DevKitM-1, resistors, capacitor, LEDs, breadboard

Read more: PWM: Faking an Analog Voltage on a Digital Pin · PWM to an Analog Voltage With an RC Filter

They will be able to

• Open a serial connection and print values from a running sketch
• Read characters back in and act on them
• Explain why printing a long line takes real time at a given baud rate

Exercise

Print the uptime, then type into the monitor and watch it echo. Change the baud rate and describe the difference. Then open the reaction timer, play twenty rounds and collect the numbers it prints.

Assessment idea

A data set of their own, twenty readings with a mean and a range, submitted with the sketch that produced it.

Parts: ESP32-C3-DevKitM-1

They will be able to

• Say what an interrupt handler is and when it runs
• Attach a handler to an edge on a pin and share a value with the main loop safely
• Explain why a long delay() loses events that an interrupt would have caught

Exercise

Read the reaction timer: it polls the button in a loop. Rewrite it so the button is on an external interrupt, using the shipped interrupt example as the reference. Then open the traffic light and explain why its wait lamp lights the instant you press, even though the sketch is inside a five second delay.

Assessment idea

The interrupt version running, plus a paragraph on what volatile is for and why the loop takes its copy with interrupts off.

Parts: Arduino Uno R3, pushbutton, piezo, buzzer, resistors, LED, breadboard

They will be able to

• Plan a build as inputs, processing and outputs before wiring anything
• Agree a simple protocol between two boards and implement both ends
• Explain why two boards that talk must share a ground

Exercise

Open it and watch one board pulse a number down a single wire while the other counts the edges and prints it. Extend the protocol so a message carries two numbers, and make the receiver say something when what arrived makes no sense.

Assessment idea

A working project shared as a link, a wiring diagram, and a two minute demonstration to the class of what it does and what went wrong on the way.

Parts: ESP32-C3-DevKitM-1, Arduino Uno R3, resistors, LEDs, breadboard