Teacher guide
Producing & implementing
≈ 165 min
Lesson 5 · Weeks 8–9
Final design, circuits & electronics
Learning intention
Build a working circuit for your chosen alarm design — off the ThinkerShield, on a breadboard or soldered — and house it in an appropriate enclosure.
Success criteria
- I can wire a circuit that runs my final code without the ThinkerShield.
- I can use LEDs with the correct series resistor, the correct polarity, and a stable power supply.
- I can present my project in a working enclosure with all connections protected and labelled.
Before class
- Inventory the electronic-component bins (LEDs, 220 Ω resistors, breadboards, jumpers, buzzers, switches, LDRs).
- Set up a soldering station with ventilation and safety glasses if that's in scope for your class.
- Pull up a working Fritzing diagram of the alarm circuit on the projector.
Materials
Per student: an Arduino Uno (no ThinkerShield) · a breadboard · jumper leads · 1 × LED + 220 Ω resistor · 1 × push button · 1 × piezo buzzer · 1 × LDR · 9 V battery + clip or USB power · enclosure (project box, recycled container, 3D-printed shell).
Demo & teacher script
- Demo the breadboard rails — power on the left, ground on the right, jumper conventions.
- Build one LED + resistor on the breadboard in front of the class; show why the resistor matters (LED-burnout demonstration is memorable but optional).
- Demo the closed-circuit test with a multimeter (continuity beep) before applying power.
- Demo joining the wires to a power source safely.
Common misconceptions & fixes
- LED polarity — anode (longer leg, flat-side notch absent) to the positive rail; cathode to ground. If it doesn't light, flip it.
- Missing series resistor — an LED with no series resistor pulls too much current and burns out.
- Common ground — every component needs a path back to ground; a buzzer that won't sound is often missing its ground wire.
- Loose breadboard contacts — wiggle every jumper; intermittent contact masquerades as code bugs.
Evidence to collect
- Working circuit on the breadboard (photograph or video).
- Schematic or Fritzing diagram for the final circuit.
- Materials list with quantities and source.
- Final enclosed project in its case.
- Safety check signed off by the teacher before power-on.
Support path
Provide a labelled wiring photograph students can copy step-by-step.
Extension path
Solder the final circuit (with appropriate WHS supervision) and add strain reliefs.
Exit reflection
What was the hardest part of getting your circuit working off the ThinkerShield? How did you fix it?
