Session 8 — Build a Smart Gadget

Duration: 75 min · Format: live online · Ages: 12–15

Session goal: by the end, students can combine a sensor, a decision, and an output into a working gadget in the simulator, tune its threshold, and document it like an engineer.

Before class — prep (5 min)

• Open Tinkercad Circuits in a tab, signed in and ready to Create new Circuit — you'll demo and screen-share.
• Have the diagram below ready to share (Sense → Think → Act).
• Have the decision sketch below open so you can paste it live.

Agenda

0:00 · Hook (5 min)

Ask the class (chat or unmute):

• "A night-light turns itself on when the room gets dark — how does it decide?"

Let them guess, then reveal: it has all three pieces they've met — a sensor to sense, code to think, and an output to act. Tell them today they snap those pieces into their own real gadget.

0:05 · Teach — Plan it: Sense → Think → Act (10 min)

Explain: every gadget starts with a plan. Share the diagram and have each student pick one idea to build.

Share this diagram:

Offer three starter ideas:

• Automatic night-light: if it's dark → turn the LED on.
• Heat alarm: if temperature is high → sound the buzzer.
• Door reminder: if the button is pressed → blink an LED.

Ask: have each student finish this sentence in the chat — "My gadget will sense ___, think (if ___), and act by ___."

0:15 · Teach — Code the decision (the "Think") (15 min)

Explain: the magic is an if statement — it lets the gadget decide for itself. Walk through the code line by line, naming the Sense, Think, and Act.

Build/type this together:

void setup() {
  pinMode(13, OUTPUT);
}

void loop() {
  int light = analogRead(A0);   // SENSE
  if (light < 400) {            // THINK: is it dark?
    digitalWrite(13, HIGH);     // ACT: light ON
  } else {
    digitalWrite(13, LOW);      // ACT: light OFF
  }
}

⚠ Watch for the #1 misconception: students expect it to work perfectly first try and give up when it doesn't. Reframe — the number 400 is a threshold you tune, and real engineers spend most of their time testing and adjusting, not getting it right the first time.

Ask: "What happens if we make the threshold 900 instead of 400? When would the LED come on then?" (Answer: it turns on much more easily — almost all the time.)

0:30 · Activity — Build, test & tune (30 min)

Students build their gadget in the simulator. Demo the first build, then circulate.

1. In Tinkercad Circuits, add the Arduino, a sensor (e.g., photoresistor on A0), and an output (LED on pin 13 with a resistor). Wire it up.
2. Add the decision code above (adapt it to their chosen gadget).
3. Start Simulation. Cover the sensor — does the LED turn on?
4. Tune the threshold: the number 400 decides when it triggers. Too sensitive, or not enough? Change it and re-test. This tuning is engineering.

Circulate and ask: "What threshold worked for your gadget? How did you know?"

Debrief: have 2–3 students share their gadget, their threshold, and one thing they changed while testing.

1:00 · Check for understanding (8 min)

Ask these aloud or drop them in the chat. Answer key (for you):

1. What are the three parts of a smart gadget? → Sense → Think → Act — a sensor, an if decision, and an output.
2. What does the if statement do? → It lets the gadget decide between options based on the sensor reading.
3. What is the threshold? → The value that triggers the action (here, 400) — you tune it by testing.

1:08 · Wrap-up + homework (7 min)

• Ask one student to explain their gadget in one sentence: what it senses, decides, and does.
• Homework — Finish the project checklist and keep it for the portfolio:
• [ ] I wrote my Sense → Think → Act plan
• [ ] I built the circuit in Tinkercad
• [ ] I wrote code with an if decision
• [ ] I tested it and tuned the threshold
• [ ] I took a screenshot for my portfolio
• [ ] I can explain how it works in one sentence

Teaching notes

• Correct this misconception: "It should work perfectly the first time." Reframe — engineers test and tune; the threshold almost always needs adjusting, and that iteration is the real skill.
• Fast finishers (extension): make it their own and document it like an engineer. Have them (1) design an independent prototype — a different sensor + output (temperature + buzzer, distance + LED) and add a second condition with else if; and (2) write a one-page engineering report: Problem → Design (Sense/Think/Act) → Build → Test results (what threshold worked) → Next steps. (Prefer software? They can build a data prototype instead — a mini analysis or model with a short report, same structure.)
• Low-tech fallback: if devices are limited, build one gadget as a class in shared Tinkercad, taking student directions for the wiring, the if decision, and the threshold to tune.

Vocabulary

Resources

• Tinkercad Circuits — build, code, and simulate.
• Arduino Project Hub — ideas to make yours cooler.
• Arduino if reference — the language guide.

Next session

Block 3 — Competition & Portfolio: the finale — students turn their work into a competition entry, a research paper, and a standout presentation.