Session 7 — Hello, Hardware!

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

Session goal: by the end, students can explain the Sense → Think → Act loop, build an LED circuit in a simulator, and write Arduino code that makes it blink.

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 two diagrams below ready to share (Sense → Think → Act and the LED circuit).
• Have the blink sketch below open so you can paste it live.

Agenda

0:00 · Hook (5 min)

Ask the class (chat or unmute):

• "How does an automatic door know when to open?"

Let them guess, then reveal the pattern: it senses you, decides to open, and acts by moving. Tell them almost every smart device works this way — and today they build the smallest version: an Arduino that makes a light blink.

0:05 · Teach — Sense → Think → Act (12 min)

Explain: a tiny computer called an Arduino connects code to the physical world through a three-step loop.

Share this diagram:

• Sense — inputs (a button, a light or temperature sensor).
• Think — the Arduino runs your code.
• Act — outputs (an LED, a buzzer, a motor).

Ask: "Take the automatic door — what's the Sense, the Think, and the Act?" (Take a couple of answers, then name one more everyday device.)

0:17 · Teach — A circuit + code, working together (15 min)

Explain: electricity needs a complete loop to flow. Show the classic first circuit — an LED with a resistor, which protects the LED.

Share this diagram:

Explain the code: an Arduino sketch has two parts — setup() runs once, loop() runs forever.

Build/type this together:

void setup() {
  pinMode(13, OUTPUT);      // pin 13 will power the LED
}

void loop() {
  digitalWrite(13, HIGH);   // LED ON
  delay(1000);              // wait 1000 ms = 1 second
  digitalWrite(13, LOW);    // LED OFF
  delay(1000);              // wait 1 second
}

⚠ Watch for the common bug: if the LED won't light, the circuit is usually not a complete loop, the resistor is missing, or the LED is backwards (LEDs only work one way). Check the loop first.

Ask: "Which line turns the LED off, and what would happen if we deleted both delay lines?" (Answer: digitalWrite(13, LOW); with no delays it blinks too fast to see.)

0:32 · Activity — Blink an LED (28 min)

No hardware needed — everyone uses the free simulator. Demo the first build yourself, then have students build on their own devices. Circulate.

1. Open Tinkercad Circuits → Create new Circuit.
2. Drag in an Arduino Uno, an LED, and a 220 Ω resistor. Wire: pin 13 → resistor → LED → GND.
3. Click Code, switch to Text, paste the blink code above.
4. Press Start Simulation. The LED blinks!

Circulate and ask: "Is your loop complete? Is the resistor in the line?"

Extension prompt (for anyone who finishes): change both delay(1000) to delay(200) — what happens? Then make it blink an SOS pattern (3 short, 3 long, 3 short).

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 steps of physical computing? → Sense → Think → Act. Input → Arduino → output.
2. What does delay(1000) do? → Pauses for 1000 milliseconds = 1 second.
3. Which part runs forever — setup() or loop()? → loop() repeats endlessly; setup() runs once at the start.

1:08 · Wrap-up + homework (7 min)

• Ask one student to explain Sense → Think → Act in one sentence using their blink circuit.
• Homework — Two-LED crossing: add a second LED on another pin and make the two blink alternately (like a level crossing). Screenshot the circuit for the portfolio and bring it to Session 8.

Teaching notes

• Correct this misconception: "The LED is broken." Usually the loop is incomplete, the resistor is missing, or the LED is inserted backwards — check those before replacing anything.
• Fast finishers (extension): add a real input so the project can sense. In Tinkercad, add a photoresistor (light sensor) to pin A0 and read it:

```cpp void setup() { pinMode(13, OUTPUT); Serial.begin(9600); // so we can see the numbers }

void loop() { int light = analogRead(A0); // read the sensor (0–1023) Serial.println(light); // print the value delay(200); } ```

Have them cover the sensor and watch the number change in the Serial Monitor. These values are the "Sense" step — next session they add the "Think" (an if) to make an automatic night-light. - Low-tech fallback: if devices are limited, screen-share Tinkercad yourself and build the blink circuit as a class, taking student directions for each wire and line of code.

Vocabulary

Resources

• Tinkercad Circuits — build & simulate Arduino, free, no hardware.
• Arduino — Built-in Blink tutorial — the official first project.
• Arduino Project Hub — thousands of project ideas.

Next session

Session 8 — Build a Smart Gadget: the Block 2 project — students combine a sensor, a decision, and an output into their own working invention.