MISSION 05 · INTERMEDIATE ARDUINO
Discover what a motion sensor notices—and what it cannot promise.
2 · Teach It to Notice
Your new skill: Test a digital sensor and its limitations.
Revisit the skill you will reuse: Previous main-path mission
Match the names to your parts before you build. New parts appear when you first need them. You can point, say the name or show a grown-up.
This reusable building board joins some holes with hidden metal strips, so we can connect parts without soldering.
Look for: Find the centre gap, row numbers and power rails. The gap separates the two halves.
Before using it: Five holes in one numbered strip usually join; the strip across the gap does not. Some power rails have a break. Match your board diagram.
Your turn: Point to two holes on the same connected strip, then two that are separated by the gap.
A wire makes an electrical connection between two points. A clip lead grips a terminal.
Look for: Jumpers have small plug ends; clip leads have metal jaws. Colour helps us track a connection.
Before using it: Colour does not change a wire's job. Check both ends and keep bare metal away from other terminals.
Your turn: Follow one wire from start to finish and name what it joins.
A resistor limits current in a path. Beside our LED it helps protect the light from too much current. Its resistance is measured in ohms.
Look for: Look for a small body with two legs and coloured bands; match its labelled value to the mission.
Before using it: A resistor can face either way. Values such as 1 kΩ and 10 kΩ are different: k means one thousand. Keep the specified value.
Your turn: Point to the resistor in the LED path. Explain why replacing it with a plain wire is not our test.
An LED turns electrical energy into light and works in one direction. We use it to show what a circuit is doing.
Look for: An untrimmed ordinary LED often has a longer anode leg and a shorter cathode leg. A flat rim often marks the cathode.
Before using it: Confirm polarity with the part card if legs are trimmed. Use the mission's resistor in series; never connect an LED straight across the battery.
Your turn: With power off, identify the two legs and point to its protective resistor.
This programmable board reads inputs and controls outputs by following a program called a sketch.
Look for: Find the USB socket, the labelled digital and analog pins, 5V and GND. The microcontroller is a small computer chip on the board.
Before using it: Our course uses the 5V Uno and USB supply. GND is the shared electrical reference, not a special part or an instruction to connect to a wall socket.
Your turn: Point to the built-in LED, a digital pin and an analog input pin without plugging in any wires.
The computer lets us write and upload a sketch. A USB data cable carries the upload and supplies the Uno in these missions.
Look for: Match the board socket and computer socket. Some cables charge only and cannot transfer a sketch.
Before using it: Use Arduino IDE and the selected Uno board and port. Disconnect USB before moving circuit wires.
Your turn: Find the upload button and the board selection before running the first sketch.
This sensor notices changes in infrared energy as a warm body moves across its view. It sends a motion signal to our board.
Look for: Look for a small module with a pale dome and labelled VCC, GND and OUT connections.
Before using it: Pin order differs between modules. It needs settling time and cannot reliably count people or prove a room is empty.
Your turn: Predict whether standing still and walking across its view will give the same result.
A video demonstration will appear here when it is ready. You can follow the written step now.
Before we build, match these names to the parts in front of you. Breadboard. This reusable building board joins some holes with hidden metal strips, so we can connect parts without soldering. Find the centre gap, row numbers and power rails. The gap separates the two halves. Five holes in one numbered strip usually join; the strip across the gap does not. Some power rails have a break. Match your board diagram. Jumper wire and clip lead. A wire makes an electrical connection between two points. A clip lead grips a terminal. Jumpers have small plug ends; clip leads have metal jaws. Colour helps us track a connection. Colour does not change a wire's job. Check both ends and keep bare metal away from other terminals. Resistor. A resistor limits current in a path. Beside our LED it helps protect the light from too much current. Its resistance is measured in ohms. Look for a small body with two legs and coloured bands; match its labelled value to the mission. A resistor can face either way. Values such as 1 kΩ and 10 kΩ are different: k means one thousand. Keep the specified value. LED or light emitting diode. An LED turns electrical energy into light and works in one direction. We use it to show what a circuit is doing. An untrimmed ordinary LED often has a longer anode leg and a shorter cathode leg. A flat rim often marks the cathode. Confirm polarity with the part card if legs are trimmed. Use the mission's resistor in series; never connect an LED straight across the battery. Arduino Uno. This programmable board reads inputs and controls outputs by following a program called a sketch. Find the USB socket, the labelled digital and analog pins, 5V and GND. The microcontroller is a small computer chip on the board. Our course uses the 5V Uno and USB supply. GND is the shared electrical reference, not a special part or an instruction to connect to a wall socket. USB data cable and computer. The computer lets us write and upload a sketch. A USB data cable carries the upload and supplies the Uno in these missions. Match the board socket and computer socket. Some cables charge only and cannot transfer a sketch. Use Arduino IDE and the selected Uno board and port. Disconnect USB before moving circuit wires. PIR motion sensor. This sensor notices changes in infrared energy as a warm body moves across its view. It sends a motion signal to our board. Look for a small module with a pale dome and labelled VCC, GND and OUT connections. Pin order differs between modules. It needs settling time and cannot reliably count people or prove a room is empty. Pause and point to the part that will do the main job in this mission. If it is missing or looks different, ask a grown-up before building.
WHAT YOU'LL USE
Kit list: match the named parts to your box and its component cards. Home list: gather these before starting; some may also be supplied in your kit. Reuse components between missions. Stop and ask a grown-up if an essential part or label is missing.
BEFORE YOU BUILD
Disconnect USB before moving any wire. Use USB to power the Uno. Every separate LED needs its own 1 kΩ series resistor. Never connect a motor, servo, or unknown buzzer to an I/O pin. Keep liquids below and away from the board. An adult checks the wiring against the printed component labels before power is connected.
YOUR REWARD
PREDICT BEFORE YOU BEGIN
What will the output do when you change the input? Say, point or draw your prediction.
YOUR CHALLENGE
NEW POWER-UP
Test a digital sensor and its limitations.
You have just practised read a gradual input and choose a measured threshold. Now: test a digital sensor and its limitations.
Each coloured strip is one connected group. Different numbered rows stay separate. This explains the board; use the mission’s exact connection reference for component positions. Check rail breaks on your supplied board.
With USB disconnected, connect D8 → 1 kΩ resistor → LED long leg (anode). Connect the LED short leg (cathode) → GND. Place the two LED legs on different connected strips; never put them in the same strip. Read the PIR module labels: VCC → 5V, GND → GND, OUT → D3. Do not infer the order from another sensor photograph. Stop if your module is unlabelled or rated for a different supply.
Copy the complete code into Arduino IDE or download the sketch. Follow the matching component card before connecting power.
const byte LED_PIN=8;
const byte PIR_PIN=3;
void setup(){pinMode(LED_PIN,OUTPUT);pinMode(PIR_PIN,INPUT);Serial.begin(9600);}
void loop(){bool motion=digitalRead(PIR_PIN)==HIGH;digitalWrite(LED_PIN,motion);Serial.println(motion?"Sensor HIGH":"Sensor LOW");delay(200);}
BUILD PATH
STEP 1 OF 7
Lay out Arduino Uno, USB data cable, Computer with Arduino IDE, Breadboard, 1 LED, 1 × 1 kΩ resistor, Jumper wires, PIR sensor module. An adult identifies the component pins from their printed labels. Unplug USB before building.
A video demonstration will appear here when it is ready. You can follow the written step now.
Lay out Arduino Uno, USB data cable, Computer with Arduino IDE, Breadboard, 1 LED, 1 × 1 kΩ resistor, Jumper wires, PIR sensor module. An adult identifies the component pins from their printed labels. Unplug USB before building.
WHAT'S REALLY HAPPENING?
A PIR module responds to changes in infrared energy across its viewing zones. Its HIGH signal and delay do not prove that a person is continuously present.
FAIR-TEST CHALLENGE
Change one feature, keep the rest the same and repeat your comparison.
CLEAN, RESET AND STORE
Disconnect USB before removing wires. Keep sensors dry. Recover and store the reusable parts.
NEXT SKILL
Measure distance and handle a missing echo.