MISSION 08 · INTERMEDIATE ARDUINO
Use a tiny damp test to calibrate a water sensor while keeping the board dry.
2 · Teach It to Notice
Your new skill: Calibrate a sensor with a dry/damp comparison.
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.
Water across this sensor's exposed tracks changes an electrical reading. We compare dry and damp readings to choose a rule.
Look for: Find the sensing tracks and labelled +, - and S or analog output on the matching module.
Before using it: Only the tracks meet a shallow damp pad. Keep plugs, the Uno and computer dry. It does not prove water is safe or measure an accurate water level.
Your turn: Locate the sensing area and the part that must stay dry before using any water.
A dropper moves a small amount of liquid, one drop at a time.
Look for: Find its squeeze bulb and narrow tip.
Before using it: Squeeze before dipping, release to draw liquid, then press gently. Rinse between samples. Never mouth-pipette. Drop size can vary.
Your turn: Practise three separate drops of clean water into a tray.
Tissue has tiny spaces between fibres. Water can travel through them; layers can also trap some particles.
Look for: Find the same tissue type for both strips in a comparison.
Before using it: Keep tissue type and water amount the same when testing strip width. A filter result is not water purification.
Your turn: Feel dry tissue, then predict what a damp edge might do.
A tray catches spills, cups hold samples or form a model, and a dry workspace protects our tools.
Look for: Choose the exact container and dry surface in the mission list.
Before using it: Experiment cups stay separate from food and drinks. Keep electronics away from liquids and clean up before storing parts.
Your turn: Show where a spill would land and where electrical parts will stay dry.
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. Analog water sensor. Water across this sensor's exposed tracks changes an electrical reading. We compare dry and damp readings to choose a rule. Find the sensing tracks and labelled +, - and S or analog output on the matching module. Only the tracks meet a shallow damp pad. Keep plugs, the Uno and computer dry. It does not prove water is safe or measure an accurate water level. Dropper. A dropper moves a small amount of liquid, one drop at a time. Find its squeeze bulb and narrow tip. Squeeze before dipping, release to draw liquid, then press gently. Rinse between samples. Never mouth-pipette. Drop size can vary. Tissue and paper strips. Tissue has tiny spaces between fibres. Water can travel through them; layers can also trap some particles. Find the same tissue type for both strips in a comparison. Keep tissue type and water amount the same when testing strip width. A filter result is not water purification. Tray cup and dry workspace. A tray catches spills, cups hold samples or form a model, and a dry workspace protects our tools. Choose the exact container and dry surface in the mission list. Experiment cups stay separate from food and drinks. Keep electronics away from liquids and clean up before storing parts. 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
Calibrate a sensor with a dry/damp comparison.
You have just practised read a digital sensor slowly and honestly. Now: calibrate a sensor with a dry/damp comparison.
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 module labels: +/VCC → 5V, −/GND → GND, S/AO → A1. Keep the board and all connectors outside the tray. Only the sensing area may touch the damp pad; never immerse the module.
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 WATER_PIN=A1;int wetThreshold=400;bool wetGivesHigher=true;
void setup(){pinMode(LED_PIN,OUTPUT);Serial.begin(9600);}
void loop(){int r=analogRead(WATER_PIN);Serial.println(r);bool wet=wetGivesHigher?r>wetThreshold:r<wetThreshold;digitalWrite(LED_PIN,wet);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, Labelled analog water-sensor module, Shallow household tray, Tissue or sponge, Dropper, Clean water. 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, Labelled analog water-sensor module, Shallow household tray, Tissue or sponge, Dropper, Clean water. An adult identifies the component pins from their printed labels. Unplug USB before building.
WHAT'S REALLY HAPPENING?
Exposed water-sensor tracks respond to electrical conduction. Water composition and contact change the reading; this is a model spill indication, not a calibrated flood or plant-health monitor.
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
Test all combinations of an AND and OR rule.