MISSION 03 · INTERMEDIATE ARDUINO
Make button messenger. Explore digital input and input_pullup.
1 · Signal Studio
Your new skill: Digital input and INPUT_PULLUP
Revisit the skill you will reuse: pocket lighthouse
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.
A switch changes whether two terminals are connected. INPUT_PULLUP keeps the released input HIGH; pressing connects it to GND.
Look for: Some switches have four legs with internally joined pairs.
Before using it: Use opposite switched contacts, not a permanently joined pair.
Your turn: Press and release while naming HIGH and LOW.
WHAT YOU'LL USE
Reuse the parts between missions; these are not 45 simultaneous installations. Red/yellow/green means those three monochrome colours. RGB is a separate component with three channels.
BEFORE YOU BUILD
Unplug USB before changing connections. Use only the USB supply for this build; never connect 9V to 5V or a signal pin, and never connect to mains. An adult verifies variant, printed pin labels and resistor values before powering. Stop and unplug if a part becomes hot or damaged.
YOUR REWARD
PREDICT BEFORE YOU BEGIN
Before the test: which input will change, and what signal or reading do you expect?
BEFORE YOU BUILD
Parent check: exact part variant, labelled pins and stated values. If a check cannot be confirmed, keep this physical build unpowered and explore the code and prediction instead.
YOUR CHALLENGE
NEW POWER-UP
Digital input and INPUT_PULLUP
You have explored closed circuit and polarity. Now try digital input and input_pullup.
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.
Copy the complete code into Arduino IDE or download the sketch. Follow the matching component card before connecting power.
// First Wonder Brain Bots 03 — Button Messenger
// USB-powered model. Unplug before rewiring. Serial Monitor: 9600 baud.
const byte buttonPins[]={2};const byte buttonCount=1;
void setup(){Serial.begin(9600);pinMode(8,OUTPUT);digitalWrite(8,LOW);pinMode(2,INPUT_PULLUP);Serial.println("Ready. Follow your mission test.");}
void loop(){
unsigned long now=millis();
digitalWrite(8,digitalRead(2)==LOW);
}
CONNECTION MAP
BUILD PATH
STEP 1 OF 6
You will explore digital input and input_pullup. Gather the kit and home materials below. Unplug USB. Match the part names and printed labels.
A video demonstration will appear here when it is ready. You can follow the written step now.
You will explore digital input and input_pullup. Gather the kit and home materials below. Unplug USB. Match the part names and printed labels.
WHAT'S REALLY HAPPENING?
Digital input and INPUT_PULLUP. The program changes a signal, while USB supplies the energy. Current needs a complete path; the series resistor limits LED current. Check your rule against an example where it should respond and one where it should not. LOW, because the switch connects input to GND.
This is a tabletop learning model. Controllers reuse inputs, decisions and outputs to automate a useful signal.
FAIR-TEST CHALLENGE
Change one input or setting at a time; keep the wiring and protection unchanged. Repeat three trials.
WHEN IT DOESN'T WORK YET
Likely cause: Wrong board, port or cable connection
Try this first: Check Arduino Uno selection and supplied data cable. Unplug external wiring before checking upload on built-in LED.
Likely cause: Pin labels, input calibration or variant differs
Try this first: Unplug. Compare every connection with the map. Return to the earlier single-input mission; test one subsystem at a time.
Likely cause: Sensor settling, target, contact or calibration
Try this first: Follow the exact test setup; allow settling, use a flat target or check module pinout unpowered. Never replace unknown with a guessed safe reading.
CLEAN, RESET AND STORE
Disconnect USB, remove wires carefully and store components dry.
NEXT SKILL
Debounced edge and stored state