IoT challenges, checked by the same engine that runs them

Each one uses parts from the STEM Engine's library, so you can build it today, and an instructor can set it as a challenge with exactly these parts. The server checks the parts, the wiring and that it powers up.

• [01]Intermediate

  Solar weather station

  An ESP32 reads temperature and humidity from a DHT22 and shows them on an LCD, running off a solar panel that charges its own battery.

  1. Wire the DHT22 data line to an ESP32 pin
  2. Put the LCD on the I2C bus
  3. Charge the 18650 cells from the solar panel through the TP4056
  4. Power it all from the battery, not USB

  Parts: ESP32 DevKit V1 · DHT22 Humid/Temp · LCD 16x2 (I2C) · Solar Panel (6V 1W) · TP4056 Charger + Protection · 2S 18650 Pack (7.4V)

• [02]Beginner

  Smart irrigation node

  A soil-moisture probe tells an ESP32 when the bed is dry, and a relay switches the pump on until it is wet again.

  1. Read the soil-moisture probe on an analogue pin
  2. Drive the relay module from a GPIO pin
  3. Keep the pump circuit on the relay's switched side
  4. Choose the dry threshold

  Parts: ESP32 DevKit V1 · Soil Moisture Sensor · 5V Relay Module (1-channel) · USB 5V Power Supply

• [03]Beginner

  Intruder alarm

  A PIR sensor watches a doorway; when someone walks past, the Arduino flashes an LED and sounds a buzzer.

  1. Wire the PIR output to a digital input
  2. Drive the LED and the buzzer from two outputs
  3. Add a push button to reset the alarm

  Parts: Arduino Uno R3 · PIR Motion Sensor · Active Buzzer · Red LED (5mm) · Push Button

• [04]Beginner

  Parking sensor

  An HC-SR04 measures the gap to the wall behind a car and the buzzer beeps faster the closer it gets.

  1. Wire TRIG and ECHO to two digital pins
  2. Turn the echo time into centimetres
  3. Map the distance to the beep rate

  Parts: Arduino Uno R3 · HC-SR04 Ultrasonic · Active Buzzer · Red LED (5mm)

• [05]Advanced

  Obstacle-avoiding rover

  A 2WD rover drives forward, and when the ultrasonic sensor on its servo head sees something close it stops, looks both ways and turns to the clearer side.

  1. Mount the motors on the chassis and wire them to the L298N
  2. Put the HC-SR04 on the SG90 servo
  3. Power the motors from the LiPo, the logic from the board
  4. Drive it in the physics sim

  Parts: 2WD Robot Chassis · DC Gear Motor (Left) · DC Gear Motor (Right) · L298N Motor Driver · Arduino Uno R3 · HC-SR04 Ultrasonic · SG90 Micro Servo · 3.7V LiPo

• [06]Intermediate

  Solar sun tracker

  Two light sensors either side of a solar panel tell a servo which way to turn, so the panel follows the sun across the sky.

  1. Read each LDR through a voltage divider on an analogue pin
  2. Compare the two readings
  3. Turn the SG90 toward the brighter side
  4. Add a dead band so it does not jitter

  Parts: Arduino Uno R3 · LDR Photoresistor · Voltage Divider (1K/2K) · SG90 Micro Servo · Solar Panel (6V 1W)

1. [01]Your instructor sets the device and the rubric
2. [02]Enter alone, or invite your group to build together
3. [03]Wire the board, sensors and actuators in 3D
4. [04]Submit; the server re-derives and scores the circuit
5. [05]Download the finished model when it is complete

• DronesSee the build →
• RoversSee the build →
• HumanoidSee the build →
• WorkshopSee the build →
• Virtual SchoolSee the build →