Smart Greenhouse Vent

Arduino · Grade 5 · Guided practice

How to code this project

What you will make: Open a model vent at 28 C and close it at 26 C, keeping the previous position between these temperatures.

Teacher-supported Uno R3 + TMP36 + positional hobby servo reference build. Two different thresholds prevent rapid opening and closing near one boundary. Demonstration thresholds are not plant-care recommendations.

Before you start

• Reference build only: Arduino Uno R3 (5 V, 10-bit analog input), TMP36 temperature sensor, breadboard and insulated jumpers. This sketch is NOT for a DHT, thermistor, CO₂ sensor, Uno R4 or a 3.3 V board without adaptation.
• Disconnect power. An adult checks the exact TMP36 package pin diagram: connect +Vs to 5 V, GND to GND and Vout to A0. Follow the manufacturer’s decoupling guidance. Do not identify pins from a generic picture or another sensor’s wire colors.
• Use a teacher-approved USB supply and dry work surface. Open Serial Monitor at 9600 baud. Check a plausible room-temperature reading before building an enclosure.
• Use a standard positional servo, not a continuous-rotation motor. Adult selects an approved regulated servo supply of the correct voltage/current. Servo signal → D9; servo ground, supply ground and Uno GND join. Servo power comes from that separate supply, NOT an I/O pin. Do not join the external positive supply to Uno 5 V in this USB-powered build.
• First test the servo with NO vent linkage attached and keep fingers clear. Teacher checks its allowed travel and supply before fitting the model. Use only gentle hand warmth for real sensor tests; never flames, hot water or heat guns.

Opening and saving: In the teacher-installed Arduino IDE, open a new sketch, replace its entire contents with the starter, and save it with a project name. Select Arduino Uno and the connected port, click Verify (check mark), then Upload (arrow). Disconnect power before wiring. If uploading fails, check the board, USB data cable and port with the teacher. These starters still require an adult bench test on your actual hardware.

Build it one step at a time

1. First verify the TMP36 using the Classroom Air Monitor lesson. Then power off before adding the teacher-checked servo circuit.
2. Paste the full sketch. Verify the Servo library is available; use the official Arduino Servo library if an install is required.
3. Leave testMode true for a dry run. With the linkage detached, upload and enter 25, 29, 27 and 25 in Serial Monitor at 9600 baud, one number per line.
4. Observe: closed, open, still open, closed. Read how the two if conditions create a band in which the previous state is kept.
5. Set testMode false and upload again to read the real TMP36. Confirm plausible readings before any sensor warming.
6. Disconnect power to fit the vent. Adult checks that the chosen 20/100-degree positions cannot jam it. Repeat tests, changing travel angles only after inspection.

Complete starter sketch

#include <Servo.h>
Servo vent;
bool isOpen = false;
const bool testMode = true; // false = real TMP36 input
float testC = 25.0;
float readC() {
  float volts = analogRead(A0) * (5.0 / 1023.0);
  return (volts - 0.5) * 100.0;
}
void setup() {
  Serial.begin(9600);
  Serial.setTimeout(100);
  vent.write(20);
  vent.attach(9);
}
void loop() {
  if (testMode && Serial.available()) {
    testC = Serial.parseFloat();
    while (Serial.available()) Serial.read();
  }
  float c = testMode ? testC : readC();
  if (!isOpen && c >= 28.0) {
    isOpen = true;
    vent.write(100);
  } else if (isOpen && c <= 26.0) {
    isOpen = false;
    vent.write(20);
  }
  Serial.print(testMode ? "SIMULATED C: " : "Measured C: ");
  Serial.print(c);
  Serial.println(isOpen ? " OPEN" : " CLOSED");
  delay(250);
}

Predict, test and record

Write your name and date on the printed page. Run every test, note the actual result, and retest after one change.

If it does not work

• Vent chatters or board resets? Stop power; adult checks supply capacity, common ground and a jammed linkage.
• Temperature never responds to the sensor? Set testMode false and re-upload.
• Servo spins continuously? Wrong motor type; disconnect and use a positional servo.

Make one change

Explain what the vent does at exactly 26 and 28 C. Choose another justified pair of thresholds with the teacher and repeat both warming and cooling sequences.

We changed __________. We predicted __________. Our test showed __________.

Teacher pacing: Use a 45-minute coding session: 5 minutes to predict, 10 to model a first working response, 20 for paired building, 7 for tests and 3 to save and explain. Continue in another meeting if setup or debugging takes longer; do not rush hardware checks.

Grade 5 support: Start with the working reference version, then explain each condition or state. Keep an input/expected/actual test log and change only one variable at a time.

Teacher learning resources

• Analog Devices: TMP36 specifications and datasheet ↗
• Arduino: analogRead reference ↗
• Arduino: basic servo control ↗

Preview resources before class. Follow this page’s specified reference build; another tutorial may use different hardware.

Print support: The lesson’s Print button includes this guide, recipe and test table.