Grade 9 · From USB to Field System: ESP32 water quality

Measure temperature with a DS18B20

Follow the student handout to build, test and document this stage of the water-quality system.

Prepared lesson material. Start this task when your teacher introduces it; it is not currently assigned homework.

For this lesson

Open student handout (Word)All Grade 9 handouts →

2 pages · Use the handout for the complete instructions, examples and response spaces.

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For diagrams, visual examples and the full layout, open the handout above.

Lesson 6: Digital Temperature Sensing with the DS18B20

Wiring, libraries, code, and response test

Grade 9 MYP Design | From USB to Field System

Name: __________________

Class / team: __________________

Date: __________________

Today’s goals • Wire the DS18B20 to GPIO4. • Use OneWire and DallasTemperature. • Explain the pull-up resistor.

Key vocabulary

Term	Working definition
digital sensor
OneWire
data line
pull-up resistor
defined state
library

1. Wiring netlist

ESP32.3V3 -> DS18B20.VCCESP32.GND -> DS18B20.GNDDS18B20.DATA -> ESP32.GPIO46.8kΩ resistor between DS18B20.DATA and ESP32.3V3

Check wire colors Probe wire colors are not universal. Confirm the supplied sensor documentation or teacher-labelled cable before applying power.

2. Libraries

☐ Install OneWire by Paul Stoffregen.

☐ Install DallasTemperature by Miles Burton.

☐ Confirm both include statements compile.

3. Test code

#include <OneWire.h>#include <DallasTemperature.h>#define DS18B20_PIN 4OneWire oneWire(DS18B20_PIN);DallasTemperature sensors(&oneWire);void setup() { Serial.begin(115200); delay(1500); sensors.begin(); Serial.print("Sensors found: "); Serial.println(sensors.getDeviceCount());}void loop() { sensors.requestTemperatures(); float tempC = sensors.getTempCByIndex(0); if (tempC == DEVICE_DISCONNECTED_C) { Serial.println("ERROR: sensor disconnected"); } else { Serial.print("Temperature_C,"); Serial.println(tempC, 2); } delay(2000);}

4. Response test

Condition	Time	Temperature (°C)	Expected direction	Notes
Room-temperature water
Cooler water
Warmer water
Return to room-temperature

5. Explain

Why does the DATA line need a resistor to 3.3V?

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What would an error value tell you to check first?