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

Integrate three sensors

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 →

3 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 9: Integrating All Three Sensors

Wiring audit, combined code, and troubleshooting log

Grade 9 MYP Design | From USB to Field System

Name: __________________

Class / team: __________________

Date: __________________

Today’s goals • Combine three sensors without losing safe power and signal conditions. • Use structured fault isolation.

Key vocabulary

Term	Working definition
integration
pin definition
common ground
subsystem
fault isolation
hypothesis
evidence

1. Pin and power map

Device	Power	Ground	Signal pin	Extra component
DS18B20	3.3V	GND	GPIO4	6.8k pull-up to 3.3V
EC board	3.3V	GND	AO → GPIO1	T1 unused
Turbidity board	5V	GND	Divider point → GPIO2	10k/20k divider

2. Integration checklist

☐ Power OFF while wiring.

☐ All grounds connect to one common-ground net.

☐ Each sensor has already worked by itself.

☐ GPIO1, GPIO2, and GPIO4 match the code.

☐ Turbidity divider point was measured below 3.3V.

☐ No raw 12V reaches ESP32 or sensors.

3. Integrated test code

#include <OneWire.h>#include <DallasTemperature.h>#include <DFRobot_EC.h>#include <EEPROM.h>#define DS18B20_PIN 4#define EC_PIN 1#define TURBIDITY_PIN 2OneWire oneWire(DS18B20_PIN);DallasTemperature tempSensor(&oneWire);DFRobot_EC ec;int averageAnalog(int pin) { long total = 0; for (int i = 0; i < 20; i++) { total += analogRead(pin); delay(10); } return total / 20;}void setup() { Serial.begin(115200); EEPROM.begin(32); tempSensor.begin(); ec.begin(); analogReadResolution(12); analogSetPinAttenuation(EC_PIN, ADC_11db); analogSetPinAttenuation(TURBIDITY_PIN, ADC_11db); Serial.println("temp_C,ec_raw,ec_mV,ec_mS_cm,turb_raw,turb_gpio_V");}void loop() { tempSensor.requestTemperatures(); float tempC = tempSensor.getTempCByIndex(0); int ecRaw = averageAnalog(EC_PIN); float ecMV = ecRaw * (3300.0 / 4095.0); float ecMS = ec.readEC(ecMV, tempC); ec.calibration(ecMV, tempC); int turbRaw = averageAnalog(TURBIDITY_PIN); float turbGPIOV = turbRaw * (3.3 / 4095.0); Serial.print(tempC, 2); Serial.print(','); Serial.print(ecRaw); Serial.print(','); Serial.print(ecMV, 1); Serial.print(','); Serial.print(ecMS, 3); Serial.print(','); Serial.print(turbRaw); Serial.print(','); Serial.println(turbGPIOV, 3); delay(2000);}

4. First integrated readings

Reading	Temperature	EC raw	EC mS/cm	Turbidity raw	Turbidity GPIO V
1
2
3

5. Troubleshooting log

Symptom	Evidence checked	Hypothesis	One change made	Result

Recommended order 1) power voltage, 2) common ground, 3) signal voltage, 4) physical pin, 5) code pin definition, 6) library/compile messages. Change one thing at a time.