Short-Duration Water-Level Experiment

Lower the water sensor step by step into a container and watch the reading climb. The sketch learns the empty and full readings as you go, reports a level, and prints LOW WATER and water OK events — then you study how repeatable it really is.

One of 7 projects in the ESP32 Plant Monitoring Learning Kit — the parts below are from that kit.

What you build and learn

• How a conductive water sensor turns depth into a voltage
• Why the response is not a straight line
• Detecting a threshold crossing as an event
• Why exposed-copper sensors corrode, and how to care for them

What this project uses

Every item is in the kit — nothing extra to buy.

◇

ESP32U

In the kit

DIY-025 conductive water sensor Water Level Sensor Module for Arduino, 3V–5V Liquid Level Detection Board, Analog Output Water Leak/Level Det… DIY-025

In the kit

breadboard Transparent 830 Points Solderless Breadboard Clear Prototype Circuit Board MB-102 High Quality DIY Electronic… DIY-295

In the kit

jumper wires Jumper Wire Assorted Pack 120 Pieces - Male-to-Male, Male-to-Female, Female-to-Female 10cm Ribbon Cables for… DIY-212

In the kit

user-supplied shallow non-metallic container and clean water Capacitive Soil Moisture Sensor Module v2.0, 3.3-5.5V, for Arduino - Moisture Detection Garden Watering DIY DIY-002

In the kit

Build this with

ESP32 Plant Monitoring Learning Kit

All 6 parts in one box, with this project and 6 more to build from them.

AED 65.00 See the kit Add kit to cart

Need only these parts? Order them loose · from AED 77.26 ▾

Used in this project tick what you still need

DIY-025 conductive water sensor Water Level Sensor Module for Arduino, 3V–5V Liquid Level Detection Board, Analog Output Water Leak/Level Det… DIY-025 · ×1

AED 24.50

In stock

breadboard Transparent 830 Points Solderless Breadboard Clear Prototype Circuit Board MB-102 High Quality DIY Electronic… DIY-295 · ×1

AED 15.75

In stock

jumper wires Jumper Wire Assorted Pack 120 Pieces - Male-to-Male, Male-to-Female, Female-to-Female 10cm Ribbon Cables for… DIY-212 · ×1

AED 25.02

In stock

user-supplied shallow non-metallic container and clean water Capacitive Soil Moisture Sensor Module v2.0, 3.3-5.5V, for Arduino - Moisture Detection Garden Watering DIY DIY-002 · ×1

AED 11.99

In stock

Selected parts AED 77.26

Add 4 parts to cart

One of each part. Packs (resistor assortment, jumper wires) already hold more than a single build needs. ESP32U: included in the kit, ask us for it loose. Delivery is AED 20, free on orders AED 100+.

Connections

Unplug USB before you change any wire. Pin names are the labels printed on the board.

Step by step

1. In Arduino IDE install the ESP32 boards package (Boards Manager → esp32 by Espressif) and, from Library Manager, Adafruit BME280 and Adafruit Unified Sensor. Select the ESP32 Dev Module board and your USB port.
2. With USB unplugged, wire the water sensor: + to 3V3, − to GND, S to GPIO35. Use longer jumpers so the electronics stay well away from the water.
3. Mark depths on the sensor with a pen: 0.5, 1, 2, 3 cm from the bottom of the tracks.
4. Upload the Short-duration water-level experiment sketch. Open Tools → Serial Monitor at 115200 baud, with the line ending set to Newline. Start with the sensor dry.
5. Lower it to each mark and hold it still for a few seconds. Write down raw and level_pct at each depth.
6. Lift it back out step by step and note whether the readings match on the way up. Watch for the LOW WATER and water OK events.
7. Unplug USB, rinse the tracks in clean water and dry them with a paper towel.
8. Plot raw against depth. Is it a straight line? Repeat tomorrow and compare.

Sketch for this project

Written for the board in the kit. Copy it into the Arduino IDE; change the pin numbers if you wire it differently.

/*
  ESP32 Plant Monitoring Learning Kit
  Project 3: Short-duration water-level experiment

  Wiring: water level sensor + to 3V3, - to GND, S to GPIO35.
  Keep the experiment short and rinse and dry the board afterwards -
  the exposed tracks corrode.

  What you learn: the sensor's tracks conduct more the deeper the water,
  so the raw value rises with the level - but not in a straight line, and
  it drifts as the tracks corrode. The sketch tracks the empty and full
  readings it has seen and reports a level between them.
*/

const int WATER_PIN = 35;
const int ADC_SAMPLES = 16;
const int LOW_WATER_PERCENT = 20;
const unsigned long REPORT_MS = 500;

int emptyRaw = 4095, fullRaw = 0;
unsigned long lastReport = 0;
bool wasLow = true;

int readAverage() {
  long sum = 0;
  for (int i = 0; i < ADC_SAMPLES; i++) { sum += analogRead(WATER_PIN); delay(2); }
  return sum / ADC_SAMPLES;
}

void setup() {
  Serial.begin(115200);
  pinMode(WATER_PIN, INPUT);
  analogReadResolution(12);
  Serial.println("Start with the sensor dry, then lower it into water step by step.");
  Serial.println("t_s,raw,empty_raw,full_raw,level_pct,state");
}

void loop() {
  if (millis() - lastReport < REPORT_MS) return;
  lastReport = millis();
  int raw = readAverage();
  if (raw < emptyRaw) emptyRaw = raw;
  if (raw > fullRaw) fullRaw = raw;
  int level = (fullRaw - emptyRaw) > 100 ? constrain(map(raw, emptyRaw, fullRaw, 0, 100), 0, 100) : 0;
  bool low = level < LOW_WATER_PERCENT;
  if (low != wasLow) { wasLow = low; Serial.println(low ? "EVENT: LOW WATER" : "EVENT: water OK"); }
  Serial.print(millis() / 1000); Serial.print(",");
  Serial.print(raw); Serial.print(",");
  Serial.print(emptyRaw); Serial.print(",");
  Serial.print(fullRaw); Serial.print(",");
  Serial.print(level); Serial.print(",");
  Serial.println(low ? "LOW" : "OK");
}

• LOW_WATER_PERCENT (20) sets the LOW WATER event threshold.
• Empty and full are learned from the lowest and highest readings since start-up. Press EN to reset them.
• REPORT_MS (500) prints twice a second; ADC_SAMPLES (16) readings are averaged each time.

What you should see

• A header t_s,raw,empty_raw,full_raw,level_pct,state.
• raw near the bottom of the range when dry, rising as you lower it into water.
• EVENT: LOW WATER when the level falls below 20 %, EVENT: water OK when it rises again.
• The water sensor's tracks are bare copper. Dip it only for short tests, keep the connector end dry, then rinse and dry it — left in water it corrodes within days.

If it doesn't work

Try next

• Try tap water against water with a pinch of salt and compare readings at the same depth.
• Use your marked depth as the water-full capture in the main build.

More from this kit

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