Fertilizer Doser Automation: Peristaltic Pump with Arduino

A fertilizer doser automation system using a peristaltic pump with Arduino delivers precise nutrient dosing for hydroponics, greenhouse fertigation, and drip irrigation — eliminating manual mixing errors and reducing fertilizer waste by 30–50%. This guide walks through building a complete automated fertilizer dosing system with peristaltic pumps, EC/TDS feedback, and timed injection cycles.

Why Automate Fertilizer Dosing
Understanding Peristaltic Pumps
Components Required
Circuit and Wiring
Arduino Dosing Code
Pump Calibration
EC Sensor Feedback Loop
Indian Agriculture Applications
Frequently Asked Questions

Why Automate Fertilizer Dosing

Manual fertilizer mixing leads to inconsistent nutrient concentrations, over- or under-feeding plants, and significant labour costs. In Indian agriculture, fertilizer represents 15–25% of crop production costs. Automated dosing provides:

Precision: Dose accuracy within ±2% vs ±20% for manual mixing
Labour savings: Reduces fertigation labour from 2–3 hours/day to 15 minutes
Yield increase: Consistent nutrient delivery improves yields by 15–30% in greenhouse crops
Fertilizer savings: Up to 35% reduction via EC-feedback dosing vs fixed-rate application
Scalability: One controller can manage 4–8 separate nutrient channels (N, P, K, micronutrients, pH up/down)

Understanding Peristaltic Pumps

Peristaltic pumps use rotating rollers to squeeze flexible tubing, pushing fluid forward without the fluid touching any pump mechanism. Key advantages for fertigation:

Self-priming — works with concentrated fertilizer solutions
No contamination between channels — each channel has dedicated tubing
Accurate volumetric dosing — calibrate once, repeatable forever
Handles viscous fertilizer concentrates (up to 500 cP)
Easy to sanitise — replace tubing annually

Common flow rates: 100 mL/min (small greenhouse) to 1000 mL/min (commercial scale). For hobby and small farms, 100–300 mL/min DC peristaltic pumps at 12V are widely available in India for ₹500–1,500 each.

Components Required

Pumps and Control Modules from Zbotic

12V DC Mini Submersible Water Pump — ₹199 (for main irrigation water supply)
5V/12V Relay Control Module — ₹89 (for controlling pumps)
Capacitive Soil Moisture Sensor — ₹129 (substrate monitoring for pot/bag culture)

Full parts list:

Arduino Uno or Mega (Mega recommended for 4+ channels)
4× Peristaltic dosing pumps (12V, 100 mL/min)
4-channel relay module (5V)
TDS/EC sensor module (analog output)
pH sensor module (optional, for pH correction channel)
16×2 LCD with I2C adapter
DS3231 RTC module
Push buttons (3×) for menu navigation
12V 5A power supply
Silicone peristaltic tubing (6mm ID)

Circuit and Wiring

Relay connections (active LOW relays):

Relay IN1 → Arduino D4 (Nutrient A pump)
Relay IN2 → Arduino D5 (Nutrient B pump)
Relay IN3 → Arduino D6 (Micronutrient pump)
Relay IN4 → Arduino D7 (pH adjustor pump)
TDS sensor AOUT → Arduino A0
pH sensor AOUT → Arduino A1
LCD SDA → Arduino A4, SCL → A5
DS3231 SDA → A4, SCL → A5 (same I2C bus)

Power all relay pump loads from a separate 12V supply. Use snubber diodes (1N4007) across pump terminals to protect relay contacts from back-EMF.

Arduino Dosing Code

#include <Wire.h>
#include <LiquidCrystal_I2C.h>
#include <RTClib.h>

LiquidCrystal_I2C lcd(0x27, 16, 2);
RTC_DS3231 rtc;

// Relay pins (active LOW)
#define PUMP_A    4   // Nutrient A (Nitrogen base)
#define PUMP_B    5   // Nutrient B (Phosphate + Potassium)
#define PUMP_MICRO 6  // Micronutrients
#define PUMP_PH   7   // pH adjustment

// Sensor pins
#define TDS_PIN   A0
#define PH_PIN    A1

// Target parameters
const float TARGET_EC  = 1.8;  // mS/cm (adjust per crop)
const float TARGET_PH  = 6.0;  // pH (adjust per crop)
const float EC_TOLERANCE = 0.2;
const float PH_TOLERANCE = 0.3;

// Pump calibration (mL per second)
const float PUMP_RATE = 1.67; // 100 mL/min = 1.67 mL/s

// Dose schedule: dose every 4 hours during day
int doseHours[] = {6, 10, 14, 18};
bool dosedThisHour[24] = {false};

void setup() {
  Serial.begin(9600);
  Wire.begin();
  lcd.init();
  lcd.backlight();
  rtc.begin();

  // Set relay pins HIGH (relay off)
  for (int p = 4; p <= 7; p++) {
    pinMode(p, OUTPUT);
    digitalWrite(p, HIGH);
  }

  lcd.setCursor(0, 0);
  lcd.print("FertiDoser v1.0");
  delay(2000);
}

float readTDS() {
  int raw = analogRead(TDS_PIN);
  float voltage = raw * (5.0 / 1023.0);
  // TDS sensor EC calculation (simplified)
  float ec = (133.42 * voltage * voltage * voltage
            - 255.86 * voltage * voltage
            + 857.39 * voltage) * 0.5 / 1000.0; // Convert to mS/cm
  return ec;
}

float readPH() {
  int raw = analogRead(PH_PIN);
  float voltage = raw * (5.0 / 1023.0);
  float ph = -5.70 * voltage + 21.34; // Calibration: adjust these values
  return ph;
}

void doseSeconds(int pumpPin, float seconds) {
  if (seconds <= 0) return;
  int ms = (int)(seconds * 1000);
  digitalWrite(pumpPin, LOW);  // Pump ON
  delay(ms);
  digitalWrite(pumpPin, HIGH); // Pump OFF
  delay(500); // Brief pause between pumps
}

void runDoseCycle() {
  float currentEC = readTDS();
  float currentPH = readPH();

  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("EC:");
  lcd.print(currentEC, 1);
  lcd.print(" pH:");
  lcd.print(currentPH, 1);

  // Dose nutrients if EC is low
  if (currentEC < TARGET_EC - EC_TOLERANCE) {
    float ecDeficit = TARGET_EC - currentEC;
    // Dose A and B in equal parts for 3 seconds minimum, up to 30s
    float doseTime = constrain(ecDeficit * 10.0, 3.0, 30.0);

    lcd.setCursor(0, 1);
    lcd.print("Dosing A+B ");
    lcd.print((int)doseTime);
    lcd.print("s");

    doseSeconds(PUMP_A, doseTime);
    doseSeconds(PUMP_B, doseTime);
    doseSeconds(PUMP_MICRO, doseTime * 0.1); // Micro = 10% of A/B
  }

  // Adjust pH if needed
  if (currentPH > TARGET_PH + PH_TOLERANCE) {
    // Dose pH down (phosphoric acid) - 2 seconds
    doseSeconds(PUMP_PH, 2.0);
    lcd.setCursor(0, 1);
    lcd.print("pH Down dosed   ");
  }
}

void loop() {
  DateTime now = rtc.now();
  int hr = now.hour();

  // Check if this is a scheduled dose hour
  for (int i = 0; i < 4; i++) {
    if (hr == doseHours[i] && now.minute() == 0 && !dosedThisHour[hr]) {
      runDoseCycle();
      dosedThisHour[hr] = true;
    }
  }

  // Reset daily dose flags at midnight
  if (hr == 0 && now.minute() == 0) {
    memset(dosedThisHour, false, sizeof(dosedThisHour));
  }

  // Display current readings every minute
  if (now.second() == 0) {
    float ec = readTDS();
    float ph = readPH();
    lcd.setCursor(0, 0);
    lcd.print("EC:");
    lcd.print(ec, 2);
    lcd.print(" mS/cm  ");
    lcd.setCursor(0, 1);
    lcd.print("pH:");
    lcd.print(ph, 2);
    lcd.print("       ");
  }

  delay(1000);
}

Pump Calibration

Accurate dosing requires calibrating each pump individually:

Place pump inlet in water, outlet into a measuring cylinder
Run pump for exactly 60 seconds
Measure volume dispensed
Calculate: mL per second = volume / 60
Update PUMP_RATE constant in code

Re-calibrate monthly as peristaltic tubing stretches slightly over time. Mark tubing with installation date — replace every 6–12 months.

EC Sensor Feedback Loop

The EC (electrical conductivity) feedback loop ensures precise dosing without over-fertilisation:

Measure current EC before each dose cycle
Calculate deficit from target EC
Dose proportionally — larger deficit = longer pump run time
Wait 5 minutes and remeasure before second dose (mixing time)
Log all doses to EEPROM for agronomist review

Indian Agriculture Applications

This system is widely applicable across Indian horticulture:

Polyhouse/net house tomato (Nasik, Pune): 4-channel dosing with EC targets 2.5–3.5 mS/cm for fruiting stage
Hydroponic leafy greens (urban farms, Bangalore, Mumbai): EC target 1.2–1.8 mS/cm for lettuce, spinach
Capsicum/bell pepper (AP, Telangana): pH 5.8–6.2 critical for nutrient availability
Strawberry (Mahabaleshwar): Low EC (0.8–1.2) with precise pH control improves Brix

Frequently Asked Questions

Can I use a relay module to directly control peristaltic pumps?

Yes, for DC 12V pumps drawing under 3A per channel. Most relay modules handle up to 10A/30VDC. Always add flyback diodes across motor terminals and use separate power supply for pumps (do not power from Arduino’s 5V rail).

What is the minimum dose volume I can achieve?

With a 100 mL/min pump, a 100ms pulse delivers ~0.17 mL. This is precise enough for hobbyist systems. For commercial precision dosing below 1 mL, use slower pumps (10–50 mL/min) or PWM speed control.

How often should I calibrate the TDS sensor?

Calibrate at installation with a reference EC solution, then verify monthly. Clean the sensor probe weekly in diluted hydrochloric acid (1:10) to remove mineral deposits that cause drift.

Can I add WiFi and remote monitoring?

Yes — replace Arduino Uno with ESP32. Add a web dashboard or ThingSpeak channel to log EC, pH, and dosing events remotely. Set up Telegram alerts when EC drifts more than 0.5 mS/cm from target.

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