Fertilizer Doser Automation: Peristaltic Pump with Arduino

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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.

Table of Contents

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

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:

  1. Place pump inlet in water, outlet into a measuring cylinder
  2. Run pump for exactly 60 seconds
  3. Measure volume dispensed
  4. Calculate: mL per second = volume / 60
  5. 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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