🍹 Automated Drink Mixer

A robotic bartender combining pumps, load cells, and a web interface.

📋 Overview

Combine liquid handling with precise weight measurement. Users select a drink recipe on a web app, and the machine dispenses exact milliliter ratios using peristaltic pumps and a load cell feedback loop.

What you'll learn: Load cell calibration (HX711), pump transistor switching, and managing complex recipe JSON data.

Estimated time: 8-10 hours. Difficulty: ⭐⭐⭐⭐⭐ Expert.

🧩 Components Needed

Component	Specification	Qty	Notes
ESP32	WiFi	1	Hosts the web UI
Peristaltic Pumps	12V	4	Food safe, easy to clean
TIP120 / MOSFETs	Transistors	4	To drive the 12V pumps
Load Cell + HX711	1kg max	1	Weighs the glass
Power Supply	12V 5A	1

📖 Step-by-Step Tutorial

Pump Circuits

Wire each 12V pump to a MOSFET, controlled by an ESP32 GPIO. Add flyback diodes across the pumps.

Calibrate Load Cell

Place an empty glass on the scale. Tare it. Pour exactly 100ml (100g) of water and calculate the HX711 calibration factor.

Web Interface

Serve a React or plain HTML page with drink recipes. E.g. "Rum & Coke: 50ml Pump 1, 150ml Pump 2".

Dispensing Logic

Turn on Pump 1. Constantly read the scale until the weight increases by 50g. Turn off Pump 1. Repeat for Pump 2.

💡

Peristaltic pumps are best for drinks because the liquid only touches the silicone tube, never the pump mechanism. They are hygienic and self-priming.

💻 Code / Configuration

drink_mixer.ino

INO

// Dispensing Logic (Snippet)
#include "HX711.h"

HX711 scale;
const int pump1 = 25;
const int pump2 = 26;

void setup() {
  scale.begin(16, 4); // DOUT, SCK
  scale.set_scale(2280.f); // Calibration factor
  scale.tare();
  
  pinMode(pump1, OUTPUT);
  pinMode(pump2, OUTPUT);
}

void pourIngredient(int pumpPin, float targetGrams) {
  scale.tare(); // Zero the scale before pouring
  float currentWeight = 0;
  
  digitalWrite(pumpPin, HIGH); // Turn pump on
  
  while (currentWeight < targetGrams) {
    currentWeight = scale.get_units(5); // Average 5 readings
    delay(50);

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