Build a Smart Drink Station with Precise Ingredient Tracking!
Meet Brewster — an Arduino drink station that uses load cells to weigh every ingredient as it dispenses, a temperature sensor to check the water, and a water level sensor to make sure it never runs dry — keeping perfect track of exactly how much of each ingredient is left.
⚖️ Say hi to Brewster, your smart drink station!
What Is a Smart Drink Station, Anyway?
Most drink machines guess how much of an ingredient to add using time — "run the motor for 2 seconds." Brewster does it smarter: it uses load cells (tiny scales) to actually weigh each ingredient as it comes out, stopping the exact moment the right amount has been dispensed. That means every drink is consistent, and Brewster always knows exactly how much of each ingredient is left.
What You'll Need
Gather these parts before you start building!
Arduino Uno
The brain that reads every sensor and runs the dispensers.
Load Cells + HX711 Amplifiers
One under each ingredient container — coffee, sugar, and milk powder.
DS18B20 Waterproof Temp Sensor
Checks the water temperature before brewing.
Analog Water Level Sensor
Warns if the water tank is running low.
SG90 Micro Servo Motors
Open a small gate on each container to dispense.
0.96" I2C OLED Display
Shows temperature, water level, and ingredient stock.
Push Buttons
Select Coffee, Latte, or Hot Chocolate.
Small Buzzer
Alerts for low stock or low water.
Small Containers
Hold coffee grounds, sugar, and milk powder.
Breadboard + ~25 Jumper Wires
Connects every sensor and servo.
The Circuit Diagram
Three load cells, a temperature probe, a water sensor, three servos, three buttons, and an OLED — all fit neatly on one Arduino Uno.
Step-by-Step Build Instructions
We'll build the sensing systems first, then the dispensers. Work with an adult on wiring and calibration!
Mount the three load cells
Fix each load cell horizontally between a small platform and the base, then place one ingredient container on each platform — coffee, sugar, and milk powder.
💡 Tip: Calibrate each load cell using a known weight (like a 100g object) before trusting its readings!Add the water temperature sensor
Place the waterproof DS18B20 probe into your water reservoir. It continuously reports the water's temperature to the Arduino.
Install the water level sensor
Mount the analog water level sensor vertically inside the reservoir so it reads a higher value as the water rises.
Build the dispenser gates
Cut a small pour-hole in the bottom of each container and attach a servo-controlled flap or gate that opens briefly to release ingredient.
Add the OLED display and buttons
Mount the OLED where it's easy to read, and place the three drink-selection buttons (Coffee, Latte, Hot Chocolate) below it.
Wire the buzzer and finish assembly
Add the buzzer for low-stock alerts, then double-check every wire against the circuit diagram before powering on.
Upload the code and test
Upload the code below, place a cup under the dispensers, and press a drink button. Watch Brewster weigh out each ingredient precisely!
The Arduino Code
This code needs the HX711, OneWire, DallasTemperature, Servo, and Adafruit_SSD1306 libraries. Copy it in, calibrate your load cells, then click Upload.
// 🥤🤖 Brewster the Smart Drink Station — Arduino Load Cell + Sensor Project // Weighs every ingredient precisely and tracks inventory as it dispenses #include <HX711.h> #include <OneWire.h> #include <DallasTemperature.h> #include <Servo.h> #include <Wire.h> #include <Adafruit_GFX.h> #include <Adafruit_SSD1306.h> // ---- Load cells (3 ingredients) ---- HX711 scale[3]; const int dtPins[3] = {2, 4, 6}; const int sckPins[3] = {3, 5, 7}; const char* names[3] = {"Coffee", "Sugar", "Milk"}; float calibration[3] = {420.0, 410.0, 415.0}; // set during calibration float lowStockGrams = 50.0; // alert threshold // ---- Temperature sensor ---- OneWire oneWire(8); DallasTemperature tempSensor(&oneWire); // ---- Water level sensor ---- const int waterPin = A0; const int waterLowThreshold = 200; // ---- Dispenser servos ---- Servo dispensers[3]; const int servoPins[3] = {9, 10, 11}; // ---- Buttons + buzzer ---- const int buttonPins[3] = {A1, A2, A3}; // Coffee, Latte, Hot Chocolate const int buzzerPin = 12; // ---- Recipes: grams of {Coffee, Sugar, Milk} per drink ---- int recipes[3][3] = { {15, 5, 0}, // Coffee {10, 0, 20}, // Latte {0, 15, 25} // Hot Chocolate }; // ---- OLED ---- Adafruit_SSD1306 display(128, 64, &Wire, -1); void setup() { for (int i = 0; i < 3; i++) { scale[i].begin(dtPins[i], sckPins[i]); scale[i].set_scale(calibration[i]); scale[i].tare(); // zero out each scale dispensers[i].attach(servoPins[i]); dispensers[i].write(0); // gate closed pinMode(buttonPins[i], INPUT_PULLUP); } pinMode(buzzerPin, OUTPUT); tempSensor.begin(); display.begin(SSD1306_SWITCHCAPVCC, 0x3C); showStatus("Brewster Ready"); } void loop() { for (int drink = 0; drink < 3; drink++) { if (digitalRead(buttonPins[drink]) == LOW) { makeDrink(drink); } } } // Checks water, then dispenses each ingredient in the recipe by weight void makeDrink(int drinkIndex) { if (!isWaterReady()) { showStatus("Check Water!"); return; } showStatus("Making Drink..."); for (int i = 0; i < 3; i++) { int grams = recipes[drinkIndex][i]; if (grams > 0) dispenseByWeight(i, grams); } tone(buzzerPin, 1500, 200); showStatus("Enjoy!"); } // Opens a gate and watches the load cell until the target weight is reached void dispenseByWeight(int index, int targetGrams) { float startWeight = scale[index].get_units(3); dispensers[index].write(90); // open gate while (true) { float current = scale[index].get_units(3); float dispensed = startWeight - current; // weight leaving container if (dispensed >= targetGrams) break; delay(50); } dispensers[index].write(0); // close gate checkStock(index); } // Warns if a container is running low void checkStock(int index) { float remaining = scale[index].get_units(3); if (remaining < lowStockGrams) { tone(buzzerPin, 400, 400); showStatus(String(names[index]) + " Low!"); delay(1500); } } // Confirms the water is warm enough and the tank isn't empty bool isWaterReady() { tempSensor.requestTemperatures(); float tempC = tempSensor.getTempCByIndex(0); int waterLevel = analogRead(waterPin); return (tempC > 60 && waterLevel > waterLowThreshold); } // Shows a short status message on the OLED void showStatus(String msg) { display.clearDisplay(); display.setTextSize(1); display.setTextColor(SSD1306_WHITE); display.setCursor(0, 20); display.println(msg); display.display(); }
How Does Brewster Actually Work?
Here are the big robotics ideas hiding inside this project:
Weight-Based Dispensing
Instead of guessing with a timer, Brewster keeps checking the load cell while the gate is open, and closes it the instant the target weight has left the container — far more precise than timing alone.
Real Inventory Tracking
Because each container sits on its own scale, Brewster always knows exactly how many grams of each ingredient remain — true live inventory, not a guess.
Sensor-Based Safety Checks
Before dispensing anything, isWaterReady() checks both temperature and water level — the drink only starts if both conditions are safely met.
Recipes as Data
Storing each drink's ingredients in the recipes array (instead of separate code per drink) makes it easy to add new drinks just by adding a new row.
🧑🔬 Safety First!
- Build with an adult, especially when wiring load cells and handling water near electronics.
- This project only monitors water temperature — it does not include a heating element. Never add a real heater without proper adult supervision and safety design.
- Keep all electronics away from spills — use a sealed or elevated base for the water reservoir.
- Use only dry, food-safe test ingredients (like rice or oats) for practice runs before trying real coffee, sugar, or milk powder.
- Clean all parts that touch ingredients before and after each use.
Frequently Asked Questions
How do I calibrate a load cell?
Place a known weight (like a 100g object) on the load cell, read the raw value it reports, then divide that raw value by 100 to get your calibration number for set_scale().
Why use grams instead of just timing the servo?
Ingredients can clump, settle, or pour at different speeds. Weighing the actual amount dispensed guarantees consistency no matter how the ingredient flows.
Can I add a fourth drink or ingredient?
Yes! Add a new load cell, servo, and button, then extend the recipes array with one more column and row for your new drink.
What age group is this project good for?
Because it combines multiple sensors and precise calibration, this project is best for kids around age 10+ working closely with an adult familiar with electronics.
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