Smart Water Bottle with Hydration Reminders and Intake Tracking using ESP32

A smart water bottle is a reusable bottle with an ESP32 microcontroller, a water-level sensor and a reminder output that measures how much water leaves the bottle, adds each sip to a daily total, and prompts the user when too long has passed without drinking. This build syncs that history to a companion dashboard over Bluetooth Low Energy.

The build senses the falling water level, converts the change into millilitres drunk, shows the remaining daily goal on a small display, and keeps the history on the dashboard for review at the end of the day.

The Problem
A smart water bottle exists because most people do not drink steadily through the day, even when they carry water everywhere. The smart water bottle in this project addresses a simple failure: a plain bottle gives no feedback at all, so a student in back-to-back lectures or a desk worker in long meetings can reach the evening having drunk far less than planned, with only thirst as the signal. Phone reminder apps try to fill the gap, but they rely on the user remembering to log every sip by hand, and a missed log makes the whole day's record wrong. Printed time markers are just as weak: they show a target hour, not what was actually drunk, and they cannot adapt when the day starts late or a refill happens. This project replaces guessing with measurement: the bottle itself records each sip, so the daily total is based on what left the bottle, not on what someone remembered to type.

From cap to dashboard, the mechanism is a short loop: sense, settle, convert, display, remind and sync. The level sensor in the smart cap watches the water, and the ESP32 firmware samples it, but it does not trust every reading — it waits until the bottle has rested upright for a settling interval, so a tilt while the bottle is carried cannot masquerade as drinking. Once a reading is stable, the firmware compares it with the last accepted level: a drop becomes millilitres drunk through the bottle's calibrated cross-section, while a rise becomes a refill that resets the baseline without touching the drunk total. The new total appears on the OLED display and the reminder timer restarts; if it runs out with no confirmed sip, the LED and buzzer prompt the user. Every event travels over Bluetooth Low Energy to the dashboard, which redraws the goal ring, hourly bars and event history, and the total clears at day's end.

1. The smart cap is fitted to a standard reusable bottle, with the level sensor positioned above the water and the ESP32 board, OLED display and buzzer mounted in the cap housing.
2. On power-up, the ESP32 reads the starting water level and sets the day's baseline, then advertises itself over Bluetooth Low Energy so the companion dashboard can connect.
3. Between sips, the firmware samples the level sensor and waits for a stable, upright reading, ignoring readings taken while the bottle is tilted or in motion.
4. When a stable level drop is confirmed, the drop is converted to millilitres using the bottle's calibrated cross-section, and the daily total and remaining goal are updated on the display.
5. If no confirmed sip arrives within the reminder interval, the LED glows and the buzzer sounds briefly; one press of the cap button snoozes the reminder once.
6. A level rise larger than a sip threshold is treated as a refill, resets the level baseline, and is logged separately so it never inflates the drunk total.
7. Each confirmed sip, refill and reminder event is sent over Bluetooth Low Energy to the dashboard, which redraws the goal ring, the hourly bars and the event history.
8. At midnight, or on a manual reset from the dashboard, the daily total clears and a new day starts with the current level as its baseline.

Comparison: smart bottle vs a regular bottle

Tech stack:

• ESP32 microcontroller (Wi-Fi + Bluetooth Low Energy)
• Water-level sensor (non-contact level sensing in the cap)
• OLED display + LED + buzzer (on-bottle feedback)
• Arduino IDE firmware (C/C++)
• HTML/CSS/JavaScript companion dashboard (single-file demo)
• Bluetooth Low Energy (bottle-to-dashboard link)

The bottle's capabilities centre on four things: measurement without manual logging, reminders that respect real use, feedback in two places, and totals that stay honest across refills. The level sensor and ESP32 turn each stable level drop into millilitres drunk, so the user never opens an app to log a sip. Reminders arrive as a gentle LED glow and a short buzzer after a quiet interval, but they pause while the bottle is tilted or moving. Feedback lives both on the bottle, where a small OLED display shows the level, the amount drunk and the amount remaining, and on the dashboard, where a goal ring, hourly bars and an event history make the day's pattern visible. Finally, refill handling keeps the record truthful: a level rise is logged as a refill and resets the baseline, never inflating the drunk total.

• [Automatic sip measurement] A level sensor under the smart cap measures the water level, and the ESP32 converts each stable drop into millilitres drunk, so intake is recorded without any manual logging.
• [Timed hydration reminders] A gentle LED glow plus a short buzzer prompt fires after a configurable quiet interval (design target: 60 minutes), and reminders pause while the bottle is tilted or moving.
• [On-bottle display] A small OLED screen shows the water level as a percentage, the millilitres drunk today, and the millilitres remaining toward the daily goal at a glance.
• [Companion dashboard] Intake by hour, the goal ring, and a reminder and sip history are shown on a single dashboard that syncs from the bottle over Bluetooth Low Energy.
• [Refill-aware totals] Refills are detected as a level rise and do not count as drinking, so the daily total only grows when water actually leaves the bottle.
• [Adjustable daily goal] The goal (design target: 2,500 ml per day for the demo profile) can be changed in the dashboard, and the reminder interval and display follow the new goal.
• [Rechargeable, cap-mounted build] The ESP32 board, sensor, display and a rechargeable lithium cell sit in a removable smart cap, so the bottle itself can still be washed separately.
• [Builder calibration note] During the build, raw level readings drifted while the bottle was carried, so the firmware only accepts a reading after the bottle has rested upright for a settling interval (design target: 5 seconds) — a fix that cut false sips in bench testing and is documented in the report as an original build note.

• ESP32 smart-cap hardware build: board, level sensor, OLED display, LED, buzzer and rechargeable cell in a removable cap
• Complete firmware source (Arduino IDE) with sip detection, refill handling, reminder logic and Bluetooth Low Energy sync
• Single-file companion dashboard demo with goal ring, hourly intake chart and reminder history
• Wiring diagram and cap-assembly guide with the settling-interval calibration note
• Project report PDF (background, sensing method, firmware logic, calibration, limitations)
• PPT presentation for final review
• Viva Q&A preparation document (ESP32, BLE, level sensing, calibration, power)