Soda Can Prevention Device

The idea was to build a product that could make someone more aware of how often they drink soda. Instead of making a normal container, we wanted the case to interrupt the habit. The user has to wait, stay calm, and put the can back before the system stops bothering them.

I do not see this as a perfect consumer product or medical solution. It is more of a behavior-aware prototype: a physical system that uses friction, feedback, and tracking to make an automatic action feel less automatic.

The system starts when the user touches the sensor. From there, the device begins a countdown, checks for loud tampering through the microphone, displays messages on the OLED, unlocks the lid through a servo, and uses the load cell to measure how much was consumed once the can is returned.

The project used two ESP32s. The first ESP32 handled the main sensors and actuators inside the case. The second ESP32 stored and displayed usage data like pickups, grams consumed, cans finished, and daily, weekly, and lifetime totals.

The enclosure had to do a lot at once. It needed to hold the can, house the electronics, support the load cell, expose the OLED and sensors, and create a locking geometry that the servo could actually control. Madeline created the initial design direction, and I pushed a lot of the later redesigns because I had the printer and could keep testing fit after fit.

A lot of the work came down to small physical details: making snug interfaces, leaving space for wires, adjusting the lock geometry, and making sure the printed parts could actually assemble around real components instead of just looking good in CAD.

The CAD went through multiple versions as the project became more real. The early can-holder shape was simple, but once the electronics, load cell, and locking mechanism were added, the geometry needed more structure. The latch and hinge area became one of the most important regions because it decided whether the lock would feel real or flimsy.

The servo was the physical lock. Once the waiting period ended, the servo moved the latch and allowed the user to access the can. The point was not just to move a part; the geometry had to make the case feel locked while still being simple enough to print, assemble, and debug.

This was one of the areas where the product became more mechanical than just electronic. The sensor logic only mattered if the lock actually controlled access to the drink.

The electronics were the densest part of the build. The main ESP32 had to connect to the touch sensor, microphone, OLED, HX711/load cell, speaker, servo control, voltage pins, and power rails. There were enough wires that the internal packaging became its own engineering problem.

My workflow was to add one component at a time. I would test a sensor by itself, debug it, confirm the code worked, then integrate the next component. That kept the project manageable instead of turning the whole system into one giant mystery.

The load cell was the foundation of the tracking system. When the user started the sequence, the device recorded the starting weight of the can. After the user returned the can, it measured the ending weight and estimated how much liquid was consumed.

This turned the prototype from a simple lockbox into something that could actually measure behavior. Instead of only blocking access, the device could report pickups, grams consumed, cans finished, and usage over time.

The second ESP32 gave the project a cleaner way to separate real-time control from stored user data. The main ESP32 handled the sensors and actuators, while the second ESP32 received usage information through ESP-NOW and tracked daily, weekly, and lifetime values.

The goal was to show the user more than just a warning. The system could tell them how often they picked up the can, how much they drank, and how their behavior changed across longer periods of time.

The final device worked as a complete sensor-based product prototype. It could detect user input, begin a timed access sequence, respond to noise, unlock with a servo, measure can weight, track consumption, and display user feedback. The system had no major hiccups by the end and proved that the concept could be built as a real physical device.

The biggest improvement would be the internal electronics packaging. A custom PCB or cleaner wiring harness would make the system sleeker, more reliable, easier to assemble, and more realistic as a consumer-facing product.

I would also redesign the internal dimensions. The prototype ended up fitting mini cans comfortably, but regular cans were too tight. A future version would have better can clearance, cleaner mounting points, and a more intentional layout for wiring, batteries, sensors, and maintenance access.