04 // Gallery
The build.
From concept to a fully working prototype -- every angle of the machine.
An automated PET bottle collection system that validates material and weight, transports via conveyor belt, and prints thermal reward coupons -- built from scratch for under Rs. 15,000.
India generates over 26,000 tonnes of plastic waste daily. Most PET bottles end up in landfills despite being fully recyclable. We wanted to build a system that makes recycling feel rewarding -- not just responsible.
The machine runs on an Arduino Uno, fits in a 600x600x600 mm enclosure on wheels, and was built entirely from off-the-shelf components. It was incubated through our college innovation program and awarded the JVTM Prize.
Users insert empty PET bottles into the intake slot. The machine validates through three automated checks, transports accepted bottles via conveyor belt into a collection bin, and at session end prints a thermal reward coupon redeemable at partner outlets.
Rejected bottles (metal or wrong weight) are returned via conveyor reversal, accompanied by 3 beeps and an LCD message. Accepted bottles get 2 beeps and a confirmation display.
Ultrasonic sensor detects an object within 10 cm of the intake slot
Inductive sensor checks for metal -- metal objects are rejected immediately
Load cell verifies weight is 15g--35g (typical empty PET bottle: 18--22g)
Conveyor belt moves the validated bottle forward into the machine
Second ultrasonic triggers servo, bottle drops into collection bin
Session ends via button -- thermal printer issues a formatted reward coupon
Every component chosen for reliability, cost-efficiency, and real-world performance on a single ATmega328P.
ATmega328P microcontroller -- central brain running all sensor logic and motor control
Firmware in Arduino C++ with PROGMEM optimization for 2KB SRAM constraint
Dual H-bridge controlling 12V DC conveyor motor direction and PWM speed
Dual sensors -- intake detection and trapdoor trigger at conveyor end
50kg load cell with 24-bit ADC, 5-reading average after outlier filtering
58mm serial printer using ESC/POS commands for formatted reward coupons
16x2 character display with real-time status messages and user prompts
Micro servo actuating the trapdoor mechanism for bottle collection
Full demonstration of bottle acceptance, rejection, conveyor transport, and coupon printing.
From concept to a fully working prototype -- every angle of the machine.
Colour-coded schematic showing all sensor, actuator, and module connections to the Arduino Uno.
Planned improvements and future directions for the platform.
ESP32 integration for real-time bottle count and usage analytics dashboard
Server-validated digital coupons replacing thermal printouts
Camera-based identification of HDPE, PET, and glass bottles
Buck converter to replace the dual 12V/5V adapter setup