DAY 1
Monday, 24/6/24
Our hardware components finally arrived and our whole group was finally present, so we began work on our prototype at the M&T Lab! We started by assembling our height sensor, which involved connecting the Arduino Board to our ultrasonic sensors and a breadboard to a laptop. Using Arduino IDE, we managed to program the height sensor, which worked much to our delight! Though we intend to have 4 ultrasonic sensors in our actual prototype, to avoid the mess and complications of many cables, we only connected 2 ultrasonic sensors to test it out first.
Since we also hope to include different coloured lights outside our bin to indicate its fullness-status, we also connected an LED light to our set-up. This allowed us to preliminarily test out whether the LED would light up if the ultrasonic sensors detected something (trash) at a distance of <5cm — it worked too!
DAY 2
Tuesday, 25/6/24
We planned to assemble the weight sensor component of our fulness sensor on this day. We began by 3D printing a mounting fame for our 50kg load sensor. It was our first time 3D printing anything, so the whole team carefully observed the process from splicing, to loading the SD card into the printer, to watching the 1st layer get printed.
It took around an hour to print each mounting frame, and we required 4 (we tested 1 first, then printed 3 simultaneously). In the meantime, we learnt how to use the resistance mode on digital multimeter to test the resistance of wires, and came up with the circuit diagram for our load sensors which we planned to connect the next day.
DAY 3
Wednesday, 26/6/24
We assembled our weight sensor today, albeit a temporary set-up, using masking tape to secure our load sensors to 4 corners of a wooden panel. The load sensor detects the mass of an object via the amount of strain experienced, hence the wooden panel acts as a surface for which items-to-be-weighed will be placed on.
We attempted cable management using masking tape – it was a little unsightly, but functional.
Next, each one of us tried soldering our load sensor wires to HX711, which is a precision 24-bit analog-to-digital converter (ADC) for weighing objects. It was a tedious but fun experience, and we made a few mistakes along the way, such as melting too much solder wire and accidentally connecting neighbouring pins together, which would have interfered with the circuit’s functioning.
Afterwards, we tested out the weight sensor: using Arduino IDE once again, we first tested whether the weight sensor worked by placing various objects on the wooden plank and their weight would be printed on the Arduino’s serial monitor. After verifying that it worked, we decided to integrate the LED as well — the LED was programmed to light up once a load exceeding 1kg was placed on the wooden plank.
We were overjoyed when it worked! Additionally, we combined both the weight sensor and ultrasonic sensors, such that if either a distance of <5cm or a weight of >1kg was detected, the LED would light up, which is indicative of a full trash bag (current values used are merely indicative, subject to change for our actual model).
This wraps up our first week of work in the lab. We successfully met our goal of completing Phase 1A!