MY LAST BLOG :(
HandPhone sterilisation box
The pandemic has drilled into us the importance of washing our hands regularly, and spurred us all to clean the surfaces in our home with renewed vigour. But have we given enough thought to the cleanliness of the thing most of us use every day – like our phones? Using our phone sterilisation box , it sanitises phones in 20 seconds by using UV light that encompasses the entire box. Cleaning will start once the sensor detects the weight of the phone. Once sterilisation is completed, a melody will play to signify the end of cleaning.
1. Team Planning, Allocation & Execution:
Here's a clearer picture of our finalised sketch on how our
product should look like!
ROLES:
Ji Hyun - CEO (Team leader)
Jia Min - CFO (Chief Financial Officer)
Aqilah - COO (Chief Operating Officer)
This is our team logo that we engraved
onto our finished prototype!
Prior to developing our prototype, our group had identify and listed out materials and components needed for this project. By using the BOM table that we learnt about in both CPDD and ICPD, the materials needed was easily consolidated in a single table:
​
Here is the Gantt Chart that Jia Min has consistently updated from the start of the project!
As seen from the photo attached below, my group mates and I have alternated switching roles to lead in different aspects of the project and have contributed equally throughout this project development. Our group took about 14 days in total to create our prototype. We allocated tasks for each other to fulfill and all of us managed to execute the required task within allocated time.
​
2. Design & Building Process + Integration:
Part 1 (3D printing of the hinge & lid - By Jia Min)
​
Jia Min's Blog:
​
​
We used iPhone 13 Pro Max as a size guide since it is one of the bigger phones in the market and we wanted our product to cater to as many handphone models as possible, regardless of the size of the phone. These are the drawings Jia Min did on Fusion 360. We also annotated the use for each part for clearer reference!
​
We forgot to take a hero shot with our 3D printed item but heres a picture of Jia Min breaking off the supports of the printed product >_<
In the process of printing !
These parameters are the original dimensions of our product but due to time constraint, we decided to just 3D print the components at 70% of its original size. It would take up to 8 hours printing both components if we print them at its original size.
Part 2 (Soldering Work - By Ji Hyun & Aqilah --> me)
​
Ji Hyun's Blog: https://sjhyun20.wixsite.com/cp5070-grp2-jihyun/post/project-development
​
The table below summarises what we have soldered:
​
Here's Ji Hyun in the process of soldering the wires together!
Part 3 (Arduino Programming - By Ji Hyun & Aqilah --> me)
​
Ji Hyun's Blog: https://sjhyun20.wixsite.com/cp5070-grp2-jihyun/post/project-development
​
Step 1
Calibration Code
​
​
Our ending calibration factor changed as we had to recalibrate to get the sensor to work again but the piucture below is how it should look like while calibrating.
Using this calibration code for a 5kg load cell scale sensor we found online after setting up the maker uno, we calibrated it to 250g which was the maximum load that we planned on setting.
We first had to download and include the HX711 libraries to the Arduino.
We then clicked on the serial monitor icon at the top right hand corner of the screen to view the weight and calibration factor readings.
To increase the desired weight during calibration, we entered ‘a’ while to decrease it enter ‘z’.
Once we were satisfied with the calibration, we noted down the calibration factor.
​
​
Step 2
Weight Measurement Code
​
With the calibration factor we derived earlier, we added it into another source code (shown above) to ensure that our calibration has been done accurately. When correctly calibrated and the code is uploaded, the weight sensor will measure the weight of the object placed on it. We tested out our calibration factor and since there was a weight reading, our calibration has been done correctly and we can move on to our final code.
​
Step 3
The Final Code
​
This is our final code for our phone sterilization box.
Due to space constraint, instead of having an extra led light and timer outside the box to signal the completions of sterilisation, we decided to add in our own melody into the code to signify the end of the sterilisation.
We also coded our sterilization box so that the UV light would only light up when it senses weight.
​
Detailed description of the final code
---> Fairy Lights:
Since our fairy light was connected to pin 13, our digitalWrite high and low are at pin output 13 as well to send the signal to the fairy light accordingly. The delay of 20000 essentially translates to the fairy light staying on for 20 seconds before it dims down. However, the fairy lights will on be turned on when a weight of more than 0 is detected on the weight sensor. Additionally, based on our research, we found out that 20 seconds are sufficient to kill 99% of germs, thus why 20 seconds were chosen.
The exit needs to be written at the end to indicate that the whole arduino system can stop after one round.
​
---> Tone Melody:
These are our codes for the tone melody. The specific notes and their duration has to be clearly specified. Once the fairy lights dim down, the melody will play once to signify the end of the sterilisation.
Here's me coding and setting up the Maker Uno :)
Part 4 (Laser Cutting - By Jia Min)
​
Jia Min's Blog: https://jiamin20.wixsite.com/cp5070-2b07-2-jiamin/post/project-development-%D9%A9-%E1%B5%95-%E0%B9%91
​
​
​
Initially, we did not have plans to laser cut as we already decided to use plastic sheets for the outer layer of our steriliser box. However, as we construct our prototype, we realised that using plastic sheets may not be ideal as it makes the wall of the box flimsy and it may not be able to support the weight of the phone. Therefore, laser-cutting was a last minute decision to improve on the aesthetics and the sturdiness of our sterilizer box.
​
​
Part 5 (Assembling of Prototype) - By ALL)
​
---> 3D printed & Laser Cutting Design
Attached is the link to Fusion 360 to access all Fusion 360 folders as despite multiple attempts for me to embed, I was still unable to embed it :/
https://a360.co/3ByoXtC (for the box lid)
https://a360.co/3gXWV1i (for sterilisation box base)
https://a360.co/3I1fPQJ (for laser cutting ph steriliser box)
​
---> Weight Sensor
​
​
​
​
​
​
​
​
​
​
The weight sensor we used is a 5kg load cell with a HX711 amplifier sensor
The output signal produced by the load cell is in range of millivolts, so we need an amplifier to convert the signal into a level that we can later transform it into a digital signal and process it. For this purpose, we use HX711 amplifier sensor. It includes a HX711 chip with analog-to-digital conversion capability in 24-bit accuracy. The HX711 module amplifies the low-voltage output of the load cell and sends it to the Arduino so that the Arduino eventually calculate weight from this data.
The load cell is a transducer which converts force into measurable electrical output.
The picture below shows how we connected the Maker Uno to the weight sensor.
​
​
​
​
​
​
​
​
​
---> Assembling of the box
​
Us with the assembled sterilisation box!!! (before attaching the Maker Uno)
Do enjoy this short montage I've made to document our prototyping process!!!
3. Problems & Solutions:
1. Coding using the Arduino Board
We had to find multiple source codes to be able to get an accurate calibration factor as majority of the source codes we found online either did not work or was not for our type of weight sensor. After multiple attempts and research, we found out that our jumper wires were the main reason why our codes were not successfully uploaded to the arduino board. Once we replaced it with newer wires, we were finally able to calibrate the weight sensor and moved on to other parts that required coding.
2. Design process
During our design process, we had planned to incorporate an adjustable clasp mechanism for the sterilisation box to fit a variety of phone models. However, due to the complexity and size constraint (as we minimise our prototype), we had to look for a replacement to hold the phone upright while it is being sanitised. Instead, we decided to keep it simple and built a bigger slot to fit multiple phone thickness.
3. 3d printing
Excessive strength was used while attempting to remove the support for the hinge that connects the lid to the wall of the steriliser, breaking into 2 separate pieces. Our reprinted part was a success and despite the time crunch we were still able to stay on schedule.
​
​
Despite the problems faced and how our product required us to use an item that we have never heard of before this, which is a weight sensor and how we were uncertain of how it may go but despite the complexity of assembling and coding the weight sensor , we managed to built up our prototype without much hassle with the help of our Lecturers, TEs and peers.
Throughout this project, we are glad that there were no miscommunications and were able to motivate each other <3
​