Hi and welcome to my blog. Here I will be writing down my documentation of my groups' journey to create our chemical device.
1. Problem
Covid 19 spread wordwide in 2020, As of now there has been more than 400 million people infected and almost 6 million dead.
To minimise the spread, our group wants to sterilize commonly touched surfaces.
Why surfaces?
Covid can last up to 28 days on smooth surface at room temperature (How long the virus can survive - CSIRO, 2022)
One of the most commonly touched areas:
DOOR HANDLES
Hence our product is a self disinfecting door handle.
We had 2 options:
Disinfecting liquid
UV light
Our team elected to use UV light as it is easier to use, not having to be refilled with disinfectant liquid regularly.
The UV light bulb is placed inside a UV-transparent acrylic (Polycast® UV, IR and Light Control Sheet | Spartech, n.d.) door handle. The UV light emits short wave UV light that will pass through the handle and sterilize the handle.(IS UV STERILIZATION EFFECTIVE FOR VIRUSES AND BACTERIA? – Advanced Biotechnologies | Your Viral Reagent Company, n.d.)
Figure 1. Sketch of Self-sterilizing handle
2. Team Planning, allocation, and execution
Team Enterprise
Finalized Bill of Materials
Gantt Chart
Actual
Task allocation
3. Design and Build Process
Part 1. Design and Build of 3D printed handle(done by Gwyn & Adam).
We wanted to make a handle that was cylindrical but we were unable to do so using the transparent acrylic sheet so we used 3D printing to create a mock-up of how the design will look like.
First I created the design in Fusion 360
Then I had to separate the parts to print. To make the print faster and more stable, I elected to print the handle in 2 parts, top and bottom by splitting the design.
I then saved it as an stl file and exported it to cura and then saved it as a gcode file, with these settings:
Part 2. Design and Build of Handle and Case (done by Adam & Darren)
Part 3. Programming of Ultrasonic proximity sensor (done by Gideon & Gwyn).
The coding was done by both Gideon and myself.
I started the code by researching what the 4 pins in the proximity sensor were. Then the connections.
The trigpin is the output because it produces the sound waves while the echopin is the input since it receives the soundwaves. The a “pulseIn” command is used to repeated detect the soundwaves. Then we had to use calculations to translate the pulses to duration and then distance.
After that, we had to make sure the LED remained off if the distance is more than the set point (which we decided in the end to be 13cm) and turn on after a delay(for the suer to use the handle and leave), turn on to sanitize the handle. – This was later edited by Gideon.
Part 4. Integration of all parts and electronics (done by Darren & Adam)
5. Problems and solutions
We had 2 main problems:
We had trouble getting some of the materials such as getting an acrylic cylinder which resulted in us having to change the design again. Initially, the plan was for me to create a holder of sorts to just attach the cylinder to the wall but then we had to adapt. I changed it to 2 possible designs where the handle was to be round or a square. We ended up going with the second design since we could not 3D print a transparent version of the cylindrical handle.
Another problem was the lack of time when using the machines. A lot of teams wanted to use the same machines: 3D printers or laser cutters. I think that our group was lucky in that we were able to get slots for the 3D printer early. This gave us some lee-way in case something were to go wrong, we could still come back to print again. For the laser cutter, we did have to come back at a later date. Initially, our teammates booked in the Fab lab to bend the acrylic but when that did not work well, we switched to the rectangular model and booked another slot. However, the machine was down and so we had to return again. I think our team was able to overcome this challenge of limited slots by starting early and adapting when things go wrong.
6. Project Design Files as downloadable files
Laser cutting dxf files: 1 2 3
Fusion 360 Final design or Alternative link to final design stl
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