Project development entry

 

Hello! So this is the final blog of the school term before the holidays and I was basically supposed to give a summary and journey of the team’s process of making the chemical product. To start off, I will briefly describe the team’s chemical device which is a UV light door handle sanitizer. 

1. Our team’s chemical device

The team wanted to work on this idea because of the pandemic that is going on now. Door handle is actually one of the most touched objects in public and with everybody touching it, it increases the risk of spreading the virus around. Thus, we wanted to eliminate the possibility of virus transmission by ensuring the door handle is sanitized after each use so that it is safe for the next user to use.

Here is the sketch of our door handle sterilizer.

2. Team Planning, allocation, and execution

Here are the roles and task allocation for each member.

CEO/Team Leader - Sebastian Ho (https://cp5070-2021-2b04-group1-sebastian.blogspot.com/)

COO - Goh Li Yin (https://cp5070-2021-2b04-group1-gohliyin.blogspot.com/)

CFO - Chong Shin Shing (https://cp5070-2021-2b04-group1-shinshing.blogspot.com/)

CSO - Khoo Jun Xiang (https://cp5070-2021-2b04-group1-junxiang.blogspot.com/)

This is the team’s Bill Of Material (BOM) table to keep track of the budget of $100 and ensure we do not overspend.

Bill of Materials (BOM) 

Project Title:		Door Handle Sterilizer
Team members:		Sebastian Ho, Goh Li Yin, Chong Shin Shing, Khoo Jun Xiang
Created by:		Group 1
Date created:		30th November 2021
BILL OF MATERIALS (BOM)
No	Description of item	Supplier  (include hyperlink to the item in website of seller)	quantity	quantity unit	unit price	Total Cost	Available at W319 Lab or FabLab? (Y/N)
1	3kg.cm 360-degree continuous rotation servo	https://sg.cytron.io/c-motor-and-motor-driver/c-dc-motor/c-servo-motor/p-3kg.cm-360-degree-continuous-rotation-servo	1 Unit	1	$10.36	$10.36	Y
2	Arduino Uno board	-	1 Unit	1	$25	$25	N
3	Infrared Sensor Module	https://sg.cytron.io/c-sensor/c-optical-infrared-sensor/p-infrared-sensor-module	1 Unit	1	$0.68	$0.68	Y
4	9V Battery	https://www.digikey.sg/en/products/detail/duracell-industrial-operations,-inc./9V-MN1604/13280363?utm_adgroup=Batteries%20Non-Rechargeable%20%28Primary%29&utm_source=google&utm_medium=cpc&utm_campaign=Shopping_Product_Battery%20Products&utm_term=&productid=13280363&gclid=Cj0KCQiAkZKNBhDiARIsAPsk0WiIIKLzVso5FN2CxMVuwalevxYk9Kcj1WoH94oeW36g8JIejLrXVLIaAqm5EALw_wcB	1 Cell	1	$3.39	$3.39	N
5	BATT CONN SNAP 9V 1 CEL 4" LEADS- to connect the battery	https://www.digikey.sg/en/products/detail/keystone-electronics/232/303804?utm_adgroup=Battery%20Holders%2C%20Clips%2C%20Contacts&utm_source=google&utm_medium=cpc&utm_campaign=Shopping_Product_Battery%20Products&utm_term=&productid=303804&gclid=Cj0KCQiAkZKNBhDiARIsAPsk0WhFnEP2QpFyezLDKLR-jH9xXmWDu8NPEt34ix6Gg18jDDV6VU_0pgoaAt22EALw_wcB	1 Piece	1	$0.77	$0.77	N
6	Gears and thread, PLA	https://shopee.sg/-SG-Stock--3D-Printing-Filament-ABS-1-75mm-1kg-i.17900571.7069234808?gclid=Cj0KCQiA5OuNBhCRARIsACgaiqVGd-xpUSoIuFFXu0Y7asPIndY7NduVBkU2OqBHqlybJnuTNBm5CtoaAjG3EALw_wcB	1kg	1	$22.50	22.50	Y
7	Casing, acrylic	https://www.monotaro.sg/g/1000025129.html	4 pieces for the sides of casing (casing is 18cm x 15cm)	180mm x 160mm per piece	$3.99	15.96	Y
8	Light strip support, curved ruler	https://shopee.sg/Superg-12--24--Curve-Ruler-Flexible-Vinyl-Drafting-Drawing-Bendy-Measure-Tool-Plastic-i.93950114.7948202910?gclid=Cj0KCQiA5OuNBhCRARIsACgaiqUAnxtP6nZLnb47kb0UQSZrtNncVR2xeHLtAGiz2MxtjKE8TdIeXrkaAqkPEALw_wcB	1 strip, 30cm	1	$3.60	$3.60	N
Grand Total Cost:						$82.29

So here is the team’s initial plan and the allocation of the task.

This gives the team a rough idea of what each member is going to do on a given day so that there is ample time for the team to revise or change any ideas if we face problems. 

Here is the finalized task allocation for each member as we go along each week.

This Project consists of 3D printing, AutoCad, Laser cutting and coding. These responsibilities were split among the team in the following way:

AutoCad:

• Sebastian 

• Li Yin

3D Printing:

• Sebastian 

• Li Yin

• Jun Xiang

Coding:

• Shin Shing

Laser Cutting:

• Shin Shing

• Jun Xiang

Although the responsibilities were split in this manner, the contributions to the team were not limited purely to the list above, members helped one another whenever necessary.

3. Design and build process

Part 1: Sketch of the door handle sterilizer (Done by: Sebastian)

Link:

Initial idea

Function of each component

Depiction of how the mechanism flexible mechanism would work

Measurement on and around the door handle and rack

Illustration of the casing and the dimension and size of the internal components

Part 2: Designing the sterilizer in fusion (Done by: Sebastian and Liyin)

Wall of the casing

3-part hinge to hold the LED lights

Design of the rack

Ball joint connected to the rack

Design of another hinge and ball joint

Design of part of the casing

Final design from the outside POV

Part 3: 3D printing and laser cutting the parts (Done by me! Jun Xiang)

3D printing

3D Printing of the gear and rack

3D Printing of the hinge and ball joint

Laser cutting

Hole for the servo motor

Casing of the box

Part 4: Creating a code for the servo motor (Done by Shin Shing)

Setup and the coding of the servo motor, LED light and the IR sensor on Thinkercad

Arduino code to program our sterilizer

Initial circuit to final circuit

Part 5: Assembling the parts together (Done by everyone)

Beginning of assembling the sterilizer

Part 6: Testing of the product (Done by everyone)

Link to video: https://youtu.be/m-497i3iWck

4. Problems and solutions

Of course in every journey, there will be obstacles faced and in order to move forward, we have to find solutions to overcome them. So here are the problems the team faced as well as how we conquer them.

1. Insufficient space to fit in all of our components.

Problem:

Our initial measurement of the product is 9cm x 10 cm x 6 cm when we first sketch it on fusion. However, the team forgot to factor in the size of the arduino board and the breadboard. Hence, the size of the product is too small. 

Solution:

To solve this problem, we redesign the sketch on fusion with larger specifications of 12 cm x 15 cm x 8 cm. This helps us to fit all the components in our product and also gives sufficient spaces between each component when fitted in so that it does not look so cramped inside.

2. Hinged parts not working

Problem

When we first printed out the hinge with 3 parts, the parts ended up merging together and were too stiff to bend. More force was applied, but ended up breaking into 3 separate pieces. The team found out that the allowance space between each parts was too close. Furthermore, we had issues during the process of printing because our product took too long to print (about 4h) and the parts did not stick to the base of the 3d Printer, which resulted in the parts moving and printing where it wasn’t supposed to, creating runaway strands of plastic on the parts. 

Solution

We change the allowance space in fusion from 0.2mm to 0.5mm so that the parts will be more loose to be able to bend. Next, we also change some settings in Cura such as the bed adhesion from skirt to raft to allow the hinge to stick to the base of the 3D printer more tightly, the quality from standard to low, the infill from 20% to 10% and increasing the printing speed from 80 mm/s to 100 mm/s to reduce the printing time (managed to reduce it to 1h 4min).

3. Gear and track would not function well in our product

Problem

The team presented our idea and progress to Dr Noel during the consultation. We wanted to use gear and track for the movement of the UV light to and from the door handle. However, he warned us that the gear would not run smoothly along the track since the teeth of the gear are too far apart to grip onto the track properly. 

Solutions

He advised us to switch to pinion and rack. By using the formula (length of rack travel = pi x diameter of the gear), we design the pinion and rack in fusion and 3D print them. We also ensure that the diameter of the screw fits tightly in the middle of the servo motor so that it does not fall off during the operation of the sterilizer. 

4. Faulty IR sensor

Problem

When we first connected the IR sensor to the arduino board, it did not react and act according to the code that we input. After trying many times, the team concluded that the IR sensor is faulty probably due to the large current flowing through the circuit, causing it to blow out. 

Solution

The team went to W3 to get a new IR sensor and added a 1k resistor onto the breadboard to reduce the current flowing through the circuit.

5. Fault in the design of the gear and rack placement

Problem

The height of the gear is too high for it to come into contact with the rack, so the gear could not run along the rack.

Solution

We use the spare acrylic we had and break them into small strips. Then we heat them up so that we are able to bend it to a desired shape and insert them under the rack to raise the level of the rack such that the middle of the track is the same level of the gear. It acts like a layer or support underneath the rack.

5. Project design files as downloadable files

Here is the link to view and download the files:

https://drive.google.com/drive/folders/16ZJAWVSaFB9lb6IH6ZLI7y0TXNekLPDo