Project development

 

1.       Our team Chemical Device

The world has changed irrevocably in the past two years. The advent of the COVID-19 virus has been on everyone's mind and limiting its spread a top priority. National health advisories encourage citizens to refrain from touching their eyes, nose and mouth after contacting outside surfaces. But we feel that this is not effective enough and want to make it so we do not have to be as afraid to touch things outside. We want to make a door handle that can sanitize itself after every use.

We used the TRIZ problem solving technique to help refine some ideas of how we want to execute our idea; our final idea: a sensor that detects handle usage that switches on UV lights to sanitize it.

Here's a preliminary sketch drawn by Ambrose which featured a pressure sensor:

 

And here the final sketch following the change to a infra-red motion sensor as well as being more comprehensive:

 

2.       Team Planning, allocation, and execution

vvHere is our final bill of materials:

This is our original project timeline using the GANNT chart:

 

And here is the actual timeline execution:

 

3.       Design and Build Process

In this section, provide documentation of the design and build process.

Part 1. Design and 3D print of handle and body (done by Edmund)

Blog link: https://cp5070-2021-2b03-group4-edmund.blogspot.com/p/project-development.html

Part 2. Programming of sensor and LED (done by me)

The coding was real simple and in fact is almost identical to a task given for the Arduino practical. The code is simply a system that detects when a hand is near the sensor and after 10 seconds turns the UV lights on for 5 seconds before turning them off.

int IRSensor = 2;

int LED = 13; 

void setup() 

{

  pinMode (IRSensor, INPUT); // sensor pin INPUT

  pinMode (LED, OUTPUT); // Led pin OUTPUT

  

}

void loop()

{

  

  if (digitalRead(IRSensor) == HIGH){

    digitalWrite(LED, LOW); // LED LOW

  }

  

  else

  {

    delay(10000);

    digitalWrite(LED, HIGH); // LED High

    delay(5000);

    digitalWrite(LED, LOW);

  }

  

}

The pins to be used after define, then I use an if-else order to say that when the sensor goes from HIGH to LOW to turn on the LED. The LED time to turn on and how long it is on is defined with the delay command and can be increased or decreased within the brackets.

This code and breadboarding is not complex and an unfortunate reason for that is the extra functions we wanted was not something I could figure out after many hours which forced me to quit.

 This function, was to turn off the lights if someone wants to use the handle. Because you wouldn't want to get exposed to intense UV I wanted a kill switch. Some of my ideas involved using the NAND gate in which if both sensor and light are on the power to the lights is cut; I couldn't figure the correct logic path needed and more importantly it was too late to procure the integrated circuit. 

Next I tried to use the reset pin of the arduino; when the hand gets exposed to the light, reset the system so it forgets the lights should have been on and turns it off. I could use a switch to perform the reset at will and felt all was well. I tried to use a transistor to get the reset pin to connect to ground but it was not only a mess of wiring it also did not work. Next I converted it to software using the && function that is the same as an AND gate, the system refused. I troubleshooted, rearranged wires, checked the code and consulted the internet but could not find a solution. I accepted my failure and purged the erroneous code and what was left is above.

This particular lesson taught me that it is easy to dream big and be filled with wonderful ideas, but when you want to execute it and don't have enough knowledge, you might not know the extent of the limits and waste time. I will use this as encouragement to learn more about coding so the next time I meet a difficult arduino problem, I will overcome it. 

Part 3. Integration of all parts and electronics (done by me)

I was the one who wired the circuitry within the door handle unit and put all the components where they needed to be. My groupmate Edmund did a good job putting enough space in general to fit the components but wiring them up was super messy. There was almost no room to work with and frankly a pair of pliers would have been tremendous help. A fatal flaw of the design though was there was not a holding position for the LEDs and sensor which meant they would be freely floating. I tried to salvage it by using the breadboard as an anchor for the components, but the board was not long enough to touch the bottom and hold the sensor and an LED so I had to stick the board to the backwall of the interior. This meant every wire connection to the board was permanent, since I would not have been able to reach in to manipulate them, this was quite nerve wrecking as time was running out. The position of the breadboard and arduino in my system that deviated from the original design was very separated which increased wiring difficulty. Another issue was there was one LED that was connected to the board by female to female wires but they were very loose and had to be taped together.

In summary design flaws of the body forced some improvisations that made wiring tricky and the electronic components looking aesthetically unpleasing. The wires being too long created a big mess and if I was doing it a different way I would have a roll of wire that I could cut to my liking instead, and would preferably solder the LEDS to wires instead of using tape.

Here is the finished product:

4.       Problems and solutions

The print time was too long and would have taken a day so it was split into four parts that were later combined together.

There was no holding space for sensors and lights, so the breadboard location was moved to function as the holder instead.

The base we wanted to attach to the back of our door handle unit was made from a sheet of acrylic, but it refused to cut even at the highest settings as well as not being thick at all. We found some ply wood and hand cut it ourselves.

We wanted to use screws to attach our handle to the back board to simulate an actual door, but as the laser cutting was not working and we could not feasibly cut a proper hole by hand, we were forced to glue it.

The handle is not fully sanitized by the lights for the front is not in line of sight. We planned to use a servo to rotate the handle around to fully sanitize it, but the code could not stop the handle when someone was using it and the printing was not too rough and there was either too much friction or the handle was too loose. So we abandoned the idea due to lack of time

5.       Project Design Files as downloadable files

Here is a folder that contains the code and the files for all the parts 3D printed and combined for our door handle: https://drive.google.com/file/d/1Fs72LL6qgozFEJyObUmcxm78MiXLREh9/view?usp=sharing

And here below is the door handle with just the body: