First Ideas

There was a popular video (see the video) where a Japanese company began to include a small space where you can sterilize your phone in 30 seconds, eliminating 99.9% of bacteria, now we need to get rid of the rest of the indesired compounds that our phones retain.

My Idea

The general project scheme is like a common paper dispenser: the machine will take your phone in a specific way in order to give a special treatment to the face side. Inside, a UV disinfection process will occur within the first 15 seconds, and then the microfiber with a compound solution will clean and remove the heavy things from the front and back faces with the help of some rollers. In about 45 seconds, your phone will be 99% bacteria-, virus-, and fat-free. You could find this machine in every meeting centre, and with a nice design, it will fit even in the most luxurious places.

Answering the questions proposed in the first week:

• Target audience: The target could be every place with the number of adults enough, universities, shopping malls, sport centers, etcetera.
• Problem to solve: The number of different substances your phone carry in the day to day could help virus and infections to easily spread and harm you.
• Primary needs and pain points: You might think but it's as simple as buying phone wipes and having a cleaning habit, but no, if people forget to brush their teeth imagine their phone.
• Similar products and differentiative point: There are tons of similar products but they aren't safe enough, look at this video of the UV discussion as refference, also, the project has a different approach due to its ease of use and accessibility.
• How intuitive and user-friendly should be: I imagine it to be as simple as a toilet paper dispenser, that will help the project to easily adapt to predefined environments that didn’t initially have a designated place.
• Environmental impact: Another key point of this item is the ability to reuse microfiber towels, reducing the amount of paper and tissues used.
• Regulations and standards: I refer to this point when I say I’m not inventing a new UV disinfecting technic, the project will have applied only scientific tested examples.

First sketches

The problem is that cell phones accumulate a lot of dirt, so we need a device that is in charge of disinfecting them. I have already seen that UV technology is very efficient for this, but I would like to add a way to clean the grease, so I need the system to include some way to spray some form of cleaner directly on the cell phone once inside, and it needs something that spreads it and cleans it, similar to a windshield wiper or that has a system of two rollers with microfibers to scrub it.

Like it's mentioned in the oficial philips page, just the Ultraviolet radiation has enough energy to break the chemical bonds between electrons and atoms. Therefore, it can be harmful to the eyes and skin (sun burns), but it is also beneficial for disinfecting surfaces and purifying the air.

We call UV type-C to the short-wave spectrum between 100 to 280 nm, UV-C works using a photolytic effect whereby the radiation inactivates the micro-organism so that it can no longer multiply. For DNA it does this by causing adjacent thymine bases to form a chemical bond thus creating a dimmer and if sufficient of these are created, DNA cannot replicate.

Viruses can live on surfaces for up to 5 days, so devices which come into regular contact or are shared between people can provide a higher risk just as everyone phones UV-C disinfection chambers are designed for the disinfection of objects.

Looking for the diodes

I couldn't found a supplier of the diodes needed here in Mexico, or the ones that i found were to expensive, so looking through online markets if found them in alibaba,aliexpress, then contacted a supplier in alibaba that helped me deciding the amount and luminous power necessary.

They told me i would need an amount of 10 of the ones they recommend me but, the price tag of the shipper was really high so i searched for a solution that matched the amount of power needed resulting in 15 of the following Leds.

I bought 20 in total for the unexpected errors, they arrived 2 weeks later, from the next supplier: Buy the UV LED from aliexpress.

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Mid term review

Progress in the first 11 weeks of the FAB Academy

the truth is that I did not have much idea about mechanical things so I was not taking into account many aspects that were the ones that would define the physical dimensions of my project, thanks to the output week and the design of machines and mechanisms I realized that I have to change the way my project works, because if in team in these two weeks we cost to implement different systems, my initial idea of using rolls and creating a reflective camera with leds in different places I see it complicated to do it in a few months, the good thing is that now I have a clearer perspective of how to make it reality.

Change of the main idea:

My main idea was to create a two-roller mechanism with rolled microfiber that would quickly pass over the surfaces of the phones like a car wash, but after the CNC week I realized that what I had to do was another way where the cell phone would enter and there would be a door and a sweep.

project operations schedule

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The initial case made during week2 needed to be replaced with a more integrated one, during week16 i remade the idea in order to have a complete system integration.

With all the pieces, I designed and built a press fit system where everything fit together and screwed the components together.

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Im using a variant of the board made during week11, the advantage of using a xiao is that in a small space they include an internal voltage regulator, a large amount of flash and sram memory, and a very high clock speed for fast communications between devices, in case you have I2C communication it is necessary to include resistors in the SDA and SCL channels, as for the PCB design I learned that it is worthwhile to add a ground and voltage pin for each digital output on practically any board, to control the servo motors it is necessary to include a capacitor with a higher voltage than they consume and the higher the capacitance the better.

I also had to design a board to power the LEDs, thanks to the tools included in Kicad it was very easy to create the track and footprint for my UV diodes with a total of 10, initially I was thinking of including one ohm resistors since these consumed between 5.5 and 7 volts and 25mA but a teacher told me it was unnecessary since that is practically the resistance of the cables, so my parallel LED matrix consumes 125mA, The width of the lines is due to the fact that the LEDs did not come with a single data sheet but a general one, so we thought that they were going to consume quite a bit more current and therefore, following the formula shown below, they needed a width of that size.

Following the same steps from the previous weeks of electronics, I used the Roland SRM-20 to produce both boards, then soldered female pins for the Xiao and male pins for the others, in addition to the capacitor.

I do not recommend anyone to solder these diodes with the soldering iron technique, it easily took about 2 hours because the tin was easily passed from the cathode to the anode, I would recommend if you have solder paste applied with a heat gun.

Pinout of the main PCB

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I did the motors testing during week9 there you can see my opinions.

toothed band for the sweep design

Test code: servo.ino.

For the operation of the toothed belt, I designed a tube holder mounted on a motor support, and the piece that will make the journey, holding the sponge, needed space for nuts and a system that could be printed in one piece. This system had to have space to go up to the phone and hold onto the toothed belt at the top.

I had to sand the surface of the piece that was going to move a little so that the bushings would fit, while the black piece fit perfectly.

One problem I encountered when assembling was aligning the toothed band and the ends of the tube, I had to use a series of washers on both sides

Rack and pinion system

Test code: servo2.ino.

In this part I was initially wrong thinking that the friction of the door would be enough to compensate for not having force in that part, another observation that I saw during the tests was that the servo base library would not work for the size of my gear while in the esp32 I have 20 degrees to spare.

Clearly it didn't work so I had to find a way to get the driving force to the other end of the door, using thread I saw that I had space behind the gear so I modified both pieces as shown in the start of the section and that solved the problem.

Bed design

Test code: servo2.ino.

At first I thought I would find a material that was permissive with UVC radiation to use as a bed, like glass, but during my research, as I was unable to find a UVC sensor that I could afford for the project, I searched on the Internet and found a video [link] in which a glass was used to show the reduction of radiation, so at first I used a wire to join the dots and then my instructor recommended that even if there were losses, I should make a pattern.

There's enough space in my pattern for the servo hands to pull out the phone, in the design i considered enough space for the fan and the related wires, so when you find yourself adjusting the fan make sure to put it as sticky as possible, surprisingly no need to use screws to adjust the servers, the only problem I found was they weren't identical and one had a largest hand.

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I did many tests during the week11 for diferent inputs to use in my final project.

I've decided to use a touch sensor that is attached to the side where the bottle has to be pressed and a VL53L0X time-of-flight sensor, as it is in direct contact at times with the sponge, it needed a case.

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In the electrical part of my project I needed a 12V 2A power supply, it turned out that my motor was relatively small and did not consume more than 400ma during my tests, then I needed a 4-output controller the ln298n can control up to 30V with 4 signals from the microcontroller, I also needed a switch and an inverted jack, below are the connections:

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VL530X Test code: Single.ino. Oled Test code: oled.ino. Final code: final.ino.

As a future software engineer i understand a diagram can help understanding the code and making it easier to code, then here is a diagram that turned out to be quite linear.

Like I mentioned in my project plan week17 the full process required the cooperation from all the parts of the project, the compilation of the small codes build the final code with the addition of helpfull interface outputs for the user in the OLED screen.

#include "Wire.h" //I2C library
#include "VL53L0X.h" //Polulu library for this sensor
#include "ESP32Servo.h" //Servo handle for esp32 family
#include "Adafruit_GFX.h" //Oled screen libraries
#include "Adafruit_SSD1306.h"

const int touchsens = D10;
const int ventilador = D2;
const int motorPin1 = D0;  // Pin 0 connected to IN1 on the L298N
const int motorPin2 = D1; // Pin 1 connected to IN2 on the L298N
const int duration = 400;  // Duration to keep the pin HIGH in milliseconds

int pos = 0;    

VL53L0X sensor;
#define HIGH_ACCURACY

Servo myservo;  // create servo object to control a servo

const int myPos = 20;  // define the step size
const int maxPos = 160;   // maximum servo angle

#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64
#define OLED_RESET     -1
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

int progress = 0; // progress of the progressbar

unsigned long previousMillis = 0;
const long interval = 4200; // Interval in milliseconds

void setup() {
  myservo.attach(D6); 
  myservo.write(pos);
  pinMode(touchsens,INPUT);
  pinMode(ventilador,OUTPUT);
  pinMode(motorPin1, OUTPUT);
  pinMode(motorPin2, OUTPUT);
  #if defined HIGH_ACCURACY
  sensor.setMeasurementTimingBudget(200000);
  #endif
}

void loop() {
  //Start
  pos = maxPos;
  myservo.write(pos);
  display.clearDisplay();
  display.drawBitmap(0, 0, myBitmap, SCREEN_WIDTH, SCREEN_HEIGHT, SSD1306_WHITE);
  display.display();
  delay(2000);
  display.clearDisplay();
  // Set text size and color
  display.setTextSize(1);
  display.setTextColor(SSD1306_WHITE);
  // Display the text
  display.setCursor(0, 0); // Set cursor to top-left corner
  display.println("Hello!!!");
  display.println("Please put your");
  display.println("phone through");
  display.println("the wall");
  display.display();
  delay(3000);

  //PROCCESS AREA
  while (vals < 141){
    (sensor.readRangeSingleMillimeters());
    //No need for a delay as the library already includes and need one for better takes
  }
  display.clearDisplay();
  // Set text size and color
  display.setTextSize(1);
  display.setTextColor(SSD1306_WHITE);
  // Display the text
  display.setCursor(0, 0); // Set cursor to top-left corner
  display.println("Now please");
  display.println("Spray the liquid");
  display.println("on the right side");
  display.display();
  int val = digitalRead(touchsens);
  while(val != HIGH){}
  digitalWrite(ventilador,HIGH);
  pos = myPos;
  myservo.write(pos);  // move the servo to the new position
  while(progress < 101) {
    unsigned long currentMillis = millis();
    if (currentMillis - previousMillis >= interval) {
            previousMillis = currentMillis;
            
            display.clearDisplay(); // Clear the display buffer
            display.drawRect(12, 21, 104, 20, WHITE);
            display.fillRect(14, 23, progress, 16, WHITE); // draw the progressbar fill
            display.setTextSize(1);
            display.setTextColor(WHITE);
            display.setCursor(33, 53);
            display.print(F("Progress: "));
            display.print(progress);
            display.print(F("%"));
            display.setTextSize(1);
            display.setTextColor(WHITE);
            display.setCursor(0, 7);
            display.println(F("Progress Bar Screen"));
            display.display(); // Display the content in the buffer
            
            progress++;
        }
    }
    //Finish
    progress = 0;
    digitalWrite(ventilador,LOW);
    val = LOW;
    pos = maxPos;
    myservo.write(pos);
    int vals2 = sensor.readRangeContinuousMillimeters();
    while(vals2<=vals){
      vals2 = sensor.readRangeContinuousMillimeters();
    }
  }
				

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For a final project I couldn't leave it with exposed mdf so I asked my teacher if it was a better option to change the structure for acrylic or make a second case, as it turned out to be the second option I made a design in solidoworks with everything and engravings, the files are in the acrylic .dxf folder.

Since the acrylic was going to be the outer layer of the project, I decided that a mirror-like material would look good. The acrylic came with its own protection to prevent scratches, and when cutting it, it had to be done from below so that the laser wouldn't reflect. I then tried to use thermoforming techniques, but I think the machine was undergoing maintenance at the fab, so I had to make the cuts and it no longer turned with rounded corners.

Some pieces like the switch had to go on top of the acrylic, so until the acrylic arrived I couldn't finish the project.

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The main objetive talking about system integration is to achieve a long-lasting project, we achieved this with many techniques applied in week 16, but in summary what we are looking for is that it does not look like a Christmas present with the contents clashing with each other.

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Intellectual Property and future posibilities

The full breakdown about this themes is reviewed on the 18th week, where i define the future scope of my project and the license choosed to achieve my goals:

Handy Germ Guard by José Antonio Espinoza Ordás is licensed under CC BY-NC-SA 4.0

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