UV-C Disinfecting Box - Advanced Tutorial

Introduction: UV-C Disinfecting Box - Advanced Tutorial

By Steven Feng, Shahril Ibrahim, and Sunny Sharma, April 6th, 2020

For the google doc version of this instruction, please see https://docs.google.com/document/d/1My3Jf1Ugp5K4MV...

Warning
UV-C light used in this project can be dangerous, please take proper precautions as recommended in the precaution part of this tutorial when building this project. Please note, keep this away from kids and pets, as they may be hurt by accidental UV exposure. Furthermore, UV light could degrade plastic and other materials over time, so it is recommended to check for functionality of the product monthly by putting a camera inside the container to see if the UV lights turn on according to the expected behaviors

Purpose of the project

In this project, we will build a disinfecting container using UV-C bulbs to disinfect personal devices, such as phones, wallets and more. This is especially useful in the current COVID 19 pandemic as the risk of contracting the virus is increasingly getting higher and thus it is vital to regularly, and routinely disinfect your personal products such as your phone, wallet, keys and more in a sustainable manner, since cleaning supply and alcohol pads are in low supply.


We hope to be able to create a sustainable solution to regularly disinfect these small personal products in a simple tutorial using common household items and materials that can be easily found online and most hardware stores. We hope to have this creation almost as a part of your furniture by design, by putting it by the front door of your house and allow you to naturally put your phones, wallets, and keys into the box for disinfecting, as you walk in, and then picking them up 15 minutes later.

Background Information

UV-C light is a subset of UV light with a wavelength of approximately 254 nanometers. UV-C lights don’t exist naturally and are germicidal since germs don’t have a natural resistance to it. This is particularly useful during the COVID-19 pandemic because coronavirus can live on surfaces for up to 72 hours [1]. Thus, as a result, you can easily re-contaminate your hands by touching these personal devices that may have traces of coronavirus and get infected despite frequently washing your hands. According to a research paper by Meecahn and Wilson, 2006 [2], UV-C bulbs takes about 12.5 minutes for it to be germicidal, so for extra safety precaution, we will up the timer to 15 minutes (900 seconds).

To make sure all surfaces of the item we wish to disinfect are disinfected properly, we will use aluminum foil panels to scatter UV lights evenly around all surfaces of the box. Furthermore, we will be using a net to suspend the object we wish to disinfect so the back sides can also be disinfected properly.

Source:

[1] The Guardian (2020), How long does coronavirus live on different surfaces. Retrieved from: https://www.theguardian.com/us-news/2020/apr/04/h...

[2] P. J. Meechan, et al (2006) Use of Ultraviolet Lights in Biological Safety Cabinets: A Contrarian View. Retrieved from https://www.ehs.ucsb.edu/files/docs/bs/Meechan_and...

Difficulties:

I have broken up the project into 2 levels of difficulties, basic and advanced, based on your technical skills.

Basic will have the core features and uses switch from bulb holders to control the lamp, with no additional safety features for ease of construction and lesser hardware requirements. Advanced has additional safety features to only allow the light to turn on when the box is closed and detects objects in it

Basic: Only requires 2 bulbs, holders, cardboard, net, and aluminum, no programming nor electrical experience required.

Advanced: Arduino, switch sensor, ultrasonic sensor, etc. basic programming and electrical experience required.

  • Switch sensor is used to detect open or closure of the box
  • Ultrasonic sensor to detect objects in the box
  • Arduino as a microcontroller to orchestrate the switch sensor, ultrasonic sensor, and give an indication of status through 2 LED lights on the outside of the box

Note: In this tutorial, we will be covering the advanced level of difficulty, please check out my other tutorial for the basic difficulty variant if you are facing challenges getting electrical components or don't feel as comfortable with hardware and programming.

Link to Basic Tutorial --> https://www.instructables.com/id/UV-C-Disinfecting...

Step 1: Usage

Usage:

  1. The disinfecting box has an ability to autodetect of items in the box and disinfect them. It also has additional safety features to minimize your chance of getting hurt by UV lights using numerous sensors
  2. There are two types of power sources for Arduino as shown in the image below: 12V barrel plug or Arduino 5V USB plug. Either of them will work. A barrel plug can be plugged directly into the wall socket, whereas a 5V USB will require you to plug it into a phone charger adapter first, then to the wall. (Notice the blue wire in the second photo)
  3. There are two 2-prong LED lights on the outside of the box. When you first start it, one LED should be on to indicate power and the other one should be off to indicate the UV light inside is off. (See image 3 for idle state) Only proceed if this is the case.
  4. Put your personal device that you wish to disinfect in the box, close the lid of the container firmly until you see the indicator LED turns on.
    1. The indicator LED that we put on the side of the box shows that the switch sensors have detected closure, and is transitioning to the disinfecting mode
  5. Wait until the indicator LED turns off (after 15 minutes), This indicates that the box is done disinfecting your personal devices and you may take it out
  6. If you need your items during the 15 minutes, turn off the bulb from the outside first by either unplugging the bulbs or using the switch that comes with your LED, then open the box
  7. Note: The UV lights may turn on and remain on if the Arduino is not powered on depends on how you wired the relay module, so make sure Arduino has consistent power (Refer to step 1 above)

Step 2: Disclaimer and Precautions

Disclaimer

For UV Light Safety, PLEASE read the UV Safety information provided first below before starting this project: https://www2.lbl.gov/ehs/safety/nir/assets/docs/u...

Health Precaution:

  1. According to Meechan, 2006 [2], UVC lights are not normally found in nature, and it is extremely dangerous to humans. Avoid direct exposure to the bulb and never look directly into the bulb as UVC light can cause severe burns to your skin and retina and may possibly cause cancer
    1. I would recommend purchasing a UV-C resistant face shield, and gloves for extra safety protection, similar to this one: https://www.fishersci.com/shop/products/uvp-uv-bl...
    2. Check your local suppliers first, as they are often cheaper with faster shipping time.
  2. In this project, you will be working with 110 V Alternating Current, which could be lethal. Be very careful when working on the project, and never do work on live wires. Aluminum foil in the project is also conductive, be careful and don’t get electrocuted by live wires touching the aluminum foil
    1. Some precautions you can take include:
      1. Never work on the project when and any component is connected to electricity
      2. For exposed electrical joints, make sure they do not come in contact with aluminum foil or other electrical joints. You can also consider building enclosures for these exposed joints using cardboard
  3. Plastic and many other materials will regard under constant UV exposure, so please reinspect the box for functionality with regular light bulbs or a camera inside the box to make sure the container is functioning properly

Step 3: License

This project is licensed under the Creative Commons Attribution License, which means you can:

Share — copy and redistribute the material in any medium or format

Adapt — remix, transform, and build upon the material for any purpose, even commercially.

Under the following terms:

Attribution — You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use.

ShareAlike — If you remix, transform, or build upon the material, you must distribute your contributions under the same license as the original.

No additional restrictions — You may not apply legal terms or technological measures that legally restrict others from doing anything the license permits.

Step 4: Bill of Material - Advance

Components

Below is the shopping list I created when I build the Disinfecting Box myself, Which includes non-affiliated link and price

https://docs.google.com/spreadsheets/d/1TzIsX05gGP...

Ultrasonic sensor

  • Alternatively, you can also use an infrared sensor, but remember to change the code to make it work. (Check comments in the program)
  • Refer to the first image for this step
  • I used Elegoo HC-SR04 Ultrasonic Module, a nonaffiliated link: https://www.amazon.ca/HC-SR04-Ultrasonic-Distance...

Switch Sensor

  • You can also use contact sensors or touch sensors. Just something that can tell when the box is closed.
  • You likely will not need to change any part of the program, but consult the manufacturer and guides on wiring those sensors as that will not be covered in this tutorial
  • Refer to the second image for this step
  • I used ARTGEAR Miniature Micro Limit Switch Momentary SPDT Snap Action Hinge Lever Type (what a tongue twister), nonaffiliated link https://www.amazon.ca/ARTGEAR-pieces-Miniature-Mo...
  • You can also just search "micro switch Arduino" and find something similar

UVC Bulb

  • Pick a UV-C bulb with a wavelength around 254nm, as UV-A and UV-B bulbs are NOT germicidal
  • Ideally, you should try to find a standardized bulb (E26, E27), if not, you can use an E17 bulb and adapter or replacement bulb and solder the "+ "side (bottom of the bulb) and "-" side (sides of the bulb) to the ground wire. Only do this if you are an experienced electrician.
  • You can refer to UV Light Options tab under the bill of material, to see some of the options I considered when I was purchasing my UV lights: https://docs.google.com/spreadsheets/d/1TzIsX05gG...

Arduino [3] and 5V power adapter or 12V barrel plug for Arduino

  • I used Arduino R3 UNO, but you can use Arduino Nano, Arduino Mega, Arduino 101 or any of the clones for this project. If you use ESP8266, make sure you set the board manager setting to NodeMCU 1.0, and if you use a Raspberry PI, you will need to program it yourself
  • Refer to the fifth image

5V Relay

  • Relay module to power AC devices. You can also build it yourself using transistors
  • I used ELEGOO 4 Channel DC 5V Relay Module with Optocoupler, a non-affiliated link: https://www.amazon.ca/ELEGOO-Channel-Optocoupler-...
  • You can use a single or duo channel based on the number of UV bulbs you are planning to control by the Arduino
  • Refer to the fourth image

E17 Bulb to wire adapter

  • Alternatively, you can use a plug to a different size bulb and then use an adapter, or soldering directly

Wire

  • Use male to male and male to female jumper wires if you don’t want to solder. Get silicone wire and wire stripper if you do

LED

  • 2 single color LEDs should suffice. Make sure you also have 1 Kohm resistor
  • Refer to the third image

Aluminum Foil

  • For maximum reflection. Alternatively, mirrors or anything reflective would also work

Storage Container

  • See suggestion of storage container below

Netting

  • A way to keep the object suspended to radiate the backside of the object. I used a laundry bag for this purpose. Alternatively, you can use plastic netting that holds fruits, or any fabric with lots of holes in it

Resistor

  • You will need four 1K ohm resistors. Other sizes will also work, ideally lower than 1K ohm

Cardboard

  • Foam board would also work, these act as support within the box [4]


[3] About Arduino

Arduino is a family of microcontrollers that can be used to take in data from sensors and process them into commands. In this case, we are taking in sensor data from ultrasonic sensors and switches and turning them into UV-C and indicator LED light on, and off commands.

In this program, I am using an Arduino R3 UNO, but any other variant should also work. You can check out this guide to find the correct Arduino that you need. https://www.digikey.ca/en/maker/projects/choosing...


[4] Suggestion for the storage box:

The box can be made out of any material and the size largely depends on your preference. You can use a banker’s box, a shoebox. In my case, I found a storage box on amazon. Size is dependent on how many devices you want to store on it. I would suggest at least 30cm x 20cm x 20cm.

Several things to watch out for:

  • Arduino Uno and 5V Relay module takes about 2.7 x 2.1 x 0.4 inches (~6.9cm x 5.3cm x 1cm) each and size of UV-C light bulbs may vary, make sure you read rest of the instruction first, and reserve enough space for the circuit components
  • The number of bulbs required depends on the size of the box and the Wattage of the bulb. There is no definite answer. Usually, 2 bulbs, about 3W each or 1 bulb around 10W would be sufficient for a 30cm x 20cm x 20cm box


Tools

Soldering Kit

  • Optional, if you don't want to solder, please use jumper wires instead

Hot glue gun

  • You can also use double-sided tape or glue alternatively

Cutting Tool

  • You can use an exact knife, scissors, or tin snips based on availability

Drill

  • I used an electric drill with 5mm drill bit for the LED, you can also use cutting tools to cut holes out on the storage box

Sewing kit

  • For the netting, alternatively, you can also just use glue or tape

Step 5: About Arduino

About Arduino (Refer to the 1st picture)

On the right-hand side of the Arduino, where the text is "digital". Those are known as digital ports and the number beside them are their names. In this tutorial, we will simply refer to them as pin #. (Note, we are not using analog pins in this project, which on the left side of the Arduino).

On the left-hand side, there the label “5V” is, represents the 5V power output from the Arduino. Normally, an Arduino would have multiple 5V outputs, but if you only have one 5V output on your Arduino for some reason, you have to connect it in parallel. Connecting it parallel means you connect all the power wires together, and then connect to the 5V output. Finally, you will find multiple “GND pins”, those are ground pins on the Arduino, those are where you can connect the negative side of your sensors.

Serial Monitor (Refer to the 2nd picture)

The serial monitor is the interface between the Arduino and the computer. Here, it is a program with the Arduino IDE that allows you to get information from sensor measurements to better tune the parameters for the sensors and identify errors such as false reading, etc.

To get it to work:

  1. Connect the Arduino to the computer using the USB serial wire (refer to image 3), upload codes on the next page, for uploading instructions, see the next code section below.
  2. Open Serial Monitor panel, set baud rate[5] to 9600 (on the bottom left corner of the screen), and you can see the following information:
    1. Timestamp, with information for Switch State and Ultrasound measurement.
    2. Switch State 0 for both switches closed, Switch State 1 for either or both opened
    3. Ultrasound measurement is in centimeters, usually “ABC.YZ”

It should look something like this:

12:47:04.312 -> Switch State: 0
Ultrasound Measurement 13.82
12:47:04.405 -> Switch State: 0
Ultrasound Measurement 13.83
12:47.04.554 -> Switch State: 0
Ultrasound Measurement 13.83

[5] Baud rate is the rate Arduino transfers data to the computer for display, I set it to 9600 in the program, so you have to set the baud rate to 9600 on the computer to display the data transferred from the Arduino properly.

Step 6: Upload Code to Arduino

Uploading Code to the Arduino:

  1. Download and open the .ino file of your choice from the links above.
  2. Connect Arduino to the computer.
  3. Go to Tools > "Board": and select “Arduino / Genuino Uno” (usually this is by default).
  4. Then, go to Tools> "Ports" and select the correct COM port. (Usually the COM port with the smallest number, or just try each available one until it uploads correctly)
  5. Finally, click the upload button, which is the 2nd one from the left

To test your serial monitor set up and upload functions correct, copy the code segment below into your Arduino and open the serial monitor (check the previous step for instruction)

If you can see "Hello World" appear in your serial monitor screen every 0.1 seconds, then that means your serial monitor works and you have configured your Arduino properly. If it doesn't, double-check your configuration and there may be a chance that your Arduino is faulty.

void setup ()
{
	Serial.begin(9600);
}
void loop ()
{
	Serial.println("Hello World");
	delay(100);
}

Your serial monitor should look something like:

00:00:00.100 ->Hello World
00:00:00.200 ->Hello World
00:00:00.300 ->Hello World

If you don't see whole numbers, like 100, 200, 300 after the decimal point, that's okay and it's completely normal! Because the Arduino also takes time to process the command too!

Step 7: Download Code

You can find the code here for with Ultrasonic Sensor:

https://github.com/KhazanahAmericasInc/Disinfectin...

You can find the code here for without Ultrasonic sensor:

https://github.com/KhazanahAmericasInc/Disinfecti...

If you are familiar with GitHub, simply git clone it, otherwise, you may download it as a zip file. To unzip the zip file, you can use a 3rd party software such as WinRAR or 7z. Otherwise, you may also just copy and paste the program into an Arduino IDE, and click upload to the board.

**Note: you do not need the codes for the basic variant. please disregard this and the next step

Step 8: Code Edits for Timer Duration and Ultrasound Distance Trigger

Ultrasound distance trigger is the distance that the ultrasound detects to register an object.

To identify the Ultrasound Distance trigger, simply plug the Arduino into the computer, and open the Serial monitor. Identify the measurements of ultrasonic sensor with and without objects on it. and set the trigger to be the average between the two.

Once you identify what that value is, go into the .ino files, and change the program in the second line of the program to what you measured.

Time duration is the amount of time the UV lights will turn on each use.

Unit for ULTRA_SOUND_TRIGGER is in centimeters, modify the “10” above to distance between the net to the ultrasonic sensor
Unit for TIME_DURATION is in millisecond (1/1000th of a second), modify the “900000” to the time you want the bulb to shine for

Step 9: Building Aluminium Side Panels

The purpose of the Aluminum is to add another layer of protection to prevent UV lights from leaking, and to add reflectivity of the UV-C light so all sides get exposed to the UV-C rays evenly

1. Measure inside dimension of the container of choice, and make cardboard cutouts of it
2. Glue a layer of aluminum foil over these cardboard cutouts to maximize reflection and allow the UV lights to distribute evenly

  • Remember to put aluminum foil in the inner side of the lid

Note: according to research done by Pozzobon, V., et al (2020), the bright side of the aluminum foil offers better specular reflection, while the matte side offers a better-defused reflection. (See Picture 3). This means if you want the light to scatter evenly throughout the box, use the matte side of the aluminum on the panel. If you want concentrated aluminum lights in a certain part of the box, with a few relatively darker spots, then I would recommend using the bright side of the aluminum foil.

Pozzobon, V., et al (2020) Household aluminum foil matte and bright side reflectivity measurements: Application to a photobioreactor light concentrator design. Retrieved on April 13, 2020, from https://www.sciencedirect.com/science/article/pii/...

Step 10: Cutting Holes

On one of the corners, carefully make a cutout that is large enough (about 2cm x 3 cm) for a single plug to go through, this is for wires to pass through in the future. One tool that I found really effective at cutting thick cardboard is tin-snip. But you can use an Exacto knife or scissors too.

Note: In the image below, I taped the size of the cutout to give it extra strength so the box doesn't fray

Drill small holes along the sides of the box for better ventilation and heat dissipation

Step 11: Wire the Electrical Components

Upload code onto the Arduino and wire according to the diagrams below. Use LED light bulbs as UV lights for now as testing.

2 prong LED lights: (Optional)

  • 2 prong LEDs (Refer to the first picture) used in most arduino and hardware kits. The longer prong is for positive and smaller prong is for negative
  • We will use 1 indicator LED to for power and a second one to indicate UV bulb status
  • Solder longer prong to a 1k ohm resistor, and solder it to port 5 for Power LED, and port 6 for Indicator LED,
  • Solder shorter prong to ground. Put wires in between if needed

Micro Switch

  • These are used to detect box closure for UV light safety. (Please refer to the 2nd image)
  • Top: Solder to a 1K ohm resistor then to 5V positive on the Arduino
  • Middle: Solder pin to GND on Arduino
  • Solder digital port to digital pin 7 for the switch on the left side, pin 8 for the switch on the right side

Ultrasonic Sensor: (Optional)

  • This is used to detect objects in the box. Since it’s wasteful to turn on the UV light for 15 minutes every time the box is closed regardless if there are objects in it
  • Most ultrasonic sensors will have pins and jumper wires come with it, you can just use those directly. (Please refer to 3rd picture)
  • On the ultrasonic sensor, connect VCC pin to 5V on the Arduino, GND to ground on the Arduino. TRIG to digital pin 9, and ECHO to digital pin 10

Relay Module 120v control (Please refer to the fourth picture)

  • Relay modules are primarily used to control AC power sources and in this case, to control the UV bulb. View safety precautions in the introduction before proceeding
  • Connect 5V to VCC pin on the relay module, you may consider putting a diode in between to prevent the relay module’s current flowing back to the Arduino, diodes[6] are directional, make sure it’s the correct direction
  • GND pin to GND on Arduino
  • Connect IN1 to digital pin 3 and IN4 to digital pin 4 on the Arduino
  • For the other side of the relay module (the side with screws to connect AC sources), connect top pin (NO, or normally open) to light bulb positive pin and the middle pin (COM, or common pin) to the hot wire If you need help with this section, refer to this instructable: https://www.instructables.com/id/Controlling-AC-l... or refer to this youtube tutorial: https://www.youtube.com/watch?v=5NxVmg8ZFEc...

[6] Diodes are circuit components that only allow currents to flow one direction. In this case, we are trying to prevent currents to flow from the AC source to the Arduino power through the VCC plug. This is completely optional since most relay modules already have diodes build in

Step 12: Initial Test - Expected Behaviors

Test the behavior of the system to make sure you wired it correctly or the sensors are functioning correctly. If the expected behavior doesn’t match, check your wiring once again. The positioning of the sensors may also cause troubles, please tune them to make sure they are activated properly.

When you are running the test, please use conventional light bulbs instead of UV-C bulbs as exposure to UV-C light could damage your skin and eye.

How to tune sensor positions: (If they are inside the box)

  • Switch sensors:
    • Position the switch sensors at the edge of the container, make sure the lever sticks out
    • Make sure when the switch is closed, the lever is parallel with the edge of the box, thus the switch sensor does not prevent the box from closing
  • Ultrasonic sensor:
    • Place it facing up directly, and read sensor data from the serial output. If it is not outputting correctly, consider readjusting the angle and position such that the ultrasonic sensor is not facing any obstructions.
    • If it is still not correct, consider using another ultrasonic sensor

Expected behavior with Ultrasonic sensor:

  • If the switch is triggered, and the ultrasonic sensor detects an object within 20cm (or the distance you set the trigger to be), and if currently, the light bulb is off, the light will turn on in 5 seconds and the indicator LED would turn on immediately
  • You can also check if the switch is triggered by looking at the serial monitor screen as mentioned before.
  • If the UV-C light bulb is turned on, the switch is triggered, and the ultrasonic sensor detects an object within 10cm, the light will turn off in 15 minutes. (you can set it to a shorter value for testing if you want, refer to later step for code changes)
  • If the UV-C light bulb is turned on, and either ultrasonic sensor fails to detect an object or the switch is untriggered, the light will immediately turn off

Expected behavior without Ultrasonic sensor:

  • If both switches are triggered, and if currently, the UV-C light bulb is off, the light will turn on in 5 seconds and the indicator LED would turn on immediately
  • If both switches are triggered, the UV-C light will turn off in 15 seconds (or the value of the timer you set it)
  • If the UV-C light is turned on, and the switch is untriggered, the light will immediately turn off

Step 13: Building UV-C Bulb Shield

  1. The purpose of the UV-C bulb shield is to block lights from the bulb from shining directly up (into your eyes when you accidentally open the box) and redirect light downward where the object you are trying to disinfect is. Refer to 2nd and third picture as installation reference

  2. Cut out two pieces of cardboard, width about 3 inches and length about 3.5 times the diameter of the bulb of choice. Fold it into a right triangle on the long edge, and curve the hypotenuse.
  3. Put aluminum foil also along the hypotenuse side. This is the bulb holder, which is also responsible for redirecting UV lights downward and blocking the UV light from shining and directly harming the user’s eyes if the fail-safes failed.
    1. Fail safes include the switch sensors and ultrasonic sensors that will turn off the light automatically when the box is opened

Step 14: Build False Bottom for Electronics

The purpose of the bottom panel is to block direct UV lights to the electrical components such as Arduino and 5V relay. We will first have to build two pillars to hold up the bottom panel

Cut two cardboard strips, approximately 12 cm in width and length should be slightly smaller than the inner width of the container Fold along the longer edge into two equilateral triangles. Glue them along the width of the box. These are the pillars to support the base plate.


  • Also, you can consider cutting 2 thin guidelines using Exacto knife along the long side to ease the fold.
  • You can also glue the two triangles on to a cardboard plate that is slightly smaller than the base of the container box, and glue Arduino and relay sensors to this plate, for better insulation and electrical safety
  • The cardboard plate will not change the design, it will simply elevate the Arduino and 5V relay to provide additional insulation

Place in aluminum plates made in step 1 and 2 on the sides of the box, make sure you match the correct sides of the box. Glue Arduino, relay sensor to the base, there’s no specific position that you have to glue it on, just make sure the Arduino’s serial wire (blue wire) is long enough. Switch sensor should be along the longer edge

Note: As mentioned in the precaution, aluminum foil is conductive, so for better electrical safety, feel free to glue Arduino and relay board onto a cardboard plate first. And then glue the plate to the base of the container box

Step 15: Attaching Micro Switch Sensors

Attach microswitch sensors to the top of the box, make sure

  1. The prong sticks above the box, so when the lid is closed, the prong will turn on the switch
  2. Cover up the side and top of the switch with cardboard, to prevent the prongs from damaging the aluminum foil cover, and short-circuiting (since aluminum around the switch is also conductive)

Step 16: Attach Indicator LEDs

Indicator LEDs are used to give users visual cues on the status of the container.

The power LED should be turned on for as long as the box is operational, and thus in no condition should both LEDs be off. (Refer to image 2 for idle status)

The indicator LED should be turned on 5 seconds before the UVC bulbs inside are turned on, and turned off as the UVC bulbs inside are turned off. (Refer to image 3 for activated status)

To build it

On the sides of the box, drill two holes for the indicator LED lights. I used 5 mm drill bit since that’s the size of the LED indicator lights. I placed them by the switch sensor since it’s visible and easy to make cutouts. However, you can place it anywhere you deem ergonomic

Step 17: Closing False Bottom for Electronics

Tuck wires to the sides of the box and put the base plate over the electronics. You can consider tapping the wire to the bottom of the box using electrical wire

Step 18: Build the Suspension Net

I used a laundry bag for the net, ideally, you just need a piece of fabric that is translucent, and can be see-through by the ultrasonic sensor. Some examples of these materials include fruit bags (Refer to 4th image for this step), laundry bags, window screens, etc.


  1. Fold the sides of the net in, and sew the sides in place, so the edges are firm on the edges. This will make this step much easier (Refer to 1st image for this step)
    1. You can also consider gluing the sides in, but it won’t look as nice as sewing
  2. Build a frame for the net so you don’t have to glue it directly onto the aluminum walls, and hopefully, this will make the repair easier. You can build this frame either from scratch using cardboard, or use the box you find from dozen of canned drinks, hollow the inside out. (Refer to 2nd image for this step)
  3. Spread the net along the side, glue it in place, make sure the net is tight (Refer to 3rd image for this step)

Step 19: Configuration Test

Using regular LED bulbs, repeat the test in previous steps to make sure the sensors are placed in optimal positions and able to act activate properly in the current setting

Note: Unfortunately in my case, the UV-C bulb did not ship in time so I am currently demoing with LED bulbs. These bulbs are significantly larger than the UV-C bulbs that I ordered. Ideally, you do not want to be able to see the bulb directly above like this, and if needed, increase the size of the top cover to fully conceal the bulb

Step 20: Add Hazard Sticker and Done!

If your previous step works as expected, then you can screw in the UVC light bulbs, put a camera into the box and do one final test as if you are disinfecting it. Review footage, and if it works, congratulations!

Tape UV Hazard sign (Refer to picture 1 of this step) on the top of your box, because you do not want your guests to accidentally open this box when the UV light is still on. Keep this item away from kids and pets.

Stay Safe, and wish you the best of luck!

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