Automatic Door Handle Cleaning Device Using Uvc Light

Study Case AUTOMATIC DOOR HANDLE CLEANING DEVICE USING UVC LIGHT Michael Kurniawan (2018123456) University of Cincinnati, 2600 Clifton Ave, Cincinnati, OH 45221, United States kurniaml@mail.uc.edu Abstract Door handles have the potential to become a medium for the transmission of bacteria such as E. coli, S. aureus, and Salmonella sp., which can interfere with user health. This study aims to develop an automatic device capable of reducing the presence of these bacteria by utilizing ultraviolet (UVC) light. The automatic system is designed using Arduino Uno as the main controller and a power bank as the power source. An HCSR04 distance sensor is used to detect the presence of people. Two limit switches function as door handle cover position sensors, which are driven by a DC motor and controlled in the direction of rotation using a mini H-bridge MX1508m. The sterilization process is carried out using a UVC LED for 25 seconds with a dose of 8 mJ/cm². Test results show that the system works well: the distance sensor is able to read accurately, the open-close mechanism runs smoothly, and the device does not harm users. The average time to open the cover is 1.607 seconds, while the closing time is 0.662 seconds. This device has been proven effective in reducing the number of E. coli, S. aureus, and Salmonella sp. bacteria. Keywords: Door handle cleaner, UVC LED, HC-SR04, Arduino Uno, MX1508 INTRODUCTION Door handles in public facilities, especially toilets, are one of the hotspots for the transmission of various types of pathogenic bacteria such as E. coli, S. aureus, and Salmonella sp. [1]. E. coli or Escherichia coli generally lives in the human intestine to maintain the balance of the digestive system. Most strains are harmless, but there are variants such as E. coli O157 that can cause severe diarrhea [2]. S. aureus or Staphylococcus aureus can trigger skin infections such as boils, impetigo, and cellulitis. If it infects an open wound, this bacterium can spread to other MICHAEL KURNIAWAN 1 Study Case organs. If the bacteria produce toxins, the body is at risk of toxic shock syndrome (TSS) [3]. The next bacterium, Salmonella sp., is a common cause of acute and chronic diarrhea, and can even lead to death in both humans and animals [4]. One effective method for killing microorganisms is to use ultraviolet light. This technology has been used for disinfection since the mid-20th century. The most effective type of UV is UVC (ultraviolet-C) with a wavelength of 100–280 nm. UVC exposure is absorbed by microorganisms and damages their DNA and RNA structures, preventing them from replicating [5]. However, excessive exposure can also damage human skin cells and increase the risk of skin cancer [6]. This study designed an automatic device that can sterilize spherical door handles using UVC rays, which is expected to reduce the number of pathogenic bacteria that adhere to them. SYSTEM DESIGN AND IMPLEMENTATION Overall System Design Figure 1. System Status Diagram As shown in Figure 1, the system mechanism begins by closing the door handle cover. If no object is detected, the UVC LED turns on for 25 seconds. After that, the LED turns off. If the sensor detects the presence of an object, the door handle cover opens and the system activates a 10-second delay. If after the pause an object is still detected, the timer is restarted; if not, the cover closes again. If during the closing process the sensor detects an object, the cover automatically reopens and the 10-second timer is restarted. MICHAEL KURNIAWAN 2 Study Case Arduino Uno programming is done with Arduino IDE based on the C language on the Windows operating system. Figure 2. Program Flowchart The program begins with Arduino I/O initialization. The distance sensor then actively reads data. If no object is detected within a radius of ≤50 cm, the sensor continues to read the distance. If an object is detected, the DC motor activates to open the cover until it hits the upper limit switch. After that, the 10-second timer runs. If after the timer expires there is still an object ≤50 cm, the timer is restarted; if not, the DC motor closes the door handle cover. During the closing process, the sensor reads the distance again; if it detects an object ≤50 cm, the cover is reopened. If there is no object ≥50 cm, the motor continues to close until the lower limit switch is pressed. After the cover is fully closed, the UVC LED turns on for 25 seconds for sterilization, then the system cycle repeats. Determination of UV Sterilization Time The sterilization time is determined based on the UVC dose required to kill microorganisms and the intensity of the LED used. MICHAEL KURNIAWAN 3 Study Case Table 1. Minimum UVC Dose for Microorganisms Research results show that the minimum dose to inactivate at least 90% of E. coli, S. aureus, and Salmonella sp. is 8 mJ/cm². Table 2. UVC LED Intensity Based on Distance Based on measurements, the UVC intensity at a distance of 4 cm is 0.32 mW/cm². Using the formula: UV Dose = UV Intensity (mW/cm²) × Exposure Time (s) The exposure time is 25 seconds. Hardware Design The device uses Arduino Uno as the main microcontroller, an H-bridge module as the motor direction controller, a DC motor, an HC-SR04 distance sensor, two limit switches as position sensors, a 20,000 mAh power bank as the power source, a 5V relay, and a UVC LED strip. MICHAEL KURNIAWAN 4 Study Case Figure 3. Device Design in Closed Condition 1. Number 1: Aluminum foil-coated device cover to prevent direct UVC exposure to the user's skin. 2. Number 2: Gear wheel, rack gear, and rack gear holder as the open-close mechanism. 3. Number 3: HC-SR04 distance sensor to detect objects ≤50 cm. 4. Number 4: Motor mount that maintains motor stability and allows manual opening when removed. 5. Number 5: Power bank compartment measuring 8 × 3 cm, used to place a 20,000 mAh power bank (e.g., Anker or Belkin, as brand equivalents in the US). Figure 4. Rear View of the Device 1. Number 1: Motor mount. 2. Number 2: Additional motor retainer to prevent upward position shift and enable manual mode. 3. Number 3: Door handle cover retainer equipped with wheels to reduce friction. 4. Number 4: Upper and lower limit switches to detect the cover position. 5. Number 5: Arduino Uno microcontroller. 6. Number 6: UVC LED. MICHAEL KURNIAWAN 5 Study Case Figure 5. System Wiring Diagram The diagram shows the nine main components of the system. The Arduino Uno functions as the controller, with the following pin configuration: Table 3. Arduino Uno Pin Configuration 1. HC-SR04 sensor: 5V pin, GND, pin 11 (trig), pin 12 (echo). 2. Mini H-Bridge: pins 6 and 7 (rotation direction), pin 5V (supply), pin GND (ground). The Mini H-Bridge output is connected to the DC motor and gearbox. 3. 5V Relay: pin 5. The power supply uses a 20,000 mAh power bank to ensure the system can operate portably. MICHAEL KURNIAWAN 6 Study Case TEST RESULTS AND DISCUSSION In this section, several tests were conducted on the designed system. The tests were divided into four parts: (1) testing the HC-SR04 distance sensor, (2) testing the open-close mechanism, (3) measuring the UV intensity on the outside of the device, and (4) testing the entire system. HC-SR04 Distance Sensor Testing This test aims to evaluate the accuracy level of the distance sensor installed on the device. Table 4. HC-SR04 Sensor Accuracy Test Results The test results show an average accuracy value of 99.33%, so it can be concluded that the distance sensor performance is quite reliable and suitable for this system. Opening-Closing Mechanism Testing The purpose of this test is to ensure that the door handle closing mechanism can operate smoothly without obstruction, as well as to determine the time required to open and close it. From 15 test trials, the device showed a 100% success rate for both opening and closing. The average opening time was 1.607 seconds, while the average closing time was 0.662 seconds. This difference in time is due to mechanical force factors: when closing, the direction of the load force is in line with the motor rotation, making the process faster; whereas when opening, the direction of the force is opposite to the motor rotation, requiring more time. MICHAEL KURNIAWAN 7 Study Case UV Intensity Testing on the Outside of the Device This test was conducted to ensure that the device is safe to use, particularly in preventing UVC radiation leakage that is harmful to the user's skin or eyes. Figure 6. UVC Intensity Measurement Positions on the Outside of the Device The results of the average UVC dose measurements around the device are as follows: 1. Front: 0.40 mJ/cm² 2. Top: 0.25 mJ/cm² 3. Bottom: 0.55 mJ/cm² 4. Left: 1.05 mJ/cm² 5. Right: 0.35 mJ/cm² When compared to the safe exposure limit for UVC on the skin and eyes, which is 30 J/m² = 3 mJ/cm² [7], all values are still well below the danger threshold. Therefore, this UVC-based automatic door handle cleaning device is safe to use under normal conditions. Overall System Testing The purpose of this test is to evaluate the integrated performance of the device, including when used by more than one person at the same time. The test was conducted by installing the device on a public toilet door and running the system 15 times. The data observed included the success of the opening process, a 10second delay, closing, and UVC LED activation. The results showed a 100% success rate in all cycles. In addition, when used by two people at the same time, the system continued to work properly without any obstacles. MICHAEL KURNIAWAN 8 Study Case CONCLUSION Based on the test results, it can be concluded that this device successfully sterilizes door handles automatically using UVC light. 1. The UVC dose required to inactivate E. coli, S. aureus, and Salmonella sp. is 8 mJ/cm², and the device is capable of delivering the appropriate dose. 2. The open-close mechanism has a 100% success rate, with an average opening time of 1.607 seconds and a closing time of 0.662 seconds. 3. UVC intensity measurements outside the device show a maximum value of 1.05 mJ/cm², which is still well below the hazardous exposure limit (3 mJ/cm²). Therefore, this automatic UVC-based door handle cleaner is deemed effective and safe for use in public environments in the United States. MICHAEL KURNIAWAN 9 Study Case REFERENCE MICHAEL KURNIAWAN 10 Study Case MICHAEL KURNIAWAN 11