# Non-Contact and Non-Intrusive Add-on IoT Device for Wireless Remote Elevator Control
## 6 Discussion and Conclusions  
This work proposes a non-contact and non-intrusive add-on Internet-of-Things (IoT) device for wireless remote control of an elevator. The IoT device has been designed as a non  
Figure 16: Minimum, maximum, and average successful scanning distances for different QR sizes. Figure 17: APR-02 mobile robot calling the elevator through the IoT device for elevator control. intrusive add-on tool to be placed over the original elevator button panel. This proposal has the advantage of not requiring any physical manipulation or wiring connection of the original elevator infrastructure. Relative to comparable works [4; 5; 7], this specific feature provides a rapid response tool in order to increase the accessibility to elevators. The experimental evaluation of the IoT device in real operation conditions has validated its non-contact control features. The IoT device is based on the use of a battery, one ESP32-S2-WOVER board as a control module, and several analog low-cost servomotors to press the original buttons of the elevator control panel. The control module provides connectivity to the wireless network used in the building and a simple web interface representing the buttons of the elevator control panel. The IoT device described in this paper has been designed to fit over the original lower button panel of the elevator located at the Polytechnic School of the University of Lleida. In this case, the button panel comprises 7 buttons: 5 to access the 5 floors of the building and two additional buttons to keep the door open and to activate the emergency alarm. The casing of the IoT device has been designed to replicate the original buttons of the control panel with cantilever-like buttons that can be used to manually interact with the original panel in case the IoT device runs out of battery. In this application case, the elevator car has two control panels. The IoT device has been mounted over the lower one, hanging from the handrail and firmly attached to the wall with a suction cup. Other implementations may be fixed only with suction cups or magnets. The IoT device for elevator control provides a communication protocol tailored to receive http requests (messages) to press and automatically release the elevator buttons. Two specific commands allow the (1) press and (2) release of the button that keeps the door of the elevator open. The use of standard http request allows the use of QR codes to call the elevator and directly access the web interface of the elevator. This approach has the advantage of avoiding the need to install proprietary APPs or to remember the name or IP address of the web interface of the elevator. The IoT device was implemented and experimentally evaluated by users accessing the elevator with their smartphone and by a mobile robot calling the elevator. The evaluation of the access to the IoT device through a smartphone has been performed in two cases: calling the elevator from outside the car and using the elevator from inside the car. The overall success rate when calling the elevator from outside the car was 89.20% and the communication problems detected were that connection was lost for a few seconds (2.80%) and connection lost for more than 10 s (8.00%). Similarly, the overall success rate when using the elevator from inside the car was 92.74% and the communication problems detected were connection lost for a few seconds (3.63%) and connection lost for more than 10 s (3.63%). These communication problems were solved by either pressing the button on the web interface again or reloading it. The communication problems registered during the experiments have been attributed to wireless connectivity problems in the building. Figure 18 shows a schematic diagram of the five plants of the building depicting the position of the access points (AP) (or antenna) that provide wireless access.