## 3 The Proposed IoT-Based Master-Slave Regionalized Intelligent LED Light-Controlling System
### Preliminaries
However, the eyes will still be a little uncomfortable because there will still be a slight brightness change. Therefore, we can improve our previous work [1] to make the sensor lights in the same zone brighten simultaneously or dim at the same time. This can minimize discomfort on the eyes, increase the sense of safety when walking, and reduce power consumption to achieve an integrated system of energy-saving, IoT, and humanization. Taking a large parking lot as an example, the proposed system divides the parking lot into several small zones in a matrix (as shown in Figure 3), and the sensor lights in this zone will operate synchronously. The LED lights in the same zone will be lowered at the same time when a vehicle or a pedestrian pass by. The power is in the low-light mode for standby. When any LED light in this zone detects a pedestrian or car passing by, it will transmit the trigger message to other LED lights in the same zone via the Wi-Fi 2.4 G wireless transmission module. Moreover, LED lights in the same zone are all turned on to high-light mode simultaneously, as shown in Figure 1.  
The user can set the zone to which the LED lights are installed according to their needs. When the LED lights are set to the same zone, they will act in synchronization. As can be seen in Figure 3, when someone approaches zone 1, LED 1 immediately transmits the trigger signal to LED 2-LED 8. There are two ways to receive it: the first is to receive the triggered signal sent by LED 1 directly, and the other is to receive it from other LED lights that received the triggered signal earlier. Taking LED 8 as an example, it can receive the triggered signal sent by LED 1. It can also receive the triggered signal turned from LED 7 (where the signal arrives first). After receiving the trigger signal of LED 1 (Master), LED 2-LED 8 (Slave) will also be immediately illuminated. LED 1-LED 8 will also be changed to the high-light mode simultaneously. Note that the LED lights in different zones will not be triggered because of the various channel settings. Figure 3: A scenario of the proposed system installed in a large parking lot. Since this work does not need to change the lamp holder of the LED lamp, the old LED lamp tube or fluorescent tube can be directly replaced with the new sensor LED light [1]. Hence, installing the proposed system in places such as building parking lots, corridors, stairwells, or toilets is recommended. The original lamp holder can be retained, with no wiring and no need to set up a server and can achieve the energy-saving purpose of the intelligent LED lighting controlling system. The price is even lower. For example, each smart T8 LED tube, only costs CNY 600 (about USD 21.4). Because the tube has a built-in sensor and control circuit, it only needs to be the same as the original one. The T8 LED tube can be replaced and adjusted. Furthermore, we compare the popular commercial product, Philips's hue smart lighting full-color situational 10 W Bulb [48], as shown in Table 2.  
Therefore, it is different from the relevant field (office, living room, or living room) of the previous works. This work is more suitable for public zones, such as buildings and communities, where people and vehicles pass by for a short time. This work is based on the LED sensor light with the low-light mode in [1] and only retains the \"low-light mode\" function. The remaining IoT, Master-Slave architecture, and regionalized synchronization functions are new and innovative. Hence, this work is more suitable for large-scale fields. The differences between this work and [1] are described as follows. The difference comparison between this work and [1] is also arranged as shown in Table 3.