# Internet of Things and Long-Range-Based Smart Lampposts for Illuminating Smart Cities
## 6 Results and Discussion  
In this study, we have proposed a smart lamppost that delivers a multitude of applications that are addressed in the above sections. However, we have developed and implemented a few components of the smart lamppost, namely, smart lighting, environmental sensing, and image sensing. Smart lighting in the lamppost assists in maintaining the light in relation to the light intensity in an outdoor environment. Generally, the smart lighting system is for controlling the intensity of the streetlight with respect to the outer environment light intensity and movement of the objects crossing the smart lamp. The intensity of streetlight is measured with the assistance of LDR sensors, and movement of the objects is sensed through the PIR motion sensor. LDR sensors are very effective, particularly in streetlight and dark sensor circuits. The working principle of LDR sensors is that when the light falls on the LDR sensor, the resistance value of the LDR decreases, thus reducing the intensity of the streetlight accordingly. The following Equation (1) explains the relationship of resistor-inductor (RL) and lux:  
\[\text{RL}=\frac{500}{\text{Lux}}\quad\text{K ohm} \tag{1}\]  
Therefore, the light intensity value sensed by the LDR sensor are represented in terms of analog value, i.e., voltage (V). The output of the LDR sensor that is receiving the voltage can be converted into lux with following Equations (2) and (3):  
\[\text{V}_{\text{o}}=\frac{5\times\text{RL}}{(\text{RL}+10)} \tag{2}\]  
where \(\text{V}_{\text{o}}\) indicates the output voltage  
\[\text{Lux}=\left(\frac{\frac{2500}{\text{V}_{\text{o}}}-500}{10}\right) \tag{3}\]  
where \(\text{V}_{\text{o}}\) indicates the output voltage  
In this study, the movement of the person or vehicle is detected through PIR sensor. At the same time, streetlights switch on at a particular dimming level as per the time scenario. Here, the LDR sensor is placed at a location on the lamppost which is not affected by the car light. The LDR sensor adjusts the intensity of the streetlight in relation to environmental sunlight and, moreover, the streetlight glowing according to the environmental intensity reduces energy consumption. The energy saving is also achieved in our system, because of 256 level AC dimmer. Briefly, the AC dimmer diverts the flow of electricity through the streetlight. As the electricity flow is diverted, the amount of electricity supplied to the streetlight also reduces and this reduces the light intensity of the streetlight. The working principle of the dimmer can be explained with firing angle equation (Equation (4)). \[\text{V}_{\text{o}}=\frac{\text{Vs}\sqrt{1/\pi(\pi-\alpha+(\sin 2\alpha)}}{2} \tag{4}\]  
where \(\text{V}_{\text{o}}\) indicates the RMS value of output voltage, Vs indicates the applied voltage, \(\alpha\) indicates the firing angle. In the dimmer, the alternating current (AC) phase method is utilized by for controlling intensity of streetlight. The RMS value of output voltage is controlled by controlling the firing angle. For example, if the firing angle is 180\({}^{\circ}\), then the RMS output voltage that is supplied to the streetlight is low. If the firing angle is less, e.g., 0\({}^{\circ}\), then the RMS output voltage that is supplied to the streetlight is high. Therefore, 256 level AC dimmer in the proposed system minimizes the energy consumption. Environmental sensing is for sensing the quality of the air, temperature and humidity. Here, we have integrated the MQ 7 gas sensor for sensing the CO level in the air and the DHT sensor is utilized for sensing the temperature and humidity. The DHT sensorprovides the temperature value in terms of \({}^{\circ}\)C and humidity value in terms of %. The MQ 7 gas sensor provides CO level in terms of parts per million (ppm). All these sensors are connected to the slave controller 1 as shown in Figure 5. Image sensing is for counting the number of pedestrians, proximity, and parking management.