**4.2 Performance assessment**

The meter was designed with technical specifications that are identified as accuracy (class 1.0); rated voltage; single-phase (230 V ! 250 V); frequency (50 Hz/30A); display (LCD), information record, and energy parameters such as power, current, voltage, power, energy, and cost of billing.

The proposed smart meter was simulated using proteus software. Proteus combines mixed mode SPIC circuit simulation and animated components with various microprocessor models, which facilitate simulation. This assists in developing design and test cases. It emerges amongst the simulation software for electronic design.

The simulated design shown in **Figure 5** displays the initialization stage of the smart energy meter. The components are interfaced through the connecting probe. It is seen that the schematic diagram within the simulation showed that the power supply is connected to a potential transformer serving as the voltage sensor. A Zener diode protects the microcontroller unit against any upsurges. The current sensing is based on the Hall effect sensor, with its output increasing by 60 mV for every

**Figure 5.** *Smart meter simulated diagram.*

ampere increment in the measured current. For the voltage sensor, when no current is flowing in the circuit, the device voltage is 0.6 Volt, which is directly proportional to an increase in voltage when increased linearly by 60 mV/A. Caution is taken to ensure that the measured voltage does not exceed the microcontroller's reference voltage. This is achieved using the zero-crossing detector for enhanced current and voltage measurement.

The zero-crossing detector is a device used for the detection of voltage and current crosses in whichever direction. However, a comparator can be used as a zero-crossing detector. Assuming our reference voltage for the comparator is chosen as zero (Vref =0), the input voltage will saturate the comparator. Therefore, two Op-Amp is employed in place of zero-crossing. Both Op-Amps are configured so that their output goes high whenever their negative input goes lower than zero. The voltage sensor minimum voltage is set to 0.6 Volt.

The circuit has a transistor-driven relay connected to the collector side. The voltage impressed on this relay is a rated full coil voltage at the peak period. Although, in OFF time, the voltage is completely zero to avoid any hazard during use. The PNP transistor is connected to control the switching of the relay. This process facilitates the selection of BC 327 PNP transistors because of their capacity to handle the current, voltage, and power supply. The transistor is also driven into

**Figure 6.** *Designed smart meter.*


#### **Table 1.**

*Result of smart energy meter when loaded with fan and air blower.*

saturation (turned ON) when the Logic 1 signal is written on the port pin. Thus, turning ON the relay. The relay is turned OFF by writing Logic 0 on the Port 5 and 13 of the ATmega328P. Also, a free-wheeling diode 1 N4148 is connected across the relay coil. This is done to protect the transistor from damage due to the back electromotive force (EMF) generated within the relay's inductive coil. Thus, the transistor is turned OFF. The energy is stored in the inductor as dissipated through the diode and the relay coil's internal resistance when the transistor is switched OFF.

The designed smart meter is depicted in **Figure 6**, while its tested results are tabularized in **Table 1**, based on the meter's response when a fan and a blower are connected. The results show the voltage, current, power, energy, the resulting cost of energy every second, and the cumulative cost of energy.
