**5. Experimental set-up**

Blood serum is obtained from the blood which has been collected with the help of the veterinary doctor Dr. Jitendra Nath Dewan, Former Deputy Director, North Eastern Regional Disease Diagnostic Laboratory. Blood serum of cow, goat, poultry are mixed with nanostructured ZnO solution for measuring biological parameters SGPT, SGOT, BUN and creatinine. As it has been observed that there is an increase in the order of the biological parameters alongwith the increasing value of resistance of blood serum, when the blood serum is mixed with nanostructured solution. And based on this principle, circuit has been developed to design the sensor.

### **5.1 Circuit diagram**

The circuit diagram has been shown below in the **Figure 14**. The basic components of the device are as follows:

a.Microcontroller–ATMEGA328P

b.LCD Module −20 x 4 display

c.I2CDriver

d.USB to TTL converter

e.PC/Laptop

f. Steel sensor probes

g.Resistance of known value-10 K

h.Five Push down tactile switches

i. Voltage regulator-7805

### **5.2 Operation of ZnO based sensor**

The heart of the circuit is an 8-bit AVR series microcontroller ATMEGA328P. This particular microcontroller has been selected as it has an inbuilt ADC. The power supply can be provided, either by using 9-12V battery or by connecting through USB port, it can be driven or by using adapter. A very popular voltage

**Figure 14.** *Circuit diagram of ZnO-NP based biosensor.*

regulator 7805 has been used to provide regulated +5V supply which gives regulated 5V with 1 Ampere current tracking. Two 100 nF ceramic capacitor are used across pin no.1 and 2 and across pin no.2 and 3 of 7805 to reduce harmonic noise or ripple.

A 20 x 4 LCD module has been used to display the calculated value and to display the result. Instead of using parallel communication, serial LCD (I2C protocol) has been used to simplify the circuit, which helps to display information from microcontroller to LCD.

Only two wires are enough for the communication, i.e., SDA (Serial Data) and SCL (Serial Clock) in case of I2C protocol. ATMEGA328P is also having inbuilt I2C support. Pin no.27 (PC4) of ATMEGA328P is SDA which is connected to the SDA pin of the LCD module for transfering the data as well as command from microcontroller to LCD serially. In I2C protocol, synchronous communication is implemented where both the device require a common clock source. In this circuit, the microcontroller is working as master and the I2C driver for LCD is working as slave. SCL pin is used for the clock pulse. Pin 28(PC5) of ATMEGA328P is connected to SCL pin of the I2C driver. Pin no.1 is assigned as "RESET" pin. For normal operation pin no.1 must be pulled up and then the device will restart if a low pulse is provided at pin no.1. Hence, a 10K resistance is connected from pin no 1 to Vcc.

In this device five push to on tactile switches are used for different purpose. To START or STOP the ADC reading, a switch is connected to pin no. 14 (PB0). To SEND the data from microcontroller to a computer system through a USB cable, as with is connected to pin no.15 (PB1).

The program executing in the computer is responsible for collecting the data from the microcontroller. This data are processed further and compared with the data already stored in database. The stored data are collected from the real sample. And data of 5 samples of bovine, avian and caprine are entered into the database. Whenever the computer receive a data from the microcontroller, it start searching for the nearest match in the sample table. To find out the nearest data, a simple mathematical formula has been derived. After retrieving the data, the application

**Figure 15.** *Measurement using steel electrode.*

program display the resultant value on the computer's screen and at the same time the data has been transferred to the microcontroller though serial communication.

The program executing in the microcontroller is responsible for retrieving the information from PC and to display the received data. USB to TTL converter has been used to transfer or communicate between PC and the hardware section. Steel probe has been used to get the resistive value of the sample .One probe is connected to ground and the other probe is connected to the ADC channel '0' of ATMEGA328P. To keep the ADC pin high at no load, 10K resistance has been used. Whenever the probe are placed on/in the sample, it returns different resistance value which is processed to predict the resultant.

Due to different resistive characteristics of different material, the probe material will affect on the result. Measurement can be taken by using electrode of any material (e.g. steel, lead) as shown in the **Figures 15** and **16** but the experiment is performed using steel electrode.
