Y2 Project Week 3

Members:

Qinglie Zhu, Zheng Zhao, Junhao Zhu, Zhiyuan Zhang

Advisor:

Valerio Selis

General Ideas:

As mentioned last week, the aim of this week is to construct the entire circuit of the sound monitoring system consisting of amplifier part, ADC converter part and analogue to digital part. Moreover, we connect the sound monitoring system with a LCD and Arduino Uno. Next, we test each part of the circuit and the entire function of it. Finally, we write the first draft of the code of the sound monitoring system and have the attempt of debugging it.

Experience of the experiment:

1.   Test the amplifier part with function generator and microphone

At the first stage of the experiment, we try to test the first part of the sound monitoring system which is amplifier circuit. The whole process is divided into 2 part. The first one is the test with function generator providing sinewave function, while the second one is the test with microphone.

As the Figure 1 shown, the test is completed with a function generator. Channel 1 is the output signal, while channel 2 is the input signal. It is clear to observe that the output signal is amplified and the voltage gain is around 185. It seems that the first part of the sound monitoring system is succeeded in constructing.

Figure 1. Test With Function Generator

As the Figure 2 shown, the test is completed by a microphone. Channel 1 is the output signal, while channel 2 is the input signal. Similarly, the voltage gain is around 185 as well.

Figure 2. Test With Microphone

2.   Build and Test the ADC Convertor part

As for the second part of the experiment, we build the ADC convertor which is used to convert a signal from AC form to DC form. The reason of it is that almost all electronic components work in DC signal. Moreover, such conversion is benefit to the rest of the experiment. The result of the second is shown by Figure 3. The input signal is a sinewave. The output is the absolute value of sinewave that is channel 2 as shown in Figure 3. The part seems to work as a filter.

 Figure 3. Test of the ADC Convertor

3.   Build and Test the Analogue to Digital part

As mentioned previously, the circuit in this part is applied to convert a analogue signal to digital signal. The reason why converting a analogue signal to digital signal is that the digital signal is more stable compared to analogue signal. Moreover, the value of digital signal will be shown on LCD more easily compared with the one of analogue signal. As shown on Figure 4, channel 2 is the output of the analogue to digital signal part.

 Figure 4. Test of the AD Convertor 

4.   Connect the LCD

In this part, we connect a LCD to the sound monitoring system so that the calculated value will be shown on the screen directly. The method of connecting LCD with Arduino is shown on Figure 5 and the result is shown as Figure 6.

Figure 5. The Method of Connecting Arduino and LCD

Figure 6. The Test of LCD

5.   Connect the Arduino Uno

Here, we connect the Arduino Uno to the sound monitoring system and put some code to test whether the sound monitoring system can work or not. The result is shown as Figure 7.

Figure 7. The Test of The Whole Circuit with Arduino Uno

Difficulties:

Owing to the limited time, we left some problem that should be solved next week. Hence, we will explain them now.

1.    The function of whole circuit

As you can see, each part of the sound monitoring system can work individually. However, while combining them together, it seems to struggle to work. The final output of the sound monitoring system is just a straight line without any change on the oscilloscope. We assume that the reason of it is that the output of the ADC convertor part is much smaller than the bias voltage. The output is around 1.2 volts, while the bias voltage is 5 volts. Therefore, the output of the third part which is analogue to digital signal part only has some small change which might not be seen easily. As for the solution, we will try to add an amplifier circuit between the second part and the third part so that the input of AD convertor part will be relatively larger.

2.    The code of Sound Monitoring System

Here, we struggled to find a formula to convert the sound level to dB value with high accuracy. The code of the first draft is not accurate enough to display the right sound level.

Conclusion:

In the week, we succeeded in constructing the whole circuit of sound monitoring system and test it individually. However, we remained some difficulties to the next week due to the limited lab time. In the next week, we will try to construct the entire sound monitoring system which can work accurately.