Week 2 - Building the Circuits


In the second week, based on the simulation results of the circuit in the first week and suggestions given by the supervisor, our group decided to divide the whole circuit into three different parts, each section have different functions and test them separately.
Before building the whole circuit, we tested the PIR sensor with amplifier at first to check its working principle, then we began to build the first part of the circuit and the diagram of first part circuit is shown below:


Figure 1: The first part of the circuit

As shown in Figure 1, the PIR sensor has three pins which connect to different components, pin 1 is the drain which is connected to the Vcc, and pin 3 is connected the ground. The source is pin 2 that used as output of PIR sensor. Between pin 2 and pin 3, there is a resistor of R2 which is 47KΩ that is used to change the current signal into voltage signal so that the amplifier will be able to amplify the signal. The capacitor and resistors were connected together that is used as filter to filter the noise and make the output signal more harmonious. Then according to the whole circuit diagram, our group built two identical circuits and shown below：

Figure 2: The diagram of whole circuit


Figure 3: The first circuit

Figure 4: The second circuit

After building the whole circuit according to the diagram, we started to test it step by step, The oscilloscope and the LED were used to observe the results, first of all, we tested the first amplification circuit, with a sine wave signal as input, however, the output is not as our expectation, we tried to do some modifications to our circuit for several times but still, no satisfying result. Our group decide to improve the circuit next week and test each section carefully.

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Week 1 - Simulation

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This project aims at the infrared sensor as well as its application. The infrared sensors are designed for the disabled people or elderly people living alone to detect their falling downs without contacting and then alarm and make some noise to call others to help. There are a few tasks in this project including simulation, building the circuits and testing and etc. As for the week 1, the main task was to do the simulation. The working principle is the sensor can detect the changes of light and then produce the current signal, in addition, the circuit is able to transfer the current signal to voltage signal so that it can be amplified. Firstly, after doing some research on the internet, a theoretical circuit was obtained. And the future work would be based on the circuit. The circuit is shown below. Figure 1 The second part is to use the Multisim to simulate the circuit on computer. There was a problem that the RE200B cannot be simulated in the software. As a result, ...
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Week 3 - Testing

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Last two weeks, the simulation of circuit have already done. Therefore, this week the key of point is to construct the other circuit and finish several tests and record it. First step is to constructed the whole circuit, according to our design paper and the circuit we have built last week, the teamwork had been done where are shown as below. Figure 1 The next step after building the two circuits was to test the waveforms of each section in the circuit on the oscilloscope. Test 1 The First stage The reaction of the first stage operational amplifier is shown in the figure below, it can be seen that when a palm is swept above, there is a signal from its terminal, the output is too tiny to be used, and the reason is about the gain of this amplifier, which can be changed by the variable resistor. Figure 2 Test 2 The second stage The goal of the second stage in this circuit is to amplify the signal so that the transformation of the signal can be more dist...
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