WEEK 6

In this week, we had our final bench presentation.

Unfortunately, we did not complete our project perfectly. We had to explain the problem and solutions after a short introduction. After presentation, supervisor suggested that the background can be light which is better to read. At ten o'clock, our tutor came to our group and listened presentation carefully. Finally, our tutor advised us to modify our project in the remaining time. We are glad to obey his suggestion and complete our project at 3 o'clock, although we had finished our presentation. In this design, we ignored the most basic component, capacitor which is use to filter wave.

Week 5

The report of working process in the last week
After modification of the past circuits, our group has changed many times of the whole circuit structure.

The oscilloscopes in the lab includes 3 types. One is newer and the other 2 are older types. However, the output waveform only appeared in the one type in old fashioned series, which can be easily zero set by us. ( The teaching assists also said they were not similar to the latest models of oscilloscope so we chose the simpler ones.) When we were applying the simulated sine-solid inputs the outputs can be considered to be reasonable. However, the magnifications are not same as we calculated. Then we changed the values of resistances and moved the capacitors many times to improve the results. In these process we found lot of mistakes. One traditional sample is we forgot to let the resistor which was connected to the source pin to ground. When we started to apply the RE200b into the circuits to test the latest circuit more problems occurred.

The output waveform turned to be abnormal. When we tried to remove some capacitors it can be better but also far away from the expected result. Then we changed to amplifier LM1458 into Lm324. But this time we still failed and cannot find the core of the problems. Then the time limit in the lab came. Our group had no more time to finish this task. It might be a pity for there process because no appropriate achievement was created although the simulation work is good.

Week 4 Test Circuit and Modulation

We have simulated the circuit in MULTISIM and output waveforms are correct. In this week, we mainly tested circuit and modify it.

In the beginning, sine waveform was used as the input signal and oscilloscope was used to display the output signal. The output signal is correct which was showed in following picture.

However, the output signal will be not correct when we connected sensor in the circuit.

 Therefore, we had to test each part of the circuit. One part includes an amplifier. Unfortunately, each part can not be found any problem. We thought that sensor is broken or the connection of it is not correct. But these guesses were denied by researching information and testing.

So we thought that our design has problem, although it can be simulation perfectly. We have to design the circuit again and test it next week.

Week 3 Improvement of the designed circuit

After the failure of the circuit design, which cannot output even a whole output waveform all times though the simulation can output a wrong wave, we attempted to change components and structures of the design. After analysis with the tutor and the technical assistance, the main possible reasons can be summarized as below. Firstly, the function of the comparator was not effective as we hope. The connection of it might be wrong. Secondly, the input A of the oscilloscope represents to the input wave and it was normal. However the input B cannot conduct an output. The input B equals to the output of the amplifier. So the function of the amplifier which connected to the oscilloscope needs to be checked. Thirdly, the results of the simulation and the real circuit on the breadboard were different. Change another breadboard and close up the circuit might help. After that, the input voltage we designed seemed to be so high. The gain of the amplifier is (R4+R5)/R5 , so the gain should be near 100. The amplified voltage needs to under the power supply. Reduce the input voltage to 20mV or 30mV would be fine. At last but not the least important, the filter of the PIR sensor could help its sensitivity. The two pictures below showed the test of the first amplifier without the comparator and its simulated output.

The completeness of the system got a basic guarantee. However, the amplitude of the gain is too small. The real circuit cannot conduct a whole output.

After adding the comparator the output started to be controllable.We will check problems next week