24/2/2012 Week 4

Today, we checked and neaten the board again. In addition, we connected a LED to the output terminal, which can show result visually.

The modified board is shown as below, when someone enter the detection range (about 3m), the LED will go out immediately. 

At the same time, the oscilloscope displays square wave when someone moves in front of the sensor. We have test several times under different conditions, such as different distance, different person, and different movement speed. The amplitudes of the result are same approximately, which is shown as below,

20/2/2012 Week 4

Because the value of the output in the primary circuit was small, we decided to build a second-class amplifying circuit as primary circuit. 

Then the modified circuit is drawn by Pspice as below,

The output of the second-class amplifying circuit has too much noise,

We considered the reasons of the condition,

1.bad contact

2.high- frequency oscillation

For the first idea, we checked all components and contacts, the output wave had no change. As a result, this condition is eliminated.

In order to solve the problem of high- frequency oscillation, we decided to add a capacitor to the second-class circuit as shown in figure below. We have tried many different values of the capacitors, and finally 68n is considered to be proper. 

The values of R8 and R9 are changed to 27k and 18k, 

Finally, when hands shaking in front of the PIR sensor, the output of the third part is shown as below

13/2/2012 Week3

The output only has tiny change, so we modified the circuit by changing resistors of different values. As a result, the voltage gain increase several times than before. At the same time, we change the values of resistors in the secondary circuit, so the input voltage of pin 2 decreased than before. When the value of pin 3 is larger than pin2, the second part can work. Finally, the output of second part can be obtained by oscilloscope.

                   

10/2/2012 Week2

Today we corrected the way to test the PIR sensor. Then we checked the primary circuit and found it can work sucessfully. When the oscilloscope sets to 0.2s and 5mV, the original Vpp of PIR sensor is 10mV.

When it sets to 0.2s and 20mV, the Vpp of the primary circut is about 124mV. The votage gain is nearly equal to the theoretical value 13. And we tested the filter and found the output signal was clearer than before. However, the second part of the circuit still not work.

Then we modified the second part by using another new design as below, but it still does not work.

After that, we changed the experimental position, because we want to store images by digital oscilloscope. Strangely,the values displayed on this oscilloscope are different from former one.

We decided to write the report first and test the circuit next time.

7/2/2012 Week 2

We read the report guide today and discussed the structure of the report. Then we wrote part of the background and discussion.Additionally, we read the material of the PIR sensor again to find some useful information to explain the theory.

Moreover, we finished to connect the second board but without testing.

6/2/2012 Week 2

Today we continued to check the circuit, a LED lamp was inserted into the circuit instead of oscilloscope to test the output. However, once the supply voltage was connected, the LED lamp changed to light and remained lighting. As a result, we thought there was mistakes in the circuit structure. On the one hand, we decided to re-build and embellish the circuit. On the other hand, we decided to divide the circuit into three parts and check them one by one.

After re-building the circuit, we tested the primary part and observed tiny pulse on the oscilloscope when hands passed in front of the PIR sensor, which proves that the primary part can work effectively (The time option is adjusted to 0.2s). However, when we tested the second part of the circuit, the waveform has no response and remained a straight line. We have checked the circuit for several times, but we cannot find the reason. 

Then we decided to build the other circuit board to find if there will be some different. However, the fist part of the second board did not work as expected, so we had to check it again to find the problem. 

After doing the experiment today, we decide to test the original output of the PIR sensor to find the amplification of the primary part of the circuit. Moreover, we will write part of the report tomorrow.  

3/2/2012 Week 1

Today, we have built the circuit according to the design circuit. In the design circuit, two 1.2M resistors are required. However, there are no exact ones in the laboratory, so we choose two resistors 1M and 220k in series instead.

This is the original circuit without embellishment, so the wires seem not neat. Though we connected the circuit, the output wave does not display as expected. When hands passed in front of the PIR sensor, the waveform remained a straight line. We have checked the circuit but cannot find the reason. Next time, we will check the whole circuit in part to find the reason.