Week 4 - Improvement and Recording

In the previous three weeks, there two circuits which have been completed. Because the circuit is too complicated and there must be some tiny mistakes in the circuit on the breadboard, the sensor cannot detect the motions sensitively and the waveforms on oscilloscope are full of noise. Therefore, what was concerned on this week was to do some improvement of the circuits and then make a testing plan to record the data.

It can be observed that if the tester is a little far from the sensor, there would be a very slight change on the output signal. In other words, the testing distance of the sensor is too short. In order to solve this problem, a lens was used to put over the sensor. The lens is able to centralize the light so that it can detect the changes of light more easily. In this way, the detecting distance is increased effectively. It can be seen in Figure 1.

Figure 1

What need to be focused on is how to connect these two circuits and make them work simultaneously to detect whether a man is falling down. We used Arduino to achieve this function. The Arduino is used to design a program to connect the circuits and make them as an upper one and a lower one. The program will light the LED and a small screen will show figures if the lower sensor detect the movement but the upper one does not. It means a man has fallen down, otherwise the LED will not be lighted. The Arduino and the screen is shown in Figure 2.

Figure 2

After some improvement, a circuit was used to record the data. The distance and the temperature were adopted to be the variable values in the condition of with or without a lens. The table below shows the specific data.

Table 1