26th FEB - The Fifth Lab - Test different movement form

This week,we had two chances to do the experiment. On Wednesday, we check the circuits again and finally we found the problems. First,we ignored that LED would interfere the waveform. Second,it is quite embarrassed to mention that. After we change the 'coupling' button from AC to DC, the perfect square waves show on the oscilloscope. But another problem comes out.The signal is very unstable when we connected the output signal to buzzer which shows like that. Yellow line represents the lower sensor.Blue line represents the upper sensor.

Figure 1 Fall down

Figure 2 Fall down and then stand up

Figure 3 Fall down and then stand up and then pass by

The problem is that the buzzer will alarm on two conditions when people pass by and fall down because this two circuits cannot synchronize completely. Therefore,on Friday we planed to add 'Arduino' Board to control the signal to make it more stable.