Process

I first built the circuit based on the graph on the website. At first I am using a solenoid. However, I failed to make it run. After using multimeter to test it, I found it was because the connection between wire and external power is too loose. But after fixing this problem, it still didn't work. Then I replaced the solenoid with fan and it works. It turns out to be that it needs higher voltage to trigger solenoid.