"Exhaust Fan" One problem: when the voltage is selected to start the 12V, the phenomenon should be: red light when the fan does not work, and when the green light to work. After the power is turned on, they found two lights have lit, and this should be a phenomenon contrary. So when using a multimeter to check the circuit where there is a problem. Repeatedly check the circuit and found 555 chip 3 terminal is not output pulse wave, and then check found himself less connected to the chip pin. Second problem: doing the simulation time, simply CD4017 chip clock enable terminal overhead, after a week's work it is no longer counted. But when the power is turned on to view, but found different results and simulation, it has been cycling to work. After searching for information, etc, to understand my received fifteen pay voltage relays to drive, it will not achieve the control effect.