Exhaust Fan exclude the air in the room

Air in the room should be promptly removed, you need to "Exhaust Fan", but for the convenience of their own people, they want to auto exhaust, so there is a timed fan. To achieve intermittent exhaust, consisting of 555 through the first duty cycle adjustable multivibrator control the first relay, the timing for the realization of the function of the total eight hours, composed by CD4017 counter multivibrator pulse number , so as to achieve the overall function of the exhaust gas intermittently timed eight hours. Designed and implemented by the timing of the room exhaust, timed shutdown feature. This can be used in addition to water vapor granary timing can also be used in the family room exhaust.