I am new to growing and just got a grow tent but I have been having heat and humidity problems so I just got a fan for exhaust and was wondering how long it should be on for I've read that every 3 minutes is good but all the timers I've found only goes up to 24 programmable timers so that would be on twice an hour for 12 hours but how do I set up the exhaust fan to come on every 3 minutes