IAm5toned
Well-Known Member
and they are also prone to short service life, and sudden failure, and are also dependent on a power supply, which is another point of failure.Although 240/120V AC fans flow more I prefer 12V fans, they are safer to use, setup and safer to adjust the flow of. using AC speed controllers that regulate voltage or resist current can cause fires.
The only correct way to dim AC fans is via PWM (Pulse Width Modulation) For that matter if anyone would like a circuit diagram of a simple AC motor speed controller I can provide a diagram. My design uses high power MOSFETs and a 555 timer. for those more technical I can provide source for a PIC circuit using a 16F628A.
- Slix
for some people, thats ok, but for me, if my fans quit, unless my lights shut down in about 5 mins or less, very bad things happen. you could say that with my grow, my fans are the most critical part.
for that reason alone, i would choose a line voltage fan over a low voltage 12v or 24vdc, the absence of a potential point of failure. plus, you simply cannot get the cfm with low volt fans as you do with ine voltage, there just isnt enough torque at low wattages to compete with say, i of 2 240vac fans that push about 450cfm. however, i also have temp overides in place, just in case... temp hits setpoint, lights shut down, and stay off untill the setpoint has been restored for 9 mins. my lighting contactor is also overridden (in addition to the temp overide) by exhaust fan status, using a go/no go CT relay on my 120v exhaust fan neutrals or one side of 240v. if the CT senses a major drop in current on any fan, it kills the lights.
safety is priority....
...and what about frequency modulation, rectifiers, and synchronous drives?