Now that our cabinet is built (see thread: ??Our new stealth cabinet!? by TxRooster97), we are trying to figure out how we want to setup the cabinet intake and exhaust.

We??ve got a 6? diameter cool tube (about 2?? long), but we are trying to determine the best way to cool this and the cabinet. We are considering doing both at the same time, with filtering.
The current idea is to have one end of the cool tube be the intake for the cabinet exhaust (vented cool tube). This would then run through a carbon filter (I??m going to build it) and then to the exhaust fan (around 500 cfm). I??m planning on making the filter in a cone shape so that it will fit inside the ducting, rather than making a filter chamber. We are planning on going with either a 400W or 600W HPS light.
My concern is that the carbon filter is going to reduce the air-flow too much to effectively cool the light and cabinet at the same time.
Has anyone ever tried this?
Does anyone have any info on how much a carbon filter reduces air-flow?
Any ideas for us to consider?
Or are we just wasting our time with this and we should go with separate exhausts for the light (make it a sealed cool tube) and cabinet?

Also,
Does anyone have any suggestions for a timer to use to control our intake and exhaust fans? I??ve seen the ones that are thermostat controlled, but what we are really looking for is something that can be set for on/off times in the range of seconds or single minutes. We??d like to have the fan cycle on for about a minute and then be off for a few minutes before it kicks back on. The only timers I??ve seen at the local building supply stores are for a minimum of 10 minute intervals (or more).
Is there even anything like this, with such small time intervals?
How much $ are we looking at for something like this?

TokeNAway Reviewed by TokeNAway on . Exhaust idea and fan-timer question Now that our cabinet is built (see thread: ??Our new stealth cabinet!? by TxRooster97), we are trying to figure out how we want to setup the cabinet intake and exhaust. We??ve got a 6? diameter cool tube (about 2?? long), but we are trying to determine the best way to cool this and the cabinet. We are considering doing both at the same time, with filtering. The current idea is to have one end of the cool tube be the intake for the cabinet exhaust (vented cool tube). This would then Rating: 5