Forced ventilation for the hushbox

After I buttoned up the hushbox, it became apparent (the projector shutting itself off) that my idea of passive ventilation wasn't going to work.

I asked my friends (I'm lucky to have so many who are technically proficient) about different ideas. Ideas were a mainframe fan, PC fans, CPU fans... but one suggestion really stood out. How about a bathroom ventilation fan? Perfect- because I didn't want the complexity of running 12V wires up to the ceiling to control it.




Even better! I found a ventilation fan that had a 3" outlet... which fit about perfectly into a plumbing fitting. The only issue... ventilation fans pull into their ceiling box and send the exhaust out the 3" outlet. Hmmm. That's the opposite that I needed. I considered rewiring the motor to spin backwards.. but that won't work, because the fan type is a centrifigal design. It has open vanes which accellerate air outwards. This slides around the edge of the box before finally going out the side. Darn, it wasn't going to work at all.

But wait... if I put the fan outside the box, it would pull from inside the box. But.. those open vanes would pull far more air from the ambient air than from in the box. How about some hot glue and aluminum foil?! Yes! I was really lucky that the fan I chose allowed me to flip the motor assembly upside down. Oh- and did I mention it was $12- the cheapest one they had at the local Lowes?






My hushbox has the wires for the projector in the same piping as where ventilation would go, so I needed a way to peel the wire off. Voila! Let the wires go up, and let the ventilation go out the side.

The next issue was how to turn it on. I didn't want it on all the time, so it needed turn on with the projector. Again, I dipped in the knowledge well. Some good ideas such as building a relay off the serial port of the projecter got discussed, but BruceK of Home Theater Shack suggested a current switch. A current switch is typically used in your workshop to turn on a fan or light when you turn on a different piece of machinery. How about when my projector turns on.. the ventilation turns on? Perfect! Even better, even after my projector turns off, the fans continue to run internally- and so does my ventilation fan.

A couple of finishing ideas- I needed to seal the top of my support where the wiring ran- a car wash sponge was very nice.

Finally, I used some 3" piping to locate the fan into a corner of the attic. This cut down on noise and vibration going into the room.

End result? Love it. The box runs cooler than the projector did sitting in open air- the internal fans never kick into high-draw mode. The overall assembly is much more quiet as well.