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Discussion Starter #1
I'm building a hush box for my dedicated HT room. My room is airtight with two supplies coming from the HVAC unit in the adjacent storage room, so it makes sense to pull the hot air out of the HT room instead of simply blowing it back into the theater room while the projector is running (i.e. when there will be people using the room). When I built the house I installed a 4" exhaust duct that exits to the outside at the basement stairwell. I'm planning to throw an AC Infinity Cloudline S4 inline blower between the hush box and the outdoor exhaust dump, but am trying to devise a way to trigger it with a time delay. Unfortunately it seems that AC Infinity doesn't offer a solution with a time delay...

I want the exhaust fan to turn on when it sees the 12V trigger from the JVC NX7 projector and remain on for ~10 minutes after the projector shuts off (i.e. the 12V trigger cuts off). I can't seem to locate a timer delay relay that will do this. Any electronics/relay wizards in here that can guide me in the right direction?
 

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I plug my ac infinity exhaust fans directly into the usb connector on my Sony projector and they keep running as long as the projector is running and cut off once the fans on the projector cut off.
 

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I plug my ac infinity exhaust fans directly into the usb connector on my Sony projector and they keep running as long as the projector is running and cut off once the fans on the projector cut off.
With a nearly sealed hush box I'm afraid I'm gonna cook the projo and lamp if there's not some evacuation of the hot air after shutdown.
 

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With a nearly sealed hush box I'm afraid I'm gonna cook the projo and lamp if there's not some evacuation of the hot air after shutdown.

I got the higher end 6” AC Infinity model that has a temperature sensor, as my sister-in-law has one and it works great for them (I’m still working on my theater and haven’t installed mine yet). Theirs comes on as needed for their equipment rack (they don’t have a PJ in their theater) and it is super quiet (totally convinced me it was the one to get). This way it will stay on even after the PJ shuts off to cool down the PJ box.
 

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I just ordered a time delay relay, small 120V-12V power supply, project box, etc to rig this inline fan up. I'll update this thread with my progress and links to items on Amazon if it works as expected.
 

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Discussion Starter #6
Also posted in my HT build thread:
While drawing out my projector box design, I decided to go with a hush box and add a 4" inline fan to get the heat out of the box and room. There is no return for the basement's HVAC loop in my theater room, just two supplies, so I thought I'd make use of an unused 4" duct that we ran during construction that was supposed to be for the equipment room (it kept overheating, so I added a ductless minisplit just for the equipment room). I'm going to tap into that 4" ducting in the equipment room, install an AC Infinity S4 inline fan on the ceiling of the equipment room, and then feed a new 4" duct through the soffit to the top of the hush box. In the pic you can see the hole where the flange will attach at the upper front of the hush box.

I rigged up a small relay box with a 120V > 12V power supply that powers a time delay relay. The logic is: JVC NX7 projector's 12V trigger powers on/off with the projector, turn projector off and the 12V trigger turns the relay and duct fan off, but the time delay on the relay will keep the power outlet for the fan hot for another 15 min to evacuate all of the hot air. Built and tested today and it works perfectly.

The hush box is going to hang from the ceiling in the back of the theater. I built a mounting plate with cutouts for the AV conduit box, 4-gang power outlet and the 4" ducting. Went to attach it to the ceiling last night and found out that my drywall guys are complete garbage - the ceiling had a bow of over 1/2" so the mounting plate wouldn't lay flush!!! Still fuming...... Not sure what I'm going to do, but it might involve brute force, hoping that it doesn't F up the drywall finish on the ceiling... (there's a big piece of 3/4" ply above the drywall mounted to the soffit framing).

Right now I'm building the lower box that will slip over the mounting plate's flange and attach to it with some #8 screws. As soon as the lower box is done and ready for paint I'll try getting that mounting plate mounted up. The back of the hush box is going to be held on with magnets and have a perforated aluminum grill to allow fresh air to be pulled through the hush box.

Amazon links for the main components for this delayed timer relay box:
Time Delay Relay: https://www.amazon.com/gp/product/B07RGT5G1X/ref=ppx_od_dt_b_asin_title_s02?ie=UTF8&psc=1
120V>12V Power Supply: https://www.amazon.com/gp/product/B00WMDZ0CQ/ref=ppx_od_dt_b_asin_title_s00?ie=UTF8&psc=1
Project Box: https://www.amazon.com/gp/product/B005T5A0W4/ref=ppx_od_dt_b_asin_title_s01?ie=UTF8&psc=1
Leviton Panel-Mount Receptacle: https://www.amazon.com/gp/product/B0036ZA94S/ref=ppx_od_dt_b_asin_title_s00?ie=UTF8&psc=1
16g Replacement Power Cord: https://www.amazon.com/gp/product/B07C9D6CXY/ref=ppx_od_dt_b_asin_title_s02?ie=UTF8&psc=1
 

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I like your solution.

I run a thermo switch in my hush box and it works very well. I use a 6UED4 switch that closes at 90F and opens at 80F. This switch will close within just a few minutes of the projector turning on and it runs the exhaust fan for 10-15 minutes after the projector shuts off. The key is to use a low thermal mass mount for the switch such as a plastic outlet cover rather than a metal cover to ensure a faster turn-on and position it above the projector exhaust port. These thermo switches are very reliable and inexpensive and can switch 0-240V. Add a metal utility box and some wire and you will have a very reliable control system for less than $15.

Mike
 

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