Need an automatic fan control/switch (1 Viewer)

[Terry Wysocki]

I mounted my Sanyo XP21N projector on the ceiling in an enclosure that has a duct from the exhaust fan up into my attic. The manual says not to have any "obstruction" within 3 feet of the exhaust port but I built a duct (not an obstruction), right? Anyway the exhaust temperature is the same as when it was un-"obstructed" at 130 degrees F.

Just to make extra sure the unit is as cool as possible (with Summer coming), I'd like to put a supplemental fan in the attic duct that would come on automatically. It could either be triggered thermally when the temp exceeds X degrees or by when the projector fan is running (the projector has "power" always).

Can anyone suggest a device I can use to accurately sense either current or temperature to trigger the fan? I can wire up something if given a bit of direction. If these ideas are too lame, what other options do I have?

 

[Rob Lloyd]

If you want a smaller one, which might be fine for a projector, there are some great computer fans with temperature sensors built in. The hotter it is, the faster the fan runs. You can get these for under $10.

To turn stuff on automatically the cheapest thing I can think of is from Sears - they have a power strip that turns on other outlets if something is turned on in the main spot. I can't seem to find it on their site but they had them last year for about $30.

If you want an attic fan they have some that are also temperature controlled. Most home centers have those.

 

[Darren Hunt]

If the computer fan with sensor is not strong enough for you, and you happen to have a few extra bucks you don't need, you can purchase a computerized temperature control system similar to a freezer control unit at any local refrigerative supply store. I ended up purchasing a JCI Digital Temperature Control Unit for around $80 CAN. It has a sensor that can be placed any in the location you want to monitor (up to 100 meters away if I remember correctly) and allows you to see what its temperature is at a glance.

I then have a 120 Vac, 120CFM quiet fan (Purchased at Home Depot) connected to it. The fan is located in the room next to my theater and is connected to my equipment closet via ducting. When my closet reaches a high temperature setpoint(I have it set around 35 degrees C), the temp control unit kicks the fan on and in no time the warm air has been sucked out of the closet, replacing it with room temperature air. When the temperature reaches the low temp setpoint (room temperature), it turns the fan off. Since the fan is not in the room, you do not know when the fan is on/off, and the area you are concerned about is kept at a safe temperature automatically. In the end it is perfect for what I wanted, just a little on the expensive side.

Darren

 

[Terry Wysocki]

Exactly what I'm looking for! Where did you get the sensor/switch unit, anywhere on the net? Does the manufacturer have a website? I did a search but can't find it online.

 

[Darren Hunt]

If you check your yellow pages under refrigeration, you should find a few local stores that deal with temperature control systems. I chose one with a digital display, and that is run on 120Vac. It also controls a 120Vac relay switch (for the fan unit) so you can use pretty well any 120Vac fan with it from Home Depot or a similar store. Give the refrigerative store in your area a call and explain what your trying to do and they should be able to help you.

Make sure when you connect your fan unit to your projector enclosure, you use ducting with alot of bends between it and the fan. Normally ducting is installed as straight as possible to ensure high air flow. In your case, I am sure you are more interested in keeping the noise of the fan to a minimum, so many bends helps attenuate any fan noises. I also lined the inside of the ducting with a foam sticky sound absorber. This helps out with attenuating the sound even more.

Hopefully you will be able to have the fan located outside the room. This will ensure that the fan isn't noticeable when it turns on and off.

Hope this helps!

Darren