CurtPalme.com Home Theater Forum

TheyDroppedMe · Joined: 25 Oct 2009 Posts: 28 Location: Atlanta, GA

Well I'm going to be getting a nice "new" projector soon (once I decide what to get), which will be going in my living room. My one big obstacle will be figuring out what to do with the ceiling fan...

I figure it can't be too close to the projector because of the motor/magnets, but how far away is far enough? Being a living room I would like to have a fan in here (although I am prepared to sacrifice for inky blacks Smile

. If say 5 feet would not be far enough away, are there any fans that wouldn't put out as much electromagnetic radiation?

Or maybe I could shield the motor much the same way speakers are shielded? I'm not afraid of reengineering products...

Thanks,
Greg

draganm · Joined: 08 Mar 2006 Posts: 8990 Location: Colorado

set it far enough away so that the blades don't smack the projector. There's no other "radiation" you need to worry about except what's coming from the CRT

Joe L. · Joined: 02 Jul 2007 Posts: 13

If radiation from the CRT strikes the fan blades, and if they are in between the lens and the screen, it is very possible to get shadows on the screen, even if you use transparent blades.

The shadows are even more distracting f the fan blades are moving, as it is guaranteed they will block different colors as they turn. This is almost as bad as the "rainbows" seen with digital projectors and their color wheels.

Seriously, anything "reflective" on the ceiling will be distracting, even if not moving. consider painting the fan flat black. Wink

Consider painting the ceiling flat black too. (or covering it with black fabric panels as I did)

TheyDroppedMe · Joined: 25 Oct 2009 Posts: 28 Location: Atlanta, GA

wow, you guys are sure the motor won't be a problem? Every ceiling fan I've see puts out tons of noise on my radio scanner... I thought the magnets and such would be a problem.

We had one surround sound install in which the man's large fan actually put a hum on his rear speakers whenever it was on, but then again that was a fan with like 4foot blades...

I'm just trying to get the most out of my future setup...

ecrabb · Posted: Mon Oct 26, 2009 2:27 pm Post subject:

For magnetic distortion to be a problem, I'd guess the fan would have to be so close to the projector, that the blades would hit it.

In your surround install, I'd guess a speed control was on the fan... Some of those put out a ton of RFI. Some motors do, too but that shouldn't really affect the projector like it would affect anything audio - especially any sort of radio receiver. I've got 4 fans in my house - all with speed controls - and I don't have any audio/RF issues with anything - including AM radios.

SC

TheyDroppedMe · Joined: 25 Oct 2009 Posts: 28 Location: Atlanta, GA

Thanks ecrabb for the serious answer. And you are correct about the fan in the surround sound install we did, it had a fan control unit. So I'm assuming that these CRT projectors are relatively insensitive to magnetic fields and would have to be pretty close to cause a problem...

If it does pose a problem, I guess I can always glue some magnets to the motor to give it some shielding. I know they need to be glued North-North or South-South, but is there some rule of thumb as to how strong the magnets would need to be? I'm a bit of a freak about emi, I even went as far as swapping out all the wiring in my living room/theater-at-night for grounded MC wire for its shielding effect. My power is pretty dirty though - so bad that I couldn't get UPB switches to work on the same circuit...

So the consensus is that if my fan is approximately 5' away from the projector it shouldn't be a problem? Thanks again guys,
Greg

rabies_70 · Posted: Mon Oct 26, 2009 3:22 pm Post subject:

In our cinema, a ceiling fan is mounted directly behind my G70 (fan blades are about 10 inches from the back). No problems at all.

draganm · Joined: 08 Mar 2006 Posts: 8990 Location: Colorado

the only time I've seen something affect the magnetics on a CRT was a basement install directly below a very large I-beam. It skewed all the rasters to the side where the beam was on so it appeared like the beam was heavilly magnetized. We didn't sprinke any Iron dust on it to make sure but there as enough adjustment in the coil centering to make up for it.
CRt PJ's though are generally immune to EMI and RFI simply because there is so much metal around everything. Especially the Marquee,it had to meet Military specs. for those things, both from the PJ and out of it.

Robert A. Hill · Joined: 19 May 2006 Posts: 182 Location: Simpsonville, SC

My projectis floor mounted directly under my ceiling fan. I have the pj raised so it is mid-screen position to minimize keystoning. The fan really helps reduce the local heating due to the projector. Since this is a "bonus room" over a garage, the builder spent no money on extra cooling. I've never see any issues with electrical noise from the fan.

Robert A. Hill · Joined: 19 May 2006 Posts: 182 Location: Simpsonville, SC

My projector is floor mounted directly under my ceiling fan. I have the pj raised so it is mid-screen position to minimize keystoning. The fan really helps reduce the local heating due to the projector. Since this is a "bonus room" over a garage, the builder spent no money on extra cooling. I've never see any issues with electrical noise from the fan.