Came across another website that uses glass that has an IR film to prevent much of the radiant heat from reaching the LCD. Sav8or1, I believe you have your temp probe mounted on the panel, am I right, and not just simply in front of the LCD. Your ambient air temp may be quite lower. (I haven't previewed the posts in awhile so I am just going by memory. I hope I haven't got you mixed up with someone else). YOur LCD is probably absorbing much of this radiant heat and your temp. reading much higher than what the acutual ambient temp readings are. Using this glass somewhere in front of your LCD might help your problem. I'll try to find the site I was on and post if anyone is interested.

You have it right. I am using a uv rated lexan and the lumenlab uv sheet and my temps are now running around 84 degrees sometimes 85, but that is when the ambient temp in the room is around 70.

I have found a way to make my box deeper without much work. This will give more room for cooling and will give me better fresnel coverage.

I will work on it in a week or so and post my results.

Hi there.

I'm currently developing a fan controller circuit for my pj, but I'm not sure how fast the fans should run at the differnt temperatures. So far I have come up with the diagram below. As you can see, the fans will run at 50% of full speed when the temperatur is 103F inside the pj, 75% when the temp is 113F and so forth. Would this cool the pj enough without damaging any coponents, or should I change the temp/rpm ratio?

Cheers.

i'd have it running 100% at 95F, minimum.

#1: I have posted this elsewhere... Relaize that you will not move as many cubic feet per minute if your resistance is high. Your resistance depends on the dimensions of your "duct," the shape of your "duct," the length of your "duct," the corners that it turns, the obstructions it passes over or through (filters, wire nests, etc), the speed of the air in the duct, and any texture the walls of the "duct" may have. so merely having the same total opening dimensions (area) on your intake as what your fan output is will not give you maximal output from the fan because the fan is working against the combined resistance of the system the air is being drawn through.

So your evercool will probably actually do 100cfm. but it will only do that with 0 resistance. You can compensate for the resistance by increasing the dimensions of the intake, taking out as many corners as possible, making the duct shorter, etc. So what the equations are missing above are resistance values, because you are not drawing 200 cfm with 2 evercool fans.

If you are interested in actually figuring out what the optimal duct specs are get a basic HVAC book and check that out or i could try to put together some useful general resistance values for some of those factors (that'll take a while to tackle).

You may want to take inspiration from some other systems. check out the cooling on the mac G5:multiple short LINEAR low speed cooling cirucuits/ducts. nice! they did that for a reason!

if your lcd is heating up, consider venting that with a separate fan. Try adding additional space between your lexan or glass and your lcd, draw air from top to bottom, cooling your light chamber as a separate entity, opening up the air intake... etc.

#2: has anyone ever checked the temperature at the top of the box vs the bottom of the box? I suspect that with a formadible heat source such as that 400w bulb in there that the air will be of fairly uniform temperature, especially if the light is shining in the entire box, hitting everything in front of it(and therefor heating everything around it. Therefore, mounting a fan at the top of the box may NOT give you any cooling advantages. In fact, maximal heat transfer happens from the heat originating system to the cooling system when you place the coolest coolant with the hottest part of the heat source(as is done in heat exchangers).

So that was my contribution of hot air I have built a test box which will soon be exercising many of these questions and getting real numbers to help steer a course for some and troubleshoot for others. more data to follow.

The goal is to keep everything cool enough. While other compents have heat issues, and requirements vary by design the one know value is that the LCD can't be allowed to exceed 105'F. I would assume that you want to have a safey margin below 105'F I'd personally pick a value of 95'F. Rather than trying to guess at fan speed vs temp. Assuming that you want the fan to be as quiet as possible, otherwise I assume you would have max speed all the time to have minimum temps you should just pick a temp and have some sort of temperature measurement near the LCD and run the fan at the slowest speed necessary to not exceed 95'F. You might want to set a sub threshold of 92'F and if the temp gets to 93'F you bump the fan speed by 5% wait a minute and if it stays at 92'F leave it there, if it stays at 93'F bump another 5%. You can come up with your own algorithm but I think you want to have a feedback control loop rather than a lookup table. I've seen various people plot thier temps over a 1-2hr projector run, which is interesting and good, but this is winter how will your PJ work during the heat of summer when hung form the ceiling and as we all know heat rises and attics get very very hot will they have enough cooling then???

I think winter time LL PJ can get more wormer than summer, when furnace keep rotating same air inside your house there will be low humidity if you don't have a humidifier this can be a reason for your PJ to get over heat fast during winter.

I have used my PJ 16 hours straight this winter never went over 28C right now I checked my PJ after using 1 hour my thermostat displays 25.7C (78.2F)

I don't know if this is the place to post it, but if anyone is interested in the "cooling after" device this is a similar product at about 1/2 the price shipped.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewI...Pr4_PcN__Stores

aha, I like your idea pagercam, I was planning something along the same lines. Based on that the maximum recommended temperature inside the projector is 95F, I created a new graph, which hopefully is more correct than the previous.

hey guys, whats the cfm needed from a fan to cool the box in the original plans? and are there any benefits of a 120v fan over a 12v fan? thanks for the help!

I believe the guide says something like ~95CFM.

Benefits? Let's see... 12VDC vs. 120VAC. Hmmmm.... No power conversion required??

when you line the inside of the box with aluminum does there need to be a gap between the aluminum and the wood in order to keep the wood from getting to hot, or do you just put the aluminum right up against the wood?

Chris

goneflyin, you can put it up against the wood.. it is just to keep from "browning" the wood.. mine is siliconed against my interior and NO problems.. Paul

thanks. I'm looking forward to getting started on my project. I'm just waiting on a few more items to come in. and I still need to track down something to use as a reflector.

chris

I'm using 1,000 mile an hour aluminum tape on the inside of the light box.
Several layers should do.
got it at an HVAC supplier, $4.95 a roll.

I understand the inside temperature of the box should not exceed 105 F. Is that 105 for the entire box area? What is the temperatures around the lighting assembly?

I am interested in this to know so I can pre-test my pastics max temperature, as the walls of my project will use plastic and not wood. Thanks.

the temperature reference is to the max temp of the LCD itself, at 105 you're just askign for problems. ideally the LCD itself will be kept under 95.

the lamp section itself will be hotter then that, that's the point of the heat barrier (tempered glass), to block some of that extra heat.

i don't remember what the exact temp ranges are, but i suppose the fact that we're using hi-temp paint and flashing in the designs says enough.

is there supposed to be a gap between the fresnel and the glass? I read some posts that said they were getting some warping in the fresnel. Just wondered if anyone wanted to comment on that.

Chris

Brain,
Earlier in this thread (Jul 11 2004, 05:32 PM) you posted your design including a picture with a tubular HQI lamp instead of the s400 mogul base light in the ultimate light kit.
Why are you using the tubular HQ1?
Does it have better specs/performance than the S400?
Why are you using/recommending one thing and selling another?

kchrisen1

I think the only reason for using the dual ended tubular is size.

I have a suggestion on fans....

Alot of people are running 12v muffin fans out of computers. While they are easily sourced and are inexpensive, they dont do a fantastic job of moving air efficiently. I would suggest a 120v squirrel cage (or crossflow). A crossflow could easily be ducted in such a way as to move alot of air from a larger area with very little noise while making it very easy to stop light escaping. I'll see what I can find and post anything good.

Here is an excellent candidate. I may pick one up and position it over a ducted slot exhaust. It would draw over the entire upper portion of the enclosure, as opposed to one corner... Just a thought.

http://www.allelectronics.com/cgi-bin/cate...-207&type=store

@V&J, why not use the Evercool PCAC? http://www.nexfan.com/evpecoairco.html
It blows 100CFM and is only 23DB (That means it is very quiet).



I think you will have a problem with the fan you posted being too loud.
I don't know what you mean about the fans in PC's being unable to move air efficiently.

Those are awesome fans for $10. I will probably buy one and use it for mine.

I think it would be a good idea to have a gap in-between them... and allow air to flow through there.

I put about a 1/2" gap between mine.

Yep, it might be loud at full speed, but that doesn't mean it has to be run at full speed. The problem with muffin fans is they have a small area to scavenge from and have a motor right in the center of them. To move a given amount of air efficiently a fan should have as little restriction as possible. Any restrictions require the fan to work harder to overcome the restriction (resulting in noise). Air must be forced around the motor and through the frame of the fan. A crossflow has less restriction and therefore can operate at a reduced speed. Consider also that HVAC systems use crossflow fans for forced air systems because of their efficiency and longevity.



This would work just fine I believe. It would likely not be as reliable as a more industrial fan would be (bay mounted pc components are not known for their quality) and 120v would be preferable to 12v IMHO (simplified wiring and no wall wart to add more heat..). Yes, I agree 23db is very quiet, on the order of a whisper. You'd be hard pressed to find a muffin fan that meets the dimensions of that fan with those CFM and DB ratings. That Evercool is maybe 2 1/4" by 5 1/4". Mounting 1 or 2 of these would be much more flexible than an 4 3/4" (120mm) square muffin fan.

Thats my 2 cents at any rate.

I recieved my Pabst crossflow blower today. I find it incredible that a fan of this quality is so cheap. It is very quiet at full speed and has almost no vibration (the cage is dampered in the end bearing carrier). Reducing speed is not as easy as with a 12v fan but it doesn't (IMHO) require it. It is roughly the size of a S400DD bulb.

So i have a question, how have you guys been wiring a 12v fan? buying a voltage converter? or tapping into the lcd's 12v power?

What is the power being supplied to the backlights? 120v? 12v? maybe you can tap into those

thanks for the input as always

foce617 backlights are run on sevral kilo-volts at low current, I think most people that use 12v use a wall adaptor

The official consensus is that the LCD power supply should not be tapped with any fan load. You would probably be safe using it as a trigger for a relay, but not much more. A wall wart (ac/dc wall adapter) seems to be the most popular, but not the most aesthetically pleasing.

Hi V&J,
Thats a sweet looking fan nice price too!
One question is the motor inclosed in sheet metal?
Or is it out in the open like in the picture?
I guess I could make a housing for it if need be....

Peter

The motor is exposed, but the coil is insulated. I wouldn't spend the time enclosing the motor, especially if it traps heat. This fan is all metal, as opposed to some of the Evercool style bay coolers that are mostly plastic.

Another option is a 12v crossflow blower designed for car amps sold by a company called Stinger. I have read different cfm for these, some as high as 75cfm.
http://www.hifisoundconnection.com/Shop/Co...sid/0/SFV/30046

Here's a pic of the two sizes available.

yeah but the pcac blowers are 95-100 cfm at 25dbs for less then 18$ a piece.

True. These have alot of press in the car audio community and reliability is high on my list.

Could someone draw me or direct me to a diagram that will have one switch with hot, common, and ground wires labeled. I believe i have one but i just want to be on the safe side.

I have two 120 volt fans and id like them to stay on until a certain temperature is met after the switch is turned off.

Thank you.

You will need a thermostat wired before the switch for the PJ and after your 10amp fuse (basically eliminating the 1st switch). This will be powered as long as the PJ is plugged in. You will wire black into fuse, black out of fuse into a power distribution block, one black to your switch for the PJ and one black out into the thermostat. A black will come out of the thermostat and into the fan and a white will attach to the otherside of the fan. The green should ground the ballast, the LCD power supply and your power switch (if applicable). This setup should turn the fans on as soon as the thermostat temp is reached and keep it running until the temp drops below the trigger temp. You can get a thermostat for an attic ventilator at Lowes/Home Depot that is adjustable and in the right temp range. You could get 2 thermostats and wire one to each of your fans and set the temps differently so you have a stepped cooling system and a level of redundancy to guard against thermostat failure. The attached schematic is a good representation and well labeled. You will need to modify it to fit your plan a bit, but it lays it all out. And as always, If you are unsure about what you are doing... 120v will get your attention real fast and the output of the ballast can kill.
Hope this helps.

I Found this earlier in the pages and it looks to be the one i want to do. Can i splice in the other fan with the fan thats already listed? Also for a terminal block would this work or would i want one with more wire holders.


As for a capacitor, which one do you guys recommend?

Also. heres the diagram i am going by.

That looks good for the fan. That distribution block looks ok as long as it is rated to carry 120v. The cap should come with the ballast and an E-Ballast would be preferable to a cap-coil ballast. The DPST switch is a little redundant but will work as shown and affords protection against a thermostat failure.

I Got the ultimate light kit from LL so its the Eballast. Im still unsure about the capacitor though since you says it comes with it. All i need to buy is the block, thermostat, and a power in cord to splice and ill lay everything out how i need to wire it.

There is no cap with the E-Ballast. Blue and Brown 120v in, Blue and Brown output to the bulb and a grounding lug. Thats it. Make sure the correct wire connects to the center terminal of the Mogul base and your good to go. The wiring schematics floating around are mostly showing the old style cap-coil ballast setup, so disregard the cap if you have the E-Ballast.

Makes sense now. Thanks so much for all your help. Hope everything goes good.

Has anyone tried fan stacking yet? I'll try to dig up an old link but the idea goes like this:

Take two fans with identical specs, face them in the same direction and secure them together, be sure to use spacers to allow 1/4" gap between them (works better that way, forgot why though).

What this does is increase the static pressure of the fans involved. In laymens terms static pressure is the equivalent to "torque" and CFM is the equivalent to "horsepower". Increased static pressure gives fans more oomph to pull air through a projectors constricted air paths....ultimately increasing CFM by default.

Using the stack method may allow some to use only one fan cut-out on their enclosure and increase static pressure, something ac/dc fans woefully lack.
Keep in mind that fan stacking only has benefits within a air constricted environment such as the labyrinth within a PJ. It will not help much in cooling a PC processor which works in a more un-constricted environment.


edit: more links to come

http://www.sunon.com.tw/english/wealth/tech/tech-06.htm (bottom diagram)
http://www.overclockers.com/tips336/index.asp Verdict: not so good for heatsinks but good for increased static pressure, be sure to read all 3 pages.

Google turns up many hits for "fan stacking", too many to post here.

interesting, i always figured one of the two would be somehow getting restricted by the other and/or interefering with the air flow of the other.

this might be something for those who slow their fans down to keep them quiet, as well as for those who want to keep a smaller then normal inlet opening.

even then though, i would think that unless they're completely in sync in terms of rpm's, the speed discrepancy would create additional noise (that's a semi intelligent guesstimate)

I used to think the same thing, until i found a huge thread somewhere explaining all the characteristics. Apparently the small gap between the two fans is as important as anything else. Some people with small form factor shuttle boxes are using this method due to lack of space and fan placements.

Going to edit in some more linkage above as i find them.

Stacking is an old concept in PC modding. It slightly increases flow, but not much. These fans will not create static pressure. Example: lay a fan face down on a table blowing down. If it was capable of creating static pressure of any significance it would slide like an air-hockey puck. It doesn't. In fact it will blow air up around the blade tips and casing. The blades must be so close to the outer casing that it would be impractical.

i hear ya,

Didn't necessarily think it was the ultimate solution, but i did think it might help in certain circumstances: those hesistant to cut a 2nd fan hole can painlessly try this method first. Testing is easy enough, if a person notices a decent temp drop then all is dandy. If a person notices no difference then no harm done really, they can proceed to cut a 2nd hole

from what i gathered the page wasn't implying anything 'huge', just that the static pressue should be close to double when stacked.