I didn't see a thread specifically for cooling, and thought it's important enough to deserve it's own topic.

Recent purchase for my projector:

2 adjustable attic fan thermostats. These little puppies are only about $11.00 USD each, and will totally eliminate the need for the manual fan switch.

What it is:
It is a thermal switch, that is normally open, until the set temperature is reached. At that point, the contacts close, allowing current flow, and power to the fan. After the temperature drops below the set point, the contacts will open, turning off the fan. This will enable the fan to run whenever the temperature of the box is above the set limit, regardless of the power state of the lamp. The temperature settings are adjustable from 50degrees Farenheit up to 120degrees Farenheit for the 'trip' setting, perfect for our needs. I will set up one of these inside the light area, but not in the direct flow of air, as well as a second one in a separate area of the light area. They will be wired in parallel, so that if EITHER thermostat senses that the temp is too high, the fan will run. Pictures and wiring diagram to follow.

Xanderphillips

The insides of the thermostat:

The cooling fan wiring diagram that I will be using. Note the redundant fan, not taking any chances that a fan that is less than 5 bucks dying will take out my LCD that is close to 300 bucks. I am also putting a 'high temp' shutoff on the lamp circuit. If the box gets over a preset temperature, it will turn off the bulb. The circuit is similar to this:incoming line voltage, a fuse, an on/off switch, then the overtemp thermostat is this side of the 'ballast/capacitor/bulb' circuit.

is that thermastat 120v or 12v? if its 120v you may want to put it before the 12v power supply.

Joe

Is the wireing to heavy of a gage for 12v, may not be the optimal.

I was always taught that wiring was like pipe, electron flow will not be stifled by larger gauge wire, only smaller gauge wire, in the same way that water flow would not be hindered by larger diameter pipe, only smaller diameter pipe...

Flyboy has it right. "Too heavy gauge" is a misnomer in this situation.

Rule of thumb when wiring something up is that "heavier" (or larger)=better because a larger diameter is more efficient (offers less resistance.) Unless you are specifically designing a circuit to include resistance, resistance is usually your enemy (i.e. power wires, speaker wires, car battery cables, etc.)

It's a simple bimetal thermal switch. It will switch 12v just fine. I would just use one in the ballast duct. I would wire it to bridge the existing fan switch, that way your fan comes on right away when you power up. As the projector warms the thermal switch will close and bridge the existing fan switch. Then when you shut down the fan will keep running until the thermal opens.

Just found information for a thermal overheat manual reset switch. Contacted the company for ordering information.

They manufacture thermal switches that will open a circuit at the voltage and current that we will be drawing for the lamp. It will remain off until manually reset. (No hot strike problem) They come in a variety of temperature trip points.

My thoughts were to put one of these near the LCD panel, and if it get's too hot, it will trip the power to the bulb.

Waiting to hear back from them.. Hopefully they don't think I'm some industry wanting to purchase 10 thousand of these suckers a year or something

A crude but perfectly effective 'countdown timer'.

I have a very active 5yr old and your solution was what I was looking for. Now the questions. I have where would the sensor be located to be accurate representative of the box temp for lcd( not blocking lcd) and how would the wires be run to protect them from the lamps heat?

Well, I don't know if it's the best, but I can tell you what I did. I put the thermostat towards the top of the box just behind the lamp mogul. I figure it should be near the top since hot air rises and if I put it right near the lamp, it should be fairly accurate as far as the temp goes.

The only thing I would recommend is not putting the thermostat next to the fan otherwise you might get cycling. In my layout the thermostat ends up in a place where it's more likely I'll get dead air. That might mean it will run longer.

I'll take a picture tonight so you can see what I did. I haven't tested the system yet, so I might be completely off, but it seems logical.

Thanks,
Zendance

I agree to keep the thermostat as close to the lamp as possible. You'd hate to have it turn the fan off too soon, then not react quick enough to restart the fan, and the residual heat fry the LCD wouldn't you?

Keep that fan running until the last BTU has been evacuated, I always say. Well, okay that's the first time I've said that, but...

Really ought not to wire it so that the thermo switch turns on the fan. It is best to use the master switch to turn on the fan and at shutdown use the thermo to hold current on the fan until the proper temp is reached. Here's a quick sketch to show how you can use a single DPST master switch (w00) in conjunction with the thermo switch for fully automated shutdown regulation.

Brainchild, could you help me understand your diagram posted above a little better?

Is the primary difference between the circuit you posted and the circuit I modified and posted, that your diagram allows the use of one master FAN switch to also provide power to the LAMP switch? Whereas I inadvertantly eliminated the 'interlock' in my diagram?

I feel as if I stuttered around a little up there, so allow me to ask in a different way: The difference between the diagrams below is the blued out section on yours, right? The left half of yours is the same as mine?

Yes Tony the fan circuit is the same in both diagrams. The only difference is that by using the thermoswitch we can get rid of the interlock and use a DPST switch; that is a single switch to start the entire projector, and the thermo to keep the fan running at shutdown. This is the circuit I will be using from now on.

OOOHHHH! Cool!

I entirely missed that we no longer needed the interlock. Thanks!

The disadvantage is that, even with the master switch OFF, we still have live wires running to the thermal switch...

Of course that's not much different than still having live wires running up to the FAN switch in the Guide's suggested configuration. I'll just have to remember to unplug before I open and adjust, with either configuration.

Always unplug!

Brain, can you draw your ckt with the internals of the DPDT please? I'm not understanding why we need it to be DT. It seems that a DPST is what we need. (AKA: what is the second on position for?)

Thanks
Xander

http://www.colehersee.com/04resource/dpdt.htm

http://www.colehersee.com/04resource/dpst.htm

Good catch. Looks like the ST ( S ingle T hrow ) is what we really need. You could use the Double Throw to activate room lighting, the rotating Disco ball, and the strobe light, to finish up the party you just had...

You're right xander, I made a error. The switch should be specified as a DPST. I will edit my posts to correct. Thanks.

Brain,

What's the difference between DPST and SPST? I've got an SPST and it's working, but I seem to have an odd problem I'm trying to diagnose.

Thanks,
Zendance

Double pole single throw versus single pole single throw. The DPST is actually two switches controlled by one lever. We wouldn't want to use a SPST in this application becuase the thermo switch would run the lamp and panel too at shutdown. We use the DPST instead which isolates the fan from the panel and lamp but still allows us to switch the projector on and off with a single switch.

I find it simplest to think of it in terms of circuit breakers. Have you noticed in your breaker panel, some breakers are tied together, connected?

That is how the DPDT switches work. It is essentially two switches like Brain said, that are tied together with one lever.

Thanks guys. I think that's what my problem is. For some reason, my lamp will sometimes come on even though the switch is in the off position. I'm using the attic fan thermostat with the fan, so it is non-switched. I'm guessing this might be causing the lamp to still have power because the fan, effectively, has power.

It's odd that it only happens sometimes though. OK, I'll get a DPST.

Thanks,
Zendance

NB: Don't rely on the sticker label for the temperature setting of the attic fan. This is a rough calibration at best. Use an accurate thermometer to set the on/off temperature at which you want your fan to operate. (Trial and error, move the knob, take a reading, etc...

X

Ok guys,

I'm confused. I just bought my rocker switch yesterday. Didn't pay any attention to DPDT or DPST but I fail to see that it makes any difference.

I had intended to wire my lamp and fan off the switch (with DPDT this seems easier, essentially one switch for the lamp/fan, one for the lcd), and then wire my thermost
directly from the mains plug to bridge it so it keeps running above required temp regardless of switch position.

Can someone please explain why this would be a bad idea?

Thanks.

Cheers,
Arkay.

Arkay, it isn't a problem it's just a pole you don't really need. If you were going to say use a 12 volt fan and a 120 volt supply to the rest of the gear, the DPDT would be what you would use since you could isolate the 12v and 120v switched legs from each other with a single switch. In our case we are using a single 120v (240v) supply but we still need two switches so the DPST is the switch we would use.

BTW people, I wired up my thermo switch tonight as per my wiring diagram earlier. Works like a charm, ran the fan for 8 minutes at shutdown. Of note: The switch cuts off 8ºf lower than it is set for. Since we don't care about the temp that the switch cuts on (since the fan is running anyway) we set the switch to the cutoff temp + 8º. My switch is set for 100ºf.

Brainchild,

Thanks. Now it's clearer

Unfortunately we haven't been able to find an adjustable thermostat... I've bought one that cuts out below 50 degreen celcius. I'm hoping, with this mounted very close to the lamp itself, that by the time the lamp hits 50 the lcd will be nice and safe. Any thought given that you know the heat characteristics of your rig?

Cheers,
Arkay.

I don't know the temp around the lamp so well, most of my measurement has been centered on the LCD and condenser. The basic thermoswitches we use in the states should function perfectly for you as well (extremely basic switch). These switches are designed to control an attic fan; there must certainly be an equivalent in AUS.

I don't think anyone has mentioned this, but, remember to set the thermostat above the ambient room temperature, otherwise your fan will run continuously.

I guess everyone is getting away from a timmer shutoff for the fan? The reason i'm asking is because im in texas and it gets hot here we use a/c all the time but when you are away you really do not use the a/c. and the room temperature will rise this would prob. turn the themastat on and run the fan? just like the timmer idea for about 5 mins after turn off. Just don't see much on it now?

Anyone using one?

Joe

I am considering adding one or two thermal fuses to the design just in case things got really hot. The fuse just may prevent a fire should the unit ever be left on and the fan dies.

Check out Thermal Fuse.

What do you all think?

Joe, what's the hottest it's ever going to be in your room? (Barring a fire)

Toblerone, not a bad idea. Of course if you happen to be watching your projector when the fan dies your lcd will turn black and liquid looking which is a good indicator that the fan has stopped.

prob. about 95deg. i guess.

Well if you set the thermo to activate around 110º you shouldn't have any issues. To be sure the thermo stays warm after shutdown mount it above your ballast since the ballast tends to stay warm for a long time. This way the fan will run until the ballast has cooled. Remember that thermos tend to shut off about 8º less that the trigger temp. I like the thermo over the timer because it runs the fan based on heat, not time.

Here is some info on bi-metal thermal switches.
http://www.stancor.com/pdfs/pg102.pdf

They cost 1$-4$. I bought a couple of the normally open type (STC-). This site has most of them.
http://www.alliedelec.com

I bought one of these on ebay to see if it's really what the guy says it is...
120v 120mm fan (claims 100+ cfm)

Ebay 120mm 120v fan

Just in case anyone is interested

Jared

thats the same one I bought - its awesome - a little loud - but thats okay - I got the fan from that guy also summaelectroncis


fast shipping - he leaves good feed back

this is the fan I won

KEST471BT

I haven't build my projector yet, but am a little concerned about the noise
of the fan.

I'm planning on ceiling mounting my projector below a suspended ceiling.
I was thinking instead of mounting the fan in the box that I could run some "dyer venting" over the ceiling into another room and attach the fan to the far end of the tubing.

See my crude drawing.

What do you think? Would this work ok. It might even let you use a higher CFM fan for better cooling since noise wouldn't be as much an issue.

you will probly have to use more than one fan for such a long vent tube. If the fan is not strong enough to pull the heat out of the box it will just build up.

tried it myself to redirect heat. found this to be a big nono. sure a 100cfm fan will push air through the dryer vent tube, but if there is any obstruction and i mean any, it will stop the airflow. i put the tip of my finger in the end and it died out. next, noise increases alot, as the inside of the tube is ridged and it makes this awful hum sound.
if i were you, and i was not going to move it.. and i was worried about fan sounds, i would (1) buy a quieter fan(the easy way out), or i would make a fan box out of wood that comes of the box and goes up into the ceiling like a (L). in fact you could make it the whole back of the box and use a bigger fan up in the ceiling that you could run at a slower speed and thus be less noisy with more pull, as long as you have enough intake air to feed the fan going into the projector. the suspended ceiling should absorb any fan noise made up there.

I'm planning out my cooling at the moment, and I don’t really want to have to faff about with dual interlocks or timing circuits, so I’ve bough some thermal switches. I was going to use the system outlined in this thread with the permanent feed to the fan through the thermal switch and a parallel feed from the main power on switch. The problem is, I just realised that they are 57 degrees Celsius, which is 135 Fahrenheit, 30 above the max. However, the 105 top is just for the lcd isn’t it?

So if I mount it somewhere on the bulb side of the tempered glass, will this work ok as by the time the bulb side is down to 130 degrees Fahrenheit I would of thought the other side should be below 105.

Also, I've just been reading the tech sheet for them and it says about they don’t actually switch, rather change resistance depending on temperature, so I think they are a different type to the ones mentioned elsewhere in this thread, and I don’t know if they are appropriate. I also have just assumed they work fine with AC as my fan is AC.

These are the switches in question:

http://documents.rs-components.com/itc_pag...106975569171021

I don't really know what im doing, so any help would be appreciated.

With a worst case resistance of 100 ohms across the device and a swicthing point of 57 celsius it is only going to be able to handle about 60 miliamps (0.060 amps) and its power dissapation goes down as the temperature goes up. You would probably need a relay, at least for the fans I have been looking at. Hope this helps.

David.

Hi Redrum,
The sensors you are looking at will not work becuase they are not a switch, they just change resistance as the temp changes. You would need to make a circuit that would activate a relay for these to work. Hope this helps.

thomAZ

I agree with the rest that you do not want to move the fan at such a distance. Best thing to do is to get a quieter fan (Low RPM). I have about 10 or 15 AC fans that has high RPMs (About 8000 RPM, maybe more!) and useless for this work. They are too noisy.

I think most of the people here are using low RPM AC or DC fans (3000 RPM or so).

I have some DC fans that are low RPM, so I am using them instead.

Ronjon

Here is a list of available fans, their cfm and dba ratings. You can find several fans from this list that will do the job quietly.
http://www.lumenlab.com/forums/index.php?showtopic=1017

Greetings! One quick question in regards to cooling... As I read the original plans, it calls for a vent slot in the top of the enclosure to allow air flow in, and the fan blowing the hot air out, ( pulling fresh air in from the top vent). Perhaps I read this wrong?... But wouldnt it make sence to have the fan, mouted as indicated, blowing fresh air in and forcing the hot air out of the top slot?... As we all know hot air rises.

PLease advise of your thoughts before I go ahead and start planning for my enclosure.

Thanks!
Hed

We just had someone with a heating problem that found that he had his fan reversed. You could cut your slot at the bottom to draw in air and have it pass over your tempered glass and out of the top side of the box through a fan. Better to suck then blow .