A question abuot a possible wiring idea

Old 09-15-04, 06:28 PM
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A question about a possible wiring idea

I'm working on a little home project. Nothing major. My problem is that I need to keep something below a certain temperature (110 deg. f.). Thats not too hot, i know. I was wondering if anyone here knows of something small and compact that i could possibly use. It can be cheap (which is preferable) but i will pay whatever i need to for it. If a device like this doesn't exist, ideas on what i could do would be very helpful.
thanks in advance,

Last edited by Calliah; 09-15-04 at 10:29 PM.
Old 09-15-04, 06:39 PM
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Put it in the refrigerator???
Turn on the air conditioner and set the thermostat???

Seriously, it's hard to comment with only a bit of information to go on. There are plenty of devices that can monitor and act on temperature, but how to cool it back down if it threatens to get hot vary a lot depending on whether you are trying to control the temperature of a microchip or an elephant.
Old 09-15-04, 06:47 PM
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oh. Duh. Sorry about that. Well, basically, I'm working on making a video projector for my computer. I've gotten the plans from a reliable online source, and used them to create my own plans. I guess i need to give a general idea of whats going on so i can give you all a clear picture of whats happening. Basically, a Metal Halide 400 watt bulb will be throwing light into an LCD panel, through tempered glass, as well as a fresnel lens. Now, after the light hits the glass, I can't have the temp go above 110 degrees. I have a fan and heat sink on the side with the bulb. Keep in mind this is all in an enclosed area (about 15" wide, 15" tall, and a depth of about 27"). What i really need is for the temp gauge to shut off the bulb if it reaches 110 or more. I can wire it so that i could have the fan continue running to cool it down, I'm sure, if i knew what to look for as far as the gauge is concerned.
THanks again, and sorry for the little bit of info first.
Old 09-16-04, 03:12 PM
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anyone out there have any ideas/suggestions/etc.?
Old 09-16-04, 03:39 PM
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The max is 110, but the minimum is????

My feeling is you are overthinking this project.

Install one or two 'boxer' fans (as in computers; many sizes and voltages to choose from) and monitor the temperature.

If you insist, you can get a 'line voltage' thermostat and use it to control fans. Most common home usage is electric baseboard heating.

Rarely is a temperature-regulated cooling system needed; I can only think of internal combustion engines or industrial processes.
Old 09-16-04, 06:16 PM
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I don't know what the temp is but can lights have over temp controls. They act like a switch. You put them in series with the power conductor. I imagine they come in different amp ratings as well.
Old 09-17-04, 12:23 PM
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Calliah, I think you'll find that this is a fairly common problem in LCD projector design. Although having a shutdown device is a good safety, if you're pushing 500 Watts worth of light through a piece of glass, a lens, directly onto an LCD in an enclosed box, the constant on and off cycling of the bulb is going to make using this thing a real challenge in patience. That is to say assuming you don't reach a point where you fry liquid crystal before the device has a chance to shut down. My suggestion is to consider some other design that might allow you to bring COOL light to the LCD. Mirrors maybe? "Cool mirrors" maybe? I think you need to find something that reflects the majority of the spectrum, but not infra-red. Of course you could just install a bunch of heat sinks and fans...

Good luck.

Doug M.
Old 09-19-04, 06:23 PM
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If you go to any of the DYI "Home Automation" sites on the web, (there's lots of them). Most have low voltage temperature sensors with a high and a low setting. They are pretty simple with an analog style clock face. You simply move the two dials to the low and high temperatures you want to trip at. When either occurs, you get a dry contact output.

I used to use them as an add to Burglar Alarm systems in homes. People were concerned about their heating system failing in the Winter when they were away. I would just set it to about 50 degrees and get a trip on the panel if that temp was reached. Then the Monitoring Station would call them and give them a heads-up.

They used to have a range of about 40 to 120 degrees. You could run 12V or 24V through them to fire a relay in your circuit. Pretty simple and pretty cheap if I recall. I used to pay about $50 for a unit. Good luck with your project.

paul o's
Old 09-19-04, 06:50 PM
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Just an idea

Have you thought about water cooling?

You could have two pieces of glass with a space of 1/4"-3/8" between. Seal it up with a system to circulate water through it.

If you back this up with fans, you will probably never have the light shut down because of high temps.

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