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Temperature controlled fans-

Posted by Krstofer Sunset 8 (ish) (My Page) on
Thu, Mar 10, 05 at 12:12

I've got a set-up like this in mine- maybe it can work for you.

Problem with my terrarium was with all the ballasts & high powered lights in there heat build up would run away... 90F was not uncommon shortly after the light timer(s) came on.

I've got a bunch of 12 volt computer fans laying around... So I decided to use them to cool the terrarium. A 12 volt 1 amp "wall wart" power supply from the thrift store (only a dollar) provides power for the thermal circuit & thus the fans.

I made a thermal fan circuit using this design. It's quite easy to make & the parts aren't too terribly hard to find.

Once that was made I bought a 12 volt relay at Radio Shack which turns off the mist unit when the fans turn on as the new cold (i hope) air will be rather dry. Once the heat has been removed then the mister(s) are allowed to turn back on & 'fix' the humidity.

I'm also using a stripped down 'house' thermostat in the big terrarium- Same setup with the relay & misters as the little terrarium- Difference with this one is the fans come on full power untill the temp drops to a point where the thermostat turns them off. Disadvantage is it can sound like a small turbine engine when the fans are on.
With the thermal circuit the fans gardually spin up as the enviornment gets hotter. It's very quiet.

Seems to work well- Have questions just ask.

Follow-Up Postings:

RE: Temperature controlled fans-

that sounds really sweet. ill probably use that variable output fan design for my mini terrarium.

now, if only i could build it inline with a humidistat on the cheap, i would be set.

RE: Temperature controlled fans-

I've gotten a few humidistats out of thrift-store humidifiers.. $3 to $5 for the whole thing. Sometimes you can even get lucky & get an ultrasonic unit.. Otherwise just look for the 'adjustable' humidifier. It's got an internal humidistat.

RE: Temperature controlled fans-

i actually hadnt thought of making my own. this place is like a graveyard for broken humidifiers. maybe ill take your advice and cannibalize one.

nice tats btw :)

RE: Temperature controlled fans-

I made that mosfet based design - very cute! (and so simple too) My only real problem with it is the fact that it wastes so much power (making it too hot to touch). I wonder if it would be posible to make a similarly simple design using switching.

RE: Temperature controlled fans-

I dunno- There's a couple of *fairly* simple PWM designes out there (trust me I looked) but they all require 7 or more components.. Living in the sticks as I do I would have had to get them from online suppliers, & finding one that had all the required 'stuff' was a frustrating search.

I ended up going with simple = good & stuck a bit of sheat metal on the transistor for a heatsink.. Called it good.

I put the control outside the terrarium so it's heat output didn't matter.

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