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Turn on 120V Box Fan on temperature rise?

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MikeMl

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Most Helpful Member
I can dream up all kinds of elaborate thermostats using thermistors or LM34/35 and an opamp driving a small relay to turn on a fan in a power supply I am building.

However, it is all getting too complicated. Anybody have any suggestions for where to get a simple make-on-rise thermostatic switch. I thought I had some in the junk box, but they turned out to be normally closed, and they open on temp rise. Also, they trip at 80C, and I would like about 50C.
 

Sceadwian

Banned
Check digikey, I doubt you'll find a single device that will switch full load current, but you should be able to find a NO thermal switch that can trip a 120V relay low current relay to drive the real load. If you search for a while and come up blank let us know, me or someone else might have better luck hunting through their search engine, which can be quiet blind.
 

Sceadwian

Banned
oh yeah, almost forgot to ask. What's the current? By box fan I'm asuming you mean this generic consumer models, so just a few amps?
 

MikeMl

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About 1/4A at 120Vac. Its just a 8"x8" Muffin Fan.
 

Hero999

Banned

Replace R2 with a thermistor and (assuming the thermistor NTC) is swap the positions of R1 and R2.
 
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nathan

New Member
This is a rather late reply, but I found the thread googling and thought it would be useful for someone else. I have a water cooler/warmer which has a single component 120V temperature switch to control the hot water heater, so I knew the part existed I just wanted to find the appropriate part. A CanTherm B12 series part should do the trick. They have several models that switch at different temperatures and cost just under $10 from Digikey.
 

Reloadron

Well-Known Member
Most Helpful Member
Maybe something like this. Small disk type thermostats that close on rise and handle more current than you need to worry about for about 13 bucks. I linked to Selco as a manufacturer and am sure besides Allied they are distributed by other parts houses. Close at 140 F and open at 110 F. or a collection of others.

<EDIT> Nevermind as I just caught the date. I would guess it is running by now and sorry for a necro post. </EDIT>

Ron
 
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