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Temp controled fan

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stuee

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Hi, i have made a pc jukebox with an amp in it too.
Ive found the heat inside is getting a bit much and turning off the pc.
I went to www.jaycar.com.au and purchased a 240v 125ma rotary fan.
Is there a way to make this fan come on when the temp gets a certain temp.
Layout out be appreciated from anyone in the know also Jaycar is my local parts store but dont have heaps of variety.

Thanks
Stu
 
The fan on my pc has its speed controlled by temperature. When the pc is thinking very hard then the fan speeds up. When the pc is idling then the fan nearly stops.
You need a 240VAC thermal switch or a circuit. My natural gas fireplace has a thermal switch for its fan.
 
Ive looked around and only found set temp thermal switches, i would like one i can adjust.
i do already have a 1k thermistor RN3436
and a 12v / 5a 240v relay omi-ss-2120m
And lots of trimpots, how can i hook all this together so i can put inline and adjust the temp. i was thinking around 40c fan on but would like to adjust to 30c - 60c ish

thanks
 
Here is something you can try. You will need a common everyday 12 Volt fan. I don't understand when you have a PC likely loaded with 12 volt power you would buy a 220 Volt mains powered fan? You can easily buy inexpensive 40, 60 and 80mm standard 12 volt fans. The linked circuit is far from fancy and would work better as they mention with a low dropout regulator but a common LM317 should work and likely even drive two fans if needed. You just won't get more than 10 volts out using the LM317. The 470 Ohm thermistor should be common and easily found. For what amounts to a few bucks in parts it's worth a try. The next step up would be to build a circuit using a thermistor around a comparator and a transistor driver for the fan. Most common 12 volt PC fans draw no more than 300mA max. Finally a plain common thermal switch to turn your fan On/Off using your 220 VAC. Commonly called Snap Disc Limit Control Switches, I just don't know where to find them in Australia. Around here any good industrial supply like Grainger or McMaster carries them. Just choose a temperature.

Ron
 
If you do go 12v fans then you can buy variable speed ones with a built in temp sensor, that control their own speed depending on the air temp.
 
I already had a 240v fan as new so figured i would use it :)
Reloadron, wouldn't i be able to hook the first circuit to the relay instead of the fan to trigger the 240v to the fan?
thanks all
 
I already had a 240v fan as new so figured i would use it :)
Reloadron, wouldn't i be able to hook the first circuit to the relay instead of the fan to trigger the 240v to the fan?
thanks all

No, because the first varies speed based on temperature. It was the simplest. You could build a circuit around a comparator that drives a relay which woule power the 220V fan. The thing is as Dr Pepper mentions there are so many inexpensive over the counter solutions from so many home computer stores and distributors do you really want to try and build your own?

Ron
 
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