G+_Phorest Sherwood Posted June 11, 2015 Share Posted June 11, 2015 I'm looking to make a temperature controlled fan that kicks on at a specific temperature. I plan on making a box for a projector, and want to use a computer fan to draw the heat for the box when it gets to a certain temp. I will only need around 12v for the fan. Ideas? Link to comment Share on other sites More sharing options...
G+_Ben Reese Posted June 11, 2015 Share Posted June 11, 2015 A lot of people would probably recommend doing this with discrete logic which would use the least amount of power. I'd probably just get an Arduino Nano or Mini (not sure if either are official Arduino product, but they should be Arduino compatible - and cheap) and connect it to a relay board. If you've just got DC you could probably use a transistor instead, but relay would give room to AC too. A potentiometer will let you adjust the thermostat after its assembled. There are 2 temp sensors that I can think of: thermistor that could vary the amperage or voltage going in and there's most likely one that will send a digital signal over something like SPI or I²C. I'd expect the later to be more precise but the former to be easier for beginners. I could be completely wrong on these suggestions too... Just what came to mind for the project. Link to comment Share on other sites More sharing options...
G+_610GARAGE Posted June 11, 2015 Share Posted June 11, 2015 The easiest solution would be to get a thermal switch. But, they are not user settable, and most likely won't be available in your temperature range. You could also get a fan controller for a computer. A more DIY version would be to use an arduino. Have an arduino monitor a 10K thermo resistor. When the temperature rises to its set point, have the arduino activate a mosfet or transistor that turn on your fan. Then when temperature drops below your set point, cut power. Or you could use PWM to control the speed of the fan. The stupid way to do it would be discrete components. I forget exactly what I did, :) but I think it was two comparator gates that monitored a thermoresistor. When the temperature rose past my set point, the comparator switched on a flip flop gate. When temperature dropped to a certain point, the flipflop gate was reset. Link to comment Share on other sites More sharing options...
G+_Eddie Foy Posted June 11, 2015 Share Posted June 11, 2015 Could use a bi-metal (coiled) switch. Thermostat in the house I grew up in used one. Link to comment Share on other sites More sharing options...
G+_Taylor Graham Posted June 11, 2015 Share Posted June 11, 2015 I've used these relays from amazon for the exact same thing. They're dirty cheap and easy. Just use a DH22 or DH11 for temp. DS18B20 is an even cheaper option if you just want basic temp. All of the above is extremely easy to use with an arduino. Can be had for >$10. http://www.amazon.com/SunFounder-Channel-Shield-Arduino-Raspberry/dp/B00E0NTPP4 Link to comment Share on other sites More sharing options...
G+_Eddie Foy Posted June 11, 2015 Share Posted June 11, 2015 LM34 (cheapest from digikey I've seen) is a nice easy to work with temp sensor. 10mv per/^F Link to comment Share on other sites More sharing options...
G+_Eddie Foy Posted June 12, 2015 Share Posted June 12, 2015 Not really. Wayne Hobbins Probably get one for a buck at a ReStore. Link to comment Share on other sites More sharing options...
G+_Eddie Foy Posted June 12, 2015 Share Posted June 12, 2015 Not sure how much range you'd need to cool a projector. Over 85F I'd turn on the fan. Link to comment Share on other sites More sharing options...
G+_Eddie Foy Posted June 12, 2015 Share Posted June 12, 2015 Cycling a fan isn't a prob. short cycling a HVAC compressor is. Link to comment Share on other sites More sharing options...
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