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Author Topic: Temperature Controlled fan.  (Read 2333 times)
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Hey guys, i am looking to fabricating big drum smokers for my local community but i would like to know what is needed just as a parts list for building a Fan controlled by a temperature sensor. E.G. Temperature drops below 200f and temperature is set to 200f the board would start feeding power to a fan with speed of the fan corresponding to how far the temperature has dropped from its set point. turning off once hitting or exceeding the set temperature point.  (also, how can i control fans that pull like 5 amps with a arduino board?) 


I got a Uno board, and i've been playing with it but to my understanding the kit i bought was just for figuring out how electronics work then its just soldering parts onto cheap breadboard to manufacture the finished product.

I am still very very new to arduino so if anyone can help me with my questions or even just to clarify what arduinos can/are used for it would be much appreciated.

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You would control fans just like any other motor - using a drive circuit. Either a shield designed for the job, or by wiring up a transistor yourself.

What you're describing sounds like a basic thermostat. Is there some reason you don't just use a thermostat?
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I would prefer to make it myself so i can learn more. also it would have to measure up to 500f for food cook temps.

(maybe i could save money making them myself?)

Could you explain to me what a shield is?
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Could you explain to me what a shield is?

Many Arduinos are built using the same form factor for a reason -- those pinouts can be stacked to add lots of functionality.

See: http://arduino.cc/en/Main/ArduinoShields
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What sort of fans are you talking about - low voltage DC fans, or something bigger hooked up to the mains?
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Dubuque, Iowa, USA
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For a 500F environment you'll want a "K type thermocouple" and a group of people that don't appreciate slow, 225F cooking temperatures smiley-wink

You also need an thermocouple interface because it cannot be read directly by the arduino with the precision necessary.

If you use a DC fan you will need a mosfet to go with it to control the current. If you use an AC fan then things get a lot trickier.
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Alright so now i am going to be looking for a DC fan, can i ask why (as simply as you can) AC would be more difficult than DC?

appreciate the help immensely, i get overwhelmed quiet often when i try to google something.
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You didn't like my DC fan link? I suppose it makes it hard to judge it since it doesn't specify the CFM of the fan.

If you'll accept turning the AC fan off and on at full speed that is possible -- that can be done with a relay. If the fan is designed for multiple speeds (like a typical house fan, I guess) then you would need one relay for each speed setting. But if you want to infinitely vary the speed of the fan then you get stuck analyzing the AC waveform and chopping the wave at a precise time -- 120 times per second.  Also, some types of AC fans will require a "variable frequency drive" (VFD) and these prices start in the low hundreds of dollars.
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Alright so now i am going to be looking for a DC fan, can i ask why (as simply as you can) AC would be more difficult than DC?

appreciate the help immensely, i get overwhelmed quiet often when i try to google something.

The AC makes control more complex but it's the main voltages which are the real problem. It means you can't simply wire your controller up to the fans using transistors and what have you - you need to use a high voltage driver circuit which isolates the Arduino from the mains voltage it is controlling. And that isolation needs to be bullet proof - which means you really need to buy a professionally designed part to do the job - because it'll be lethal if that fails.
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As far as the sensing the temperature, I did this for my smoker... I went to the auto parts store and bought a water temp sensor for a V8. I took the torch and blew a hole just smaller than the threads on the sensor and screwed it into the  smoke chamber. I figured this could withstand the heat.  I'm not sure but I believe it worked out that a 2.2K resistor was perfect for making the voltage divider with the sensor.  I mainly monitor it for <175F up to >300F.  I dont control any fans but the system outputs to two RGB leds that replace the mantles in a Coleman lantern so I can see from a distance how the temp is doing. It also has a RF link to send the current temp into the house. LEDs go from blue to red depending on temp... green for 200-225F.  The calibration was done by reading the temp gauge (dial) on the smoker while reading the sensor voltages. The sensor has been working great, at least for 5 or 6 uses over the last year.
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Hey Gumby83,
I am doing the exact same thing (for my personal smoker). I just started and I'm not that experience with Arduino either but I have a few thoughts. As for output (fan), I planning to go with a squirrel fan  that is controlled by the arduino via a MOSFET (as recommeneded by Chagrin). 

As for input, I already have a temp probe from my Maverick thermometer that I am just hooking up to the Arduino, so I can't help you there.  I'll you posted once I get it all hooked up.

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