I need the fan to change its speed depending on temperature changes.
Arduino is being powered by a 12V 500ma power supply connected to the DC barrel connector (Vin).
I'm really new to this thing, I'm good with coding but I'm struggling with the electrical part. (I am building an automated grow box, I want to expand it to a fully automated greenhouse - this is just the beginning).
Fan Specs:
*Voltage 12VDC
*Current 0.16A
*Input 1.92W
Trying to use a S8050 transistor. I do not have a 1K Ohm resistor right now so I'm trying to use two 2k Ohms in parallel. Is it correct? My issue now is that I don't know what to do with the 3rd pin on my fan (the schematic do not have an option for 3 wires).
Third pin ? is this a brushless motor or a servo motor. I would use a 9 volt on barrel and a separate supply to feed the fan thru a power transistor or MOSFET. You want to isolate any high current from the arduino it is simply a low current driver to feed a pwm signal to turn transistor off and on ie base current and the collector emiter/fan /12v arrangement. And your temp sensor needs connecting to an analog input look up the love o meter project on this site. The output to leds would be you transistor base drive. Then the collector to +12 (NPN) with fan and current limit resistor and emitter to gnd
Fritzy spaghetti images can not be verified. Please draw a proper circuit diagram first - hand drawn, or using CAD software such as KiCAD or EagleCAD.
Make sure you know what the third wire of your fan is for, it's probably for a control signal. If it's a brushless DC motor a PWM regulation on the supply line will not work. It'll only mess up the built-in motor controls.
Hi,
Welcome to the forum.
Please read the first post in any forum entitled how to use this forum.
http://forum.arduino.cc/index.php/topic,148850.0.html
Can you please post a copy of your circuit, in CAD or a picture of a hand drawn circuit in jpg, png?
How are you powering the fan?
Thanks.. Tom.. 
If you provide a link to the actual fan you're using we'd have a better chance of knowing what we're dealing with. Many fans can be controlled with simple PWM. Many others can't. In some the 3rd wire is just for reading the speed. In others it's a control.
Steve
Thanks for all the answers! I am really new to this so I am sorry if the question and diagram weren't helpful.
I have no previous experience with electronics.
It's a DC controlled fan, I found that the 3rd wire is tach signal, only for reading fan speed.
This is the fan: http://www.coolermaster.com/cooling/case-fan/blue-led-silent-fan-120-si3/
I do not want to use an external 9v battery because this system will be on 24h a day and I imagine that would consume a lot of battery.
How I am powering the fan is what I am trying to figure. Can't I power it with the same source I am powering the Arduino? I plugged the fan into the Arduino + but I can't get enough energy.
I will try and draw the circuit but I am still getting the hang out of reading those...
Thanks again.
purplebrain:
Can't I power it with the same source I am powering the Arduino?
Possibly. But I can't be more definite because you haven't said what source you are using to power the Arduino.
Steve
It's on my first post, Arduino is being powered by a 12V 500ma power supply connected to the DC barrel connector (Vin).
Just connect the fan power terminals to your 12V supply, correctly, of course, but the web site specs give you no help there.
The speed is set at 1200 rpm +/- 10%, according to the specs, and there is no indication that you can control it. It is probably brushless, and it may be that your only options are on or off.
