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Author Topic: 12v fan and arduino  (Read 1109 times)
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Hello All,

I am new to electronics and the Arduino. I am trying to determine what would be the correct diode to use to restrict the reverse current flow for my fan, here is my setup.

ARDUINO PIN OUT ----> 1K resistor to the base of ----> NPN 2SD313 Transistor ----> Archer RS4005 1 amp 600V diode (only one I had lying around that seemed suitable) between collector and emitter. Power source to fan is a PC DC 12V 3AMP. The fan is a 12V 0.23A. Fan ground to Transistor Collector. Transistor Emitter to ground. They all share a common ground. Sorry for no diagram.

Everything to me seems to work fine. I'm not sure i'm using the correct Diode.

Thanks for your assistance.
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Diode goes across the inductive load (fan) not across the transistor.  Diode goes for +12 to Collector, same as the fan.  Make sure the Cathode (negative) side goes to +12 and the Anode (positive) side goes to the Collector.
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Look at the setup as so.

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Thanks for the reply. I guess i'm even asking myself more questions now. I find a lot of similar setups such as this one I've attached. What is this accomplishing?

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Quote
Thanks for the reply. I guess i'm even asking myself more questions now. I find a lot of similar setups such as this one I've attached. What is this accomplishing?
Note: the TIP120 aready has a diode from the Collector to the emitter. See:  http://www.adafruit.com/datasheets/TIP120.pdf
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Diode goes across the inductive load (fan) not across the transistor.  Diode goes for +12 to Collector, same as the fan.  Make sure the Cathode (negative) side goes to +12 and the Anode (positive) side goes to the Collector.
He has said what you should do.
See: http://en.wikipedia.org/wiki/Flyback_diode
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The way you have it in your schematic isn't the same as how you have it wired up!

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You also might want to add a capacitor parallel to the fan as well. It just to smooth out the signal.
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hello,

i am working on a similar project, and finding this helpful.  i am using a TIP120 transistor, so is it correct that the only diode i should have in the circuit connects to the transistor collector with the anode and into the + strip at the top of the breadboard with its cathode?  not sure if i am understanding correctly.  any help would be welcome!  thank you.
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