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Topic: 12v fan and arduino (Read 1 time) previous topic - next topic

painstream

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.

johnwasser

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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HazardsMind

Look at the setup as so.

My GitHub:
https://github.com/AndrewMascolo?tab=repositories

painstream

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?


LarryD

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
Quote
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
The way you have it in your schematic isn't the same as how you have it wired up!

HazardsMind

You also might want to add a capacitor parallel to the fan as well. It just to smooth out the signal.
My GitHub:
https://github.com/AndrewMascolo?tab=repositories

pwdarden

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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