12v fan and arduino

Projects General Guidance
1

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.

2

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.

3

Look at the setup as so.

4

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?

5

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

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: Flyback diode - Wikipedia

6

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

7

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.