I am trying to teach myself, and control a PC fan from an Arduino nano. The fan will be 12v and pull anywhere from 100mA to around 2 Amps. Looking around I have come up with this:
http://i.imgur.com/9ugrK.png
But I'm getting very confused, looking at data sheets, I don't understand.
- I calculated the R1 value as ~190 Ohm, as 5v from nano - 1.2v drop across the opto LED / 20ma. Then I'm not sure from the datasheet what the current output will be from the optocoupler will be.
- I'm not sure what the optocoupler protects against exactly? If the 12v/GND lines on the motor side are the same on the arduino side, will it protect anything?
- I currently have a TIP41C or 2SD882 for the transistor, and the main thing is I'm getting lost trying to calculate what R2 should be, or if ether transistor is even suitable. I'm not sure what information from the datasheets I need to be looking at? Hfe?
Thanks
http://i.imgur.com/9ugrK.png
But I'm getting very confused, looking at data sheets, I don't understand.
- I calculated the R1 value as ~190 Ohm, as 5v from nano - 1.2v drop across the opto LED / 20ma. Then I'm not sure from the datasheet what the current output will be from the optocoupler will be.
- I'm not sure what the optocoupler protects against exactly? If the 12v/GND lines on the motor side are the same on the arduino side, will it protect anything?
- I currently have a TIP41C or 2SD882 for the transistor, and the main thing is I'm getting lost trying to calculate what R2 should be, or if ether transistor is even suitable. I'm not sure what information from the datasheets I need to be looking at? Hfe?
Thanks