Hi, I'm new to Arduino and electronic at all so transistors for me is a kind of magic.
I want to make something like this Fan control project, but i will have two LM35 sensors and up to 8 fans.
Project will compare temperature difference between two sensor and turn fans faster or lower based on this difference (e.g if difference less then 2c it will turn off, else it will speed up fans up to 100% when difference is 30 or higher).
SO the only problem I have is transistor, BD139 has limitation of 0,5A (or 1,5A in other docs) current. Each fan is 12v DC / 0,25A, so 8 fans will take up to 2A. (Fans and Arduino board will be powered by 12v 4A power supply)
Am I right that I need something like BD437S? There is not a lot of electronic stores in my city so I will be very appreciate if you advise some easy-to-find transistor.
Forget bipolar transistors for power switching, you need a darlington or a MOSFET,
the latter are preferred and will run much cooler (so long as logic level and low enough
R-on, <0.02 ohm is readily obtainable)
Single bipolar transistors need 5 to 10% of collector current at the base to saturate,
so a 2A load needs 100 to 200mA of base current, way beyond the Arduino pin's
specification.
MarkT:
Forget bipolar transistors for power switching, you need a darlington or a MOSFET,
the latter are preferred and will run much cooler (so long as logic level and low enough
R-on, <0.02 ohm is readily obtainable)
Single bipolar transistors need 5 to 10% of collector current at the base to saturate,
so a 2A load needs 100 to 200mA of base current, way beyond the Arduino pin's
specification.
Hm, I didn't think about this... thanks, but now I have to dig into MOSFET's
