I’m pretty new to Pi and electronics.
I need to use my Pi as fans controller. I got two 12V fans and need to control it from Pi. I want to use external power supply (12V) to give them propper power.
I have a ready example that works great, for one device (fan):
But now I need two fans and control it independently, alternately (so as not to overload PI).
- Is it possible to modify this circuit to control two fans?
- Should I make two such circuits and connect them in parallel to a 12v power supply?
- Or maybe make another better layout, someone from ‘ekektroda’ told me that the circuit is wrong…
I am using two transistors to drive two fans. Is the following circuit OK?
(1) Ib = 3V / 300R = 3000 / 300 mA ~= 10 mA.
(2) Transistor current amplification factor (h(fe)) > 100.
(3) Ic = Ib x 100 = 10mA x 100 = 1000 mA.
(4) Motor resistance would limit Ic to << 1000 mA, possibly < 200 mA.
What you have shown is NOT a “schematic”, it is a layout diagram, but is too vague to determine exactly what you have (although we can guess), but seems unnecessarily complex.
RPi_GPIO_Interface_Circuits shows output circuits which should work for your small motors. (The Driving a relay is most appropriate).
If using a single transistor you should use a smaller base resistor (~270Ω – although the exact value is not critical).
If using a complementary Darlington pair (as I guess you are currently) a lower base current would suffice.
Use 2 circuits – one for each motor if you want independent control, but you should be able to drive 2 motors in parallel.