I have a raspberry and a fan for it. But fan is noisy and I want to start it only when CPU temperature is about some value.
Fan needs 300mA and 5V.
I use this scheme:
I use a 2N5551L transistor. Its current gain is 80. When I apply a voltage to the blue wire, the current on the base is 2.7mA, but the fan gets about 50mA, when he should get at least 2.7 * 80 = 216 mA. I used 1K resistor, but I was trying to use a 100 Om resistor, but current on the fun still was too small. I don't want to try smaller resistanse, because the current on raspberry GPIO will be too big. Do you know how to fix it?
Later I want to control fan speed using PWM. Scheme will be similar, but I will replace slable 3.3V with hardware PWM. Will it work?
EDITED: I founded that when fan is disconnected, voltage on the diode is 5V, but when I connect It, voltage is only 3V