Hi there as the title suggests I would like to control a 5v 500mah DC fan using an arduino pro mini to turn it on and off.
I read that the arduino pins are rated as only 40ma output.
Should I use a DC motor driver such as L9110 H-bridge controller or other?
What options are there?
Many thanks in advance
How are you powering the Arduino?
A driver or H bridge is only necessary if the motor needs to run in both directions.
A fan blows in only one direction so all that is needed is a simple transistor.
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Do you need to rotate fan in opposite direction? If no (a most fans doesn't need this) - you don't need H-bridge.
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I only need one direction rotation
which transistor is recommended/efficient for 5v operation? Thanks
This circuit with MOSFET IRLB8721 should work.
IRLB8721
Datasheet, IRLB8721
10k for R1 is too much
R1 is pull down resistor to pull the gate of the MOSFET at logic level LOW, right? what difference does it makes if R1 is 10k or lower value such as 4k7 ?
I ordered a mixed box of transistors like these:
And I will experiment with this circuit using NPN transistors
The larger this resistor, the slower the charge will drain from the gate and the longer the transient will last when the mosfet is turned off.
(corrected, see #13)
if you want to use PWM - the slower gate discharged, the more the mosfet will heat up
lower resistor meaning the electrons will have less "road" to do to ground? and therefore gate will be close and open faster?
is it possible to calculate the time of the gate open and close?
Sure
Mosfet datasheet contains a capacitanse of the gate, the charge rate is calculated by the standard formula for the capacitor.
But I was wrong about the R1 - if you switch off the mosfet by changing the state of the arduino pin to LOW, then the gate will be discharged through the resistor R2, the resistance R1 does not play a significant role in this process.
Thanks to @Paul_B for this correction.
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