32mA on Digital Pins

Using Arduino Project Guidance
#1

Hi there,

So having done some research I can see that the max output on the digital pins is 40mA, and the recommended is 20mA. I've purchased a 5V fan (https://www.amazon.co.uk/gp/product/B06XQWMFDQ/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1) that runs at 32mA, when I set the pin (12) to high it can't start the fan but a slight tap on the blades and it gets going. Now I know I can run this through the 5v pin but is there any other way around this besides using an external power supply, ie setting a digital pin as ground and using the 5v as a source?

#2

The safe way is to use a tiny NPN transistor or N-Channel MOSFET between the fan and Ground to switch the fan on and off. See: Gammon Forum : Electronics : Microprocessors : Driving motors, lights, etc. from an Arduino output pin

#3

You need a transistor or MOSFET or other driver.

0.32mA is 320mA, not 32mA. You are "stressing" the Arduino and you could damage it.

#4

johnwasser:
The safe way is to use a tiny NPN transistor or N-Channel MOSFET between the fan and Ground to switch the fan on and off. See: Gammon Forum : Electronics : Microprocessors : Driving motors, lights, etc. from an Arduino output pin

Thats perfect, thanks very much for the help - seems like an NPN transistor is the smallest and easiest workaround, so I’d be alright with using the 5v as the power supply and the digital pin as the switch?

#5

@DVDdoug, you might want to remove a m :wink:

#6

DVDdoug:
You need a transistor or MOSFET or other driver.

0.32mA is 320mA, not 32mA. You are "stressing" the Arduino and you could damage it.

Just to alleviate any future confusion 0.32mA IS 0.32mA, not 320mA (that would be 0.32Amp) and not 32mA (which is 0.032Amp)

#7

320 mA is too much for most small signal transistors or MOSFETs, get one that is rated at 1A. The startup current of that fan is likely higher than the rated current.

#8