PWM Control for Fan

Hey guys,

I'm pretty new to Arduino to start. I'm trying to create a program that will use a temp sensor to ultimately control a fan for climate control. The problem I'm having is the fan (5v 0.45A) works fine when plugged in to 5v and ground, but when I use PWM pin 3 on my UNO, it nudges but doesn't turn unless I assist it. I'm using analogWrite(255) for 100% duty cycle. Do the PWM pins have less current availability than the 5v pin? Any thoughts on why this might occur?

Thanks! Jim

0.45 amps is about 20 times the current that a Uno output can source. Over 40mA will eventually damage the output. You will need an external supply for the fan and a transistor or MOSFET to control the fan with PWM.

You need a driver transistor for the motor/fan. Check this URL for details.
http://bildr.org/2012/03/rfp30n06le-arduino/

I may be overthinking what I need for my project, that looks like it will save a lot of extra components 8)

[quote author=jack wp link=topic=188800.msg1396974#msg1396974 date=1379550505] You need a driver transistor for the motor/fan. Check this URL for details. http://bildr.org/2012/03/rfp30n06le-arduino/ [/quote]

groundfungus: 0.45 amps is about 20 times the current that a Uno output can source. Over 40mA will eventually damage the output. You will need an external supply for the fan and a transistor or MOSFET to control the fan with PWM.

I had a hunch that was the problem. Any idea why the 5v output will drive the fan no problem but the PWM pin at 100% DC barely nudges it?

Jimbo57: Any idea why the 5v output will drive the fan no problem but the PWM pin at 100% DC barely nudges it?

Every idea. The 5V output comes from the regulator IC which is - briefly - capable of supplying this current, but even then you are overloading it - it will overheat and shut down soon.

The ATMega output device is a tiny FET which is never intended to consistently provide more than 20 mA - as the datasheet specifies.

Paul__B:

Jimbo57: Any idea why the 5v output will drive the fan no problem but the PWM pin at 100% DC barely nudges it?

Every idea. The 5V output comes from the regulator IC which is - briefly - capable of supplying this current, but even then you are overloading it - it will overheat and shut down soon.

The ATMega output device is a tiny FET which is never intended to consistently provide more than 20 mA - as the datasheet specifies.

Great, thanks!