Simple hardware question.

After learning how to power a dc motor on the arduino I picked up a 4 pin computer fan to experiment with as it was pretty cheap and a fun concept. I cut off the 4 pin connectors and knocked the fan down to just its positive, ground, and what I am assuming is the wire for digital (red,black, and yellow). I have plugged the fan in just as if it were the dc motor I was powering and it works fine except, it seems to be running backwards. I tried just switching the positive and negative wires like I can do on a dc motor to change the direction the fan was spinning and it doesnt work. My question is why will this work with a dc motor but not a computer fan?

Brushless motors only go one way. It won't be "backwards", it'll be the way that blows the air in the right direction for cooling, according to the slant of the vanes.

The other 2 wires, btw, will be tach for measuring the speed, and the other to control the speed.

JimboZA:
Brushless motors only go one way. It won't be "backwards", it'll be the way that blows the air in the right direction for cooling, according to the slant of the vanes.

The other 2 wires, btw, will be tach for measuring the speed, and the other to control the speed.

I was just using pwm to control the speed in the same way I had a dc motor, running it through a pnp transistor. I wasnt sure if the direction could be changed or not so at least I know it isnt backwards even if it looks like it is to me lol.

Was that PWM on the power liner actually working? I thought the control line had to be used: those fans have a tiny controller built in, and do their speed control by signals to that, not by pwm-ing the power.

It seemed to be working fine, the fan speeds up, reaches max speed, slows down, and stops.

Hi,on the side of the fan housing should be a couple of arrows, these indicate the direction the fan should run and what direction the air will be pumped through it.

Tom.... :slight_smile: