Wind Velocity Control in Wind Tunnel

[nephyrias]

I am trying to find a solution for my small wind tunnel that will allow me to maintain a set wind velocity of 0.06 – 0.3 m/s within the tunnel. Currently, I am using a 5v computer fan w/a potentiometer, but I can’t get the fan slow enough. It just stops turning. I am also using a simple telescoping hot wire anemometer to verify wind velocity.

Does all that make sense?

 

[SLK001]

Most computer fans are brushless, which means that they are either "ON" or "OFF". If you want to control the speed, you'll need a PWM controller for the fan so that you can control the on-off at the rate which will give you different speeds.

 

[SLK001]

To get the full torque of your motor, you will need a PWM control. What I said about the on or off is not correct - your fan will turn slower with a lower voltage. However, a pot control (unless it is a 2 ohm reostat) will likely starve your motor of the current it needs.

 

[FvM]

I would consider the possibility that the used brushless fans simply don't support the intended slow speed. PWM won't help much in this case, unless you accept a few Hz "stutter" operation as continuous pwm. Lookout for special brushless motors with speed control input.

 

[KlausST]

Hi,

0.06m/s ..0.3m/s is just a 1:5 ratio.
Therefore i recommend to run the fan at full speed and us some mechanical wind shiled to get the desired 0.3m/s (maybe add a bit of headroom).
Then reduce the voltage and see if you reach the 0.06m/s. If not then use another fan with more dynamics.

Klaus

 

[FvM]

0.06m/s ..0.3m/s is just a 1:5 ratio.

And scarcely a wisp of wind...