DC fan (reversible)

[MisterKoenig]

I am trying to find a DC fan that I can reverse. I am looking for something about the size of a computer cooking fan 3"-5" square. Preferably a throughput up around 100 cfm but that's negotiable. Thanks for any help.

 

[plasgears]

Reverse the DC power input polarity and the motor will turn in reverse. Use a double throw / double pole switch with crossover connections. On one side pole 1,2 connects to motor +/-; on the other side pole 1,2 connects to motor -/+.

Regarding the fan, it should be a propeller fan so that it can work in both directions.

 

[MisterKoenig]

Okay well I know you can reverse polarity and it should turn in reverse. I have been told that modern brushless DC fans will not operate in this fashion. At the moment I am trying to get my hands on one so I can give it a try. Thanks for the response.

 

[Lewish]

You were told correctly. Reverse the power on a brushless DC fan, like those used in a computer, and you will fry the controller IC built into the motor cage.

 

[ProUnion]

Got to like the good OLD fashioned technology of yesterday! LOL

 

[lcsjk]

I've worked with DC fans since they started. The standard Brushless DC fan will not work when the polarity is reversed. You may or may not kill it based on the manufacturer. I am not sure if you can buy a DC fan which uses a brush type DC motor, but that motor will reverse direction when polarity is reversed. You will also have the problem of finding a fanblade which blows effectively when reversed. One possibility is to buy two Brushless DC fans and mount them back to back. Then use a switch to turn on one and or the other. A single pole double throw (SPDT) switch will do. The voltage is not critical, but should not be very much higher than allowed by the fan "running" specs. ( A 12 VDC fan will run at 15VDC). Never violate the absolute max specs.

 

[eur]

If a brushless DC fan has separate output stages (darlington transistors) instead of an integrated IC, it can be reversed.

I have reversed several fans with a CMOS 4053 analog mux. Mail me for pics and schematics.
eur@fiwihex.nl

The only fan that I know of that you can buy is this one:

http://www.papst.de/pdf_dat_e/td1-gb.pdf

it is very expensive and big (6.8" diameter)