×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Contact US

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

DC fan (reversible)

DC fan (reversible)

DC fan (reversible)

(OP)
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.

RE: DC fan (reversible)

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.

RE: DC fan (reversible)

(OP)
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.

RE: DC fan (reversible)

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.

RE: DC fan (reversible)

  Got to like the good OLD fashioned technology of yesterday!  

RE: DC fan (reversible)

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.

RE: DC fan (reversible)

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)

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login



News


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close