Can I run a "brushless DC FAN" backwards?
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From: mike on 2 Aug 2010 03:35 I have a project that needs reversible fans. Can I make a brushless fan go backwards? Is it as simple as swapping the leads on the coils? Or is there more to it, like wrong phase for the magnetic pulse into the hall device? And then there's the question whether the blades will move as much air running backwards. The muffin fan is the ideal form factor for this job. Only other cost effective thing I can think to do is put two fans in series and run either one. I really don't want to spend the money to buy reversible fans even if they're available. I gots boxes of muffin fans. Ideas? Thanks, mike
From: Grant on 2 Aug 2010 04:22 On Mon, 02 Aug 2010 00:35:51 -0700, mike <spamme0(a)go.com> wrote: >I have a project that needs reversible fans. >Can I make a brushless fan go backwards? >Is it as simple as swapping the leads on the coils? >Or is there more to it, like wrong phase for the magnetic pulse >into the hall device? > >And then there's the question whether the blades will >move as much air running backwards. > >The muffin fan is the ideal form factor for this job. > >Only other cost effective thing I can think to do is >put two fans in series and run either one. > >I really don't want to spend the money to buy reversible fans >even if they're available. I gots boxes of muffin fans. > >Ideas? Open one up and swap the hall switch connections? Grant.
From: Nobody on 2 Aug 2010 09:19 On Mon, 02 Aug 2010 00:35:51 -0700, mike wrote: > I have a project that needs reversible fans. > Can I make a brushless fan go backwards? > Is it as simple as swapping the leads on the coils? > Or is there more to it, like wrong phase for the magnetic pulse > into the hall device? It would work if you could mirror *everything*. If it uses a Hall-effect sensor, you would have to mirror the position of the sensor. But that would create a reversed fan, not a reversible one. > And then there's the question whether the blades will > move as much air running backwards. Probably not; they're quite far from symmetrical.
From: oparr on 2 Aug 2010 14:36 > I really don't want to spend the money to buy reversible fans > even if they're available. I gots boxes of muffin fans. Use two fans and switch the voltage according to desired air flow direction. On Aug 2, 3:35 am, mike <spam...(a)go.com> wrote: >
From: Rich Grise on 2 Aug 2010 18:31
On Mon, 02 Aug 2010 00:35:51 -0700, mike wrote: > I have a project that needs reversible fans. Can I make a brushless fan go > backwards? Is it as simple as swapping the leads on the coils? Or is there > more to it, like wrong phase for the magnetic pulse into the hall device? > > And then there's the question whether the blades will move as much air > running backwards. > > The muffin fan is the ideal form factor for this job. > > Only other cost effective thing I can think to do is put two fans in > series and run either one. > > I really don't want to spend the money to buy reversible fans even if > they're available. I gots boxes of muffin fans. ^^^^^^^^^^^^^^^^^^^^^^^^^^^ > I think you've answered your own question here - use the two fans. But be sure that the one that's not running doesn't provide a sneak path for the air that the other one is supposed to be moving past the work area. Have Fun! Rich |