Laurav wrote:

On Jun 16, 1:33 pm, Jamie
t wrote:

The only way
to properly regulate that is to measure the air mass flow and use that
as the feed back.


I suggested that to the guy who makes them. It would be great if you
could set 5 CFM on the dial and be done with it.
Roughly how much more expensive would that be? The web link you gave
for the brushless DC motor is $1300. He charges $250 for this
motor.


RPM's is going to vary to maintain flow.

Not much in my experience, I'm adjusting the rheostat manually and if
I were standing by it, I could adjust the flow well enough.


You seem to think what
you have is some high volume unit?

No, it's a low volume of air. However it pushes the air at high
pressure, because it has to go through many feet of hose. He said it
has high static pressure. Do you know how that changes the controller
picture?


Seeing that this is a medical device you have

It's an industrial safety device actually.


You need to keep an eye on the brushes! They don't last
like you think they should.


Yes, the brushes have worn out twice on me already. The motor just
quits without warning and exposes me to allergens. That gives me
an idea though - if you open the motor housing, is it easy to tell how
worn the brushes are?

Laura

Yes, you can inspect the brushes. Normally they should still have enough
on them to have a good spring holding tension against the commutator..
Many of them put a mark on the side of the brush or crimp something on
the lead wire to indicate when they should be changed.

Also, if you have gone through that many brushes already, it's a good
chance the commutator is close to its life cycle. You need to inspect it
for uneven surface wear which may include deep grooves.


Jamie