Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

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Default supplying accurate output voltage input voltage

Can one get a control where you can specify the output AC voltage very
accurately, even though the input voltage isn't accurate?
It would be for input to my air turbine. The air turbine always needs
input voltage much lower than the line voltage. So the control
wouldn't need step-up circuitry.
With the rheostat that comes with my air turbine, it's very sensitive
to changes in the line voltage.
So I was thinking about bypassing the rheostat instead of buying a
power conditioner and trying to supply very accurate voltage to the
rheostat.
Laura
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Does the voltage have to be regulated -- that is, automatically adjust as
the line voltage changes?

If not -- just stick a cheap DVM on the turbine!


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On Jun 15, 8:37*am, "William Sommerwerck"
wrote:
Does the voltage have to be regulated -- that is, automatically adjust as
the line voltage changes?


I'm not sure. The turbine is very sensitive to changes in line
voltage. A change of 1 volt in line voltage causes a noticeable
change in airflow. However, there's a rheostat between the turbine
and the power source, could be the rheostat is very sensitive to
changes in line voltage. I could check that with my voltmeter I
guess.

If not -- just stick a cheap DVM on the turbine!

Digital voltmeter?

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On Jun 15, 5:29*am, Laurav wrote:
Can one get a control where you can specify the output AC voltage very
accurately, even though the input voltage isn't accurate?
It would be for input to my air turbine. *The air turbine always needs
input voltage much lower than the line voltage. *So the control
wouldn't need step-up circuitry.
With the rheostat that comes with my air turbine, it's very sensitive
to changes in the line voltage.
So I was thinking about bypassing the rheostat instead of buying a
power conditioner and trying to supply very accurate voltage to the
rheostat.
Laura


you didn't say how much power the turbine takes. and if it cycles once
in a while, or a lot.

Two ways come to mind:
1. you can use a passive 'regulator' [by Solar?] It's a resonating
transformer, so you have to specificy 50 or 60Hz. Very large for the
amount of power that goes through them, but they regulate to 1%, which
is around 1 Volt, then you could put a Variac after the regulator and
adjust the voltage pretty exactly. Not much wasted power here.

2. Another, but complicated way, is to use a Saturable Core Reactor in
series with your load. No current through control winding on core,
very small voltage to load. Maximum DC current through control winding
on core, and the reactor 'disappears', gone, so you get a lot of
voltage to the load, but not all. Combine with simple AC to DC bridge
circuit, resistors, and feed that current back into the control
winding [right phase] and voila! pretty EXACT voltage, and automatic.
If the technology is too daunting, post your request on craigslist,
http://YOUR_REGION.craigslist.org/egr for like $25 you can pick up a
technician or engineer who'll put it all together for you.

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On Jun 15, 9:31*am, Robert Macy wrote:

you didn't say how much power the turbine takes. and if it cycles once
in a while, or a lot.

I checked the output voltage of the rheostat on the AC setting of the
voltmeter, and it's about 104 volts.
I turn it up sometimes briefly. It uses about 1-2 amps.
Laura


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On 6/15/2012 7:34 AM, Laurav wrote:
On Jun 15, 9:31 am, Robert wrote:

you didn't say how much power the turbine takes. and if it cycles once
in a while, or a lot.

I checked the output voltage of the rheostat on the AC setting of the
voltmeter, and it's about 104 volts.
I turn it up sometimes briefly. It uses about 1-2 amps.
Laura

I have a regulator box that has inside a motorized variac.
Moves the variac to compensate for input voltage changes.
But its reaction time isn't very fast.
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On Jun 15, 6:31*am, Robert Macy wrote:
On Jun 15, 5:29*am, Laurav wrote:

Can one get a control where you can specify the output AC voltage very
accurately, even though the input voltage isn't accurate?
It would be for input to my air turbine. *The air turbine always needs
input voltage much lower than the line voltage. *So the control
wouldn't need step-up circuitry.
With the rheostat that comes with my air turbine, it's very sensitive
to changes in the line voltage.
So I was thinking about bypassing the rheostat instead of buying a
power conditioner and trying to supply very accurate voltage to the
rheostat.
Laura


you didn't say how much power the turbine takes. and if it cycles once
in a while, or a lot.

Two ways come to mind:
1. you can use a passive 'regulator' [by Solar?] It's a resonating
transformer, so you have to specificy 50 or 60Hz. Very large for the
amount of power that goes through them, but they regulate to 1%, which
is around 1 Volt, then you could put a Variac after the regulator and
adjust the voltage pretty exactly. Not much wasted power here.


The cheapest Sola constant voltage transformer still costs several
hundred dollars.
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On 6/15/2012 5:29 AM, Laurav wrote:
Can one get a control where you can specify the output AC voltage very
accurately, even though the input voltage isn't accurate?
It would be for input to my air turbine. The air turbine always needs
input voltage much lower than the line voltage. So the control
wouldn't need step-up circuitry.
With the rheostat that comes with my air turbine, it's very sensitive
to changes in the line voltage.
So I was thinking about bypassing the rheostat instead of buying a
power conditioner and trying to supply very accurate voltage to the
rheostat.
Laura

You could use a Uninterruptible Power Supply (UPS). You'd need the kind
that is always regulating the output voltage (an online UPS), rather
than just turning on when power is lost or sagging badly (a standby UPS).

See this article for further explanation:
http://www.pcmag.com/encyclopedia_te...i=53509,00.asp

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On Fri, 15 Jun 2012 08:30:50 -0700 (PDT), spamtrap1888
wrote:

The cheapest Sola constant voltage transformer still costs several
hundred dollars.


Times have changed. While Sola products are rather expensive, there
are plenty of cheap constant voltage transformers on the market. For
example:
http://www.ebay.com/itm/260591849083
http://www.ebay.com/itm/360320802787
Like all good resonant power transformers, they buzz and run warm.

--
Jeff Liebermann
150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
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spamtrap1888 wrote:

The cheapest Sola constant voltage transformer still costs several
hundred dollars.


http://www.ebay.com/itm/Sola-Constan...em3f0eab 6e29

Yes, for *very* small values of 'several hundred'.

--Winston


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On Jun 15, 9:19*am, Winston wrote:
spamtrap1888 wrote:
The cheapest Sola constant voltage transformer still costs several
hundred dollars.


http://www.ebay.com/itm/Sola-Constan...er-23-22-125-H...

Yes, for *very* small values of 'several hundred'. *


In that case: even the cheapest Mercedes still costs $300, because
that's how much someone wants for one in the Penny Saver.
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spamtrap1888 wrote:
On Jun 15, 9:19 am, wrote:
spamtrap1888 wrote:
The cheapest Sola constant voltage transformer still costs several
hundred dollars.


http://www.ebay.com/itm/Sola-Constan...er-23-22-125-H...

Yes, for *very* small values of 'several hundred'.


In that case: even the cheapest Mercedes still costs $300, because
that's how much someone wants for one in the Penny Saver.


Yup.

There aren't too many $300 Mercedes that the seller will
accept back if the buyer is not satisfied however.

BTDT, forgot to pick up the teeshirt.

--Winston
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Laurav wrote:

Can one get a control where you can specify the output AC voltage very
accurately, even though the input voltage isn't accurate?
It would be for input to my air turbine. The air turbine always needs
input voltage much lower than the line voltage. So the control
wouldn't need step-up circuitry.
With the rheostat that comes with my air turbine, it's very sensitive
to changes in the line voltage.
So I was thinking about bypassing the rheostat instead of buying a
power conditioner and trying to supply very accurate voltage to the
rheostat.
Laura


Ah, now comes the clue.... You don't have problems with your
voltage..

It's a simple matter of mass air flow and your motor design..

You need a closed loop PID controller to keep that steady..


Jamie



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On Jun 15, 11:49*am, Bennett wrote:

You could use a Uninterruptible Power Supply (UPS). *You'd need the kind
that is always regulating the output voltage (an online UPS), rather
than just turning on when power is lost or sagging badly (a standby UPS).


Would a UPS that outputs voltage exact to within 1% or so be very
expensive?
Also, can one get a UPS with adjustable output voltage?
Laura
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On Jun 15, 11:49 am, Bennett wrote:

You could use a Uninterruptible Power Supply (UPS). You'd need the kind
that is always regulating the output voltage (an online UPS), rather
than just turning on when power is lost or sagging badly (a standby UPS).


Would a UPS that outputs voltage exact to within 1% or so be very
expensive?
Also, can one get a UPS with adjustable output voltage?
Laura


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On Jun 15, 7:43*pm, Jamie
t wrote:
* Ah, now comes the clue.... You don't have problems with your
voltage..

* *It's a simple matter of mass air flow and your motor design..

* You need a closed loop PID controller to keep that steady..


No, it's definitely very voltage-sensitive.
The guy who makes and sells the turbine told me that the motor speed
is linear with the voltage, in the range of 100-120 V.
The motor speed varies greatly over that range, from close to zero to
max.
Laura
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Laurav wrote:

On Jun 15, 7:43 pm, Jamie
t wrote:

Ah, now comes the clue.... You don't have problems with your
voltage..

It's a simple matter of mass air flow and your motor design..

You need a closed loop PID controller to keep that steady..



No, it's definitely very voltage-sensitive.
The guy who makes and sells the turbine told me that the motor speed
is linear with the voltage, in the range of 100-120 V.
The motor speed varies greatly over that range, from close to zero to
max.
Laura


Yes, I hear you and still, it is a mass air flow and motor design
problem..

You most likely got a split phase shaded pole/capacitor motor that
is improperly being controlled.

Just your basic window fan motor that shifts greatly in speed under
just slightly altered conditions, including mass flow.

You need to closed loop controller...

Jamie


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On Jun 15, 8:58*pm, Jamie
t wrote:

* Yes, I hear you and still, it is a mass air flow and motor design
problem..


I haven't noticed that the motor speed is sensitive to anything else
besides voltage, and the guy who makes the motor says that's the only
thing that causes changes in speed.
You could send your suggestions to Turbine Products, see what he says.
In any case I need to deal with this particular motor, not some future
version.
Laura

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Laurav wrote:

On Jun 15, 8:58 pm, Jamie
t wrote:


Yes, I hear you and still, it is a mass air flow and motor design
problem..



I haven't noticed that the motor speed is sensitive to anything else
besides voltage, and the guy who makes the motor says that's the only
thing that causes changes in speed.
You could send your suggestions to Turbine Products, see what he says.
In any case I need to deal with this particular motor, not some future
version.
Laura

Regulating the voltage is only going to fix part of your problem, the
issues are that your motor design is very sensitive to RPM changes with
load changes.

If you were to sit down and attempt to calculate the difference in
voltage needed per RPM, you'll find that it's all over the place..

Motor speed in your case is like an inverse log, once you get it out
of the hole, it'll speed up greater than expected. It's all about slip
in an AC motor under load changes. AC motors do not have much torque at
the lower RPM, unless of course, you're doing vector mode, and I know
for a fact you're not doing that.

Your problem will not go away that easy how ever, a thyristor
controller may work a little better over having a rheostat, but then
again, you may have a slight drop on the high end of those.

what you have there is a low end design.. What you should have is a
brushless DC motor which requires a speed controller.. THey do make
integrated Brushless DC motors. We use them at work in vacuum loaders
and they are good at maintaining speed. They are integrated motors of
high RPM with a 0..10 volt input speed control reference. They are a
closed loop and thus can monitor its own RPM.


Jamie

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On Jun 15, 6:02*pm, Laurav wrote:
On Jun 15, 8:58*pm, Jamie

t wrote:
* Yes, I hear you and still, it is a mass air flow and motor design
problem..


I haven't noticed that the motor speed is sensitive to anything else
besides voltage, and the guy who makes the motor says that's the only
thing that causes changes in speed.
You could send your suggestions to Turbine Products, see what he says.
In any case I need to deal with this particular motor, not some future
verarsion.


Have you considered that Turbine Products, whatever that may be, have
sold you a piece of unusable garbage? Why are they not modifying their
equipment to make it usable? Or at least providing you the
applications support that you are seeking here? They're responsible
for the halfassed design of this POS.


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On 6/15/2012 5:29 PM, Laurav wrote:
On Jun 15, 11:49 am, Bennett wrote:

You could use a Uninterruptible Power Supply (UPS). You'd need the kind
that is always regulating the output voltage (an online UPS), rather
than just turning on when power is lost or sagging badly (a standby UPS).


Would a UPS that outputs voltage exact to within 1% or so be very
expensive?
Also, can one get a UPS with adjustable output voltage?
Laura

They are pretty expensive - $350 and up. Output voltage usually not
adjustable; the built in rheostat that you've got would adjust the voltage.

BTW, what is an Air Turbine; what does it do?

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On Jun 15, 11:10*pm, Bennett wrote:

BTW, what is an Air Turbine; what does it do?


It pushes air through a long hose to an airline respirator. So unlike
a fan, it's pushing a small amount of air, 4-5 CFM typically, but high
pressure is needed to push the air.
Really, the people who are criticizing the motor design should send
their ideas to Turbine Products. I'd be interested to hear what he
has to say.
Laura

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On Jun 15, 11:10*pm, Bennett wrote:

BTW, what is an Air Turbine; what does it do?


It pushes a small airflow, like 4-6 CFM, through a long hose to a
respirator. It needs to generate a lot of pressure to push the air,
unlike a fan.
Laura
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"Laurav" wrote in message
...
On Jun 15, 11:10 pm, Bennett wrote:

BTW, what is an Air Turbine; what does it do?


It pushes air through a long hose to an airline respirator. So unlike
a fan, it's pushing a small amount of air, 4-5 CFM typically, but high
pressure is needed to push the air.
Really, the people who are criticizing the motor design should send
their ideas to Turbine Products. I'd be interested to hear what he
has to say.
Laura


_______

Do you have a link to any additional information, pictures, specs, etc.?

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On Fri, 15 Jun 2012 18:02:58 -0700 (PDT), Laurav
wrote:

On Jun 15, 8:58*pm, Jamie
wrote:

* Yes, I hear you and still, it is a mass air flow and motor design
problem..


I haven't noticed that the motor speed is sensitive to anything else
besides voltage, and the guy who makes the motor says that's the only
thing that causes changes in speed.
You could send your suggestions to Turbine Products, see what he says.
In any case I need to deal with this particular motor, not some future
version.
Laura

Greetings Laura,
Can you supply any info on the motor itself? Not the current draw but
the type of motor? Maybe a picture of the motor? I suspect it is a
shaded pole motor. Also, you wrote about a rheostat controlling the
motor speed. Is that all there is to control the motor speed? Just a
variable resistor like a volume control in a radio?
Thanks,
Eric


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On Jun 16, 12:57*am, wrote:
Can you supply any info on the motor itself? Not the current draw but
the type of motor?


He said it's a universal motor. It has brushes.
It would be enough to control the input voltage, that's what I'm now
trying to do by hand. I think if I were standing by the rheostat all
the time, I could control the motor speed well enough.
It's in a metal box, I don't know what's inside the box.
What Jamie seemed to be saying is that there's some kind of feedback
loop that might make the motor very voltage-sensitive, that he said
would apply to a fan motor. This isn't a fan, it's an air turbine.
In any case, this is what I have, and what I'd like to get running
more evenly.
It's not like there are a huge variety of airline respirators on the
market. I'm not sure if the very expensive NIOSH-certified ones have
more sophisticated motor control or not. I somewhat doubt it - I
called one company and he said the innards were about the same for his
NIOSH-certified version vs the home use version.
These airline respirators are used by auto body workers or hobbyists,
sandblasters, etc. Precise volume control might not be necessary for
them.
The voltage at an outlet does seem to vary more than the utility co.
voltage, so I may have electrical problems that can be fixed and would
give more even airflow.
Laura
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Here's what the guy who makes the respirator said, relevant to voltage
sensitivity:
"the motor speed change should be proportional to the voltage change,
but that effect is amplified by the lowering of static pressure and
the head loss in the air line, so the air flow reduction at free flow
(at the air pump with no hose) would be reduced even more if measured
at the end of the air hose."
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The following sounds sarcastic, but the question is unavoidable...

WHY does the flow have to be so precisely regulated? Are you worried about
bursting the lungs of the person on the respirator?

It would be much easier to have the turbine run at a constant speed and use
a simple valve at the patient's end to bleed off excess flow. (Of course, if
respirators were made that way, we wouldn't be discussing how to regulate
the turbine speed.)


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On Jun 16, 9:45*am, "William Sommerwerck"
wrote:

WHY does the flow have to be so precisely regulated? Are you worried about
bursting the lungs of the person on the respirator?


Because the motor is too noisy at high speed. Yes, excess flow passes
through a valve to the outside.

Laura
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On Jun 15, 8:51*pm, Laurav wrote:
On Jun 15, 11:10*pm, Bennett wrote:

BTW, what is an Air Turbine; what does it do?


It pushes air through a long hose to an airline respirator. *So unlike
a fan, it's pushing a small amount of air, 4-5 CFM typically, but high
pressure is needed to push the air.
Really, the people who are criticizing the motor design should send
their ideas to Turbine Products. *I'd be interested to hear what he
has to say.


You are the only person here who is their customer. You have a
contractual relationship. You have a legitimate complaint with the
product you gave them your hardearned money in exchange. Any queries a
merely curious third party -- like the posters here -- might have can
be safely ignored.



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On Jun 16, 6:15*am, Laurav wrote:
On Jun 16, 12:57*am, wrote:

Can you supply any info on the motor itself? Not the current draw but
the type of motor?


He said it's a universal motor. *It has brushes.
It would be enough to control the input voltage, that's what I'm now
trying to do by hand. *I think if I were standing by the rheostat all
the time, I could control the motor speed well enough.
It's in a metal box, I don't know what's inside the box.
What Jamie seemed to be saying is that there's some kind of feedback
loop that might make the motor very voltage-sensitive, that he said
would apply to a fan motor. *This isn't a fan, it's an air turbine.
In any case, this is what I have, and what I'd like to get running
more evenly.
It's not like there are a huge variety of airline respirators on the
market. *I'm not sure if the very expensive NIOSH-certified ones have
more sophisticated motor control or not. *I somewhat doubt it - I
called one company and he said the innards were about the same for his
NIOSH-certified version vs the home use version.
These airline respirators are used by auto body workers or hobbyists,
sandblasters, etc. *Precise volume control might not be necessary for
them.


So it's OK if something designed to protect human life works like
crap? I'm not sure how they figured that that was OK.

The voltage at an outlet does seem to vary more than the utility co.
voltage, so I may have electrical problems that can be fixed and would
give more even airflow.
Laura


You said that the speed varied completely within a 20 VAC range --
100-120VAC -- that the input voltage was critical to fan speed.
Turbine Products did not design a product to cope with normal voltage
fluctuations, which can easily be +/-10%.

Is this UL approved? Is there some safety standard it's supposed to
comply with? Have you contacted NIOSH to tell them of your complaint?
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Actually the other brands of airline respirators that I looked at
don't even have a volume control. They just push air at a very high
volume. Very loud.
Laura
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WHY does the flow have to be so precisely regulated? Are
you worried about bursting the lungs of the person on the
respirator?


Because the motor is too noisy at high speed. Yes, excess
flow passes through a valve to the outside.


Okay. Then why is such tight regulation required?


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On Jun 16, 10:53*am, "William Sommerwerck"
wrote:

Okay. Then why is such tight regulation required?


Because it's noisy at high speed. Both inside and outside the mask.

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On Jun 15, 11:10*pm, Bennett wrote:
They are pretty expensive - $350 and up. *Output voltage usually not
adjustable; the built in rheostat that you've got would adjust the voltage.


About how much would a UPS cost that regulates output voltage within
1% ?
The turbine uses about 1-2 A on the usual setting. On the highest
setting it uses 9 A, but I never use it that high.
Laura


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On Jun 16, 12:24*pm, Laurav wrote:
On Jun 15, 11:10*pm, Bennett wrote:

They are pretty expensive - $350 and up. *Output voltage usually not
adjustable; the built in rheostat that you've got would adjust the voltage.


About how much would a UPS cost that regulates output voltage within
1% ?
The turbine uses about 1-2 A on the usual setting. *On the highest
setting it uses 9 A, but I never use it that high.
Laura


ps Can anyone point me to such a UPS?
thanks
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Laurav wrote:

Here's what the guy who makes the respirator said, relevant to voltage
sensitivity:
"the motor speed change should be proportional to the voltage change,
but that effect is amplified by the lowering of static pressure and
the head loss in the air line, so the air flow reduction at free flow
(at the air pump with no hose) would be reduced even more if measured
at the end of the air hose."


If you remove the load from a series wound motor (universal), it'll
increase in RPM's, greatly in many cases.

That type of motor is very sensitive to supply and exhaust flow..

essentially, you have a vacuum loader/cleaner motor.. The only way
to properly regulate that is to measure the air mass flow and use that
as the feed back. RPM's is going to vary to maintain flow.

In a series wound motor, like you have, it is almost a natural.

P.S.
They make Brushless vacuum/blower motors that produce high volumes
with integrated electronics for speed control of a simple 0..10 volts.

They just cost more... Are you getting the image now?

http://www.grainger.com/Grainger/DOM...VY4?Pid=search

That is the idea of what I am talking about, however, that unit there
is far to large for what you're talking about. You seem to think what
you have is some high volume unit? It is actually very small compared to
what I deal with. In your case, I can understand why. You don't need to
be over inflated!

Seeing that this is a medical device you have, I don't see you getting
much help from those that cold make that unit more suitable for your
needs, even though there are many that can do it for you. I think you
understand what I am talking about there, it's to bad but that has what
the world has turned to.

Personally, I can't believe they put in a universal motor, in the
first place? You need to keep an eye on the brushes! They don't last
like you think they should. It's called cheap, cheap!...

Jamie



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Default supplying accurate output voltage input voltage

On 6/15/2012 5:29 AM, Laurav wrote:
Can one get a control where you can specify the output AC voltage very
accurately, even though the input voltage isn't accurate?
It would be for input to my air turbine. The air turbine always needs
input voltage much lower than the line voltage. So the control
wouldn't need step-up circuitry.
With the rheostat that comes with my air turbine, it's very sensitive
to changes in the line voltage.
So I was thinking about bypassing the rheostat instead of buying a
power conditioner and trying to supply very accurate voltage to the
rheostat.
Laura

I wonder whether a viable alternative is to control the air pressure
rather than the voltage. Set the turbine output somewhat high and let
an air pressure controller deliver the correct pressure to the mask.

Take a look at, e.g.,
http://www.regulatorstore.com/
http://www.controlair.com/index.php/regulatorproducts

I wouldn't worry too much about the motor's brushes wearing out too
quickly. Lots of home appliances (vacuum cleaner, blender, hair dryer,
coffee grinder) have brushes and last for years (albeit with
intermittent duty).


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Default supplying accurate output voltage input voltage

Bennett wrote:

On 6/15/2012 5:29 AM, Laurav wrote:

Can one get a control where you can specify the output AC voltage very
accurately, even though the input voltage isn't accurate?
It would be for input to my air turbine. The air turbine always needs
input voltage much lower than the line voltage. So the control
wouldn't need step-up circuitry.
With the rheostat that comes with my air turbine, it's very sensitive
to changes in the line voltage.
So I was thinking about bypassing the rheostat instead of buying a
power conditioner and trying to supply very accurate voltage to the
rheostat.
Laura

I wonder whether a viable alternative is to control the air pressure
rather than the voltage. Set the turbine output somewhat high and let
an air pressure controller deliver the correct pressure to the mask.

Take a look at, e.g.,
http://www.regulatorstore.com/
http://www.controlair.com/index.php/regulatorproducts

I wouldn't worry too much about the motor's brushes wearing out too
quickly. Lots of home appliances (vacuum cleaner, blender, hair dryer,
coffee grinder) have brushes and last for years (albeit with
intermittent duty).


She needs a Dyson Air multiplier

Jamie

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Default supplying accurate output voltage input voltage

On Jun 16, 9:25*am, Laurav wrote:
On Jun 16, 12:24*pm, Laurav wrote:

On Jun 15, 11:10*pm, Bennett wrote:


They are pretty expensive - $350 and up. *Output voltage usually not
adjustable; the built in rheostat that you've got would adjust the voltage.


About how much would a UPS cost that regulates output voltage within
1% ?
The turbine uses about 1-2 A on the usual setting. *On the highest
setting it uses 9 A, but I never use it that high.
Laura


ps Can anyone point me to such a UPS?
thanks


didn't see any specific responses, so

try search for UPS in the 200+VA range, to be certain it'll give no
problems find something 400+ VA that is constantly running.

When you find something that you 'think' might work within budget;
post a URL here and everyone will look at it and give excellent
critiques.

Then you can buy it and be done with it.
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