Looking for RPM circuit to read fan speed

J

Junkmail789

Guest
I'm looking for a circuit that would read the speed of a dc fan that runs at
5hz. I would like the speed indicated on 3 7 segment displays with a
decimal after the first digit. The circuit would need to be able to be
mounted on the shaft of the fan.

Can anyone point me in the right direction?

Would it be possible to design such a thing using a rotary encoder?

Thanks,

Matt S.
 
"Junkmail789" <junkmail789@comcast.net> wrote in message
news:rM-dnUVxkcxvOhmiRVn-iA@giganews.com...
I'm looking for a circuit that would read the speed of a dc fan that runs
at
5hz. I would like the speed indicated on 3 7 segment displays with a
decimal after the first digit. The circuit would need to be able to be
mounted on the shaft of the fan.

Can anyone point me in the right direction?

Would it be possible to design such a thing using a rotary encoder?

Thanks,

Matt S.
Click to expand...
A mirror on the fan shaft, a reflector opto coupler and a counter circuit.
If you want more accuracy, use more mirrors. for example, with eight
mirrors at 5 Hz, you will get 40 counts per second. Assuming that by 5 Hz
you mean 5 revolutions per second.

From your description you seem to want to mount the whole circuit on the
shaft. Won't that, at 5 Hz, make it a bit difficult to read, unless you
grab the fan and swing round with it! So I'm assuming you only want the
sensor on the fan.

For the counter and display, there are purpose built modules available, at
relatively low prices.

Regards

John
 
John,

I'll double check today but I believe there is a little bit of the shaft
protruding from the rear of the assembly. These are small fans (about the
size of those used in computer power supplies). So yes you are correct in
that I only want the sensor part on the shaft itself.

Thanks for the response, this is a great group :)

Matt S.

"John Fortier" <jfortier@rochester.rr.com> wrote in message
news:Ty4hb.6875$Sc7.2177@twister.nyroc.rr.com...
"Junkmail789" <junkmail789@comcast.net> wrote in message
news:rM-dnUVxkcxvOhmiRVn-iA@giganews.com...
I'm looking for a circuit that would read the speed of a dc fan that
runs
at
5hz. I would like the speed indicated on 3 7 segment displays with a
decimal after the first digit. The circuit would need to be able to be
mounted on the shaft of the fan.

Can anyone point me in the right direction?

Would it be possible to design such a thing using a rotary encoder?

Thanks,

Matt S.



A mirror on the fan shaft, a reflector opto coupler and a counter circuit.
If you want more accuracy, use more mirrors. for example, with eight
mirrors at 5 Hz, you will get 40 counts per second. Assuming that by 5 Hz
you mean 5 revolutions per second.

From your description you seem to want to mount the whole circuit on the
shaft. Won't that, at 5 Hz, make it a bit difficult to read, unless you
grab the fan and swing round with it! So I'm assuming you only want the
sensor on the fan.

For the counter and display, there are purpose built modules available, at
relatively low prices.

Regards

John
Click to expand...
 
"Junkmail789" <junkmail789@comcast.net> wrote in message
news:faadneJ3yrfdpBiiRVn-sg@giganews.com...
John,

I'll double check today but I believe there is a little bit of the shaft
protruding from the rear of the assembly. These are small fans (about the
size of those used in computer power supplies). So yes you are correct in
that I only want the sensor part on the shaft itself.

Thanks for the response, this is a great group :)

Matt S.

"John Fortier" <jfortier@rochester.rr.com> wrote in message
news:Ty4hb.6875$Sc7.2177@twister.nyroc.rr.com...

"Junkmail789" <junkmail789@comcast.net> wrote in message
news:rM-dnUVxkcxvOhmiRVn-iA@giganews.com...
I'm looking for a circuit that would read the speed of a dc fan that
runs
at
5hz. I would like the speed indicated on 3 7 segment displays with a
decimal after the first digit. The circuit would need to be able to be
mounted on the shaft of the fan.

Can anyone point me in the right direction?

Would it be possible to design such a thing using a rotary encoder?

Thanks,

Matt S.



A mirror on the fan shaft, a reflector opto coupler and a counter
circuit.
If you want more accuracy, use more mirrors. for example, with eight
mirrors at 5 Hz, you will get 40 counts per second. Assuming that by 5
Hz
you mean 5 revolutions per second.

From your description you seem to want to mount the whole circuit on the
shaft. Won't that, at 5 Hz, make it a bit difficult to read, unless you
grab the fan and swing round with it! So I'm assuming you only want the
sensor on the fan.

For the counter and display, there are purpose built modules available,
at
relatively low prices.

Regards

John





Then there was the old "shining a light through the fan blades intro an opto
Click to expand...
transistor or device to your choice " trick ??

--
Regards ............... Rheilly Phoull
 
On Wed, 8 Oct 2003 20:12:20 -0400, "Junkmail789"
<junkmail789@comcast.net> wrote:

I'm looking for a circuit that would read the speed of a dc fan that runs at
5hz.
Click to expand...
on my site under electronics there is a schematics for non tach wire
PC fans adapter for measuring Rpm on computer, maybe can help that too
4 you before counter with display ...



-- Regards, SPAJKY
& visit site - http://www.spajky.vze.com
Celly-III OC-ed,"Tualatin on BX-Slot1-MoBo!"
E-mail AntiSpam: remove ##
 
"Rheilly Phoull" <Rheilly@bigpond.com.au> wrote in message
news:bm3hdo$i8p3r$1@ID-151145.news.uni-berlin.de...
"Junkmail789" <junkmail789@comcast.net> wrote in message
news:faadneJ3yrfdpBiiRVn-sg@giganews.com...
John,

I'll double check today but I believe there is a little bit of the shaft
protruding from the rear of the assembly. These are small fans (about
the
size of those used in computer power supplies). So yes you are correct
in
that I only want the sensor part on the shaft itself.

Thanks for the response, this is a great group :)

Matt S.

"John Fortier" <jfortier@rochester.rr.com> wrote in message
news:Ty4hb.6875$Sc7.2177@twister.nyroc.rr.com...

"Junkmail789" <junkmail789@comcast.net> wrote in message
news:rM-dnUVxkcxvOhmiRVn-iA@giganews.com...
I'm looking for a circuit that would read the speed of a dc fan that
runs
at
5hz. I would like the speed indicated on 3 7 segment displays with
a
decimal after the first digit. The circuit would need to be able to
be
mounted on the shaft of the fan.

Can anyone point me in the right direction?

Would it be possible to design such a thing using a rotary encoder?

Thanks,

Matt S.



A mirror on the fan shaft, a reflector opto coupler and a counter
circuit.
If you want more accuracy, use more mirrors. for example, with eight
mirrors at 5 Hz, you will get 40 counts per second. Assuming that by
5
Hz
you mean 5 revolutions per second.

From your description you seem to want to mount the whole circuit on
the
shaft. Won't that, at 5 Hz, make it a bit difficult to read, unless
you
grab the fan and swing round with it! So I'm assuming you only want
the
sensor on the fan.

For the counter and display, there are purpose built modules
available,
at
relatively low prices.

Regards

John





Then there was the old "shining a light through the fan blades intro an
opto
transistor or device to your choice " trick ??

--
Regards ............... Rheilly Phoull
Click to expand...
Assuming the blades don't overlap.

John
 
John Fortier wrote:
Assuming the blades don't overlap.

John
Click to expand...
Then you set them at an angle to see between the blades.
--


Michael A. Terrell
Central Florida
 
"Junkmail789" <junkmail789@comcast.net> wrote in message news:<rM-dnUVxkcxvOhmiRVn-iA@giganews.com>...
I'm looking for a circuit that would read the speed of a dc fan that runs at
5hz. I would like the speed indicated on 3 7 segment displays with a
decimal after the first digit. The circuit would need to be able to be
mounted on the shaft of the fan.

Can anyone point me in the right direction?

Would it be possible to design such a thing using a rotary encoder?

Thanks,

Matt S.
Click to expand...
Are there any disturbances on the power-supply leads that you could
read to determine the RPM?
(from one who avoids mechanical design)
 
"Wade Hassler" <wadeh@neti.saber.net> wrote in message
news:d44d2251.0310100754.6b4fec45@posting.google.com...
"Junkmail789" <junkmail789@comcast.net> wrote in message
news:<rM-dnUVxkcxvOhmiRVn-iA@giganews.com>...
I'm looking for a circuit that would read the speed of a dc fan that
runs at
5hz. I would like the speed indicated on 3 7 segment displays with a
decimal after the first digit. The circuit would need to be able to be
mounted on the shaft of the fan.

Can anyone point me in the right direction?

Would it be possible to design such a thing using a rotary encoder?

Thanks,

Matt S.

Are there any disturbances on the power-supply leads that you could
read to determine the RPM?
(from one who avoids mechanical design)
Click to expand...


I think I've seen a typical app in one of Linear Tech's op-amp data sheets
which does exactly that. But I'm not sure what type of motor it is suitable
for. I think the rpm info should be present in the power lines, it's just a
matter of how easy it is to clean it up.

Smart idea!

Costas
 
You must log in or register to reply here.

Welcome to EDABoard.com

Sponsor

Back
Top