Airflow sensor

On Sun, 30 May 2004 14:11:32 +0200, "The Al Bundy"
<the_al_bundy@*^no-spam!^*hotmail.com> wrote:

"Dan Major" <nospam@this.address> wrote
news:Xns94F8B3A2EE6A8soonerboomergbronlin@68.12.19.6...
"The Al Bundy" <the_al_bundy@*^no-spam!^*hotmail.com> wrote in
news:c98dt7$aq9$1@news4.tilbu1.nb.home.nl:

Mechanical solutions frequently can beat
electronic ones due to simplicity, cost, ruggedness, and ease of
implementation.


OK, I agree with this. The only thing is that I can't use any mechanical
sensing device such like a DC fan, flap and switch or anything like. The
reason why is that it must be placed on a PCB without any adjustments for
calibrating the sensor, and it must be as small as possible (if possible
even no through-hole device)

I will just put something together with a self heating diode and a measuring
diode and see how it reacts. Will post the results:)

Thanks everyone for the ideas!
Al
Click to expand...
Put a surface mount microphone on the board and feed it to a bandpass
filter tuned to the fundamental acoustic frequency of the fan.



Regards,

Boris Mohar

Got Knock? - see:
Viatrack Printed Circuit Designs http://www3.sympatico.ca/borism/
 
I have a handheld kestrel weather station, with a wind speed meter, but I
can't figure how it senses the rotation. There no electrical or optical
connections to the sensor module, which pops out for replacement. Also, it
senses the fan's rotation up to 1/4 inch away from the rest of the
instrument!


http://www.usairnet.com/backroads/wind_and_weather/wind/kestrel_3000.html

I've not replaced the battery in 4 years.
 
"Dave VanHorn" <dvanhorn@cedar.net> wrote in message
news:zvSdnQmjHIkHeSbdRVn-jg@comcast.com...
I have a handheld kestrel weather station, with a wind speed meter, but I
can't figure how it senses the rotation. There no electrical or optical
connections to the sensor module, which pops out for replacement. Also,
it
senses the fan's rotation up to 1/4 inch away from the rest of the
instrument!


http://www.usairnet.com/backroads/wind_and_weather/wind/kestrel_3000.html

I've not replaced the battery in 4 years.

Does a paper clip stick to it?
Click to expand...

:)
 
"Rich Grise" <null@example.net> wrote in message
news:eek:7Vuc.19998$oh7.7445@nwrddc01.gnilink.net...
"Dave VanHorn" <dvanhorn@cedar.net> wrote in message
news:zvSdnQmjHIkHeSbdRVn-jg@comcast.com...

I have a handheld kestrel weather station, with a wind speed meter, but
I
can't figure how it senses the rotation. There no electrical or optical
connections to the sensor module, which pops out for replacement. Also,
it
senses the fan's rotation up to 1/4 inch away from the rest of the
instrument!



http://www.usairnet.com/backroads/wind_and_weather/wind/kestrel_3000.html

I've not replaced the battery in 4 years.

Does a paper clip stick to it?

:)
Click to expand...
my thoughts exactly. Unless of course waldo was right.

Cheers
Terry
 
"Dave VanHorn" <dvanhorn@cedar.net> wrote in message
news:YeWdnc0wAYHfuCHdRVn-gg@comcast.com...
Does a paper clip stick to it?

Nope, aluminum rotor.

you can glue a magnet to an aluminium rotor
Click to expand...

Cheers
Terry
 
On a sunny day (Tue, 1 Jun 2004 13:50:01 +1200) it happened "Terry Given"
<the_domes@xtra.co.nz> wrote in <fiRuc.12788$XI4.447823@news.xtra.co.nz>:

"Paul Hovnanian P.E." <Paul@Hovnanian.com> wrote in message
news:40B929CF.8B74D051@Hovnanian.com...
Jan Panteltje wrote:

On a sunny day (Sat, 29 May 2004 22:39:19 GMT) it happened Dan Major
nospam@this.address> wrote in
Xns94F8B3A2EE6A8soonerboomergbronlin@68.12.19.6>:

"The Al Bundy" <the_al_bundy@*^no-spam!^*hotmail.com> wrote in
news:c98dt7$aq9$1@news4.tilbu1.nb.home.nl:

For a project I need to have an airflow sensor to protect a circuit
in
case of a fan failure. However this airflow sensor needs to be fitted
on a PCB, and if possible only SMD.
snip...
So my question is if someone knows such
sensor or how to build one with simple components?

The best, simplest, most failure-resistant design I've seen was a small
flap attached to a microswitch. The flap was positioned in the
airstream.
When there was airflow, the flap kept the switch open. When there was
no
airflow, the switch was closed. Mechanical solutions frequently can
beat
electronic ones due to simplicity, cost, ruggedness, and ease of
implementation.
Objection! I have seen this solution in the old Ampex VTRs, and it was a
frequent
source of failures.
The things would get stuck, damaged by maintenance (you just needed to
touch it),
and usually cause severe damage to overheating to the equipment if they
did
not work.
Tacho is good.
And proportional too:

CPU core: +1.66 V (min = +1.53 V, max = +1.73 V)
I/O: +3.33 V (min = +3.13 V, max = +3.43 V)
+5V: +4.83 V (min = +4.70 V, max = +5.23 V)
+12V: +12.07 V (min = +11.39 V, max = +12.44 V)
CPU Fan: 4787 RPM (min = 4687 RPM, div = 2)
P/S Fan: 2824 RPM (min = 2700 RPM, div = 2)
CPU Temp: +57.6°C (limit = +63°C, hysteresis = +65°C)
SYS Temp: +38.9°C (limit = +45°C, hysteresis = +48°C)
VIA686a Temp:
+26.3°C (limit = +38°C, hysteresis = +40°C)

Ain't Linux COOL :)
This was lm-sensors.
JP

The temperature data is probably as helpful as the tach data. If a fan
stops, you have time to shut down before the temp rises. But if the
airflow is blocked (and the fan keeps going), you'll be glad you had
overtemp alarms too.

Interesting question: If the airflow is blocked, what happens to the fan
speed? Vacuum cleaners speed up when you block the hose. If the P/S or
CPU fans do so as well to a significant degree, maybe a fan overspeed
alarm could be added to the code.

--
Paul Hovnanian mailto:paul@Hovnanian.com

I looked at a little AC drive (50kW or so) in our service dept. once, that
kept tripping on over-temperature fault. The IP56 (ish) drive was in a milk
powder manufacturing plant. The heatsink was an extrusion with 1.6mm slots
spaced about 5mm, and had 1.6mm Al plates glued in place for the fins (we
later changed to mechanical staking as it was better. And Aussie stopped
selling us the weapons-grade Al powder we had used for 10 years to allegedly
improve the thermal conductivity of the epoxy - later tests showed the Al
did bugger all). So the fin-to-fin gap was about 3.4mm. Except this drive -
the entire heatsink was a solid block of baked milk powedr & Al - water
blasting wouldnt get rid of it, we had to replace the whole damned heatsink.
Other than that, the drive worked - yay for thermal protection circuitry.

Cheers
Terry
Yep, these things are there for a reason, long time ago I designed some
Click to expand...
interfaces to PLC for motor temp sensors, these had to be galvanically
separated etc.. You do NOT expect these to trigger in a normal situation.
Anyways they were starting up a new plant, big pumps, and the technician came
back very happy: 'Your sensors worked!'.
So I inquired how he knew...
They had one of these big pumps and the valve was closed, the PLC switched it
on, and as it did see no fluid, it stayed on, until the temp alarm came in...
again and again and again... until the operators finally figured what was
happening.
Big motor, many kW, VERY hot..
JP
 
"Terry Given" <the_domes@xtra.co.nz> wrote in message
news:7UWuc.12941$XI4.450987@news.xtra.co.nz...
"Dave VanHorn" <dvanhorn@cedar.net> wrote in message
news:YeWdnc0wAYHfuCHdRVn-gg@comcast.com...


Does a paper clip stick to it?

Nope, aluminum rotor.

you can glue a magnet to an aluminium rotor
Click to expand...
None present.
 
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