air flow sensor on PCB...

[Jan Panteltje]

On a sunny day (Fri, 07 Apr 2023 13:11:41 -0700) it happened John Larkin
<jlarkin@highlandSNIPMEtechnology.com> wrote in
<t0u03i16eflutmlu9gc8jmukuk2t3od4rd@4ax.com>:

On Fri, 7 Apr 2023 14:53:10 -0400, Bob Engelhardt
BobEngelhardt@comcast.net> wrote:

On 4/6/2023 12:35 AM, John Larkin wrote:
Given a PC board in a crate, like PCIe or PXI or VME or something,
what would be a good way to check air flow across the board, to verify
that the box fans and filters are OK? [...]

Am I missing something: you want to check airflow so that you can
prevent the board from overheating, right?

No, this particular board won\'t get very hot. But it would be a
feature if it reported proper air flow in the crate that it controls.

If so, why don\'t you just
measure the temperature directly? There must be spots on the board that
would be the first to overheat and give the alarm.

We\'d report local board temp of course, and the crate power supply
voltages. That\'s easy.

So many ways to do simple airflow test..

If it uses a fan, put a LED (IR if needed) outside the fan and a photo diode on the inside.
As long as the fan rotates the photo diode should see the blades frequency.. AC coupling, rectifier, capaciter.
logical output.

An other way is an air pressure sensor, or 2, one looking into the fan and the other the other way.
I have some BMP085 in use as barometric sensor, may clog up with dust though...

A simple mchanical flap with spring that pushes against a contact when it is bended by the airflow..

More advanced is correlation
2 mikes (or whatever audio sensors) a few cm apart and one of those variabele shift ICs shifs the data so those match
gives you travel speed (fan noise is good data).

Sign:
Insert wet finger for airflow check
OK forget it

Or if it is really hot look how long it takes to make your pizza.

 

[Clifford Heath]

On 08/04/23 14:04, John Larkin wrote:

On Sat, 8 Apr 2023 13:50:11 +1000, Clifford Heath <no.spam@please.net
wrote:

On 08/04/23 10:47, John Larkin wrote:
On Sat, 8 Apr 2023 10:40:16 +1000, Clifford Heath <no.spam@please.net
wrote:

On 07/04/23 11:49, John Larkin wrote:
On Fri, 7 Apr 2023 11:12:50 +1000, Clifford Heath <no.spam@please.net
wrote:

On 07/04/23 09:18, John Larkin wrote:
On Thu, 6 Apr 2023 14:41:35 -0700 (PDT), Fred Bloggs
bloggs.fredbloggs.fred@gmail.com> wrote:

On Thursday, April 6, 2023 at 12:36:04?AM UTC-4, John Larkin wrote:
Given a PC board in a crate, like PCIe or PXI or VME or something,
what would be a good way to check air flow across the board, to verify
that the box fans and filters are OK? Assume this board can\'t access
the fan tachs or anything like that.

I was thinking that I might stick a small thinfilm RTD in the air
stream and measure its temperature at two different voltages, to
estimate its self-heating, which would vary with air flow.

The classic broken light bulb hot-wire anemometer is a nuisance.

Carbon comp resistor?

This can\'t be a new problem. Any other suggestions?

A piezoelectric air flow sensor is more in line with detecting the presence/ absence of air flow. The signal conditioning then becomes simplified. TI has this crazily named thing:

https://www.ti.com/lit/ug/tidu372/tidu372.pdf

Dunno if that leaf shaped sensor is supposed to flutter or the flexure changes its resonance. Seems I\'ve seen those for sale separately for ~ $10.

System Description
This Piezoelectric Airflow Sensor is intended for
use in systems that require fan airflow detection.
This can include server intake/exhaust airflow
detection, as well as desktop computer airflow.
The Piezoelectric Airflow Sensor design is a
simple, low cost solution which would help
designers who are looking for a means to detect
the presence or absence of fan airflow in existing
systems.

That\'s insanely complex. Not hardly \"simple, low cost.\"

Do you have any idea how the piezo sensors measure air flow?

Shift in time-of-flight. The projects I\'ve seen use four in a square,
and measure TOF across the diagonals. Needs temperature and humidity
compensation to be accurate.

Both of the piezos in the TI diagram seem to be receivers. And the
signal path includes rectifiers and \"smoothing.\" That doesn\'t look
like TOF.

Haven\'t looked at the schematic or app note,

You can\'t say much about them if you don\'t.


Don\'t be a dill. Ultrasonic air-speed sensors are as old as the hills.

Read the schematic and explain it to us.

Simple: It\'s amplifying and detecting low-frequency noise from fan
blades and air turbulence (a result of airflow) using PVDS piezo film
sensors. As in, it\'s a fancy kind of low frequency microphone amplifier
with a rumble detector.

They use PVDS in guitar pickups, it\'s very effective and easy to use.
You can even buy it by the A4 sheet and cut it with scissors.

Happy?

 

[John Larkin]

On Sat, 8 Apr 2023 21:36:53 +1000, Clifford Heath <no.spam@please.net>
wrote:

On 08/04/23 14:04, John Larkin wrote:
On Sat, 8 Apr 2023 13:50:11 +1000, Clifford Heath <no.spam@please.net
wrote:

On 08/04/23 10:47, John Larkin wrote:
On Sat, 8 Apr 2023 10:40:16 +1000, Clifford Heath <no.spam@please.net
wrote:

On 07/04/23 11:49, John Larkin wrote:
On Fri, 7 Apr 2023 11:12:50 +1000, Clifford Heath <no.spam@please.net
wrote:

On 07/04/23 09:18, John Larkin wrote:
On Thu, 6 Apr 2023 14:41:35 -0700 (PDT), Fred Bloggs
bloggs.fredbloggs.fred@gmail.com> wrote:

On Thursday, April 6, 2023 at 12:36:04?AM UTC-4, John Larkin wrote:
Given a PC board in a crate, like PCIe or PXI or VME or something,
what would be a good way to check air flow across the board, to verify
that the box fans and filters are OK? Assume this board can\'t access
the fan tachs or anything like that.

I was thinking that I might stick a small thinfilm RTD in the air
stream and measure its temperature at two different voltages, to
estimate its self-heating, which would vary with air flow.

The classic broken light bulb hot-wire anemometer is a nuisance.

Carbon comp resistor?

This can\'t be a new problem. Any other suggestions?

A piezoelectric air flow sensor is more in line with detecting the presence/ absence of air flow. The signal conditioning then becomes simplified. TI has this crazily named thing:

https://www.ti.com/lit/ug/tidu372/tidu372.pdf

Dunno if that leaf shaped sensor is supposed to flutter or the flexure changes its resonance. Seems I\'ve seen those for sale separately for ~ $10.

System Description
This Piezoelectric Airflow Sensor is intended for
use in systems that require fan airflow detection.
This can include server intake/exhaust airflow
detection, as well as desktop computer airflow.
The Piezoelectric Airflow Sensor design is a
simple, low cost solution which would help
designers who are looking for a means to detect
the presence or absence of fan airflow in existing
systems.

That\'s insanely complex. Not hardly \"simple, low cost.\"

Do you have any idea how the piezo sensors measure air flow?

Shift in time-of-flight. The projects I\'ve seen use four in a square,
and measure TOF across the diagonals. Needs temperature and humidity
compensation to be accurate.

Both of the piezos in the TI diagram seem to be receivers. And the
signal path includes rectifiers and \"smoothing.\" That doesn\'t look
like TOF.

Haven\'t looked at the schematic or app note,

You can\'t say much about them if you don\'t.


Don\'t be a dill. Ultrasonic air-speed sensors are as old as the hills.

Read the schematic and explain it to us.


Simple: It\'s amplifying and detecting low-frequency noise from fan
blades and air turbulence (a result of airflow) using PVDS piezo film
sensors. As in, it\'s a fancy kind of low frequency microphone amplifier
with a rumble detector.

They use PVDS in guitar pickups, it\'s very effective and easy to use.
You can even buy it by the A4 sheet and cut it with scissors.

Happy?

No. Spinning fan blades make noise even if air flow is blocked.

More, usually.

 

[John Larkin]

On Sat, 08 Apr 2023 06:03:20 GMT, Jan Panteltje <alien@comet.invalid>
wrote:

On a sunny day (Fri, 07 Apr 2023 13:11:41 -0700) it happened John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote in
t0u03i16eflutmlu9gc8jmukuk2t3od4rd@4ax.com>:

On Fri, 7 Apr 2023 14:53:10 -0400, Bob Engelhardt
BobEngelhardt@comcast.net> wrote:

On 4/6/2023 12:35 AM, John Larkin wrote:
Given a PC board in a crate, like PCIe or PXI or VME or something,
what would be a good way to check air flow across the board, to verify
that the box fans and filters are OK? [...]

Am I missing something: you want to check airflow so that you can
prevent the board from overheating, right?

No, this particular board won\'t get very hot. But it would be a
feature if it reported proper air flow in the crate that it controls.

If so, why don\'t you just
measure the temperature directly? There must be spots on the board that
would be the first to overheat and give the alarm.

We\'d report local board temp of course, and the crate power supply
voltages. That\'s easy.

So many ways to do simple airflow test..

If it uses a fan, put a LED (IR if needed) outside the fan and a photo diode on the inside.
As long as the fan rotates the photo diode should see the blades frequency.. AC coupling, rectifier, capaciter.
logical output.

Most fans have tachs. And air flow can be blocked.

>

As explained, the controller board will plug into a VME crate and has
no access to the fans.

An other way is an air pressure sensor, or 2, one looking into the fan and the other the other way.
I have some BMP085 in use as barometric sensor, may clog up with dust though...

A DP measurement across the module front panel would be interesting.
We\'d need to pop a little hole in the panel, out into the room, for
one side of the sensor.

Some crates will have positive internal pressure, some negative,
depending on how they do their fans. There are tribal disputes about
that.

 

[bitrex]

On 4/8/2023 10:17 AM, John Larkin wrote:

On Sat, 08 Apr 2023 06:03:20 GMT, Jan Panteltje <alien@comet.invalid
wrote:

On a sunny day (Fri, 07 Apr 2023 13:11:41 -0700) it happened John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote in
t0u03i16eflutmlu9gc8jmukuk2t3od4rd@4ax.com>:

On Fri, 7 Apr 2023 14:53:10 -0400, Bob Engelhardt
BobEngelhardt@comcast.net> wrote:

On 4/6/2023 12:35 AM, John Larkin wrote:
Given a PC board in a crate, like PCIe or PXI or VME or something,
what would be a good way to check air flow across the board, to verify
that the box fans and filters are OK? [...]

Am I missing something: you want to check airflow so that you can
prevent the board from overheating, right?

No, this particular board won\'t get very hot. But it would be a
feature if it reported proper air flow in the crate that it controls.

If so, why don\'t you just
measure the temperature directly? There must be spots on the board that
would be the first to overheat and give the alarm.

We\'d report local board temp of course, and the crate power supply
voltages. That\'s easy.

So many ways to do simple airflow test..

If it uses a fan, put a LED (IR if needed) outside the fan and a photo diode on the inside.
As long as the fan rotates the photo diode should see the blades frequency.. AC coupling, rectifier, capaciter.
logical output.

Most fans have tachs. And air flow can be blocked.



As explained, the controller board will plug into a VME crate and has
no access to the fans.

An other way is an air pressure sensor, or 2, one looking into the fan and the other the other way.
I have some BMP085 in use as barometric sensor, may clog up with dust though...

A DP measurement across the module front panel would be interesting.
We\'d need to pop a little hole in the panel, out into the room, for
one side of the sensor.

Some crates will have positive internal pressure, some negative,
depending on how they do their fans. There are tribal disputes about
that.

What about an acoustic sensor? I believe the way some automatic \"vape\"
devices work (there are also some where the user has to trigger them by
pushing a button, or combination) is they know when to apply heat to the
coils by mounting a lil microphone by the mouthpiece and listening for
the user sucking on it

 

[John Larkin]

On Sat, 08 Apr 2023 07:08:26 -0700, John Larkin
<jlarkin@highlandSNIPMEtechnology.com> wrote:

On Sat, 8 Apr 2023 21:36:53 +1000, Clifford Heath <no.spam@please.net
wrote:

On 08/04/23 14:04, John Larkin wrote:
On Sat, 8 Apr 2023 13:50:11 +1000, Clifford Heath <no.spam@please.net
wrote:

On 08/04/23 10:47, John Larkin wrote:
On Sat, 8 Apr 2023 10:40:16 +1000, Clifford Heath <no.spam@please.net
wrote:

On 07/04/23 11:49, John Larkin wrote:
On Fri, 7 Apr 2023 11:12:50 +1000, Clifford Heath <no.spam@please.net
wrote:

On 07/04/23 09:18, John Larkin wrote:
On Thu, 6 Apr 2023 14:41:35 -0700 (PDT), Fred Bloggs
bloggs.fredbloggs.fred@gmail.com> wrote:

On Thursday, April 6, 2023 at 12:36:04?AM UTC-4, John Larkin wrote:
Given a PC board in a crate, like PCIe or PXI or VME or something,
what would be a good way to check air flow across the board, to verify
that the box fans and filters are OK? Assume this board can\'t access
the fan tachs or anything like that.

I was thinking that I might stick a small thinfilm RTD in the air
stream and measure its temperature at two different voltages, to
estimate its self-heating, which would vary with air flow.

The classic broken light bulb hot-wire anemometer is a nuisance.

Carbon comp resistor?

This can\'t be a new problem. Any other suggestions?

A piezoelectric air flow sensor is more in line with detecting the presence/ absence of air flow. The signal conditioning then becomes simplified. TI has this crazily named thing:

https://www.ti.com/lit/ug/tidu372/tidu372.pdf

Dunno if that leaf shaped sensor is supposed to flutter or the flexure changes its resonance. Seems I\'ve seen those for sale separately for ~ $10.

System Description
This Piezoelectric Airflow Sensor is intended for
use in systems that require fan airflow detection.
This can include server intake/exhaust airflow
detection, as well as desktop computer airflow.
The Piezoelectric Airflow Sensor design is a
simple, low cost solution which would help
designers who are looking for a means to detect
the presence or absence of fan airflow in existing
systems.

That\'s insanely complex. Not hardly \"simple, low cost.\"

Do you have any idea how the piezo sensors measure air flow?

Shift in time-of-flight. The projects I\'ve seen use four in a square,
and measure TOF across the diagonals. Needs temperature and humidity
compensation to be accurate.

Both of the piezos in the TI diagram seem to be receivers. And the
signal path includes rectifiers and \"smoothing.\" That doesn\'t look
like TOF.

Haven\'t looked at the schematic or app note,

You can\'t say much about them if you don\'t.


Don\'t be a dill. Ultrasonic air-speed sensors are as old as the hills.

Read the schematic and explain it to us.


Simple: It\'s amplifying and detecting low-frequency noise from fan
blades and air turbulence (a result of airflow) using PVDS piezo film
sensors. As in, it\'s a fancy kind of low frequency microphone amplifier
with a rumble detector.

They use PVDS in guitar pickups, it\'s very effective and easy to use.
You can even buy it by the A4 sheet and cut it with scissors.

Happy?


No. Spinning fan blades make noise even if air flow is blocked.

More, usually.

It would be possible, maybe even practical, to analize the voltage and
PWM into a fan and the tach output, and compute pressure drop or flow.

That wouldn\'t help my case, where I don\'t own the fans, but it might
be useful elsewhere.

A small fan used in tach-only mode, PWM=0, would be a cheap flow or DP
sensor.

 

[Lasse Langwadt Christensen]

lørdag den 8. april 2023 kl. 17.29.41 UTC+2 skrev bitrex:

On 4/8/2023 10:17 AM, John Larkin wrote:
On Sat, 08 Apr 2023 06:03:20 GMT, Jan Panteltje <al...@comet.invalid
wrote:

On a sunny day (Fri, 07 Apr 2023 13:11:41 -0700) it happened John Larkin
jla...@highlandSNIPMEtechnology.com> wrote in
t0u03i16eflutmlu9...@4ax.com>:

On Fri, 7 Apr 2023 14:53:10 -0400, Bob Engelhardt
BobEng...@comcast.net> wrote:

On 4/6/2023 12:35 AM, John Larkin wrote:
Given a PC board in a crate, like PCIe or PXI or VME or something,
what would be a good way to check air flow across the board, to verify
that the box fans and filters are OK? [...]

Am I missing something: you want to check airflow so that you can
prevent the board from overheating, right?

No, this particular board won\'t get very hot. But it would be a
feature if it reported proper air flow in the crate that it controls.

If so, why don\'t you just
measure the temperature directly? There must be spots on the board that
would be the first to overheat and give the alarm.

We\'d report local board temp of course, and the crate power supply
voltages. That\'s easy.

So many ways to do simple airflow test..

If it uses a fan, put a LED (IR if needed) outside the fan and a photo diode on the inside.
As long as the fan rotates the photo diode should see the blades frequency.. AC coupling, rectifier, capaciter.
logical output.

Most fans have tachs. And air flow can be blocked.



As explained, the controller board will plug into a VME crate and has
no access to the fans.

An other way is an air pressure sensor, or 2, one looking into the fan and the other the other way.
I have some BMP085 in use as barometric sensor, may clog up with dust though...

A DP measurement across the module front panel would be interesting.
We\'d need to pop a little hole in the panel, out into the room, for
one side of the sensor.

Some crates will have positive internal pressure, some negative,
depending on how they do their fans. There are tribal disputes about
that.
What about an acoustic sensor? I believe the way some automatic \"vape\"
devices work (there are also some where the user has to trigger them by
pushing a button, or combination) is they know when to apply heat to the
coils by mounting a lil microphone by the mouthpiece and listening for
the user sucking on it

I suspect that they might just use the microphone as a cheap pressure sensor

 

[bitrex]

On 4/8/2023 12:17 PM, Lasse Langwadt Christensen wrote:

lørdag den 8. april 2023 kl. 17.29.41 UTC+2 skrev bitrex:
On 4/8/2023 10:17 AM, John Larkin wrote:
On Sat, 08 Apr 2023 06:03:20 GMT, Jan Panteltje <al...@comet.invalid
wrote:

On a sunny day (Fri, 07 Apr 2023 13:11:41 -0700) it happened John Larkin
jla...@highlandSNIPMEtechnology.com> wrote in
t0u03i16eflutmlu9...@4ax.com>:

On Fri, 7 Apr 2023 14:53:10 -0400, Bob Engelhardt
BobEng...@comcast.net> wrote:

On 4/6/2023 12:35 AM, John Larkin wrote:
Given a PC board in a crate, like PCIe or PXI or VME or something,
what would be a good way to check air flow across the board, to verify
that the box fans and filters are OK? [...]

Am I missing something: you want to check airflow so that you can
prevent the board from overheating, right?

No, this particular board won\'t get very hot. But it would be a
feature if it reported proper air flow in the crate that it controls.

If so, why don\'t you just
measure the temperature directly? There must be spots on the board that
would be the first to overheat and give the alarm.

We\'d report local board temp of course, and the crate power supply
voltages. That\'s easy.

So many ways to do simple airflow test..

If it uses a fan, put a LED (IR if needed) outside the fan and a photo diode on the inside.
As long as the fan rotates the photo diode should see the blades frequency.. AC coupling, rectifier, capaciter.
logical output.

Most fans have tachs. And air flow can be blocked.



As explained, the controller board will plug into a VME crate and has
no access to the fans.

An other way is an air pressure sensor, or 2, one looking into the fan and the other the other way.
I have some BMP085 in use as barometric sensor, may clog up with dust though...

A DP measurement across the module front panel would be interesting.
We\'d need to pop a little hole in the panel, out into the room, for
one side of the sensor.

Some crates will have positive internal pressure, some negative,
depending on how they do their fans. There are tribal disputes about
that.
What about an acoustic sensor? I believe the way some automatic \"vape\"
devices work (there are also some where the user has to trigger them by
pushing a button, or combination) is they know when to apply heat to the
coils by mounting a lil microphone by the mouthpiece and listening for
the user sucking on it

I suspect that they might just use the microphone as a cheap pressure sensor

Yeah I think you\'re right, just using sound they might not be able to
easily distinguish sucking out of the device from blowing in:

<https://youtu.be/qgdzo-7HYQI>

 

[a a]

On Friday, 7 April 2023 at 03:53:57 UTC+2, Bertrand Sindri wrote:

a a <mant...@gmail.com> wrote:
I am living on an old Dell PC and when I power it on, it starts with
fans at higher speed to remove debris collected from the air


The reason the fans start at high speed is that the PWM controlled fans
that Dell installed do not startup at anything other than a high duty
cycle PWM waveform. Once spinning, they can be throttled down to their
usual RPM sufficient to maintain cooling. But to initially get started
spinning, they require that high speed jolt.

ChatGPT-5 > Call it what you can with your little mind, but Dell is smart, setting PC fans to start at max speed to remove any clogging debris at first

 

[a a]

On Saturday, 8 April 2023 at 18:57:13 UTC+2, bitrex wrote:

On 4/8/2023 12:17 PM, Lasse Langwadt Christensen wrote:
lørdag den 8. april 2023 kl. 17.29.41 UTC+2 skrev bitrex:
On 4/8/2023 10:17 AM, John Larkin wrote:
On Sat, 08 Apr 2023 06:03:20 GMT, Jan Panteltje <al...@comet.invalid
wrote:

On a sunny day (Fri, 07 Apr 2023 13:11:41 -0700) it happened John Larkin
jla...@highlandSNIPMEtechnology.com> wrote in
t0u03i16eflutmlu9...@4ax.com>:

On Fri, 7 Apr 2023 14:53:10 -0400, Bob Engelhardt
BobEng...@comcast.net> wrote:

On 4/6/2023 12:35 AM, John Larkin wrote:
Given a PC board in a crate, like PCIe or PXI or VME or something,
what would be a good way to check air flow across the board, to verify
that the box fans and filters are OK? [...]

Am I missing something: you want to check airflow so that you can
prevent the board from overheating, right?

No, this particular board won\'t get very hot. But it would be a
feature if it reported proper air flow in the crate that it controls.

If so, why don\'t you just
measure the temperature directly? There must be spots on the board that
would be the first to overheat and give the alarm.

We\'d report local board temp of course, and the crate power supply
voltages. That\'s easy.

So many ways to do simple airflow test..

If it uses a fan, put a LED (IR if needed) outside the fan and a photo diode on the inside.
As long as the fan rotates the photo diode should see the blades frequency.. AC coupling, rectifier, capaciter.
logical output.

Most fans have tachs. And air flow can be blocked.



As explained, the controller board will plug into a VME crate and has
no access to the fans.

An other way is an air pressure sensor, or 2, one looking into the fan and the other the other way.
I have some BMP085 in use as barometric sensor, may clog up with dust though...

A DP measurement across the module front panel would be interesting.
We\'d need to pop a little hole in the panel, out into the room, for
one side of the sensor.

Some crates will have positive internal pressure, some negative,
depending on how they do their fans. There are tribal disputes about
that.
What about an acoustic sensor? I believe the way some automatic \"vape\"
devices work (there are also some where the user has to trigger them by
pushing a button, or combination) is they know when to apply heat to the
coils by mounting a lil microphone by the mouthpiece and listening for
the user sucking on it

I suspect that they might just use the microphone as a cheap pressure sensor
Yeah I think you\'re right, just using sound they might not be able to
easily distinguish sucking out of the device from blowing in:

https://youtu.be/qgdzo-7HYQI

ChatGPT-5 > sound control is smart

 

[a a]

>

Yet one more #veryStupidByLowIQaa post.

 

[a a]

>

Darius the Dumb has posted yet one more #veryStupidByLowIQaa article.

 

[Clifford Heath]

On 09/04/23 02:00, John Larkin wrote:

On Sat, 08 Apr 2023 07:08:26 -0700, John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote:

On Sat, 8 Apr 2023 21:36:53 +1000, Clifford Heath <no.spam@please.net
wrote:

On 08/04/23 14:04, John Larkin wrote:
On Sat, 8 Apr 2023 13:50:11 +1000, Clifford Heath <no.spam@please.net
wrote:

On 08/04/23 10:47, John Larkin wrote:
On Sat, 8 Apr 2023 10:40:16 +1000, Clifford Heath <no.spam@please.net
wrote:

On 07/04/23 11:49, John Larkin wrote:
On Fri, 7 Apr 2023 11:12:50 +1000, Clifford Heath <no.spam@please.net
wrote:

On 07/04/23 09:18, John Larkin wrote:
On Thu, 6 Apr 2023 14:41:35 -0700 (PDT), Fred Bloggs
bloggs.fredbloggs.fred@gmail.com> wrote:

On Thursday, April 6, 2023 at 12:36:04?AM UTC-4, John Larkin wrote:
Given a PC board in a crate, like PCIe or PXI or VME or something,
what would be a good way to check air flow across the board, to verify
that the box fans and filters are OK? Assume this board can\'t access
the fan tachs or anything like that.

I was thinking that I might stick a small thinfilm RTD in the air
stream and measure its temperature at two different voltages, to
estimate its self-heating, which would vary with air flow.

The classic broken light bulb hot-wire anemometer is a nuisance.

Carbon comp resistor?

This can\'t be a new problem. Any other suggestions?

A piezoelectric air flow sensor is more in line with detecting the presence/ absence of air flow. The signal conditioning then becomes simplified. TI has this crazily named thing:

https://www.ti.com/lit/ug/tidu372/tidu372.pdf

Dunno if that leaf shaped sensor is supposed to flutter or the flexure changes its resonance. Seems I\'ve seen those for sale separately for ~ $10.

System Description
This Piezoelectric Airflow Sensor is intended for
use in systems that require fan airflow detection.
This can include server intake/exhaust airflow
detection, as well as desktop computer airflow.
The Piezoelectric Airflow Sensor design is a
simple, low cost solution which would help
designers who are looking for a means to detect
the presence or absence of fan airflow in existing
systems.

That\'s insanely complex. Not hardly \"simple, low cost.\"

Do you have any idea how the piezo sensors measure air flow?

Shift in time-of-flight. The projects I\'ve seen use four in a square,
and measure TOF across the diagonals. Needs temperature and humidity
compensation to be accurate.

Both of the piezos in the TI diagram seem to be receivers. And the
signal path includes rectifiers and \"smoothing.\" That doesn\'t look
like TOF.

Haven\'t looked at the schematic or app note,

You can\'t say much about them if you don\'t.


Don\'t be a dill. Ultrasonic air-speed sensors are as old as the hills.

Read the schematic and explain it to us.


Simple: It\'s amplifying and detecting low-frequency noise from fan
blades and air turbulence (a result of airflow) using PVDS piezo film
sensors. As in, it\'s a fancy kind of low frequency microphone amplifier
with a rumble detector.

They use PVDS in guitar pickups, it\'s very effective and easy to use.
You can even buy it by the A4 sheet and cut it with scissors.

Happy?


No. Spinning fan blades make noise even if air flow is blocked.

More, usually.

It would be possible, maybe even practical, to analize the voltage and
PWM into a fan and the tach output, and compute pressure drop or flow.

That wouldn\'t help my case, where I don\'t own the fans, but it might
be useful elsewhere.

A small fan used in tach-only mode, PWM=0, would be a cheap flow or DP
sensor.

The fan blade noise is probably much higher frequency than the rumble of
vortex shedding airflow around items in the case. These sensors look to
be optimised for this very low frequency rumble. A full schematic would
give you more idea what frequency range they\'re looking at, but I
suspect it\'s in the 2-10Hz range, not the 100\'s Hz that you\'d get from
fan blades.

 

[John Larkin]

On Sun, 9 Apr 2023 11:16:15 +1000, Clifford Heath <no.spam@please.net>
wrote:

On 09/04/23 02:00, John Larkin wrote:
On Sat, 08 Apr 2023 07:08:26 -0700, John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote:

On Sat, 8 Apr 2023 21:36:53 +1000, Clifford Heath <no.spam@please.net
wrote:

On 08/04/23 14:04, John Larkin wrote:
On Sat, 8 Apr 2023 13:50:11 +1000, Clifford Heath <no.spam@please.net
wrote:

On 08/04/23 10:47, John Larkin wrote:
On Sat, 8 Apr 2023 10:40:16 +1000, Clifford Heath <no.spam@please.net
wrote:

On 07/04/23 11:49, John Larkin wrote:
On Fri, 7 Apr 2023 11:12:50 +1000, Clifford Heath <no.spam@please.net
wrote:

On 07/04/23 09:18, John Larkin wrote:
On Thu, 6 Apr 2023 14:41:35 -0700 (PDT), Fred Bloggs
bloggs.fredbloggs.fred@gmail.com> wrote:

On Thursday, April 6, 2023 at 12:36:04?AM UTC-4, John Larkin wrote:
Given a PC board in a crate, like PCIe or PXI or VME or something,
what would be a good way to check air flow across the board, to verify
that the box fans and filters are OK? Assume this board can\'t access
the fan tachs or anything like that.

I was thinking that I might stick a small thinfilm RTD in the air
stream and measure its temperature at two different voltages, to
estimate its self-heating, which would vary with air flow.

The classic broken light bulb hot-wire anemometer is a nuisance.

Carbon comp resistor?

This can\'t be a new problem. Any other suggestions?

A piezoelectric air flow sensor is more in line with detecting the presence/ absence of air flow. The signal conditioning then becomes simplified. TI has this crazily named thing:

https://www.ti.com/lit/ug/tidu372/tidu372.pdf

Dunno if that leaf shaped sensor is supposed to flutter or the flexure changes its resonance. Seems I\'ve seen those for sale separately for ~ $10.

System Description
This Piezoelectric Airflow Sensor is intended for
use in systems that require fan airflow detection.
This can include server intake/exhaust airflow
detection, as well as desktop computer airflow.
The Piezoelectric Airflow Sensor design is a
simple, low cost solution which would help
designers who are looking for a means to detect
the presence or absence of fan airflow in existing
systems.

That\'s insanely complex. Not hardly \"simple, low cost.\"

Do you have any idea how the piezo sensors measure air flow?

Shift in time-of-flight. The projects I\'ve seen use four in a square,
and measure TOF across the diagonals. Needs temperature and humidity
compensation to be accurate.

Both of the piezos in the TI diagram seem to be receivers. And the
signal path includes rectifiers and \"smoothing.\" That doesn\'t look
like TOF.

Haven\'t looked at the schematic or app note,

You can\'t say much about them if you don\'t.


Don\'t be a dill. Ultrasonic air-speed sensors are as old as the hills.

Read the schematic and explain it to us.


Simple: It\'s amplifying and detecting low-frequency noise from fan
blades and air turbulence (a result of airflow) using PVDS piezo film
sensors. As in, it\'s a fancy kind of low frequency microphone amplifier
with a rumble detector.

They use PVDS in guitar pickups, it\'s very effective and easy to use.
You can even buy it by the A4 sheet and cut it with scissors.

Happy?


No. Spinning fan blades make noise even if air flow is blocked.

More, usually.

It would be possible, maybe even practical, to analize the voltage and
PWM into a fan and the tach output, and compute pressure drop or flow.

That wouldn\'t help my case, where I don\'t own the fans, but it might
be useful elsewhere.

A small fan used in tach-only mode, PWM=0, would be a cheap flow or DP
sensor.


The fan blade noise is probably much higher frequency than the rumble of
vortex shedding airflow around items in the case. These sensors look to
be optimised for this very low frequency rumble. A full schematic would
give you more idea what frequency range they\'re looking at, but I
suspect it\'s in the 2-10Hz range, not the 100\'s Hz that you\'d get from
fan blades.

A cheap electret microphone, located close to fan blades, makes a
gigantic signal.

 

[Jan Panteltje]

On a sunny day (Sat, 08 Apr 2023 09:00:08 -0700) it happened John Larkin
<jlarkin@highlandSNIPMEtechnology.com> wrote in
<3l333i5qc147isbtmf23c12lhkk8k4as31@4ax.com>:

A small fan used in tach-only mode, PWM=0, would be a cheap flow or DP
sensor.

Yes that is how my wind speed meter works;
https://www.ebay.com/itm/275688480186

 

[John Larkin]

On Sun, 09 Apr 2023 05:32:59 GMT, Jan Panteltje <alien@comet.invalid>
wrote:

On a sunny day (Sat, 08 Apr 2023 09:00:08 -0700) it happened John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote in
3l333i5qc147isbtmf23c12lhkk8k4as31@4ax.com>:

A small fan used in tach-only mode, PWM=0, would be a cheap flow or DP
sensor.


Yes that is how my wind speed meter works;
https://www.ebay.com/itm/275688480186

I have a couple like that, but they are too big to check air flow
inside some assemblies, like a loaded card cage. So I got one of these
https://www.newark.com/multicomp-pro/mp780109/hot-wire-thermal-anemometer-0/dp/42AH0486

which has a small hot-wire probe.

We drilled a row of holes in the top cover of this

https://www.dropbox.com/s/gr57bhafemypi63/P940_box_9.jpg?dl=0

so we can poke in the probe and see how air flow is distributed
between the boards. There is a baffle that shapes the two fire-hoses
of air from the fans and evens out the flow per slot. The goal is to
have at least 200 LFPM over any of the eight boards.

This is not the application where I want flow sensors. We\'ll monitor
fan tachs on this box, and measure temperature of every plugin card.

We will modulate the fans, to keep the noise down. The high-flow 48
volt fans are screamers at full speed.

 

[Bertrand Sindri]

In article <bffeb1b5-d695-4be5-918c-19c07c7bbf6cn@googlegroups.com> you wrote:

On Friday, 7 April 2023 at 03:53:57 UTC+2, Bertrand Sindri wrote:
a a <mant...@gmail.com> wrote:
I am living on an old Dell PC and when I power it on, it starts
with fans at higher speed to remove debris collected from the air

The reason the fans start at high speed is that the PWM controlled
fans that Dell installed do not startup at anything other than a
high duty cycle PWM waveform. Once spinning, they can be throttled
down to their usual RPM sufficient to maintain cooling. But to
initially get started spinning, they require that high speed jolt.

Call it what you can with your little mind, but Dell is smart,
setting PC fans to start at max speed to remove any clogging debris
at first

My, you really are as stupid and have as low an IQ as several group
members are already saying about you.

The \"start at high speed\" mode has *noting* to do with removing
clogging debris. That is nothing more than a false illusion you made
up in your head because you are not intelligent enough to reason out
the actual purpose for the high-speed start.

The high-speed start is because whatever model fan Dell sourced to
build into your machine needs some seconds of \'full power\' applied at
startup in order to get spinning from zero RPM.

Further, high speed air-flow from the fans at 100%, but in the usual
air-flow direction, simply will not dislodge clogging debris. The
faster airflow, in the same direction as always, will only further
embed any \'clogging debris\' into whatever they are stuck upon.

The fans would have to start in reverse airflow direction for a short
time to have any hope of \"dislodging clogging debris\".

 

[Jan Panteltje]

On a sunny day (Sun, 09 Apr 2023 07:11:11 -0700) it happened John Larkin
<jlarkin@highlandSNIPMEtechnology.com> wrote in
<5sg53id2re7ktgqknd9jigrcm4j63l1bk7@4ax.com>:

On Sun, 09 Apr 2023 05:32:59 GMT, Jan Panteltje <alien@comet.invalid
wrote:

On a sunny day (Sat, 08 Apr 2023 09:00:08 -0700) it happened John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote in
3l333i5qc147isbtmf23c12lhkk8k4as31@4ax.com>:

A small fan used in tach-only mode, PWM=0, would be a cheap flow or DP
sensor.


Yes that is how my wind speed meter works;
https://www.ebay.com/itm/275688480186

I have a couple like that, but they are too big to check air flow
inside some assemblies, like a loaded card cage. So I got one of these
https://www.newark.com/multicomp-pro/mp780109/hot-wire-thermal-anemometer-0/dp/42AH0486

Very expensive! (compared to my 10 dollar ebay thing).

which has a small hot-wire probe.

We drilled a row of holes in the top cover of this

https://www.dropbox.com/s/gr57bhafemypi63/P940_box_9.jpg?dl=0

so we can poke in the probe and see how air flow is distributed
between the boards. There is a baffle that shapes the two fire-hoses
of air from the fans and evens out the flow per slot. The goal is to
have at least 200 LFPM over any of the eight boards.

This is not the application where I want flow sensors. We\'ll monitor
fan tachs on this box, and measure temperature of every plugin card.

We will modulate the fans, to keep the noise down. The high-flow 48
volt fans are screamers at full speed.

Yes that is common technology, my Samsung laptop does that too, normally very quiet, but if
you run some CPU intensive stuff it becomes noisy.


That thermal thing goes with some Si diodes too, for a fraction of the price.
https://panteltje.nl/panteltje/pic/wind_pic_thermal_udp/
with ethernet interface (optionally POE).
the north - south and east - west diodes are around a center bar, so if wind is for example from N
then the S diodes are shielded from it and vice versa.
I used 2 diodes in series to get some more voltage change.
N
d
W d O d E
d
S
It is not a precision instrument, but was just one of the wind speed and direction experiments I did.

I was thinking, if you used that 10 dollar ebay thing, you could put a webcam on it to read the 7 segment display..
https://panteltje.nl/panteltje/7s_parser/index.html
would need some code changes for LCDs.
But then a webcam pointed to some [wind] vane would work too or even better.

 

[John Larkin]

On Sun, 09 Apr 2023 15:00:04 GMT, Jan Panteltje <alien@comet.invalid>
wrote:

On a sunny day (Sun, 09 Apr 2023 07:11:11 -0700) it happened John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote in
5sg53id2re7ktgqknd9jigrcm4j63l1bk7@4ax.com>:

On Sun, 09 Apr 2023 05:32:59 GMT, Jan Panteltje <alien@comet.invalid
wrote:

On a sunny day (Sat, 08 Apr 2023 09:00:08 -0700) it happened John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote in
3l333i5qc147isbtmf23c12lhkk8k4as31@4ax.com>:

A small fan used in tach-only mode, PWM=0, would be a cheap flow or DP
sensor.


Yes that is how my wind speed meter works;
https://www.ebay.com/itm/275688480186

I have a couple like that, but they are too big to check air flow
inside some assemblies, like a loaded card cage. So I got one of these
https://www.newark.com/multicomp-pro/mp780109/hot-wire-thermal-anemometer-0/dp/42AH0486

Very expensive! (compared to my 10 dollar ebay thing).

It\'s trivial if it helps up get a multi-million-dollar product right,
or saves even a day of engineering time.

We compared it against a couple of the propeller-type air speed meters
and it agreed nicely.

The other gadget, much cheaper, is to go to Chinatown and buy a bunch
of incense sticks and use the smoke to visualize air flow patterns.

which has a small hot-wire probe.

We drilled a row of holes in the top cover of this

https://www.dropbox.com/s/gr57bhafemypi63/P940_box_9.jpg?dl=0



so we can poke in the probe and see how air flow is distributed
between the boards. There is a baffle that shapes the two fire-hoses
of air from the fans and evens out the flow per slot. The goal is to
have at least 200 LFPM over any of the eight boards.

This is not the application where I want flow sensors. We\'ll monitor
fan tachs on this box, and measure temperature of every plugin card.

We will modulate the fans, to keep the noise down. The high-flow 48
volt fans are screamers at full speed.

Yes that is common technology, my Samsung laptop does that too, normally very quiet, but if
you run some CPU intensive stuff it becomes noisy.


That thermal thing goes with some Si diodes too, for a fraction of the price.
https://panteltje.nl/panteltje/pic/wind_pic_thermal_udp/
with ethernet interface (optionally POE).
the north - south and east - west diodes are around a center bar, so if wind is for example from N
then the S diodes are shielded from it and vice versa.
I used 2 diodes in series to get some more voltage change.
N
d
W d O d E
d
S
It is not a precision instrument, but was just one of the wind speed and direction experiments I did.

I was thinking, if you used that 10 dollar ebay thing, you could put a webcam on it to read the 7 segment display..
https://panteltje.nl/panteltje/7s_parser/index.html
would need some code changes for LCDs.
But then a webcam pointed to some [wind] vane would work too or even better.

 

[John Larkin]

On Sun, 09 Apr 2023 14:35:49 GMT, Bertrand Sindri
<bertrand.sindri@yahoo.com> wrote:

In article <bffeb1b5-d695-4be5-918c-19c07c7bbf6cn@googlegroups.com> you wrote:
On Friday, 7 April 2023 at 03:53:57 UTC+2, Bertrand Sindri wrote:
a a <mant...@gmail.com> wrote:
I am living on an old Dell PC and when I power it on, it starts
with fans at higher speed to remove debris collected from the air

The reason the fans start at high speed is that the PWM controlled
fans that Dell installed do not startup at anything other than a
high duty cycle PWM waveform. Once spinning, they can be throttled
down to their usual RPM sufficient to maintain cooling. But to
initially get started spinning, they require that high speed jolt.

Call it what you can with your little mind, but Dell is smart,
setting PC fans to start at max speed to remove any clogging debris
at first

My, you really are as stupid and have as low an IQ as several group
members are already saying about you.

Gosh, you\'re nasty. And probably wrong; nasty and wrong correlate.