pcb-mount air flow sensor

[John Larkin]

Anybody know of a good one?

I guess we could make our own. I was thinking about maybe using two
LM71 temperature sensors, one mounted on a copper pour with a resistor
heater. We don't need a lot of accuracy... this would be mostly a fan
fail sensor.


--

John Larkin Highland Technology, Inc

jlarkin at highlandtechnology dot com
http://www.highlandtechnology.com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom laser drivers and controllers
Photonics and fiberoptic TTL data links
VME thermocouple, LVDT, synchro acquisition and simulation

[Jim Thompson]

On Tue, 31 Jul 2012 10:22:53 -0700, John Larkin
<jla...@highlandtechnology.com> wrote:

>
>
>Anybody know of a good one?
>
>I guess we could make our own. I was thinking about maybe using two
>LM71 temperature sensors, one mounted on a copper pour with a resistor
>heater. We don't need a lot of accuracy... this would be mostly a fan
>fail sensor.

Use two thermistors, one heated by current flow thru it... refer to my
BSEE thesis of 1962, where I used that technique to measure blood flow
in the heart... unlike Obama's thesis, mine _is_ available in the
Harvard Library (joint thesis MIT/Harvard Med School :-)

In later days, for GenRad portable equipment, I simply sensed the
commutation current fall-to-zero glitch (DC, "electronic" fans) to
flag a stalled or dragging fan.

In a more amusing situation, that sudden cessation of fan current at
the commutation point was magnetically coupling to a _very_close_by_
CRT. Cured that by adding a feedback loop to make the fan "constant
current".

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

[Michael A. Terrell]

John Larkin wrote:
>
> Anybody know of a good one?
>
> I guess we could make our own. I was thinking about maybe using two
> LM71 temperature sensors, one mounted on a copper pour with a resistor
> heater. We don't need a lot of accuracy... this would be mostly a fan
> fail sensor.

Use three wire fans. That's what they're designed for. If the pulse
output stopps, or drops below a certain rate then the fan is bad or
blocked. Use one of SLoman's 555 as a missing pulse detector, if you
can't just monitor it on an extra input on the MPU.

[John Larkin]

On Tue, 31 Jul 2012 10:52:21 -0700, Fred Abse
<excret...@invalid.invalid> wrote:

>On Tue, 31 Jul 2012 10:22:53 -0700, John Larkin wrote:
>
>>
>>
>> Anybody know of a good one?
>>
>> I guess we could make our own. I was thinking about maybe using two LM71
>> temperature sensors, one mounted on a copper pour with a resistor heater.
>> We don't need a lot of accuracy... this would be mostly a fan fail sensor.
>

>Fans with stall sensing are pretty common, these days. Why not use those?

This will be on a couple of PCI Express crate controllers that plug
into VME or VXI crates. We thought it would be cool if we reported
crate power supply voltages, power supply noise, air temperature, and
air flow. We don't have access to the fans.

We could use a couple of SOT23 transistors (something like 300 K/W in
still air) running at the same currents but different dissipations,
and look at the Vbe difference.

[Jim Thompson]

Yep. $4.99 at Fry's ;-)

[Spehro Pefhany]

On Tue, 31 Jul 2012 11:14:41 -0700, Jim Thompson
<To-Email-Use-Th...@On-My-Web-Site.com> wrote:

>On Tue, 31 Jul 2012 14:04:59 -0400, "Michael A. Terrell"
><mike.t...@earthlink.net> wrote:
>
>>
>>John Larkin wrote:
>>>
>>> Anybody know of a good one?
>>>
>>> I guess we could make our own. I was thinking about maybe using two
>>> LM71 temperature sensors, one mounted on a copper pour with a resistor
>>> heater. We don't need a lot of accuracy... this would be mostly a fan
>>> fail sensor.
>>
>>
>> Use three wire fans. That's what they're designed for. If the pulse
>>output stopps, or drops below a certain rate then the fan is bad or
>>blocked. Use one of SLoman's 555 as a missing pulse detector, if you
>>can't just monitor it on an extra input on the MPU.
>
>Yep. $4.99 at Fry's ;-)
>
> ...Jim Thompson

Or, if a DC fan, monitor the current. They're commutated by the
rotation of the blades, and there is no internal filtering, so if the
current stops wobbling then the fan has stopped spinning. Of course
that does not detect the case of something blocking the intake or the
pathological cases of someone cutting the blades off with a Dremel or
extending the wires and moving the fan into another area.

Eg. this garage electric eye installation:

http://www.checkthishouse.com/wp-content/uploads/garage-door-opener-safety-sensors-improperly-installed-above-the-opener-at-ceiling-level.jpg

[lang...@fonz.dk]

On 31 Jul., 19:22, John Larkin <jlar...@highlandtechnology.com> wrote:
> Anybody know of a good one?
>
> I guess we could make our own. I was thinking about maybe using two
> LM71 temperature sensors, one mounted on a copper pour with a resistor
> heater. We don't need a lot of accuracy... this would be mostly a fan
> fail sensor.
>

standard way is to compare the self heating in two temperature
sensors,
one exposed to the airflow, the other only to the air temperature.
or just one selfheated sensor and compensate for temperature measured
in
some other way, like you suggest

you probably have one in you car, a platinum wire in the air intake
held
at a constant temperature, heating power and the air intake
temperature
gives airflow

well really air mass flow

-Lasse

[Jeff Liebermann]

On Tue, 31 Jul 2012 10:22:53 -0700, John Larkin

<jla...@highlandtechnology.com> wrote:

>Anybody know of a good one?

Yep. Lift the hood of your vehicle and you'll find a MAF (mass air
flow sensor). There are various methods. This shows most of them.
<http://www.autoshop101.com/forms/h34.pdf>
Basically, two hot wires in a bridge derangement. One in the air
flow, and the other to act as a reference. Also used in weather
stations for a no-moving-parts anemometer. They're very sensitive at
low airspeeds, and

Or, just buy a commercial vane switch:
<http://www.sensata.com/klixon/airflow-sensor.htm>

If you have a fair amount of CFM airflow to work with, a pitot tube,
as used on aircraft, can be made to work. Add a pressure transducer
or limit switch. I built one using a flex stainless pickup tube,
acrylic pressure body, plastic ball, and emitter-optoisolator pair. If
the ball hit bottom, it would block the light beam and trip the alarm.
I was used to trigger on loss of air flow in a server rack plenum
where the vendor did not want me "mounting" anything into their
ducting. So, I found a hole, inserted the stainless pickup tube, and
lived happily ever after.

If you're lazy, insert a 2nd fan in the airflow path. However,
instead of using it for moving air, use it as a generator. When the
generated voltage disappears, the air flow has stopped. Some butchery
of the fan internal wiring will be required.

>I guess we could make our own. I was thinking about maybe using two
>LM71 temperature sensors, one mounted on a copper pour with a resistor
>heater. We don't need a lot of accuracy... this would be mostly a fan
>fail sensor.

If the board is partly isolated from the air flow, you'll be measuring
the thermal gradient across the board instead of the air flow. The
sensors really need to be in a duct, or at least fairly close
together.


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

[Jim Thompson]

On Tue, 31 Jul 2012 15:26:43 -0400, Spehro Pefhany
<spef...@interlogDOTyou.knowwhat> wrote:

>On Tue, 31 Jul 2012 11:14:41 -0700, Jim Thompson
><To-Email-Use-Th...@On-My-Web-Site.com> wrote:
>
>>On Tue, 31 Jul 2012 14:04:59 -0400, "Michael A. Terrell"
>><mike.t...@earthlink.net> wrote:
>>
>>>
>>>John Larkin wrote:
>>>>
>>>> Anybody know of a good one?
>>>>
>>>> I guess we could make our own. I was thinking about maybe using two
>>>> LM71 temperature sensors, one mounted on a copper pour with a resistor
>>>> heater. We don't need a lot of accuracy... this would be mostly a fan
>>>> fail sensor.
>>>
>>>
>>> Use three wire fans. That's what they're designed for. If the pulse
>>>output stopps, or drops below a certain rate then the fan is bad or
>>>blocked. Use one of SLoman's 555 as a missing pulse detector, if you
>>>can't just monitor it on an extra input on the MPU.
>>
>>Yep. $4.99 at Fry's ;-)
>>
>> ...Jim Thompson
>
>Or, if a DC fan, monitor the current. They're commutated by the
>rotation of the blades, and there is no internal filtering, so if the
>current stops wobbling then the fan has stopped spinning.

As I mentioned in...

NNTP-Posting-Date: Tue, 31 Jul 2012 12:44:02 -0500
From: Jim Thompson <To-Email-Use-Th...@On-My-Web-Site.com>
Newsgroups: sci.electronics.design
Subject: Re: pcb-mount air flow sensor
Date: Tue, 31 Jul 2012 10:44:02 -0700
Message-ID: <jo5g18dn43rqpi7j2...@4ax.com>

>Of course
>that does not detect the case of something blocking the intake or the
>pathological cases of someone cutting the blades off with a Dremel or
>extending the wires and moving the fan into another area.
>
>Eg. this garage electric eye installation:
>
>http://www.checkthishouse.com/wp-content/uploads/garage-door-opener-safety-sensors-improperly-installed-above-the-opener-at-ceiling-level.jpg
>
>

Gads!

[Jon Elson]

John Larkin wrote:

>
>
> Anybody know of a good one?
>
> I guess we could make our own. I was thinking about maybe using two
> LM71 temperature sensors, one mounted on a copper pour with a resistor
> heater. We don't need a lot of accuracy... this would be mostly a fan
> fail sensor.
>
>

At least some years ago, there were PTC thermistor devices that were made
for this purpose. You applied a voltage with a series resistor, and
the device went into thermal runaway if the airflow was too little.
So, you had a large variation in voltage across the device due to
a small change in heat removal. I think if you look for PTC thermistor
you should be able to find such devices.

Jon

[mike]

On 7/31/2012 10:22 AM, John Larkin wrote:
>
>
> Anybody know of a good one?
>
> I guess we could make our own. I was thinking about maybe using two
> LM71 temperature sensors, one mounted on a copper pour with a resistor
> heater. We don't need a lot of accuracy... this would be mostly a fan
> fail sensor.
>
>

Are you measuring what you really care about?
Is there some component that depends on air flow?
Measure the temperature of that???

If you need an independent sensor, try this.
You need a spare microcontroller pin, or one that
can be shared by another button or sensor or indicator or...

Tie a thermistor to VCC.
Cap to ground with the processor pin in the middle.
Discharge the cap then measure the time for the pin to go high.
Hold the cap at ground long enough to heat the thermistor
and measure the time again. Time difference should depend
on air flow.

[lang...@fonz.dk]

On 31 Jul., 21:30, Jeff Liebermann <je...@cruzio.com> wrote:
> On Tue, 31 Jul 2012 10:22:53 -0700, John Larkin
>

> <jlar...@highlandtechnology.com> wrote:
> >Anybody know of a good one?
>
> Yep.  Lift the hood of your vehicle and you'll find a MAF (mass air
> flow sensor).  There are various methods.  This shows most of them.
> <http://www.autoshop101.com/forms/h34.pdf>
> Basically, two hot wires in a bridge derangement.  One in the air
> flow, and the other to act as a reference.  Also used in weather
> stations for a no-moving-parts anemometer.  They're very sensitive at
> low airspeeds, and
>

the coolest no-moving-parts anemometer I've seen is basically three
ultrasonic
transceivers arranged in a triangle

you can get some that have more transceivers that measures air speed
in
three instead of two dimensions

-Lasse

[John Larkin]

On Tue, 31 Jul 2012 13:09:19 -0700, mike <spa...@gmail.com> wrote:

>On 7/31/2012 10:22 AM, John Larkin wrote:
>>
>>
>> Anybody know of a good one?
>>
>> I guess we could make our own. I was thinking about maybe using two
>> LM71 temperature sensors, one mounted on a copper pour with a resistor
>> heater. We don't need a lot of accuracy... this would be mostly a fan
>> fail sensor.
>>
>>
>Are you measuring what you really care about?

I want to measure air flow across a PC board. It's in a card cage with
a fan tray blowing air up through the boards, and we'd like to roughly
measure flow and report it to our customers. Some surface-mount part
would be ideal.

[George Herold]

On Jul 31, 4:44 pm, John Larkin <jlar...@highlandtechnology.com>
wrote:

> On Tue, 31 Jul 2012 13:09:19 -0700, mike <spam...@gmail.com> wrote:
> >On 7/31/2012 10:22 AM, John Larkin wrote:
>
> >> Anybody know of a good one?
>
> >> I guess we could make our own. I was thinking about maybe using two
> >> LM71 temperature sensors, one mounted on a copper pour with a resistor
> >> heater. We don't need a lot of accuracy... this would be mostly a fan
> >> fail sensor.
>
> >Are you measuring what you really care about?
>
> I want to measure air flow across a PC board. It's in a card cage with
> a fan tray blowing air up through the boards, and we'd like to roughly
> measure flow and report it to our customers. Some surface-mount part
> would be ideal.
>
> --
>
> John Larkin         Highland Technology, Inc
>

> jlarkin at highlandtechnology dot comhttp://www.highlandtechnology.com

>
> Precision electronic instrumentation
> Picosecond-resolution Digital Delay and Pulse generators
> Custom laser drivers and controllers
> Photonics and fiberoptic TTL data links
> VME thermocouple, LVDT, synchro   acquisition and simulation

I like the thermistor idea, or is that too expensive?
Maybe a thermocouple heated by current running through it? (Or two of
them!)

George H.

[John Larkin]

Not too expensive. It would be nonlinear, and sensitive to ambient
temperature as well as air flow.

>Maybe a thermocouple heated by current running through it? (Or two of
>them!)

A pair of back-to-back thermocouples would measure differential
temperature (close enough) and one could be heated by a resistor or
something. But I don't know of any surface-mount thermocouples, so
we'd be doing hand assembly. It would need an opamp and an ADC to
resolve microvolts.

I guess you could slam some voltage across a 1206 platinum RTD, then
turn it off and measure temperature vs time as it cools off. Both
theta and tau would depend on air flow. That sounds like fun, where
engineering budgets constrain fun.

The two LM71s, one heated, isn't bad. All surface mount, SPI data, and
it acquires ambient temp too. The trick would be to make sure the
heater+sensor pair gets most of its cooling from air flow, and less
from conduction into the copper planes of the PC board.

Rob has suggested two temp sensors with a heater between them. Air
flow cools one sensor and heats the other. That does have a good
zero-flow indication. It doesn't pick up ambient temp very well, so
would need a third sensor for that.

[George Herold]

On Jul 31, 5:39 pm, John Larkin <jlar...@highlandtechnology.com>
wrote:

OK for Rob's idea turn off the heater to get the local temp.

You're not in any hurry to know the fan has stopper are you?

George H.

[Phil Hobbs]

Jim Thompson wrote:
>
> On Tue, 31 Jul 2012 10:22:53 -0700, John Larkin
> <jla...@highlandtechnology.com> wrote:
>
> >
> >
> >Anybody know of a good one?
> >
> >I guess we could make our own. I was thinking about maybe using two
> >LM71 temperature sensors, one mounted on a copper pour with a resistor
> >heater. We don't need a lot of accuracy... this would be mostly a fan
> >fail sensor.
>
> Use two thermistors, one heated by current flow thru it... refer to my
> BSEE thesis of 1962, where I used that technique to measure blood flow
> in the heart... unlike Obama's thesis, mine _is_ available in the
> Harvard Library (joint thesis MIT/Harvard Med School :-)
>
> In later days, for GenRad portable equipment, I simply sensed the
> commutation current fall-to-zero glitch (DC, "electronic" fans) to
> flag a stalled or dragging fan.
>
> In a more amusing situation, that sudden cessation of fan current at
> the commutation point was magnetically coupling to a _very_close_by_
> CRT. Cured that by adding a feedback loop to make the fan "constant
> current".
>

Two thermistors in series. One on a copper pour, the other not, measure
voltage at the midpoint. Their resistance goes vaguely like
exp(-0.03*T). With constant voltage drive, sensitivity will go up as
exp(+0.03*T), because the resistor ratios will have the same dependence
on delta-T, but the temperature rise will go as V**2/R.

With constant current, dissipation falls as T increases, so sensitivity
will drop as well as voltage. So if you make the voltage go down a bit
with increasing temperature, you can have constant bridge sensitivity.

Cheers

Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510
845-480-2058

hobbs at electrooptical dot net
http://electrooptical.net

[lang...@fonz.dk]

don't think you need to turn it off,
if you know how much power you put in and what its
resistance(temperature) is
you get something that depends on air flow and air temperature
which you could measure with another rtd with a much lower measurement
current

so something like 2x current source, 2xRTD, 2xADC

there will be an offset for the power lost in the pcb so use thin
tracks

-Lasse

[Jim Yanik]

Jeff Liebermann <je...@cruzio.com> wrote in
news:56bg18li8jkjg7ftf...@4ax.com:

I took apart a failed MAF from my Nissan Sentra,and there's considerable
signal conditioning circuitry connected to the thin-film sensor. all on a
ceramic substrate,imbedded in clear,flexible silicone goop.It has a bare IC
chip (COB) about .25" square,and you can see the gold wires connecting it
to the substrate pads.

--
Jim Yanik
jyanik
at
localnet
dot com

[Nico Coesel]

John Larkin <jla...@highlandtechnology.com> wrote:

>On Tue, 31 Jul 2012 10:52:21 -0700, Fred Abse
><excret...@invalid.invalid> wrote:
>
>>On Tue, 31 Jul 2012 10:22:53 -0700, John Larkin wrote:
>>
>>>
>>>
>>> Anybody know of a good one?
>>>
>>> I guess we could make our own. I was thinking about maybe using two LM71
>>> temperature sensors, one mounted on a copper pour with a resistor heater.
>>> We don't need a lot of accuracy... this would be mostly a fan fail sensor.
>>
>>Fans with stall sensing are pretty common, these days. Why not use those?
>
>This will be on a couple of PCI Express crate controllers that plug
>into VME or VXI crates. We thought it would be cool if we reported
>crate power supply voltages, power supply noise, air temperature, and
>air flow. We don't have access to the fans.

I'd leave it out if it ain't required. If it ain't there it cannot
break down and the customer can't complain or ask difficult questions
about it.

--
Failure does not prove something is impossible, failure simply
indicates you are not using the right tools...
nico@nctdevpuntnl (punt=.)
--------------------------------------------------------------

[Jim Thompson]

In my case I got an output (once temperature compensated) very much
like CMOS ID versus VDS and VGS curves.

Temperature compensation was the crux of my thesis... this was in
Germanium days ;-)

[Jamie]

John Larkin wrote:
>
> Anybody know of a good one?
>
> I guess we could make our own. I was thinking about maybe using two
> LM71 temperature sensors, one mounted on a copper pour with a resistor
> heater. We don't need a lot of accuracy... this would be mostly a fan
> fail sensor.
>
>

I've always like the use of DIODES pasted on the part of interest and
attached to a sense circuit.

Use them for high wattage RF ceramic transistors, thermo sensing..
Jamie

[Jeff Liebermann]

On Tue, 31 Jul 2012 17:19:19 -0500, Jim Yanik <jya...@abuse.gov>
wrote:

>I took apart a failed MAF from my Nissan Sentra,and there's considerable
>signal conditioning circuitry connected to the thin-film sensor. all on a
>ceramic substrate,imbedded in clear,flexible silicone goop.It has a bare IC
>chip (COB) about .25" square,and you can see the gold wires connecting it
>to the substrate pads.

I wasn't suggesting that John crams a expensive MAF into his design.
Just to use the basic concepts on how they work on his air flow
sensor.

I'm now at 3 successes out of 4 attempted MAF repairs on friends
vehicles. The OBD2 box belches an error code that announces yet
another expensive repair. I remove the MAF assembly, clean it out
with the approved cleaner:
<http://www.autozone.com/autozone/accessories/CRC-Mass-air-flow-sensor-cleaner/_/N-255s?itemIdentifier=36011>
let it dry, ohmmeter check, put it back, reset the error message, and
it usually works. Cleaning it while in the vehicle hasn't worked very
well. There are several YouTube videos on how it's done. This one
seems tolerable:
<http://www.youtube.com/watch?v=gd640ImE9Ec>
(milliohms???)

--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
# http://802.11junk.com je...@cruzio.com
# http://www.LearnByDestroying.com AE6KS

[John Larkin]

On Tue, 31 Jul 2012 22:20:49 GMT, ni...@puntnl.niks (Nico Coesel)
wrote:

>John Larkin <jla...@highlandtechnology.com> wrote:
>
>>On Tue, 31 Jul 2012 10:52:21 -0700, Fred Abse
>><excret...@invalid.invalid> wrote:
>>
>>>On Tue, 31 Jul 2012 10:22:53 -0700, John Larkin wrote:
>>>
>>>>
>>>>
>>>> Anybody know of a good one?
>>>>
>>>> I guess we could make our own. I was thinking about maybe using two LM71
>>>> temperature sensors, one mounted on a copper pour with a resistor heater.
>>>> We don't need a lot of accuracy... this would be mostly a fan fail sensor.
>>>
>>>Fans with stall sensing are pretty common, these days. Why not use those?
>>
>>This will be on a couple of PCI Express crate controllers that plug
>>into VME or VXI crates. We thought it would be cool if we reported
>>crate power supply voltages, power supply noise, air temperature, and
>>air flow. We don't have access to the fans.
>
>I'd leave it out if it ain't required. If it ain't there it cannot
>break down and the customer can't complain or ask difficult questions
>about it.

But the customer can specify "The crate controller shall include..."
and disqualify our competition. And some potential customers may
think these features are cool, or even useful.

We're planning to include some other unnecessary stuff, like mux-able
SMB test connectors on the front panel to allow scoping stuff, and
some registers that can control and measure bus transaction times. And
some spiffy LEDs.

I once bid against LeCroy, who were shipping an expensive, flakey
product. They discovered that they would have competition, so they
dropped their bid price in half. My customer picked an obscure feature
of our unit, made it mandatory, and disqualified them.

[Nico Coesel]

John Larkin <jla...@highlandtechnology.com> wrote:

>On Tue, 31 Jul 2012 22:20:49 GMT, ni...@puntnl.niks (Nico Coesel)
>wrote:
>
>>John Larkin <jla...@highlandtechnology.com> wrote:
>>
>>>On Tue, 31 Jul 2012 10:52:21 -0700, Fred Abse
>>><excret...@invalid.invalid> wrote:
>>>
>>>>On Tue, 31 Jul 2012 10:22:53 -0700, John Larkin wrote:
>>>>
>>>>>
>>>>>
>>>>> Anybody know of a good one?
>>>>>
>>>>> I guess we could make our own. I was thinking about maybe using two LM71
>>>>> temperature sensors, one mounted on a copper pour with a resistor heater.
>>>>> We don't need a lot of accuracy... this would be mostly a fan fail sensor.
>>>>
>>>>Fans with stall sensing are pretty common, these days. Why not use those?
>>>
>>>This will be on a couple of PCI Express crate controllers that plug
>>>into VME or VXI crates. We thought it would be cool if we reported
>>>crate power supply voltages, power supply noise, air temperature, and
>>>air flow. We don't have access to the fans.
>>
>>I'd leave it out if it ain't required. If it ain't there it cannot
>>break down and the customer can't complain or ask difficult questions
>>about it.
>
>But the customer can specify "The crate controller shall include..."
>and disqualify our competition. And some potential customers may
>think these features are cool, or even useful.

True. But only if you can keep track of budget (time & money). I've
seen too many projects going way over budget because people had no
clue how much work was involved.

>We're planning to include some other unnecessary stuff, like mux-able
>SMB test connectors on the front panel to allow scoping stuff, and
>some registers that can control and measure bus transaction times. And
>some spiffy LEDs.

You should allow the customer to configure the color of the leds :-)

>I once bid against LeCroy, who were shipping an expensive, flakey
>product. They discovered that they would have competition, so they
>dropped their bid price in half. My customer picked an obscure feature
>of our unit, made it mandatory, and disqualified them.

I once put blinking leds on a device. Because of timing those leds
could blink simultaneously or alternating. It took me quite a while to
convince the customer that it was not a problem.

[John Larkin]

On Wed, 01 Aug 2012 01:18:37 GMT, ni...@puntnl.niks (Nico Coesel)

With uPs and FPGAs and cheap parts, featuritis is a serious problem,
deciding what goodies to include, knowing when to quit. If the uP has
an ADC, why not add a mux and digitize all the power supplies? Then
why not compute noise? That's about where we are, trying to add
sensible features that don't overload the engineering time.

>
>>We're planning to include some other unnecessary stuff, like mux-able
>>SMB test connectors on the front panel to allow scoping stuff, and
>>some registers that can control and measure bus transaction times. And
>>some spiffy LEDs.
>
>You should allow the customer to configure the color of the leds :-)

We do have one nice orange LED called USR on our VME modules. A guy at
Pratt&Whitney wanted his own led to control, and we don't tell that
guy no. We call it Dean's LED.

https://dl.dropbox.com/u/53724080/PCBs/V220_front.JPG

https://dl.dropbox.com/u/53724080/PCBs/V220_Leds.JPG

>
>>I once bid against LeCroy, who were shipping an expensive, flakey
>>product. They discovered that they would have competition, so they
>>dropped their bid price in half. My customer picked an obscure feature
>>of our unit, made it mandatory, and disqualified them.
>
>I once put blinking leds on a device. Because of timing those leds
>could blink simultaneously or alternating. It took me quite a while to
>convince the customer that it was not a problem.

In a crate full of modules, our "CPU" heartbeat LEDs tend to start
together, and gradually drift out of sync.

[Michael A. Terrell]

Nico Coesel wrote:
>
> You should allow the customer to configure the color of the leds :-)

We had customers specify that all the LEDs in the products they
bought had to come from the same bin.

[Michael A. Terrell]

Jim Thompson wrote:

>
> Spehro Pefhany wrote:
> >
> >Eg. this garage electric eye installation:
> >
<http://www.checkthishouse.com/wp-content/uploads/garage-door-opener-safety-sensors-improperly-installed-above-the-opener-at-ceiling-level.jpg>
>
> Gads!

There'll be no skilled workers on your job!

[k...@att.bizzzzzzzzzzzz]

On Tue, 31 Jul 2012 18:54:13 -0700, John Larkin

Don't forget testing time. If it's there, it has to be tested.
<...>

[k...@att.bizzzzzzzzzzzz]

I had one project where there was a note added to Agile telling purchasing
that Engineering had to be notified before a new reel of LEDs was used.
Management forced me to use blue LEDs on a board where the highest rail was
3.3V. IIRC, the ballast resistor was about 15ohms to get the brightness
demanded.

[John Larkin]

Designed, coded, tested, documented in the manual.


--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators

Custom timing and laser controllers

Photonics and fiberoptic TTL data links

VME analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators

[josephkk]

On Wed, 01 Aug 2012 01:18:37 GMT, ni...@puntnl.niks (Nico Coesel) wrote:

>
>>We're planning to include some other unnecessary stuff, like mux-able
>>SMB test connectors on the front panel to allow scoping stuff, and
>>some registers that can control and measure bus transaction times. And
>>some spiffy LEDs.
>
>You should allow the customer to configure the color of the leds :-)

Maybe and maybe not. There are HMI standards that limit color choices for
indicators for various functions. Some of the standards conflict, and
specific case / application / system functional requirements normally
overrule general case standards. e.g. MV switchgear indication colors
(somewhere in the ANSI/IEEE C37 series) versus the general case
Mil-STD-1472.

[Michael A. Terrell]

These were those annoying HP 'Intelligent LED Displays' that could be
scrolled.

[Tom Del Rosso]

Jim Thompson wrote:
> On Tue, 31 Jul 2012 15:26:43 -0400, Spehro Pefhany
> <spef...@interlogDOTyou.knowwhat> wrote:
>
> > Of course
> > that does not detect the case of something blocking the intake or
> > the pathological cases of someone cutting the blades off with a
> > Dremel or extending the wires and moving the fan into another area.
> >
> > Eg. this garage electric eye installation:
> >
> > http://www.checkthishouse.com/wp-content/uploads/garage-door-opener-safety-sensors-improperly-installed-above-the-opener-at-ceiling-level.jpg
> >
> >
>
> Gads!

Why are those things considered so important when they are likely to be
defeated occasionally when somebody's foot is under the door but not inside
enough to block the sensor? Even a car wouldn't block it if it has a high
clearance.


--

Reply in group, but if emailing add one more
zero, and remove the last word.

[miso]

On 7/31/2012 10:22 AM, John Larkin wrote:
>
>
> Anybody know of a good one?
>
> I guess we could make our own. I was thinking about maybe using two
> LM71 temperature sensors, one mounted on a copper pour with a resistor
> heater. We don't need a lot of accuracy... this would be mostly a fan
> fail sensor.
>
>

I read through the suggestions. I think the chances of a false positive
are too high. Nothing is worse than some protection circuit cutting in
when there is nothing to protect. I'd scrap the air flow idea. Seems to
me the air temp sensor is good enough, and that is a reliable circuit.

The mass air flow sensor on a car is just a wire that is heated by
current flowing through it and then has it's resistance sensed. These
MAFs are really flaky.

> http://en.wikipedia.org/wiki/Mass_flow_sensor

I like the old weather vane. Yeah, it would stick sometimes, but it was
purely mechanical. All you had to do is clean it.

The hot wire is OK. I'm had one fail due to driving through a socal
fire. The fine soot coated the wire. The car was under warranty, so it
was easy just to have it replaced on the dealers dime. Otherwise you
have to take it apart and clean the sensor with alcohol, or pay through
the noise for a new unit.

I can't wait until electric cars can replace internal combustion
vehicles. All this sensor crap will be gone.

[Uwe Hercksen]

Michael A. Terrell schrieb:

> We had customers specify that all the LEDs in the products they
> bought had to come from the same bin.

Hello,

even if there are LEDs in more than one colour?

Bye

[Michael A. Terrell]

miso wrote:
>
> I can't wait until electric cars can replace internal combustion
> vehicles. All this sensor crap will be gone.

You'd rather have blackouts like India?

[Michael A. Terrell]

You need to find out what bin means in optoelectronics. It has
nothing to do with color.

[k...@att.bizzzzzzzzzzzz]

Engineering test takes a lot of time but so does manufacturing test. Though
you don't have high quantities so it might not matter as much (but have less
incentive to automate/BIST).

[Nico Coesel]

Spehro Pefhany <spef...@interlogDOTyou.knowwhat> wrote:

>On Tue, 31 Jul 2012 11:14:41 -0700, Jim Thompson
><To-Email-Use-Th...@On-My-Web-Site.com> wrote:

>
>>On Tue, 31 Jul 2012 14:04:59 -0400, "Michael A. Terrell"
>><mike.t...@earthlink.net> wrote:
>>
>>>
>>>John Larkin wrote:
>>>>
>>>> Anybody know of a good one?
>>>>
>>>> I guess we could make our own. I was thinking about maybe using two
>>>> LM71 temperature sensors, one mounted on a copper pour with a resistor
>>>> heater. We don't need a lot of accuracy... this would be mostly a fan
>>>> fail sensor.
>>>
>>>

>>> Use three wire fans. That's what they're designed for. If the pulse
>>>output stopps, or drops below a certain rate then the fan is bad or
>>>blocked. Use one of SLoman's 555 as a missing pulse detector, if you
>>>can't just monitor it on an extra input on the MPU.
>>
>>Yep. $4.99 at Fry's ;-)
>>
>> ...Jim Thompson
>
>Or, if a DC fan, monitor the current. They're commutated by the
>rotation of the blades, and there is no internal filtering, so if the
>current stops wobbling then the fan has stopped spinning. Of course

>that does not detect the case of something blocking the intake or the
>pathological cases of someone cutting the blades off with a Dremel or
>extending the wires and moving the fan into another area.
>
>Eg. this garage electric eye installation:
>
>http://www.checkthishouse.com/wp-content/uploads/garage-door-opener-safety-sensors-improperly-installed-above-the-opener-at-ceiling-level.jpg

This has been discussed here before. I still don't understand why
infrared is mandatory. Over here all the electric garage doors have a
pressure switch and a rubber hose running along the edge of the door.

[Tim Williams]

"Tom Del Rosso" <td...@verizon.net.invalid> wrote in message
news:jvagk5$99e$1...@dont-email.me...

> Why are those things considered so important when they are likely to be
> defeated occasionally when somebody's foot is under the door

^^^^ ^^^^
<grin> :)

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms

[Uwe Hercksen]

Michael A. Terrell schrieb:

> You need to find out what bin means in optoelectronics. It has
> nothing to do with color.

Hello,

I already knew that before.

Bye

[Spehro Pefhany]

They're mainly supposed to help reduce deaths of children. Here's the
ruling:

http://www.cpsc.gov/cpscpub/prerel/prhtml93/93024.html

and an update

http://www.cpsc.gov/volstd/garage/gdoupdate.pdf

Worth it?


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
sp...@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

[spamtrap1888]

On Jul 31, 10:44 am, Jim Thompson <To-Email-Use-The-Envelope-I...@On-

My-Web-Site.com> wrote:
> On Tue, 31 Jul 2012 10:22:53 -0700, John Larkin
>

> <jlar...@highlandtechnology.com> wrote:
>
> >Anybody know of a good one?
>
> >I guess we could make our own. I was thinking about maybe using two
> >LM71 temperature sensors, one mounted on a copper pour with a resistor
> >heater. We don't need a lot of accuracy... this would be mostly a fan
> >fail sensor.
>

> Use two thermistors, one heated by current flow thru it... refer to my
> BSEE thesis of 1962, where I used that technique to measure blood flow
> in the heart... unlike Obama's thesis, mine _is_ available in the
> Harvard Library (joint thesis MIT/Harvard Med School :-)

Columbia College requires no thesis for graduation -- did Obama write
one for the fun of it?

[Tom Del Rosso]

Spehro Pefhany wrote:
>
> They're mainly supposed to help reduce deaths of children. Here's the
> ruling:
>
> http://www.cpsc.gov/cpscpub/prerel/prhtml93/93024.html
>
> and an update
>
> http://www.cpsc.gov/volstd/garage/gdoupdate.pdf
>
> Worth it?

For that alone it's worth it, but it should do more than just avoid crushing
kids. A contact sensor with redundant switches should be at least as
reliable. It could reverse the door except when it's within an inch of the
bottom, at which point it could stop without reversing.

Fortunatly the ruling allows that as an option, instead of the usual
micromanagement.

[Jim Yanik]

Jeff Liebermann <je...@cruzio.com> wrote in
news:64og18h90t4hppr36...@4ax.com:

> On Tue, 31 Jul 2012 17:19:19 -0500, Jim Yanik <jya...@abuse.gov>
> wrote:
>
>>I took apart a failed MAF from my Nissan Sentra,and there's
>>considerable signal conditioning circuitry connected to the thin-film
>>sensor. all on a ceramic substrate,imbedded in clear,flexible silicone
>>goop.It has a bare IC chip (COB) about .25" square,and you can see the
>>gold wires connecting it to the substrate pads.
>
> I wasn't suggesting that John crams a expensive MAF into his design.
> Just to use the basic concepts on how they work on his air flow
> sensor.

Yes,I got that.
I just wanted to bloviate about taking my old sensor apart!
It's a neat piece of technology.When I was at TEK,I sawed apart one of the
mixed analog/digital hybrids from the 2465 scopes,the ones that look like
little cylinder heads and bolt down to the motherboard.

>
> I'm now at 3 successes out of 4 attempted MAF repairs on friends
> vehicles. The OBD2 box belches an error code that announces yet
> another expensive repair. I remove the MAF assembly, clean it out
> with the approved cleaner:
><http://www.autozone.com/autozone/accessories/CRC-Mass-air-flow-sensor-c
>leaner/_/N-255s?itemIdentifier=36011>
> let it dry, ohmmeter check, put it back, reset the error message, and
> it usually works. Cleaning it while in the vehicle hasn't worked very
> well. There are several YouTube videos on how it's done. This one
> seems tolerable:
><http://www.youtube.com/watch?v=gd640ImE9Ec>
> (milliohms???)
>

I've used that CRC sensor cleaner.
but my MAF failure was a total one. I was able to find a replacement sensor
online for $78,while most places would only sell the sensor AND housing for
$300-400...with exchange.
(they want the old housing back so they can scam another person...)
Naturally,they used 5-lobed Tor-X type security screws to mount the sensor
in the housing,but I worked around that.



--
Jim Yanik
jyanik
at
localnet
dot com

[Jim Thompson]

AIUI, It is Harvard who locked up Obama's law school thesis...
probably because it advocates communism.

And a lot of schools have stopped having theses in "recent" years. For
instance MIT no longer requires an undergraduate thesis.

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

[Spehro Pefhany]

The bins of visible LEDs are usually ranges of (milli) candelas, which
is the LED power output weighted by the spectral sensitivity function
of the human eye.

[xiaoshanj]

On Tuesday, July 31, 2012 11:22:53 AM UTC-6, John Larkin wrote:
> Anybody know of a good one? I guess we could make our own. I was thinking about maybe using two LM71 temperature sensors, one mounted on a copper pour with a resistor heater. We don't need a lot of accuracy... this would be mostly a fan fail sensor. -- John Larkin Highland Technology, Inc jlarkin at highlandtechnology dot com http://www.highlandtechnology.com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom laser drivers and controllers Photonics and fiberoptic TTL data links VME thermocouple, LVDT, synchro acquisition and simulation


If you don't require a lot of accuracy and only need the fan fail signal (On/OFF signal), the Flexpoint Bend resistant Sensor can meet your requirement. The sensor is cheap, if you have any interested in the sensor, you can check the link

http://www.flexpoint.com,

also, you will find a flow meter vedio for a similar application. http://www.flexpoint.com/videos/video.html.

Electrical Engineer
Fengfeng

[bloggs.fred...@gmail.com]

On Tuesday, July 31, 2012 2:06:51 PM UTC-4, John Larkin wrote:
> On Tue, 31 Jul 2012 10:52:21 -0700, Fred Abse
>

> <excret...@invalid.invalid> wrote:

>
>
>
> >On Tue, 31 Jul 2012 10:22:53 -0700, John Larkin wrote:
>
> >
>
> >>
>
> >>
>
> >> Anybody know of a good one?
>
> >>
>
> >> I guess we could make our own. I was thinking about maybe using two LM71
>
> >> temperature sensors, one mounted on a copper pour with a resistor heater.
>
> >> We don't need a lot of accuracy... this would be mostly a fan fail sensor.
>
> >
>

> >Fans with stall sensing are pretty common, these days. Why not use those?
>
>
>
> This will be on a couple of PCI Express crate controllers that plug
>
> into VME or VXI crates. We thought it would be cool if we reported
>
> crate power supply voltages, power supply noise, air temperature, and
>
> air flow. We don't have access to the fans.
>
>
>

> We could use a couple of SOT23 transistors (something like 300 K/W in
>
> still air) running at the same currents but different dissipations,
>
> and look at the Vbe difference.
>

The output is linearized with Vaf by maintaining the Vbe in ratio. This one has been around a while: http://electronicdesign.com/article/test-and-measurement/series-connected-transistors-use-differential-heat but it's probably more parts intensive than you hoped for.

[miso]

Electric cars and blackouts can be mutually exclusive with good
engineering. Engineering in India is barely better than Arizona.

[josephkk]

Depends on what you pay for, the military has required peak wavelength
binning as well. They paid for it too.

?-)

[josephkk]

That is a useful method as well. My garage door opener has a force sensor
that causes the door to reverse and open again if too much force is
detected. I can reverse it with my arm a foot (300 mm) from my body.

?-)

[lektr...@gmail.com]

What about a single strain gauge element stuck up into the air flow,
mounted from the pcb on stiff wires. Have three more resistors on the
board to complete a Wheatstone bridge. Strain gauge elements are
usually a resistive material on a plastic (kapton) backing. Air flow
would cause the element to bend in proportion to air flow, changing
voltage across bridge..

[miso]

> AIUI, It is Harvard who locked up Obama's law school thesis...
> probably because it advocates communism.
>
> And a lot of schools have stopped having theses in "recent" years. For
> instance MIT no longer requires an undergraduate thesis.
>
> ...Jim Thompson
>

More likely you are full of shit that the thesis advocates communism.
For one thing, he didn't study economics, so communism is extremely
unlikely. Further, communism was called command economics and/or planned
economics in that era.

I'd suggest you stick to something you know like electronics, but we are
all doubtful about that too.

[bloggs.fred...@gmail.com]

I don't think there is a thesis for Harvard Law. The controversial thesis was a 44-page document entitled Aristocracy Reborn, which was required for a senior seminar in his political science major at Columbia University. Ten pages have been released, somewhere. It's nothing exciting, just some brain dead undergrad ranting about plutocracy and knocking the Constitution for failing to address distribution of wealth. It is at least somewhat relevant, in contradistinction to that wimpy English major at Brigham Young University.

[Jon Kirwan]

Google dropped this out quickly in a search:

http://www.americanthinker.com/blog/2009/10/obamas_columbia_thesis_excerpt.html

It's an apology of sorts:

"In a blog post today I wrote about a report on a thesis
that President Obama produced while at Columbia and
provided a quote from that about the Constitution. My
source for that was Michael Ledeen at PJM. Since then I
have not been able to verify the claim at any source
other than Ledeen and one obscure blog that was Mr.
Ledeen's source. I now believe the story is totally
false and Mr. Ledeen has also just recently stated that
he will pull the story. I regret that I jumped the gun
and did not verify this as fully as is is now evident I
should have."

Jon

[bloggs.fred...@gmail.com]

Okay, good catch. Now I'm finding a quote from his professor at Columbia, Michael Baron:
"paper as a "thesis" or "senior thesis" in several interviews, and said that Obama spent a year working on it. Baron recalls that the topic was nuclear negotiations with the Soviet Union.

"My recollection is that the paper was an analysis of the evolution of the arms reduction negotiations between the Soviet Union and the United States," Baron said in an e-mail. "At that time, a hot topic in foreign policy circles was finding a way in which each country could safely reduce the large arsenal of nuclear weapons pointed at the other ... For U.S. policy makers in both political parties, the aim was not disarmament, but achieving deep reductions in the Soviet nuclear arsenal and keeping a substantial and permanent American advantage. As I remember it, the paper was about those negotiations, their tactics and chances for success. Barack got an A."
Read more at http://www.snopes.com/politics/obama/columbiathesis.asp#VDpU1EH7redCQuvJ.99

[Michael A. Terrell]

The customer had ordered some equipment, when it first hit
production, then additional units about five years later. Needless to
say, the newer LEDs were brighter, and it bothered them so they shipped
the equipment back. The lowest available bin was as close as we could
get to an exact match, unless they wanted to spend about $500 a unit to
have the older models modified.

[Michael A. Terrell]

Yawn. We are in dire need of new power plants, and the extra load
from electric cars can cause problems. The dumb ass liberals want to
shut down coal & nuclear, then advocate those crappy oversized electric
skateboards.

[miso]

Pajamas Media. Yep, no bias there. ;-)

[miso]

Never met a dumb ass liberal. I've met lots of fucking shit head
conservatives idiots.

[Jon Kirwan]

On Thu, 02 Aug 2012 22:44:15 -0700, miso <mi...@sushi.com>
wrote:

>Pajamas Media. Yep, no bias there. ;-)

Hehe. It's really hard to underestimate just how low media
standards have become and how much they have merely become
finches in trees, parroting mindlessly; rather than providing
research and thoughtful consideration and context. I think
the latter is now a thing of the past and the former all that
they have come to believe as news.

I'm depressed again.

Jon

[dagmarg...@yahoo.com]

On Aug 2, 3:16 pm, miso <m...@sushi.com> wrote:
> > AIUI, It is Harvard who locked up Obama's law school thesis...
> > probably because it advocates communism.
>
> > And a lot of schools have stopped having theses in "recent" years. For
> > instance MIT no longer requires an undergraduate thesis.
>
> >                                          ...Jim Thompson
>
> More likely you are full of shit that the thesis advocates communism.
> For one thing, he didn't study economics,

Roger that.

--
Cheers,
James Arthur

[dagmarg...@yahoo.com]

On Aug 3, 1:46 am, miso <m...@sushi.com> wrote:
> Never met a dumb ass liberal. I've met lots of fucking shit head
> conservatives idiots.

I spent about an hour yesterday talking to a Democrat campaign
worker. She insisted it's impossible for the U.S. government to run
out of money because unlike Europe's PIIGS, we're a nation of states
"ruled by a federal government" and have "with checks and balances."

She reacted angrily when I described last year's deficit as $1,300
billion, comparing that to Obama's "tax hike on the rich," which I
compute as (39.6% - 35%) x $550B (income over $250K) = $25 billion a
year. IOW, $25B is a trivial, non-solution to a $1,300B problem.

She said saying 1,300 was dishonest, deliberately misleading. "That's
$1.3 trillion," she said.

I said "Yeah, that's the same thing." She pounced--I'd confessed,
proving her point.

Scary.

We talked at length, quite friendly overall, and she thanked me in the
end. We actually had a lot fewer differences than she'd imagined, and
both wanted to make things better.

--
Cheers,
James Arthur

[Jim Thompson]

On Fri, 3 Aug 2012 05:20:58 -0700 (PDT), dagmarg...@yahoo.com
wrote:

Hot Air is reporting it contains anti-Constitution statements.

[miso]

We need a president with a MBA. What, you said we tried that once
before> Oh yeah, George W. Bush!

Just how did that work out?

[dagmarg...@yahoo.com]

On Aug 3, 6:36 pm, miso <m...@sushi.com> wrote:

> On 8/3/2012 5:20 AM, dagmargoodb...@yahoo.com wrote:
>
>
>
>
>
>
>
>
>
> > On Aug 2, 3:16 pm, miso <m...@sushi.com> wrote:
> >>> AIUI, It is Harvard who locked up Obama's law school thesis...
> >>> probably because it advocates communism.
>
> >>> And a lot of schools have stopped having theses in "recent" years. For
> >>> instance MIT no longer requires an undergraduate thesis.
>
> >>>                                           ...Jim Thompson
>
> >> More likely you are full of shit that the thesis advocates communism.
> >> For one thing, he didn't study economics,
>
> > Roger that.
>
>

> We need a president with a MBA.

MBA <> "studied economics." Last week I heard Geithner and Steny
Hoyer both say the economy's slowing, so gov't needs to spend more
money. Brilliant.

> What, you said we tried that once
> before> Oh yeah, George W. Bush!
>
> Just how did that work out?

Not well, but trillions and trillions (and about 7 million jobs)
better than now.

Hey, here's an epic fail: GM got $50B in bailouts, $27B illegally
looted from bond and shareholders, all the assets of GM, and $20B
swindled from a public offering to investors Nov., 2010[1]. ($50B +
$27B + $20B) = $97B in cash alone. Today it has a closing market
value of ... tada, $31B.

http://finance.yahoo.com/q?s=gm&ql=1

[1] there's a suit by those suckers too. Apparently Gov't Motors lied
on the offering, presenting production figures as sales. Investors
paid $34/sh; their investment closed at $20 today.

So, by turning ($97B in cash + ??? in assets) into $31B--and losing
most of the jobs anyhow--BHO "saved it."

Yeah, some basic economic and investing know-how sure would help.

--
Cheers,
James Arthur

[dagmarg...@yahoo.com]

On Aug 1, 11:24 am, xiaoshanj <jingfengf...@gmail.com> wrote:
> On Tuesday, July 31, 2012 11:22:53 AM UTC-6, John Larkin wrote:
> > Anybody know of a good one? I guess we could make our own. I was thinking about maybe using two LM71 temperature sensors, one mounted on a copper pour with a resistor heater. We don't need a lot of accuracy... this would be mostly a fan fail sensor.
>

> If you don't require a lot of accuracy and only need the fan fail signal (On/OFF signal), the Flexpoint Bend resistant Sensor can meet your requirement. The sensor is cheap, if you have any interested in the sensor, you can check the link
>
> http://www.flexpoint.com,
>
> also, you will find a flow meter vedio for a similar application.http://www.flexpoint.com/videos/video.html.

A real mechanical sensor would be fun to make--say some optically-
sensed windmill, or your flex sensor. In real life I'd worry about
cobwebs and dust though.

Just two diodes in series, one on a copper pour, constant-current
drive, sense the voltage in the middle, that should be pretty good.
Might even be simpler to drive than Phil's thermistors.

A fin or a grid of Cu posts for the sensing diode, sticking up in the
air, might be better than a pour--that improves the thermal interface
to the air stream, and you could orient it to respond to airflow in
the desired direction.

--
Cheers,
James Arthur

[Jasen Betts]

On 2012-08-03, Michael A. Terrell <mike.t...@earthlink.net> wrote:

> The customer had ordered some equipment, when it first hit
> production, then additional units about five years later. Needless to
> say, the newer LEDs were brighter, and it bothered them so they shipped
> the equipment back. The lowest available bin was as close as we could
> get to an exact match, unless they wanted to spend about $500 a unit to
> have the older models modified.

If the leds are protected from the customer you just need the right permanent marker...

--
⚂⚃ 100% natural

--- Posted via news://freenews.netfront.net/ - Complaints to ne...@netfront.net ---

[josephkk]

On Thu, 02 Aug 2012 22:46:16 -0700, miso <mi...@sushi.com> wrote:

>
>Never met a dumb ass liberal. I've met lots of fucking shit head
>conservatives idiots.

So you NEVER look in a mirror. No wait, you are willfully ignorant
fucking shithead liberal idiot.

?-)

[Bill Sloman]

On Aug 4, 1:25 am, dagmargoodb...@yahoo.com wrote:
> On Aug 3, 6:36 pm, miso <m...@sushi.com> wrote:
>
>
>
>
>
>
>
>
>
> > On 8/3/2012 5:20 AM, dagmargoodb...@yahoo.com wrote:
>
> > > On Aug 2, 3:16 pm, miso <m...@sushi.com> wrote:
> > >>> AIUI, It is Harvard who locked up Obama's law school thesis...
> > >>> probably because it advocates communism.
>
> > >>> And a lot of schools have stopped having theses in "recent" years. For
> > >>> instance MIT no longer requires an undergraduate thesis.
>
> > >>>                                           ...Jim Thompson
>
> > >> More likely you are full of shit that the thesis advocates communism.
> > >> For one thing, he didn't study economics,
>
> > > Roger that.
>
> > We need a president with a MBA.
>
> MBA <> "studied economics."  Last week I heard Geithner and Steny
> Hoyer both say the economy's slowing, so gov't needs to spend more
> money.  Brilliant.
>
> > What, you said we tried that once
> > before> Oh yeah, George W. Bush!
>
> > Just how did that work out?
>
> Not well, but trillions and trillions (and about 7 million jobs)
> better than now.

Sure - he sat on hios hands while a house bubble blew up - generating
lots of jobs, for a while - and then burst, removing all those jobs,
many of them before he vacated the White House. Great economic
management - in James Arthur's rather biased opinion.

> Hey, here's an epic fail: GM got $50B in bailouts, $27B illegally

in James Arthur's bizarre opinion

> looted from bond and shareholders, all the assets of GM, and $20B
> swindled from a public offering to investors Nov., 2010[1]. ($50B +
> $27B + $20B) = $97B in cash alone.  Today it has a closing market
> value of ... tada, $31B.
>
> http://finance.yahoo.com/q?s=gm&ql=1

With James Arthur's Tea Party co-delusionists in Congress busy
screwing the economy in the hope of getting re-elected, it's
surprising that it's worth that much

> [1] there's a suit by those suckers too.  Apparently Gov't Motors lied
> on the offering, presenting production figures as sales.  Investors
> paid $34/sh; their investment closed at $20 today.
>
> So, by turning ($97B in cash + ??? in assets) into $31B--and losing
> most of the jobs anyhow--BHO "saved it."

Saved as much as could be saved. No doubt James Arthur thinks that
some right-wing nitwit could have done better, but that's a permanent
delusion with him.

> Yeah, some basic economic and investing know-how sure would help.

But nowhere near as much as if Dubbya had had insight in that area and
damped down the house prices rises before they blew up into a bubble
that had to burst.

The Karl Rove approach to economic management - elect a Republican,
watch him wreck the economy, then criticise the Democrats for not
getting fast-enough recovery. The kind of strategy that can only
succeed if the electorate is as poorly informed as the right-wing
nitwit clowns who post here.

--
Bill Sloman,

[Michael A. Terrell]

Jasen Betts wrote:
>
> On 2012-08-03, Michael A. Terrell <mike.t...@earthlink.net> wrote:
>
> > The customer had ordered some equipment, when it first hit
> > production, then additional units about five years later. Needless to
> > say, the newer LEDs were brighter, and it bothered them so they shipped
> > the equipment back. The lowest available bin was as close as we could
> > get to an exact match, unless they wanted to spend about $500 a unit to
> > have the older models modified.
>
> If the leds are protected from the customer you just need the right permanent marker...

You aren't very smart, are you? One look at units from the the two
contracts made it obvious that some were brighter than others. As I
stated in another message, they were 'intelligent ASCII displays', not
just LEDs.

[Michael A. Terrell]

Liberals remind me of the Road Runner cartoons I watched as a kid.
The Road Runner is self sufficient, but the coyote is always scheming,
instead of working. He never pays for anything, and always fails at
anything he attempts. The fool can't even blow himself up with sticks
of TNT and do it right.

The moral to this story? When you see a Flaming Liberal with TNT you
need to run like hell, even if you set the roads on fire. After all,
Liberals will steal more money to fix it, since they'll have no way
around the hole caused by that low yield 'Liberal Brand TNT' who's motto
is '666 out of 1000 isn't bad'.

[whit3rd]

On Tuesday, July 31, 2012 3:19:19 PM UTC-7, Jim Yanik wrote:

> I took apart a failed MAF from my Nissan ....It has a bare IC
>
> chip (COB) about .25" square,and you can see the gold wires connecting it
>
> to the substrate pads.

Probably the big chip is the absolute air pressure sensor, uses piezoresistivity
of the strained silicon (with a sealed vacuum chamber on one side, and atmospheric
pressure on the other).

[Bill Sloman]

On Aug 4, 8:46 pm, "Michael A. Terrell" <mike.terr...@earthlink.net>
wrote:

> dagmargoodb...@yahoo.com wrote:
>
> > On Aug 3, 1:46 am, miso <m...@sushi.com> wrote:
> > > Never met a dumb ass liberal. I've met lots of fucking shit head
> > > conservatives idiots.
>
> > I spent about an hour yesterday talking to a Democrat campaign
> > worker.  She insisted it's impossible for the U.S. government to run
> > out of money because unlike Europe's PIIGS, we're a nation of states
> > "ruled by a federal government" and have "with checks and balances."
>
> > She reacted angrily when I described last year's deficit as $1,300
> > billion, comparing that to Obama's "tax hike on the rich," which I
> > compute as (39.6% - 35%) x $550B (income over $250K) = $25 billion a
> > year. IOW, $25B is a trivial, non-solution to a $1,300B problem.
>
> > She said saying 1,300 was dishonest, deliberately misleading.  "That's
> > $1.3 trillion," she said.
>
> > I said "Yeah, that's the same thing."  She pounced--I'd confessed,
> > proving her point.
>
> > Scary.
>
> > We talked at length, quite friendly overall, and she thanked me in the
> > end.  We actually had a lot fewer differences than she'd imagined, and
> > both wanted to make things better.
>
>    Liberals remind me of the Road Runner cartoons I watched as a kid.

You are a right-wing nitwit, so of course you identify the baddy with
liberals.

> The Road Runner is self sufficient, but the coyote is always scheming,
> instead of working.  He never pays for anything, and always fails at
> anything he attempts.  The fool can't even blow himself up with sticks
> of TNT and do it right.

Real life is kind of different from cartoons. When Mitt Romney set up
Bain, he created a clever scheme to milk failing companies by making
them look good for a short while, until he'd sold them on to gullible
investors.

This is definitely a Road Runner tactic, but in real life it worked,
and now Mitt Romney is very rich, and spending his money on trying to
get to be elected as president, so he can pull the same trick on an
even larger scale.

>    The moral to this story?  When you see a Flaming Liberal with TNT you
> need to run like hell, even if you set the roads on fire.  After all,
> Liberals will steal more money to fix it, since they'll have no way
> around the hole caused by that low yield 'Liberal Brand TNT' who's motto
> is '666 out of 1000 isn't bad'.

The take-away message is reasonable - don't trust crooks.
Unfortunately, Republican candidates are rarely honest. Mitt Romney
made his money out of a scheme which skirts fraud by the narrowest
possible margin.

Karl Rove - or one of his successors - will find some way to distract
the electorate from this insight, in the same way that the electorate
were distracted from the point that Dubbya was effectively a draft
dodger, who had been able to evade service in Vietnam via his father's
political connections, while John Kerry was a decorated Vietnam
veteran.

--
Bill Sloman, Nijmegen

[John Larkin]

On Tue, 31 Jul 2012 10:22:53 -0700, John Larkin
<jla...@highlandtechnology.com> wrote:

>
>
>Anybody know of a good one?
>
>I guess we could make our own. I was thinking about maybe using two
>LM71 temperature sensors, one mounted on a copper pour with a resistor
>heater. We don't need a lot of accuracy... this would be mostly a fan
>fail sensor.

I tried an LM45 and an 0805 heater resistor on a small copper island
on a board, and the temperature change versus air flow is
unimpressive. Too much heat is being lost to the board.

A 2N4400 (NPN, TO92) transistor is better, sticking up off the board
into the air flow. If we run it at constant current and snoop Vbe, Vbe
changes as a function of air flow. At 750 mW dissipation, Vbe changes
about 60 mV from zero air to 150 LFPM.

We were thinking that we could run it at constant current and switch
Vbe from, say, 2.5 to 12 volts and measure Vbe in both cases. That
gives us an indication of Theta-ja that should be pretty independent
of individual transistor variations.

I guess we'll put that on the board layout and, if it works, announce
the feature.


--

John Larkin Highland Technology, Inc

jlarkin at highlandtechnology dot com
http://www.highlandtechnology.com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom laser drivers and controllers
Photonics and fiberoptic TTL data links
VME thermocouple, LVDT, synchro acquisition and simulation

[John Larkin]

Bubba lit the fuse when he signed the bill that killed the
Glass�Steagall Act, made worse by Fannie Mae buying up unlimited
amounts of bad paper, taking the banks off the hook for home loans.
The government manufactured the crisis.

W is on record as having warned about the real estate bubble, but
nobody in Congress was listening. Too many people were getting "rich"
from the appreciation of their real estate.

Of course, the same things were happening in Ireland and Spain and the
UK.

Why do people think that rising house prices are a good thing?

>
>The Karl Rove approach to economic management - elect a Republican,
>watch him wreck the economy, then criticise the Democrats for not
>getting fast-enough recovery. The kind of strategy that can only
>succeed if the electorate is as poorly informed as the right-wing
>nitwit clowns who post here.

Hardly anyone - the public, Congress, economists, certainly not the
President - is thinking long-term. If you keep doing stuff that feels
good now, but accumulated longterm damage, eventually things get
worse.

[lang...@fonz.dk]

On 7 Aug., 00:27, John Larkin <jlar...@highlandtechnology.com> wrote:
> On Tue, 31 Jul 2012 10:22:53 -0700, John Larkin
>

> <jlar...@highlandtechnology.com> wrote:
>
> >Anybody know of a good one?
>
> >I guess we could make our own. I was thinking about maybe using two
> >LM71 temperature sensors, one mounted on a copper pour with a resistor
> >heater. We don't need a lot of accuracy... this would be mostly a fan
> >fail sensor.
>
> I tried an LM45 and an 0805 heater resistor on a small copper island
> on a board, and the temperature change versus air flow is
> unimpressive. Too much heat is being lost to the board.
>
> A 2N4400 (NPN, TO92) transistor is better, sticking up off the board
> into the air flow. If we run it at constant current and snoop Vbe, Vbe
> changes as a function of air flow. At 750 mW dissipation, Vbe changes
> about 60 mV from zero air to 150 LFPM.
>
> We were thinking that we could run it at constant current and switch
> Vbe from, say, 2.5 to 12 volts and measure Vbe in both cases. That
> gives us an indication of Theta-ja that should be pretty independent
> of individual transistor variations.
>
> I guess we'll put that on the board layout and, if it works, announce
> the feature.
>

I looked at a data sheet for the sensor for a thick film mass air flow
meter.
it had a schematic showing the internal and the principle of how to
drive it

looked like it basically had a ~1000R platinum sensor (at a low
current) to measure air temperature,
and a ~45R platinum sensor at a higher current i the airflow.

the measured output was the power(voltage) need to keep the heater
some degrees
higher than the air temperature

so something like a 2*pt1000, two resistors and an opamp

-Lasse

[John Larkin]

On Mon, 06 Aug 2012 15:27:56 -0700, John Larkin

<jla...@highlandtechnology.com> wrote:

>On Tue, 31 Jul 2012 10:22:53 -0700, John Larkin
><jla...@highlandtechnology.com> wrote:
>
>>
>>
>>Anybody know of a good one?
>>
>>I guess we could make our own. I was thinking about maybe using two
>>LM71 temperature sensors, one mounted on a copper pour with a resistor
>>heater. We don't need a lot of accuracy... this would be mostly a fan
>>fail sensor.
>
>
>I tried an LM45 and an 0805 heater resistor on a small copper island
>on a board, and the temperature change versus air flow is
>unimpressive. Too much heat is being lost to the board.
>
>A 2N4400 (NPN, TO92) transistor is better, sticking up off the board
>into the air flow. If we run it at constant current and snoop Vbe, Vbe
>changes as a function of air flow. At 750 mW dissipation, Vbe changes
>about 60 mV from zero air to 150 LFPM.
>
>We were thinking that we could run it at constant current and switch
>Vbe from, say, 2.5 to 12 volts and measure Vbe in both cases. That

^^^^ Vce, I meant. That will toggle power dissipation.

[John Larkin]

That would work, but we'd have to get the RTDs up off the PCB surface
somehow. We have some thinfilm RTDs in stock, little ceramic things
with tiny leads, but they look flimsy to mount up off the PCB. We have
1206 RTDs, but they would be heat sunk by the PCB a bunch.

An axial, maybe quarter-watt size, resistor with a high TC would work.
It could be spaced up off the board.

The TO92 is at least a standard part, and should be rugged mounted a
ways off the PCB surface, in the air stream. It costs 4 cents.

We had some other ideas that were mechanically difficult to implement
on a PC board. My favorite was a heated metal tube with a temp sensor
inside. A little air flow would make a huge difference to the sensor
temp. But that's messy mechanically.

We considered an electret microphone and a bandpass amplifier, to pick
up low frequency turbulence. Vortex shedding flowmeters work vaguely
like that.

[Tim Williams]

"John Larkin" <jla...@highlandtechnology.com> wrote in message
news:6uq0289vnij1albee...@4ax.com...

> We had some other ideas that were mechanically difficult to implement
> on a PC board. My favorite was a heated metal tube with a temp sensor
> inside. A little air flow would make a huge difference to the sensor
> temp. But that's messy mechanically.

Put some nice tall electrolytics beside it, get some venturi / skyscraper
effect?

Or if you use some conspicuous heatsinks (in the sense that they are
heatsinks, but not being used to sink heat), you might get more
directionality.

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms

[whit3rd]

On Monday, August 6, 2012 3:27:56 PM UTC-7, John Larkin wrote:
> On Tue, 31 Jul 2012 10:22:53 -0700, John Larkin

[ on sensing airflow parallel to a board]

> >Anybody know of a good one?
>
> >
>
> >I guess we could make our own. I was thinking about maybe using two
>
> >LM71 temperature sensors, one mounted on a copper pour with a resistor
>
> >heater. We don't need a lot of accuracy... this would be mostly a fan
>
> >fail sensor.

No need for a fancy IC; just a couple of cheap diodes (or diode-connected
transistors) in a bridge, will do ya. Heater in the middle, the one
downwind of the heater is ... warmer.

Or, you could try putting a teensy fan on the PCB, and monitor its
current draw. High current, it's bucking the forced airflow. Intermediate
current, airflow is small or absent. Low current, airflow is in the fan direction.

[Bill Sloman]

On Aug 7, 12:40 am, John Larkin <jlar...@highlandtechnology.com>
wrote:

> On Sat, 4 Aug 2012 02:36:55 -0700 (PDT), Bill Sloman
>

> <bill.slo...@ieee.org> wrote:
> >On Aug 4, 1:25 am, dagmargoodb...@yahoo.com wrote:
> >> On Aug 3, 6:36 pm, miso <m...@sushi.com> wrote:
>
> >> > On 8/3/2012 5:20 AM, dagmargoodb...@yahoo.com wrote:
>
> >> > > On Aug 2, 3:16 pm, miso <m...@sushi.com> wrote:
> >> > >>> AIUI, It is Harvard who locked up Obama's law school thesis...
> >> > >>> probably because it advocates communism.
>
> >> > >>> And a lot of schools have stopped having theses in "recent" years. For
> >> > >>> instance MIT no longer requires an undergraduate thesis.
>
> >> > >>>                                           ...Jim Thompson
>
> >> > >> More likely you are full of shit that the thesis advocates communism.
> >> > >> For one thing, he didn't study economics,
>
> >> > > Roger that.
>
> >> > We need a president with a MBA.
>
> >> MBA <> "studied economics."  Last week I heard Geithner and Steny
> >> Hoyer both say the economy's slowing, so gov't needs to spend more
> >> money.  Brilliant.
>
> >> > What, you said we tried that once
> >> > before> Oh yeah, George W. Bush!
>
> >> > Just how did that work out?
>
> >> Not well, but trillions and trillions (and about 7 million jobs)
> >> better than now.
>

> >Sure - he sat on his hands while a house bubble blew up - generating

The government certainly didn't do anything to stop it. The bankers
had been campaigning for the Changes in the Glass-Steagall Act for
mnay years, and eventually got what they wanted, but Fannie Maue
didn't actually buy up any "bad paper" - homes loans made under the
Community Reinvestment Act

http://en.wikipedia.org/wiki/Community_Reinvestment_Act

sustained much the same default rate as regular home loans. It was the
sub-prime - ninja - loans from the bottom feeding mortgage lenders
that defaulted on a large scale in the aftermath of the sub-prime
mortgage crisis.

James Arthur claimed otherwise immediately after the bubble burst, but
he was - as usual - seeing what he wanted to see. When the numbers
came in, the Community Reinvestment Act loans turned out to have been
made to good credit risks who rarely defaulted.

It was the bottom-feeding end of the banking community who
manufactured the crisis. Every last one of them should now be doing
hard labour in a chain gang, but I don't think that anybody has been
either charged or convicted of making loans to people who shouldn't
have got them or charged with fraud for selling them on as if they
were regular home loans to people who looked likely to pay them back.

> W is on record as having warned about the real estate bubble, but
> nobody in Congress was listening.

It isn't the executive branch's business to warn about problems -
their job is to anticipate them. If Dubbya was actually worried, it
was his duty to get off his behind and do something to solve the
problem before it turned into a crisis.

> Too many people were getting "rich" from the appreciation of their real estate.

And were too dumb to realise that the appreciation was going to be
transient.

> Of course, the same things were happening in Ireland and Spain and the
> UK.

Ireland was a very rapidly developing economy at the time. Property
prices collapsed when the world economy stopped growing, and with it
the Irish economy, and a whole lot of property that could have been
useful to a rapidly growing economy became worthless.

Spain was building a lot to serve the tourist trade, but that's a
luxury industry - the global financial crisis meant that a lot people
decided not to go to Spain for their vacation, or put off buying a
vacation house there; again, the Spanish economy had been growing
rapidly - recovering from the after-effects of Franco's right-wing
nitwit economic policies and the global financial crisis hit them very
hard.

The U.K. did have a house property price bubble, as they'd also had
several times in the period when I was working there, and the global
financial crisis made sure that it burst. It wasn't anything like as
bad a the US version, and the consequences were less dramatic. The
Northern Rock Building Society was the famous casualty

http://en.wikipedia.org/wiki/Northern_Rock

but "In 2006 the bank (Northern Rock)had moved into sub-prime lending
via a deal with Lehman Brothers. Although the mortgages were sold
under Northern Rock's brand through intermediaries, the risk was being
underwritten by Lehman Brothers."

> Why do people think that rising house prices are a good thing?

The can borrow against the higher value of their houses ...

> >The Karl Rove approach to economic management - elect a Republican,
> >watch him wreck the economy, then criticise the Democrats for not
> >getting fast-enough recovery. The kind of strategy that can only
> >succeed if the electorate is as poorly informed as the right-wing
> >nitwit clowns who post here.
>
> Hardly anyone - the public, Congress, economists, certainly not the
> President - is thinking long-term. If you keep doing stuff that feels

> good now, but accumulated long-term damage, eventually things get
> worse.

But James Arthur's idea of thinking long term is to minimise debt at
the expense of everything else. Keynes pointed out that killing the
economy isn't a a great way to save it. Your Democratic administration
is doing what Keynesian pump-priming it can, but the Republican
majority in Congress really doesn't want the economy to actually
recover until after the presidential election.

As far as I can seen, you current administration is thinking long-
term, but - like all politicians - their primary interest is coping
with the situation as it is now, and that means dealing with a series
of short term problems, many of them created by the Tea Party.

--
Bill Sloman, Nijmegen

[Bill Sloman]

On Aug 7, 3:26 am, John Larkin <jlar...@highlandtechnology.com> wrote:
> On Mon, 6 Aug 2012 16:54:03 -0700 (PDT), "langw...@fonz.dk"

Vortex shedding flow meters only work if the air flow past them is
fast enough to be turbulent. Then any kind of bluff body sheds a
series of vortices in alternating directions at a rate which is
linearly dependent on air speed, over a very substantial range of air
speeds. The one I worked on in 1974 incorporated what was effectively
a capacitance microphone to detect the alternation, but the actual
moving part was two very thin stainless steel membranes electron-beam
welded onto either side of our rectangular "bluff body" and the
capacitance measured was between the membranes and fixed electrodes
just behind them (inside the block)in a space filled with thin oil.

http://en.wikipedia.org/wiki/Vortex_shedding

http://www.waset.org/journals/waset/v53/v53-179.pdf

I can't remember what sort of shedding frequencies we saw in air - it
must have been something in the audio region. The second URL does
mention a specific frequency (around 200Hz) and includes enough
discussion about Strouhal numbers that you could work out what it
would be in your application.

--
Bill Sloman, Nijmegen

[Bill Sloman]

Too many moving parts. Vortex shedding is nicer. A thermistor behind
the bluff body would see very different air speeds as one vortex
detached and the next started up, rotating in the opposite direction.

--
Bill Sloman, Nijmegen

[John Larkin]

On Tue, 7 Aug 2012 01:44:09 -0700 (PDT), whit3rd <whi...@gmail.com>
wrote:

>On Monday, August 6, 2012 3:27:56 PM UTC-7, John Larkin wrote:
>> On Tue, 31 Jul 2012 10:22:53 -0700, John Larkin
>[ on sensing airflow parallel to a board]
>
>> >Anybody know of a good one?
>>
>> >
>>
>> >I guess we could make our own. I was thinking about maybe using two
>>
>> >LM71 temperature sensors, one mounted on a copper pour with a resistor
>>
>> >heater. We don't need a lot of accuracy... this would be mostly a fan
>>
>> >fail sensor.
>
>No need for a fancy IC; just a couple of cheap diodes (or diode-connected
>transistors) in a bridge, will do ya. Heater in the middle, the one
>downwind of the heater is ... warmer.

It's warmer at low air flows, then gets cooler again at higher
velocity.


--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators

Custom timing and laser controllers

Photonics and fiberoptic TTL data links

VME analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators

[Jim Thompson]

On Tue, 07 Aug 2012 06:57:01 -0700, John Larkin
<jjla...@highNOTlandTHIStechnologyPART.com> wrote:

>On Tue, 7 Aug 2012 01:44:09 -0700 (PDT), whit3rd <whi...@gmail.com>
>wrote:
>
>>On Monday, August 6, 2012 3:27:56 PM UTC-7, John Larkin wrote:
>>> On Tue, 31 Jul 2012 10:22:53 -0700, John Larkin
>>[ on sensing airflow parallel to a board]
>>
>>> >Anybody know of a good one?
>>>
>>> >
>>>
>>> >I guess we could make our own. I was thinking about maybe using two
>>>
>>> >LM71 temperature sensors, one mounted on a copper pour with a resistor
>>>
>>> >heater. We don't need a lot of accuracy... this would be mostly a fan
>>>
>>> >fail sensor.
>>
>>No need for a fancy IC; just a couple of cheap diodes (or diode-connected
>>transistors) in a bridge, will do ya. Heater in the middle, the one
>>downwind of the heater is ... warmer.
>
>It's warmer at low air flows, then gets cooler again at higher
>velocity.

Description lacks in mechanical details. How to best do this would
depend on structure of air flow.

[Bill Sloman]

On Aug 7, 3:57 pm, John Larkin
<jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
> On Tue, 7 Aug 2012 01:44:09 -0700 (PDT), whit3rd <whit...@gmail.com>

> wrote:
>
>
>
>
>
>
>
>
>
> >On Monday, August 6, 2012 3:27:56 PM UTC-7, John Larkin wrote:
> >> On Tue, 31 Jul 2012 10:22:53 -0700, John Larkin
> >[ on sensing airflow parallel to a board]
>
> >> >Anybody know of a good one?
>
> >> >I guess we could make our own. I was thinking about maybe using two
>
> >> >LM71 temperature sensors, one mounted on a copper pour with a resistor
>
> >> >heater. We don't need a lot of accuracy... this would be mostly a fan
>
> >> >fail sensor.
>
> >No need for a fancy IC; just a couple of cheap diodes (or diode-connected
> >transistors) in a bridge, will do ya.  Heater in the middle, the one
> >downwind of the heater is ... warmer.
>
> It's warmer at low air flows, then gets cooler again at higher
> velocity.

That's why you need a couple of temperature sensors, one to measure
the ambient temperature and the other to measure self-heating of the
dissipating sensor with respect to that ambient.

--
Bill Sloman, Nijmegen

[John Larkin]

On Tue, 07 Aug 2012 07:38:46 -0700, Jim Thompson
<To-Email-Use-Th...@On-My-Web-Site.com> wrote:

>On Tue, 07 Aug 2012 06:57:01 -0700, John Larkin
><jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>
>>On Tue, 7 Aug 2012 01:44:09 -0700 (PDT), whit3rd <whi...@gmail.com>
>>wrote:
>>
>>>On Monday, August 6, 2012 3:27:56 PM UTC-7, John Larkin wrote:
>>>> On Tue, 31 Jul 2012 10:22:53 -0700, John Larkin
>>>[ on sensing airflow parallel to a board]
>>>
>>>> >Anybody know of a good one?
>>>>
>>>> >
>>>>
>>>> >I guess we could make our own. I was thinking about maybe using two
>>>>
>>>> >LM71 temperature sensors, one mounted on a copper pour with a resistor
>>>>
>>>> >heater. We don't need a lot of accuracy... this would be mostly a fan
>>>>
>>>> >fail sensor.
>>>
>>>No need for a fancy IC; just a couple of cheap diodes (or diode-connected
>>>transistors) in a bridge, will do ya. Heater in the middle, the one
>>>downwind of the heater is ... warmer.
>>
>>It's warmer at low air flows, then gets cooler again at higher
>>velocity.
>
>Description lacks in mechanical details. How to best do this would
>depend on structure of air flow.
>
> ...Jim Thompson

Be careful. Geezers can get serious injuries waving your hands around
like that.

[Jim Thompson]

On Tue, 07 Aug 2012 08:27:00 -0700, John Larkin

So how the air flows doesn't matter? You just can't resist being a
crap-head, can you?

[Charlie E.]

On Mon, 06 Aug 2012 15:40:40 -0700, John Larkin
<jla...@highlandtechnology.com> wrote:

>UK.
>
>Why do people think that rising house prices are a good thing?
>
>

Or, why do they seem to think that low interest rates are a good
thing? Right now, I can't get a CD that makes better than 1% interest
unless I am willing to lock up my money for more than three years!
Anyone that has been consciencious (sp?) and saved their money are now
being penalized big time. Banks don't want to pay interest to get
your money, they get their money for free from the government, and
then get to charge you big interest to borrow it. It looks like we
are going to have to take our IRAs over to Etrade and invest them into
dividend paying stocks just to break even... :-(

Charlie

[John Larkin]

On Tue, 07 Aug 2012 09:54:50 -0700, Charlie E. <edmo...@ieee.org>
wrote:

Right. There seems to be a "natural" interest rate of around 3% that
makes an economy work well. [1]

I think the current politically-enforced zero interest rates are a fat
dude sitting on the safety valve. As you note, it's forcing people
into stocks, which the pros on Wall Street skim for fun and profit.
Thieves and idiots are in charge.

[1] Jane Austen in "Pride and Prejudice" refers to people having their
money in "the three per cents."

[Les Cargill]

Dubya/greenspan were *concerned about deflation*. And here we are...
They were, roughly trying to keep very low inflation while still
having something (housing price ) to give people the feeling they had
money.

Dubya is right now doing his "the 4% solution" book tour ( not really
his book, but it's done under the auspices of a think tank that's named
for him ) and what's in it probably won't help. It's more
talking points.

>
> Bubba lit the fuse when he signed the bill that killed the

> Glass�Steagall Act, made worse by Fannie Mae buying up unlimited

> amounts of bad paper, taking the banks off the hook for home loans.
> The government manufactured the crisis.
>

No; the industry did. For one, Glass-Steagall probably had nothing
to do with it ( source Micheal Lewis ), Fannie/Freddie didn't either
(I forget the source ).

Government contribution wasn't *sero*, but it wasn't enough to crash the
thing or even damage things. Also also, several folks have noted that
the housing bubble had nearly nothing to do with the financial crisis,
Scott Sumner prime among them.

bear stearns went to the overnight repo market and failed. That was
the financial crisis.


Sumner thinks there's been inadequate actual liquidity added by the Fed,
the mirror image of the 1970s inflation. That could in fact cause Bear's
failure.

> W is on record as having warned about the real estate bubble, but
> nobody in Congress was listening. Too many people were getting "rich"
> from the appreciation of their real estate.
>

"Houses always go up". Except when they don't. Like ...four?? times
in the 20th Century alone...

> Of course, the same things were happening in Ireland and Spain and the
> UK.
>

Similar, but not the same. Ireland was much more nuts. Spain ... it's
not that clear what happened there, other than Spain having
a poor balance of trade within the EU.

Greece was mainly just graft.

> Why do people think that rising house prices are a good thing?
>
>

Because they'll take that in lieu of rising wages. Even *that*
is more questionable now; the "median income has stagnated" thing
begins to look like "the economy has gotten better at keeping
people with low marginal product employed."

http://www.thebigquestions.com/2012/07/30/the-numbers-racket/

Right now, the fed is paying interest on reserves, which makes all the
monetary easing do ... nothing. So we have the "debt" without actually
having any increase in the useable money supply.


http://blogs.wsj.com/economics/2009/09/16/fed-paying-interest-on-reserves-a-primer/

it's a firehose, but:
http://www.econtalk.org/archives/2012/01/sumner_on_money.html

Not everybody holds to the Sumner theory, but it's little more
than warmed over Milton Friedman. Not a strange thing at all.

>>
>> The Karl Rove approach to economic management - elect a Republican,
>> watch him wreck the economy, then criticise the Democrats for not
>> getting fast-enough recovery. The kind of strategy that can only
>> succeed if the electorate is as poorly informed as the right-wing
>> nitwit clowns who post here.
>
> Hardly anyone - the public, Congress, economists, certainly not the
> President - is thinking long-term. If you keep doing stuff that feels
> good now, but accumulated longterm damage, eventually things get
> worse.
>
>

Hard to actually say that. Lots of stuff can be scrapped if we manage
this properly. The stuff that works is phenomenally
productive.

--
Les Cargill

[Les Cargill]

John Larkin wrote:
> On Tue, 07 Aug 2012 09:54:50 -0700, Charlie E. <edmo...@ieee.org>
> wrote:
>
>> On Mon, 06 Aug 2012 15:40:40 -0700, John Larkin
>> <jla...@highlandtechnology.com> wrote:
>>
>>> UK.
>>>
>>> Why do people think that rising house prices are a good thing?
>>>
>>>
>>
>> Or, why do they seem to think that low interest rates are a good
>> thing? Right now, I can't get a CD that makes better than 1% interest
>> unless I am willing to lock up my money for more than three years!
>> Anyone that has been consciencious (sp?) and saved their money are now
>> being penalized big time. Banks don't want to pay interest to get
>> your money, they get their money for free from the government, and
>> then get to charge you big interest to borrow it. It looks like we
>> are going to have to take our IRAs over to Etrade and invest them into
>> dividend paying stocks just to break even... :-(
>>
>> Charlie
>
> Right. There seems to be a "natural" interest rate of around 3% that
> makes an economy work well. [1]
>

Right - against a trend background of 4% annual GDP growth.

> I think the current politically-enforced zero interest rates are a fat
> dude sitting on the safety valve. As you note, it's forcing people
> into stocks, which the pros on Wall Street skim for fun and profit.

Wall Street per se doesn't even do stocks any more, really.

> Thieves and idiots are in charge.
>

It's possible that our collected fear of inflation is really
at fault. People are still scared of 1979 - you'll see that
on blog postings all the time.

> [1] Jane Austen in "Pride and Prejudice" refers to people having their
> money in "the three per cents."
>
>

--

Les Cargill

[lang...@fonz.dk]

On 7 Aug., 03:26, John Larkin <jlar...@highlandtechnology.com> wrote:
> On Mon, 6 Aug 2012 16:54:03 -0700 (PDT), "langw...@fonz.dk"

I've used PT1000s in "to92" (flat only two legs) but they are not
4cents



-Lasse

[whit3rd]

On Tuesday, August 7, 2012 7:34:17 AM UTC-7, Bill Sloman wrote:
> On Aug 7, 3:57 pm, John Larkin
>
> <jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
>
> > On Tue, 7 Aug 2012 01:44:09 -0700 (PDT), whit3rd <whit...@gmail.com>
>
> > wrote:

> > >No need for a fancy IC; just a couple of cheap diodes (or diode-connected
>
> > >transistors) in a bridge, will do ya.  Heater in the middle, the one
>
> > >downwind of the heater is ... warmer.

> > It's warmer at low air flows, then gets cooler again at higher
>
> > velocity.

I guess I wasn't clear. It's not enough to look at temperature (because
heat shedding by conduction to substrate, or by directed airflow, are indistinguishable).
The intent, rather, was to look at a direction-dependence that only occurs
with airflow IN THAT DIRECTION. So, the sensed quantity is directional heat flow
asymmetry. It works without excellent coupling to the airflow, because
the printed wiring board temperature profile takes on the asymmetry.