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'PIC-based angle sensor...'
1997\12\04@111834 by Jeff Cesnik

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Does anyone have any sources for low-cost micromachined printed-circuit
mount gyroscopes?  I'm contemplating building a pic based 2-axis angle
sensor with serial output, but I can't find the gyro parts anywhere...

-Jeff Cesnik

1997\12\04@154313 by Andrew Mayo

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You *might* be able to do what you want with an accelerometer. Analog
Devices make a monolithic unit with good resolution. Three of these
mounted at right angles will sense pitch yaw and roll, possibly with
adequate resolution for what you want.

{Quote hidden}

1997\12\04@155624 by John Shreffler

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part 0 968 bytes
-----Original Message-----
From:   Andrew Mayo [SMTP:andrewspamKILLspamGEAC.CO.NZ]
Sent:   Thursday, December 04, 1997 3:40 PM
To:     .....PICLISTKILLspamspam.....MITVMA.MIT.EDU
Subject:        Re: PIC-based angle sensor...

You *might* be able to do what you want with an accelerometer. Analog
Devices make a monolithic unit with good resolution. Three of these
mounted at right angles will sense pitch yaw and roll, possibly with
adequate resolution for what you want.

{Quote hidden}

1997\12\04@170231 by TONY NIXON 54964

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I'm making a single axis angle sensor using an ADXL05. It's accurate
down to 1/10th of a degree over about 120 degrees as long as there is
some sort of temperature stabilization/compensation.


Tony


Just when I thought I knew it all,
I learned that I didn't.

1997\12\04@173252 by Raak, Cory

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I have heard of something on the net that used several of these Analog
Devices sensors and therefore would possibly give you your gyro effect,
they were based on the ADXL05 sensor and I believe that an ADXL05 is a
micromachined sensor.  As you turn the sensor array in any direction you
would get a several analog voltages out depending on which way you
rotate the array, sending these voltages into a pic you get differences
between them which could be extrapolated into position of direction on
or in a sphere.  Does that make sense to anybody, maybe someone else
could explain that better!!!
Now going farther you can use that to control a device that thrusts
upward with some type of thrust vectoring control and now you have a
vertical take off and landing craft, I was thinking of a disc shaped
object with a fan jet blowing down and then controlling which way the
air stream is directed according to where your sensor says your tip
angles and where you want to go!!!
Well that is a long enough reply!!!
Sorry about the bandwidth waste but I think several picks could do this
rather well!!!!!!!!!

{Quote hidden}

1997\12\04@192842 by Bob Blick

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About how much do ADXL05's cost? Analog Devices has a small orders
department as I recall, though it seems like something that would be
available from other retail sources.

On Fri, 5 Dec 1997, TONY NIXON 54964 wrote:

{Quote hidden}

1997\12\04@194756 by Andy Kunz

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At 11:14 AM 12/4/97 -0500, you wrote:
>Does anyone have any sources for low-cost micromachined printed-circuit
>mount gyroscopes?  I'm contemplating building a pic based 2-axis angle
>sensor with serial output, but I can't find the gyro parts anywhere...

Try RemoveMEskipTakeThisOuTspamrcboats.com

He has a sensor which measure angle, not angular momentum (a gyro would).

They're cheap enough, and I can help you with code to drive it.

Andy


==================================================================
Andy Kunz - Montana Design - 409 S 6th St - Phillipsburg, NJ 08865
         Hardware & Software for Industry & R/C Hobbies
       "Go fast, turn right, and keep the wet side down!"
==================================================================

1997\12\04@225310 by TONY NIXON 54964

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Analog Devices has a starter kit for the ADXL05's which includes a
small demo board, 2 ADXL05's and documentation for $80.00 Aus.

I just picked one up this morning.


Tony


Just when I thought I knew it all,
I learned that I didn't.

1997\12\05@005644 by Walter Banks

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Andy Kunz wrote:

>Does anyone have any sources for low-cost micromachined printed-circuit
>mount gyroscopes?  I'm contemplating building a pic based 2-axis angle
>sensor with serial output, but I can't find the gyro parts anywhere...

Two sources for small gyro's. Some of the model helicopter
guys are using gyros in control stablization. he smallest of
these are about the size of a dime and twice as thick. One
of the battery powered helicopters in Japan was about a half
a meter long with two gyros in it.

Gyration has some reference designs for embedding gyros that
may be larger than you need at about 1 inch square.

Walter Banks

1997\12\05@081003 by Jeff Cesnik

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I recall seeing the ADXL05 in single units at about $26.00 US (Allied
Electronics).

- Jeff Cesnik


Bob Blick wrote:

{Quote hidden}

1997\12\05@082223 by Jeff Cesnik

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My (vague) understanding of accelerometers is that they can only measure
inertial force, not orientation.  Is there a formula to extract angular
rate information from an accelerometer reading over time? Sure would
save a lot of money on tiny little gyroscopes!  I'm trying to come up
with a fairly accurate (and relatively cheap) way to track position over
time in 2-axis.

- Jeff Cesnik


TONY NIXON 54964 wrote:

> I'm making a single axis angle sensor using an ADXL05. It's accurate
> down to 1/10th of a degree over about 120 degrees as long as there is
> some sort of temperature stabilization/compensation.
>
> Tony
>
> Just when I thought I knew it all,
> I learned that I didn't.

1997\12\05@084545 by Sean Breheny

face picon face
At 08:18 AM 12/5/97 -0500, you wrote:
>My (vague) understanding of accelerometers is that they can only measure
>inertial force, not orientation.  Is there a formula to extract angular
>rate information from an accelerometer reading over time? Sure would
>save a lot of money on tiny little gyroscopes!  I'm trying to come up
>with a fairly accurate (and relatively cheap) way to track position over
>time in 2-axis.
>
>- Jeff Cesnik
>

The problem with using accelerometers to measure position information is
that it requires integrating twice (accel = 2nd deriv of position) and this
means that any little offset error in the output of the accelerometer gets
accumulated over time. So, the setup would be accurate for a little  while
but after a few minutes (a guess abt exact length of time), the whole setup
would need recalabration to be accurate.

If you place an accelerometer at the end of a rod that is in the plane of
roataion which you are trying to sense, the formula for angular
acceleration from the accelerometer output is:

ang. accel. = R * accel. output

where R is the distance along the rod from the axis of rotation to the
accelerometer.

This formula is assuming that the whole setup has no linear acceleration,
ie. it is only rotating, not moving otherwise. If it is also moving, you
can correct for this by placing another accelerometer on the other end of
the rod, such that you now have a rod, the midpoint of which which passes
through the axis of rotation, which lies in the plane of rotation, and has
an accelerometer on each end. Now, the formula becomes:

ang. accel = R/4 * ( accel#1 - accel#2)

where R is the TOTAL length of the rod
and accel#1 and accel#2 are the accelerometer outputs.



Now, you can integrate ang. accel. with respect to time and get an
approximate answer.

IMHO, a gyro would be much more accurate and maybe even not as expensive
(if you end up needing two accelerometers). There is one consideration with
the gyro, though. Due to friction in the gyro bearings and other factors,
the gyro will begin to precess and re-align its axis after a while. So, it
is difficult in general to sense angle by inertial means.

I think that you probably just want to use a plumb weight and an optical
encoder wheel! :-)


Good Luck

Sean




+--------------------------------+
| Sean Breheny                   |
| Amateur Radio Callsign: KA3YXM |
| Electrical Engineering Student |
+--------------------------------+
http://www.people.cornell.edu/pages/shb7
Web Page Under Construction!
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1997\12\05@093739 by Andy Kunz

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>inertial force, not orientation.  Is there a formula to extract angular
>rate information from an accelerometer reading over time? Sure would

Integration.  That's what we do in the "heading hold" gyros for helis.

Andy

==================================================================
Andy Kunz - Montana Design - 409 S 6th St - Phillipsburg, NJ 08865
         Hardware & Software for Industry & R/C Hobbies
       "Go fast, turn right, and keep the wet side down!"
==================================================================

1997\12\05@134412 by Jeff Cesnik

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I completely forgot about R/C heli gyros (I used to fly R/C).  What kind
of output do you get from them?  PWM?  How accurate are they with regard
to temperature and gyroscopic precession?

- Jeff Cesnik


Andy Kunz wrote:

{Quote hidden}

1997\12\05@144236 by XYGAX

picon face
In a message dated 04/12/97  22:49:37, you write:

<< Now going farther you can use that to control a device that thrusts
upward with some type of thrust vectoring control and now you have a
vertical take off and landing craft, I was thinking of a disc shaped
object with a fan jet blowing down and then controlling which way the
air stream is directed according to where your sensor says your tip
angles and where you want to go!!! >>

Could this method be adapted be adapted for Goat transportation from off the
rockery therby saving the roses :---))))

Steve.....

1997\12\06@035804 by Pekka Ritamaki

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I may also inform, that I have just finished 3-axis accelerometer datalogger
for measuring vibration placing new rod under old houses, which are moving.
One such place is in Turku, Finland, where an old  apartment house is moving
near the river Aura. It costs about 5million USD, to correct the problem.
Now local technical University is making standards how contractors can
hammer rod into ground and my company ( PROBYTE) is providing tools for
measurements.
I  used Analog Device's ADXL05 sensor. I designed  PIC-serial output into
sensor, but I used Siemens 80C717A cpu to put data to CMOS-file system. From
there they are moved to Excel-files for further investications. The same
sensor can be used independently as angle, vibration ( mm/s) or
accereration. Output is serial, frequency or voltage, It needs 12V 50mA to
operate. Size is 40*20*30 mm.

1997\12\06@113308 by Andy Kunz

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At 01:36 PM 12/5/97 -0500, you wrote:
>I completely forgot about R/C heli gyros (I used to fly R/C).  What kind
>of output do you get from them?  PWM?

Standard RC-servo style PWM.  They attempt to correct for rotational errors.

The output signal is proportional (not always linearly <G>) to the RATE of
rotation.  That is, a sudden yaw will produce a larger signal than a
smaller one.

>How accurate are they with regard to temperature and gyroscopic precession?

No precession - they are piezo.

As for temperature - they are sensitive to input, but the small changes you
find in "normal" operating temperature range are easily compensated for
with your trims.

The trick is to let the craft achieve the same ambient temperature as it
will have during operation.

Post a note with the title "Arcamax" or "R/C Heli Gyro Help Needed" and you
might get a few more responses.

Whatcha tryin ta do?

Andy

==================================================================
Andy Kunz - Montana Design - 409 S 6th St - Phillipsburg, NJ 08865
         Hardware & Software for Industry & R/C Hobbies
       "Go fast, turn right, and keep the wet side down!"
==================================================================

1997\12\06@174224 by Alf Riisnaes

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I have not been able to read this entire thread, so please ignore if I'm
way off topic!!

RC aircrafts use something called "pilot assist". This is a device that
keeps an aircraft flying in the plane of the earths surface, without the
pilot's input.

One of these devices works as follows: On the bottom of the airplane a
small dome is placed. This dome is equipped with 4 "windows" placed in a
ring, 90 degrees from each other. The device have four "light sensors"
looking out of these windows. By measuring the difference in light
comming into the window, the system is able to determine if the current
window is pointed up into the sky or down towards the ground. Now the
unit can compensate by changing the inputs to the control servos and
move the plane to fly horizontal with the ground. These units normally
controlls the ailerons and the elevator on RC aircrafts.

There are many sources for error in these units, but they work
suprisingly well.

Unfortunately I don't know where you coud get hold of a unit, but there
are plenty of RC magazines or mailorder stores out there.

I hope this is useful for somebody!!

Alf Riisnaes

1997\12\06@192224 by Bob Nelson

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>

About 20 years ago  a man by the name of Maynard Hill for worked for NASA at
Ames research center,  I believe, came up with a very simple auto pilot for
RC planes.  I have the details on this. If any one wants further info on
this please feel free to contact me. I built and tested on of these and it
worked fantastic.   The down side of this is he used  a small RADIO ACTIVE
PARTICLE on the sensor.  You used to be able to buy these in any record
shop. They were attached to little brushes for removing the dust from
records.
With out these I doubt the system would work.

Bob Nelson

TakeThisOuTrinelsonEraseMEspamspam_OUTtcccom.net

1997\12\07@110612 by Mcorio

picon face
In a message dated 97-12-06 19:46:54 EST, you write:

<< About 20 years ago  a man by the name of Maynard Hill for worked for NASA
at
Ames research center,  I believe, came up with a very simple auto pilot for
RC planes.  I have the details on this. If any one wants further info on
this please feel free to contact me. >>

Could you share some overview with us?

Mark A. Corio
Rochester MicroSystems, Inc.
200 Buell Road, Suite 9
Rochester, NY  14624
Tel: 716-328-5850
Fax: 716-328-1144
http://www.frontiernet.net/~rmi
***** Designing Electronics for Industry & Research *****

1997\12\07@192633 by Ram Krishnan

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There are anti-static brushes still being used in the photography biz.
These come in a variety of sizes, and contain a polonium cartridge that's a
mild (so I am told!) radioactive emitter. I also remember reading in an R/C
Modelling magazine (in 1974?) about someone who built a diffrential
electrostatic field sensor with electrodes mounted on each wingtip. The
sensors picked up the gradient of the earth's electrostatic field. If
memory serves, the device was switched in when the plane went into an
uncontrolled spin, and would correct it to level flight. Interestingly
enough, I never heard of this again!

In theses days of femtoamp bias input opamps, rigging one of these should
be a lot easier.

1997\12\08@044805 by n/a
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Ram Krishnan wrote:
>
> I also remember reading in an R/C
> Modelling magazine (in 1974?) about someone who built a diffrential
> electrostatic field sensor with electrodes mounted on each wingtip. The
> sensors picked up the gradient of the earth's electrostatic field. If
> memory serves, the device was switched in when the plane went into an
> uncontrolled spin, and would correct it to level flight.


The Electrostatic Autopilot was developed by Maynard Hill, of the Johns
Hopkins Applied Physics Lab. They apparently flew it many times,
although the unit was susceptible to unstable weather- eg. thunderstorms
in the vicinity.

There was a full article (schematics, theory, etc.) in a "Journal of
Aircraft" or "AIAA Journal" from the late 70's IIRC.


---------------------------------------
           Anton Coetzee
      RemoveMEAnton.CoetzeespamTakeThisOuTvip.co.za

      FibreFlight Composites

---------------------------------------

1997\12\08@125806 by Bryson, William G (Bill)

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I once made a negative ion generator that was based on one of these
devices.  The one I used was .5 micro-curie of radium sulfate.  This was
placed in a plastic housing that was designed to sit next to the
spinning record..  I attached the device to a wire mesh screen to which
I applied a negative 600 volts.  A fan blew the negative ions off the
screen.  Don't know if this device is still available.  That was back in
1964...

-------------------------------------------------
Work all day & night,
deliver on time & on budget,       Regards,
and justice for all...             Bill Bryson


>{Original Message removed}

1997\12\08@150950 by Sean Breheny

face picon face
What is the purpose in putting radioactive substances in these brushes? Is
it to help ionize the air so there will be less static buildup?

Sean


At 11:55 AM 12/8/97 -0600, you wrote:
{Quote hidden}

>>{Original Message removed}

1997\12\08@163437 by DREITEK

picon face
In a message dated 97-12-08 13:45:18 EST, you write:

<<
I once made a negative ion generator that was based on one of these
devices.  The one I used was .5 micro-curie of radium sulfate.  This was
placed in a plastic housing that was designed to sit next to the
spinning record..  I attached the device to a wire mesh screen to which
I applied a negative 600 volts.  A fan blew the negative ions off the
screen.  Don't know if this device is still available.  That was back in
1964...
 >>
Static Master makes these in all shapes and sizes!  We use them on our
machinery to cut static buildup on a moving Mylar web.

Dave Duley
V.P. Dreitek Inc.
http://www.dreitek.com

1997\12\08@195158 by Bob Nelson

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Due to the large number of responses I have had to the Maynard Hill " auto
pilot" I thought that a responce here would be OK rather than send a
responce to everyone..

I can't put my hands on the magazine at this time but will try to find it.
For now I will try to explain as best I can remember.
The theory of operation is that there is a static charge in the atmosphere.
The radio active particles keep the sensors from building up any static
charge.  They used 4 sensors in 2 pairs. one on each wing tip for roll
stabilization, and one on the nose and tail for up and down stabilization.
The sensor were then input to a op amp and the output from it tied into the
radio control servo of  the necesary control.

As someone had commented anything that would upset this static field would
interfer with
the auto pilot.  one time when a thunder storm was about 30 miles away I
turned it on and the thing went crazy.  It was so sensative that to test it
you would run a comb through your hair and hold it next to a sensor.When it
was  about 6 inches away the control would start to deflect.

I will try to find the article, but for those that are really interested I
think that the article was in a 1974 issue of FLYING MODELS.

Also any one wishing to may contact me.
Bob Nelson         rinelsonEraseMEspam.....tcccom.net

1997\12\08@204921 by Larry G. Nelson Sr.

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I remember that article. I think you could also use the source from an
ionizing type of smoke detector. This is what made the system function. You
are correct. Without a radioactive source it would not work. I forget if it
was in Flying Models or Model Airplane News. I think it was Flying Models.


At 06:10 AM 12/7/97 -0600, you wrote:
{Quote hidden}

Larry G. Nelson Sr.
RemoveMEL.NelsonEraseMEspamEraseMEieee.org
http://www.ultranet.com/~nr

1997\12\08@211925 by Andy Kunz

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At 08:42 PM 12/8/97 -0500, you wrote:
>was in Flying Models or Model Airplane News. I think it was Flying Models.

I might have the FM issue - I have tons of them.  They are local for me, in
fact the former editor (Bob Hunt) lives 15 minutes from my house and was
just over the other night to borrow my video camera.

They are cool guys.

If you ever happen to be in northern NJ and are interested, give them a
call and check out their "museum" lobby.  The best of all the Carstens
stuff through the ages, trains and all.

Definitely check it out.

Andy


==================================================================
Andy Kunz - Montana Design - 409 S 6th St - Phillipsburg, NJ 08865
         Hardware & Software for Industry & R/C Hobbies
       "Go fast, turn right, and keep the wet side down!"
==================================================================

1997\12\09@004243 by Gary Sutcliffe

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>
> I also remember reading in an R/C
> Modelling magazine (in 1974?) about someone who built a diffrential
> electrostatic field sensor with electrodes mounted on each wingtip. The
> sensors picked up the gradient of the earth's electrostatic field. If
> memory serves, the device was switched in when the plane went into an
> uncontrolled spin, and would correct it to level flight.


Yes, that was an interesting article.  The electrodes were small
radioactive sources similar to those used in smoke detectors.  The were
connected to a differential instrumentation amplifier and gave a voltage
relative to the angle.

I experimented with the idea for another application.  It was pretty
sensitive for detecting tilt, but we could not use it for our application.
From time to time you would get false readings in the wind. It seemed there
were small pockets of ionized air that would blow by causing the false signal.

- Gary


------------------------------------------------------------------------
Gary Sutcliffe,  W9XT          Unified Microsystems
RemoveMEppvvppspam_OUTspamKILLspammixcom.com              PO Box 133 Slinger, WI 53086
http://www.qth.com/w9xt        414-644-9036

1997\12\09@085931 by Mcorio

picon face
In a message dated 97-12-08 19:54:20 EST, you write:

<<  can't put my hands on the magazine at this time but will try to find it.
For now I will try to explain as best I can remember.
The theory of operation is that there is a static charge in the atmosphere.
The radio active particles keep the sensors from building up any static
charge.  They used 4 sensors in 2 pairs. one on each wing tip for roll
stabilization, and one on the nose and tail for up and down stabilization.
The sensor were then input to a op amp and the output from it tied into the
radio control servo of  the necesary control.
 >>
What are the sensors detecting as a reference field? The ionosphere?

Mark A. Corio
Rochester MicroSystems, Inc.
200 Buell Road, Suite 9
Rochester, NY  14624
Tel: 716-328-5850
Fax: 716-328-1144
http://www.frontiernet.net/~rmi/
****** Designing Electronics for Research and Industry ******

1997\12\09@104939 by Robert Nansel

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<snip>
> The theory of operation is that there is a static charge in the atmosphere.
> The radio active particles keep the sensors from building up any static
> charge.  They used 4 sensors in 2 pairs. one on each wing tip for roll
> stabilization, and one on the nose and tail for up and down stabilization.
> The sensor were then input to a op amp and the output from it tied into the
> radio control servo of  the necesary control.
>  >>
>What are the sensors detecting as a reference field? The ionosphere?
>
>Mark A. Corio
>Rochester MicroSystems, Inc.

No, it's sensing the electric potential that naturally exists in the
atmosphere, the same one responsible for lightning. With a sensitive
instrumentation amp you can measure the voltage difference between your
feet and your head (usually a couple hundred volts over six feet).

--BN



----------------------------------------------------------------------------
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  69 S. Fremont Ave. # 2     for education and industry"
  Pittsburgh, PA 15202
----------------------------------------------------------------------------

1997\12\09@115134 by bcarlin

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Gary Sutcliffe wrote:
{Quote hidden}

I was told about a company that developed a platform that would replace
gyroscopes in image stabilizers for cameras.  The platform, as it was
described to me, has three accelerometers.  I don't know if it's good
for only one axis (probably so--a camera doesn't need as much control as
an aircraft).  According to the guy who told me about this, it was half
the price of the gyroscopic image stabilizer.

1997\12\09@121453 by Martin R. Green

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face
This might not have much impact.  For one product to supplant another
it must usually be an order of magnitude cheaper or an order of
magnitude better.  Saving 50% is probably not enough to overcome the
inertia facing a new product.

CIAO - Martin.

On Sat, 8 Feb 1997 08:57:15 -0800, bob carlin <EraseMEbcarlinspamspamspamBeGoneSJ.BIGGER.NET>
wrote:

{Quote hidden}

Martin R. Green
elimarSTOPspamspamspam_OUTNOSPAMbigfoot.com

To reply, remove the NOSPAM from the return address.
Stamp out SPAM everywhere!!!

1997\12\09@140332 by Mcorio

picon face
In a message dated 97-12-09 11:11:30 EST, you write:

<< No, it's sensing the electric potential that naturally exists in the
atmosphere, the same one responsible for lightning. With a sensitive
instrumentation amp you can measure the voltage difference between your
feet and your head (usually a couple hundred volts over six feet).
 >>

Is higher potential "always" up??

Mark A. Corio
Rochester MicroSystems, Inc.
200 Buell Road, Suite 9
Rochester, NY 14624
Tel: 716-328-5850
Fax: 716-328-1144
http://www.frontiernet.net/~rmi/
****** Designing Electronics for Research and Industry ******

1997\12\09@142153 by paulh

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face
On Tue, 9 Dec 1997, Mcorio wrote:

> In a message dated 97-12-09 11:11:30 EST, you write:

> << No, it's sensing the electric potential that naturally exists in the
>  atmosphere, the same one responsible for lightning. With a sensitive
>  instrumentation amp you can measure the voltage difference between your
>  feet and your head (usually a couple hundred volts over six feet).
>   >>

> Is higher potential "always" up??

Usually, in calm weather, away from metal structures and far away from
things like high tension lines and megawatt transmitters.  Those are the
prefered conditions for flying RC airplanes, so the device works fine for
that.

I have this old monitor that can create an impressive electric potential.
I suspect that "up" is towards that monitor, whenever it is on.

I don't think I could use one of these devices on my 2 wheeled robot.  The
robot stays upright because the heavy battery is underneath the axle.  If
it accelarates too fast, the robot bangs its head on the floor.  In my
application, sonar from the floor should work just fine.  It has the added
advantage that the robot will be able to detect stairs.

--
spamBeGonepaulhSTOPspamspamEraseMEhamjudo.com  http://www.hamjudo.com
The April 97 WebSight magazine describes me as "(presumably) normal".

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