Searching \ for '[ot]: little gyro question' in subject line. ()
Help us get a faster server
FAQ page: massmind.org/techref/index.htm?key=little+gyro+question
Search entire site for: 'little gyro question'.

Exact match. Not showing close matches.
'[ot]: little gyro question'
2001\10\10@200133 by

hello,

I was thinking of trying to make an electronic level.  And I thought the
tiny gyros might be used to do this.

I don't have one and I was wondering if someone had a recomendation for
an inexpensive one that could do the task?

Do these things have a built in zero point that you can check against to
tell when something is tilting a degree up or down?  Or how do they work
exactly?  Do you turn them on, and then they align themselves to the
vertical?

or what?

Thanks

--
http://www.piclist.com hint: The list server can filter out subtopics
(like ads or off topics) for you. See http://www.piclist.com/#topics

Hi!

You don't want to use tiny gyros (which are, AFAIK, all rate gyros) because
they only output rate of rotation. So, you actually have to integrate their
output to get angle. This means that they do not know the difference
between level and a 45 deg angle, they can only tell you how much you
rotated from a starting angle. In addition, any tiny offset error in their
output gets integrated to a continuous drift (rise or fall in output
angle). They are best for situations where you need to determine how
something is rotating even when it is not an inertial frame (i.e., if it is
accelerating).

If you simply want to make a level which will sit still on top of something
and tell you whether it is tilted, an accelerometer would be a better
choice. Accelerometers can measure the force of gravity (indirectly, by
actually measuring the force which is preventing the accelerometer from
falling) and so if they are tilted, they will register a somewhat reduced
value for gravity. You can even get a 2-axis accelerometer (ADXL202 from
http://www.analog.com) and then you can read out not only tilt angle but also
direction (is it tilted with the left end up or the right end up?). You
could actually do this with only a single axis accelerometer, but you can
get a more accurate reading by using both accelerometers and I don't think
the 202 is any more expensive than its single axis cousins, and it has a
PWM output (instead of pure analog) which makes it easier for a PIC to
handle. I think Analog Devices even has an app note on using them as level
sensors. Note that this only works when the thing is sitting still(or
moving at a constant velocity). It is not accurate if you are jerking it
around or otherwise accelerating it, since it actually measures applied
force, not gravity itself.

Sean

At 07:00 PM 10/10/01 -0500, you wrote:
{Quote hidden}

----------------------------------------------------
Only \$9.95 per month!
http://my.netzero.net/s/signup?r=platinum&refcd=PT97

--
http://www.piclist.com hint: The list server can filter out subtopics
(like ads or off topics) for you. See http://www.piclist.com/#topics

I'm not a technical bod but I use a gyroscopic sensor for orientation
tracking for virtual environments. The thing is that the gyroscope does
not have any external reference, used for tracking it is its opening
orientation that provides the reference to which all other measurements
are made. If one wanted to make a level it is exactly this kind of
reference that one would need. You'd need a level to set up your level!!
Having said that it might give you an accurate measure of any deviation
off of that reference. Having said that in 3d graphics the maths that
you need to do that within a 3d environment is not straight forward.

If what I've said is wrong I'd be very interested in hearing the
reasons why.

all the best,

Mark

On Wed, 10 Oct 2001 19:00:42 -0500 rad0 <rden25MINDSPRING.COM> wrote:

{Quote hidden}

************************************************
Dr Mark Palmer
Arts & Humanities Research Board Fellow
School of Art & Design
Staffordshire University
Stoke-on-Trent
ST4 2DE
tel:    +44 (0)1782 294802 (direct)
fax:    +44 (0)1782 294873
M.W.Palmerstaffs.ac.uk
************************************************

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.

The original post was actually concerned with how to make a decent
electronic level indicator.

If the level indicator is used in the normal way that a bubble
level indicator is used (i.e. to measure inclination of a stationary
object, such as a table top or brick wall), then you can make
a quite simple one using a potentiometer. You start with a flat base.
This becomes the part that will rest on the surface whose inclination
you want to measure. At a right angle to the base you attach an
upright that is several inches tall. Mounted to this upright
is a standard linear pot. Something in the range from 1k to 50k
would be fine. It is not important what the pot's value is, but
you want a pot that has low friction at the shaft.

The body of the pot is firmly fixed to the upright. Rotate the
pot to the approximate center of rotation. To the pot's
shaft attach a stiff metal rod that has a reasonable sized weight
attached to the far end of the rod. Connect one side of the pot
to ground, the other side to a voltage source, such as +5 v.

Output is measured between the ground and the wiper of the pot.
Let's assume you are using a PIC to measure the inclination angle.
Place assembly on a known flat surface. Push "level" button.
PIC reads voltage and stores it as zero reference. Incline
unit some predefined calibration angle, such as 30 degrees.
Push the "calibrate 30" button. PIC measures voltage, finds
difference between level and 30 degree values, divides by 30 and
comes up with the delta value per degree of inclination.

Now, as the device is placed at various degrees of inclination,
the PIC reads the current voltage, subtracts it from the
reference voltage, determines +/- , if it is negative, then
a minus sign is displayed and the value is converted to its
positive equivalent. The current delta value is divided by the
delta value per degree and then this value is displayed on the

Instead of a PIC you could use a couple of op amps and a few
trim pots to adjust zero point and circuit gain so that the
output voltage would be scaled to something like .1 volt per
degree. You could drive an analog or digital voltmeter
direct with this arrangement.

Fr. Tom McGahee

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.

>
> hello,
>
> I was thinking of trying to make an electronic level.  And I thought the
> tiny gyros might be used to do this.
>
> I don't have one and I was wondering if someone had a recomendation for
> an inexpensive one that could do the task?

http://www.bubblesoftonline.com/projects/incline.html

--
Best regards

Tony

mICros
http://www.bubblesoftonline.com
salesbubblesoftonline.com

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.

rad0, I think that you are mixing two things here. I think that the little
gyros you mention are actually Tokin and Murata pizoceramic rate gyros.
These only indicate change of radial speed (angular acceleration) and have
no zero or verticality indication.

For an inclinometer try an inclinometer (or clinometer) sensor. These are
mass produced for the automotive industry (alarms). You can also use a
monolithic 2-axis accelerometer (ADXL...) for the same thing. You can also
diy using a pendulum or half wheel in various combinations.

Peter

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.

Hi Peter,

I agree with your conclusions, but just one correction: the piezoelectric
rate gyros indicate angular speed directly, not angular acceleration. In
other words, you only have to integrate once to get position. Because of
the need for integration and a starting reference, they are not suitable
for a level sensing application, but they aren't quite as bad as, say,
using accelerometers to get position, where you have to integrate twice.

Sean

At 01:12 AM 10/12/01 +0200, you wrote:
{Quote hidden}

----------------------------------------------------
Only \$9.95 per month!
http://my.netzero.net/s/signup?r=platinum&refcd=PT97

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.

{Quote hidden}

Yeah, I had seen a circuit in Elektor Electronics a couple of years back
(1998 ?)
Which did this using a single Analog Accelerometer and two led bars.
It was titled "Electronic Spirit Level". It did'nt use any Micros.
Perhaps you could find it on the elektor website.

Jeethu Rao

--
http://www.piclist.com#nomail Going offline? Don't AutoReply us!
email listservmitvma.mit.edu with SET PICList DIGEST in the body

thanks to the gentleman who suggested the
two axis ADL device, I think I'll check that out...

what I really wanted was something I could put on top
of a post, that could help me align it vertically...

--
http://www.piclist.com hint: To leave the PICList
piclist-unsubscribe-requestmitvma.mit.edu

A non-electric analog method:

Find a string and a weight, something pointy is good.  Hold the loose end at the top of the post, and line it up with the weighted string.  Works on most planets.  with a decent gravitational field.

alice
--

_______________________________________________
Sign-up for your own FREE Personalized E-mail at Mail.com
http://www.mail.com/?sr=signup

--

2001\10\14@113737 by
yeah, if you have room, and you have a way to connect it,
and you don't want to make a generalized product...

thanks for the contribution...

{Original Message removed}
> what I really wanted was something I could put on top
> of a post, that could help me align it vertically...

You definitely need an inclinometer. The easiest is a plumb line, followed
by a bubble level, but this uses no pics...

Peter

--

> A non-electric analog method:
>
> Find a string and a weight, something pointy is good.
> Hold the loose end at the top of the post, and line it
> up with the weighted string.  Works on most planets.
> with a decent gravitational field.
>
> alice

Hello Alice,

Your answer is correct, if considering the planet a perfect spherical shape.
Are the Earth planet a good spherical shape? The planet (as almost others
around) is a little bit "fatty" at the Equator, so, what happens at 19
degrees south or north? the pointy weight will be pointing to the
gravitational field center, but the vertical line will not be exactly at 90
degrees relative to the horizontal surface... a little bit off, right?  The
buildings will not fall down, but the grounds would seems to be descending
when walking toward the poles, isn't it?

The american expression "up north" seems a little bit wrong. Walking from
the North Pole or South Pole towards the Equator, it is always UPWARD the
terrain, so, americans should say UP-SOUTH or DOWN-NORTH instead...

messing, eh?

:)

----------------------------------------------------------------------------
----
Wagner Lipnharski - Director - wagnerustr.net
UST Research Inc. - Orlando - FL - http://www.ustr.net

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.

'[ot]: little gyro question'
2001\11\01@235752 by
> > A non-electric analog method:
> >
> > Find a string and a weight, something pointy is >

> Hello Alice,
>
> Your answer is correct, if considering the planet a perfect spherical shape.
> Are the Earth planet a good spherical shape? The planet (as almost others
> around) is a little bit "fatty" at the Equator, so, what happens at 19
> degrees south or north? the pointy weight will be pointing to the
> gravitational field center, but the vertical line will not be exactly at 90
> degrees relative to the horizontal surface... a little bit off, right?  The
> buildings will not fall down, but the grounds would seems to be descending
> when walking toward the poles, isn't it?

Well, it's actually even worse than you describe.  Any tall mass will deflect the plumb bob.  The Brits in the 18th century had a heck of a time measuring the height of Mt Everest, because its mass deflected the plumb bob of the surveyor, and the vertical angle to the peak was always off.  That, and the mountain has a big 'root' beneath it, that adds even more mass off at an angle.

In fact, that's the way they proved that most mountains Have roots by measuring local deflections in the gravitational field.

I suppose we even need to take the thickness of the sring into account, and use monofilament instead of hairy old twine for more accuracy.

welcome back

alice
--

_______________________________________________
Sign-up for your own FREE Personalized E-mail at Mail.com
http://www.mail.com/?sr=signup