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'[EE] ADXL311 axis orientation'
2005\06\08@182838 by Mike Hord

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Has anyone any info about the axis orientation on the
ADXL311 accelerometer?

The package in question is the 8-CLCC, which when
viewed undercarriage up has the Vdd at the top,
Xout and Yout on the left, and ST and COM on the
right, with a(an?) NC at the bottom.

My initial impulse is that X goes "left-right" (i.e., the
3-pin sides represent the left and right, and the X-axis
is orthogonal to those edges), while Y goes "up-down".
Of course, we all know what happens when we make
assumptions. ;-)

TFM unfortunately doesn't specify this, nor does the
only app note on the device page at analog.com.  The
axis orientation is important because I'm using two
ADXL chips mounted orthoganally to give me three-
axis acceleration sensing, and I need to know which
of the two axes I need to pull a signal from on the
second chip.

And yes, I do know that there are one- and three-axis
chips out there.  I'm using the ADXL311 because it's
cheap and was in stock at Digikey, it's small (crucial),
and its range meets my needs without vastly exceeding
them.  I know it's being phased out, but that's not
important as this is a one-off.

Mike H.

2005\06\09@112843 by Electron

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>And yes, I do know that there are one- and three-axis

Can you name some of these 3-axis please?


>Mike H.




2005\06\09@122601 by Mike Hord

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> >And yes, I do know that there are one- and three-axis
>
> Can you name some of these 3-axis please?

Analog Devices has one that'll be available RSN; Freescale
makes several.

The only one I see on the Freescale site is the MMA7260Q;
not in stock anywhere I can find.  At any rate, the package
is too large.

Apparently, per Digikey, STMicro makes some, too.  I see
at least three right off labeled as "TRPL AXIS".  Check it
out- I did a DK search on "accelerometer" and selected the
link under "Sensors" in the results.

Mike H.

2005\06\09@125138 by Anthony Van Herrewege

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You could make a simple test jig to check the orientation (with gravity). Of course you're going to need to be carefull not to solder the legs of, but it should't be do-able. If you've got a solder oven it should be a piece of cake.

Anthony


Website: http://members.lycos.nl/anthonyvh

               
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2005\06\09@131317 by Mike Hord

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> You could make a simple test jig to check the orientation
>(with gravity). Of course you're going to need to be carefull
> not to solder the legs of, but it should't be do-able. If you've
>got a solder oven it should be a piece of cake.

Since the end result is essentially a test jig, that's what I'll
do.  I marvel that this information is not bluntly and obviously
presented in the datasheet.

Mike H.

2005\06\09@143506 by Spehro Pefhany

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At 12:13 PM 6/9/2005 -0500, you wrote:
> > You could make a simple test jig to check the orientation
> >(with gravity). Of course you're going to need to be carefull
> > not to solder the legs of, but it should't be do-able. If you've
> >got a solder oven it should be a piece of cake.
>
>Since the end result is essentially a test jig, that's what I'll
>do.  I marvel that this information is not bluntly and obviously
>presented in the datasheet.
>
>Mike H.

The ADXL311 is in phase-out status according to AD. The
suggested replacement (ADXL320) has the information on the data
sheet (page 10). Maybe it's the same..

The ADXL320 is a lot less bulky than the ADXL311 (< half the volume). ;-)

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
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Embedded software/hardware/analog  Info for designers:  http://www.speff.com
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2005\06\09@144616 by Anthony Van Herrewege

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Indeed, it's weird. Check the ADXL203 or 213 datasheet, it's in there and chances are it's probably the same (but then you're assuming, right ;)).

Mike Hord <.....mike.hordKILLspamspam@spam@gmail.com> wrote:

> Since the end result is essentially a test jig, that's what I'll
> do. I marvel that this information is not bluntly and obviously
> presented in the datasheet.

> Mike H.



Website: http://members.lycos.nl/anthonyvh

               
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2005\06\09@144940 by Windman

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Allow me to speculate:

The positive X axis runs parallel to the 1-3 pin side with the + X direction
at the pin 1 end and the Y axis is perpindicular to that and the + Y axis
pointing toward the 5 pin.Something like this:

  +X
1 |^                  | 7

2 |                    | 6

3 |=====> +Y | 5

   Top View

I have no great expectation that the diagram will come out correctly
however.

HTH

Vic
___________________________________________________

Vic Fraenckel
KC2GUI
victorf AT windreader DOT com

2005\06\09@152837 by Steve Murphy

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It is pretty annoying that they don't explain it better. My bet is Y is
the long orientation of the package and X is at a right angle to that,
both on a plane parallel to the circuit board.. Please report back and
let us know.

Mike Hord wrote:

{Quote hidden}

2005\06\09@154126 by Mike Hord

picon face
> My initial impulse is that X goes "left-right" (i.e., the
> 3-pin sides represent the left and right, and the X-axis
> is orthogonal to those edges), while Y goes "up-down".
> Of course, we all know what happens when we make
> assumptions. ;-)

Unbelievable.  I truly expected this would be the way of
it.  Experimentation has shown otherwise.

Thus, let it be hereafter known for eternity in the PICList
archive that the 8-CLCC package of the ADXL311
accelerometer (and likely, Analog Devices' other similar
two-axis devices) has the Y-axis running between pins
2 and 6 and the X-axis between pins 4 and 8.

Random.  But at least it's not in the datasheet!

Mike H.

2005\06\09@160159 by Mike Hord

picon face
> The ADXL311 is in phase-out status according to AD. The
> suggested replacement (ADXL320) has the information on the data
> sheet (page 10). Maybe it's the same..

I think the package is too dissimilar to extract useful information
from it.  They chose a very interesting method for conveying the
information, too.

Phase-out isn't important; one-off and all that.

Plus, the +/-5g range is a little more than I need.  Since this is
going to be used to measure tremors caused by pharmaceuticals,
the actual acceleration range is pretty small- well within the range
of the ADXL311.

> The ADXL320 is a lot less bulky than the ADXL311 (< half the volume). ;-)

Since this thing is being mounted dead-bug (if you can say that,
for a chip with no "legs"), smaller is only better to a point.
This will be dead-bugged to a substrate (piece of Delrin), which
the wires will lead away from to connect to the amp/signal
conditioning box, which then feeds into the rest of the data
acquisition system.

Mike H.

2005\06\09@161514 by Mike Hord

picon face
> It is pretty annoying that they don't explain it better. My bet is Y is
> the long orientation of the package and X is at a right angle to that,
> both on a plane parallel to the circuit board.. Please report back and
> let us know.

The irksome thing is that there IS no "long orientation":  the package
is square, with pads 1, 2, and 3 along one side, 5, 6, and 7 along
the opposite side, and 4 and 8 opposite each other on the other two
edges.

What's more, in the datasheet, the chip is usually pictured from
the underside, with pin 8 being at the "top" of the diagram, and
numbering clockwise from there with 1 at the upper right.

That diagram MIGHT lead one to believe that the X-axis would go
"left-right" (as I speculated in the OP), with the Y-axis orthogonal.
One would be wrong. ;-)  The actual orientation is the other way:
Y goes "left-right" and X "up-down".  Grrr.

Mike H.

2005\06\09@173820 by Steve Murphy

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I for one will sleep better knowing that!  :-)

Mike Hord wrote:

{Quote hidden}

2005\06\10@041908 by Alan B. Pearce

face picon face
>Phase-out isn't important; one-off and all that.
>
>Plus, the +/-5g range is a little more than I need.
>Since this is going to be used to measure tremors
>caused by pharmaceuticals, the actual acceleration
>range is pretty small- well within the range
>of the ADXL311.

<VBG> and once you have built one, and shown the terrific results achieved,
they will want another 5000 for the world wide testing ... ;))

2005\06\10@083630 by Mike Hord

picon face
> >Phase-out isn't important; one-off and all that.
> >
> >Plus, the +/-5g range is a little more than I need.
> >Since this is going to be used to measure tremors
> >caused by pharmaceuticals, the actual acceleration
> >range is pretty small- well within the range
> >of the ADXL311.
>
> <VBG> and once you have built one, and shown the terrific results achieved,
> they will want another 5000 for the world wide testing ... ;))

Nah.  At best, we write a paper on it, publish it, and then finding
the parts is a problem for some sucker in another research lab
somewhere else in the world! ;-)

Mike H.

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