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texaslabrat |
2009-09-13
, 22:56
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Posts: 271 |
Thanked: 220 times |
Joined on Sep 2009
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#251
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Originally Posted by kenny
They are pizeoresistive elements that change their resistance values according to how much mechanical stress they are under. Thus, by measuring how much resistance the element has, you can calculate the force it is being exposed to...and by extension the acceleration (F=ma). There are 3 axis in which these elements are aligned, so you can, with some fancy math, calculate the 3-d force vector the device as a whole is experiencing at a given moment. With the proper axis alignment and equations, you can "simulate" a gyroscope's ability to measure angle changes in most cases.
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2009-09-13
, 23:12
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Posts: 227 |
Thanked: 53 times |
Joined on Feb 2008
@ Lyon, France
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#252
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A DigiTimes article from 2008 said that there would be gyroscopes in smartphones in 2009.
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2009-09-14
, 00:40
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Posts: 271 |
Thanked: 220 times |
Joined on Sep 2009
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#253
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Originally Posted by vinc17
I guess if you were trying to build an inertial guidance system, they would be useful (if you had something against gps, or couldn't use it for some reason). However, the simple task of detecting the orientation of the handset is easily accomplished with the accelerometer (gravity points down...look for the force vector corresponding to 9.8m/s^2 acceleration and compare to baseline axis orientation to get degrees from vertical)..plus the accelerometer does other things as well (in addition to being immune from the need to be reset/calibrated). For just about every use case I can think of, gps + accelerometer + digital compass trumps the need for a gyroscope set for a non-mission-critical, non-military customer. Since those items have other functions that are useful in their own right...I just can't see the justification for adding the cost of a gyroscope set (3 axes would be an additional $150 plus the added challenge of show-horning them in to an already crowded case).
A DigiTimes article from 2008 said that there would be gyroscopes in smartphones in 2009.
But that's just me...
Last edited by texaslabrat; 2009-09-14 at 01:43.
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2009-09-14
, 01:14
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Posts: 81 |
Thanked: 115 times |
Joined on Jan 2008
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#254
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Originally Posted by texaslabrat
By mechanical stress, do you mean that there is moving parts in there (like a ball that rolls up and down when you tilt it), or what else does it do to induce mechanical stress?
They are pizeoresistive elements that change their resistance values according to how much mechanical stress they are under. Thus, by measuring how much resistance the element has, you can calculate the force it is being exposed to...and by extension the acceleration (F=ma). There are 3 axis in which these elements are aligned, so you can, with some fancy math, calculate the 3-d force vector the device as a whole is experiencing at a given moment. With the proper axis alignment and equations, you can "simulate" a gyroscope's ability to measure angle changes in most cases.
Also wondering if information from accelerometer can be used to make a pedometer app.
Do the current cheap $20 pedometers use accelerometers inside or some other technology?
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2009-09-14
, 01:31
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Posts: 30 |
Thanked: 34 times |
Joined on Aug 2009
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#255
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Originally Posted by iKneaDough
There are a couple of designs for accelerometers. The one that texaslabrat describes doesn't really have (easily visible) moving structures or elements per se. Basically, the way that design works is that you get a crystal structure that has piezoresistive properties. That is, the crystal changes resistance depending on the amount of mechanical force exerted upon it (think about the sensations your body feels when the car accelerates and imagine that your body could change resistance accordingly
By mechanical stress, do you mean that there is moving parts in there (like a ball that rolls up and down when you tilt it), or what else does it do to induce mechanical stress?
Also wondering if information from accelerometer can be used to make a pedometer app.
Do the current cheap $20 pedometers use accelerometers inside or some other technology?
). There are also crystals that have piezoelectric properties which, as you can probably guess, generate a voltage when a mechanical force is induced upon it. There's even a method for building accelerometers by determining changes in capacitance in objects. And to answer your second question, yes, you can build a a pedometer app that uses the accelerometer. Nokia made one for Symbian S60 3rd devices (I used it on my Nokia N95 and it works pretty nicely). I'm not sure but I'd expect the stand-alone pedometers to use both analog as well as accelerometers to detect steps.
Last edited by BadMojoUT; 2009-09-14 at 07:26.
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2009-09-14
, 01:48
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Posts: 81 |
Thanked: 115 times |
Joined on Jan 2008
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#256
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@BadMojoUT : Thanks for your reply! very informative.
Originally Posted by BadMojoUT
Do you mean something like g-force ?
That is, the crystal changes resistance depending on the amount of mechanical force exerted upon it (think about the sensations your body feels when the car accelerates and imagine your body changed resistance accordingly
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2009-09-14
, 01:50
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Posts: 271 |
Thanked: 220 times |
Joined on Sep 2009
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#257
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Originally Posted by iKneaDough
yep...exactly
@BadMojoUT : Thanks for your reply! very informative.
Do you mean something like g-force ?
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2009-09-14
, 21:51
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Posts: 227 |
Thanked: 53 times |
Joined on Feb 2008
@ Lyon, France
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#258
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Originally Posted by texaslabrat
According to Wikipedia, "Relatively inexpensive (less than US$10 per part as of 2009) vibrating structure gyroscopes using MEMS technology are available." That's far from $150.
I just can't see the justification for adding the cost of a gyroscope set (3 axes would be an additional $150 plus the added challenge of show-horning them in to an already crowded case).
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2009-09-14
, 22:58
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Posts: 271 |
Thanked: 220 times |
Joined on Sep 2009
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#259
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Originally Posted by vinc17
Well, I pulled the $150 from the $50 per single-axis MEMS gyroscope I saw priced via a google search. Feel free to show me a source of actual, purchasable gyroscopes of the proper size to fit inside the already crowded case of a phone like the N900 if you like. In any case, as I've outlined...gyroscopes are largely superfluous anyway as the accelerometer can replace them in virtually all use cases you'd want with a phone (with gps and/or digital compass filling in the gaps) plus, as I've also said before, gyroscopes require occasional resetting/calibration and thus are not a "fire and forget" proposition. What is it with you and gyroscopes, anyway? You own stock in a gyroscope manufacturer?
According to Wikipedia, "Relatively inexpensive (less than US$10 per part as of 2009) vibrating structure gyroscopes using MEMS technology are available." That's far from $150.
Last edited by texaslabrat; 2009-09-14 at 23:02.
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2009-09-14
, 23:43
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Posts: 227 |
Thanked: 53 times |
Joined on Feb 2008
@ Lyon, France
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#260
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Originally Posted by texaslabrat
With a Google Search: US$4 for a single-axis gyro sensor. The size is 5x5x1.5mm. But miniature gyroscopes are very specific, and I suppose that large companies like Nokia would have better sources than a quick search on Google.
Well, I pulled the $150 from the $50 per single-axis MEMS gyroscope I saw priced via a google search. Feel free to show me a source of actual, purchasable gyroscopes of the proper size to fit inside the already crowded case of a phone like the N900 if you like.
Originally Posted by texaslabrat
This isn't just me. Look at all the articles on the web. From the Digitimes article: To make their mobile devices appeal to more consumers, smartphones launched by Nokia, Samsung Electronics, Motorola, LG Electronics, Sony Ericsson and Apple, are all expected to come with MEMS gyroscopes in 2009, the sources said. And why does the PS3 controller have a gyroscope instead of accelerometer?
What is it with you and gyroscopes, anyway?
Originally Posted by texaslabrat
LOL!
You own stock in a gyroscope manufacturer?