Is it level or not...Memsic 2125

deno

Hello fellow stampers...again..

Been playing around with Memsic 2125 Dual-Axis Accelerometer and have just a couple of questions about it.

1. If the device is plugged into the breadboard, and the breadboard is level (using a two axis bubble level) on the work table, how level should the readings from the device showing in the DEBUG window be? I am refering to the computed degree reading? · What is the tolarance?

2.What is pin 1...labeled "T out"?

3. With the breadboard standing vertical in either axis, I read a max of about 60 degrees, is this right?

I should say that the degree reading doesn't mean much to me, as I will be using the raw readings to produce the necessary motor drive outputs, but I was just wondering if the device should be reading zero when on a level plane.

Thanks...Deno

Post Edited (deno) : 8/25/2005 1:41:32 AM GMT

cyberbiota

Deno-

According to the Memsic datasheet:

"TOUT – This pin is the buffered output of the temperature sensor. The analog voltage at TOUT is an indication of the die temperature. This voltage is useful as a differential measurement of temperature from ambient and not as an absolute measurement of temperature."

As for your other questions- I have not used this device, but would be surprised if the values at 0 and 90 degrees were exactly right. There is bound to be some offset which will need to be dealt with in code.

peter

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Peter C. Charles

Director, Research and Technology
CyberBiota, Incorporated
Peter.charles@cyberbiota.com
http://www.cyberbiota.com

Chris Savage

deno,

·· You can find additional information about the device here at the bottom of the page.

http://www.parallax.com/detail.asp?product_id=28017

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Chris Savage
Parallax Tech Support
csavage@parallax.com

T!

deno said...
Hello fellow stampers...again..

Been playing around with Memsic 2125 Dual-Axis Accelerometer and have just a couple of questions about it.

1. If the device is plugged into the breadboard, and the breadboard is level (using a two axis bubble level) on the work table, how level should the readings from the device showing in the DEBUG window be? I am refering to the computed degree reading? · What is the tolarance?

2.What is pin 1...labeled "T out"?

3. With the breadboard standing vertical in either axis, I read a max of about 60 degrees, is this right?

I should say that the degree reading doesn't mean much to me, as I will be using the raw readings to produce the necessary motor drive outputs, but I was just wondering if the device should be reading zero when on a level plane.
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As the device changes temperature the raw numbers will change a bit.· Also remember that the chip itself may not quite be level as soldered on the 6 pin header.· And the header may not be perfectly level in the breadboard.· So a level breadboard does not mean a perfectly level 2125.· How I got around this was to use a button and code that grabs a raw reading and then uses that to offset or correct for zero, the button becomes a "This is zero" input.
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Pin 1 has been addressed by others...but it could be used to stabilize the drifting raw numbers.
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The math used by many to calculate the angle falls off in accuracy as the angle aproaches 90 degrees.
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T!

Noodles

The memsic code supplied from both memsic and parallax has some fatal errors (If you ask me). They neglect to adjust for timeing differences between the stamps. Parallax code snips for the memsic and other PWM input projects can fix this I have placed conditional compile blocks in each of the code snips to adjust for the differences in timing without theese you will be very confused as to why the data looks like trash...as was I because the memsic and parallax bothl assume that you have used this type of input and are aware of the different time units used or own a bsII and could care less, but thats a bad habit and you should always attemt to write you code for a broad platform where possible this helps others and you if you ever move to another stamp you will not go nuts tring to port the code. well without further adue here is my memsic code, fully commented where available. eMail me at rjdaggett@gmail if there are errors or questions...as i'll be more then happy to help, correct or complain.

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·"We Are Not Human Beings Having·A Spiritual Experience,

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Noodles

P.s. dont use the raw data to level as it would be impossible to level the PC board on you bread board, when mounted use the software to set this as your reference point (calibration) unless it's grossly off. I have used this on my tilt pan and I am able to get +/- 45 deg from level this is a hardware limit if you look at how the unit operates it is not able to collect unough data to make a good angular reading, case in point the rotation file above use the sensor mounted 90 deg verticlly to dertermine the angle of rotation this is the only data availble at this sensor position.

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·"We Are Not Human Beings Having·A Spiritual Experience,

··············... We Are··Spiritual Beings Having·A·Human Experience"