Accelerometer

Hi,

I am controlling a single axis DC motor to follow the elevation of the Sun using two light sensors. The motor moves 180 degrees in a day.

The control circuitry of the motor ( solar tracker) will be mounted on the moving solar panel mechanical assembly. I want to know the changing tilt / position.


I choose the following accelerometer to calculate the tilt from dimension engineering

https://www.dimensionengineering.com/datasheets/DE-ACCM3D.pdf

The accelerometer part number is ADXL335B. The accelerometer is 3 axis. It operates at 3.3V with sensitivity of 333mV/g. Its data sheet is as follows

http://www.analog.com/media/en/technical-documentation/data-sheets/ADXL335.pdf


My questions are

1. How to choose the accelerometer for such an application?
2. Did I choose the right accelerometer? Can it follow 180 degrees? How should I proceed with the software?

jess

 

[Jasen Betts]

On 2015-11-29, jsscshaw88@gmail.com <jsscshaw88@gmail.com> wrote:

Hi,

I am controlling a single axis DC motor to follow the elevation of the Sun using two light sensors. The motor moves 180 degrees in a day.

The control circuitry of the motor ( solar tracker) will be mounted on the moving solar panel mechanical assembly. I want to know the changing tilt / position.


I choose the following accelerometer to calculate the tilt from dimension engineering

https://www.dimensionengineering.com/datasheets/DE-ACCM3D.pdf

The accelerometer part number is ADXL335B. The accelerometer is 3 axis. It operates at 3.3V with sensitivity of 333mV/g. Its data sheet is as follows

http://www.analog.com/media/en/technical-documentation/data-sheets/ADXL335.pdf


My questions are

1. How to choose the accelerometer for such an application?

it seems ok.

2. Did I choose the right accelerometer? Can it follow 180 degrees?
How should I proceed with the software?

I would have chosen with with built-in DAC

180 degrees is no probelem

atan2()

--
\_(ツ)_

 

Hi,

The thing is that I measured single x axis tilt with respect to earth. The accelerometer was sitting flat on the table. I used arc sin to calculate the tilt. I used protractor to confirm the calculated tilt. It was ok.

Then I measured single y axis tilt and used arc sin and the result was good..

I get confused when I tried to measure the tilt with x and y axes. Someone advised me to measure the tilt using "arc tan" and with respect to z axis. How does this work?

I will mount the accelerometer on the box and the box will move with the panel from its resting position. There will be some values of x, y and z. I will subtract these values from the future values of the x, y and z and calculate the tilt or current position using arc tan.

I sound confused and horrible. Please help what direction should I take.
jess

 

[Tim Wescott]

On Mon, 30 Nov 2015 07:08:35 -0800, jsscshaw88 wrote:

Hi,

The thing is that I measured single x axis tilt with respect to earth.
The accelerometer was sitting flat on the table. I used arc sin to
calculate the tilt. I used protractor to confirm the calculated tilt. It
was ok.

Then I measured single y axis tilt and used arc sin and the result was
good.

I get confused when I tried to measure the tilt with x and y axes.
Someone advised me to measure the tilt using "arc tan" and with respect
to z axis. How does this work?

I will mount the accelerometer on the box and the box will move with the
panel from its resting position. There will be some values of x, y and
z. I will subtract these values from the future values of the x, y and
z and calculate the tilt or current position using arc tan.

I sound confused and horrible. Please help what direction should I take.
jess

You haven't defined your axes.

Each axis should respond to the acceleration due to gravity as cos
(theta), where theta is the angle of _that axis_ from vertical (so you
really have theta_x, theta_y, theta_z).

You ought to be able to work backwards from there, after coiling yourself
in much trigonometry. It's best to do the math yourself -- that way you
know that it applies to your situation, and you're not depending on
someone else's competence or assumptions.

--
www.wescottdesign.com