Motor Control

My mechanical system allows only 40 degrees tilt on both sides.

How can I map the Sun's angle of elevation to my mechanism? I am controlling the motor with micro. and feed back is an accelerometer.

If I go with less than 15 degrees every hour then will I be able to follow the Sun for more hours. 

So, with this horizontal axis tracker, there will be significant errors that can not be taken care of by any means. I can not change the mechanical setup of this tracker in any ways. Am I  correct?

What are your thoughts about " Back Tracking" as sown in the following link 


 https://www.youtube.com/watch?v=SJ-DbQwTO-c 


Any suggestions on avoiding the shadow casting of one panel on another! 

On 12/23/15 8:04 PM, Jessica Shaw wrote:
> Hi,
>
> You mentioned that as elevation tracking works if the tracker is near
> the equator but as we move more north or south azimuth becomes
> important.
>
> I am confused that my solar tracking is single axis and my solar
> panel is facing East with tilt -40 degrees measured with my
> accelerometer, the solar panel will travel to +40 degrees facing the
> Sun in the west.
>
> Since, its single axis tracking how can it follow azimuth angle at
> all. Because according to my understanding, I need dual axis motor to
> follow both azimuth ( north to south) and elevation ( east to west)
> to follow the Sun.
>
> In single axis system I can only do east to west and follow just
> elevation angle. How can I follow azimuth with single axis?
>

First, it sounds like you are measuring Zenith angle, not Elevation 
(they are related but measured differently). Elevation is 0 when 
pointing at the horizon, and goes up to 90 when pointing straight up.

Zenith is 0 when pointing straight up, and goes to 90 degrees at the 
horizon (and sign can be used to distinguish direction of rotation).

One way to see why you can use elevation nearer the Equator and Azimuth 
nearer the Poles is look at what happens as we move off the idea point 
and get to mid latitudes. At (local) noon, the panels with the Elevation 
mount will be pointing straight up, but the sun will not be not be 
straight up, but will have a zenith angle roughly equal to the latitude 
(give or take about 23 degrees based on season). This gives you about 
70% efficiency {cos(45 deg)}, slightly better in summer, worse in the 
winter. As you move towards morning and evening, you have a similar 
angle, but the math gets complicated.

If we wanted to convert the system to an Equatorial type mount, you 
raise the Northern end (assuming you are north of the equator) so that 
at noon the panels point directly at the sun at noon (this tip angle 
will again be equal to the latitude). Now the rotation angle is aligned 
with the rotation axis of the earth, and this is called equatorial. For 
solar panels, the question will come at what point does it pay to do 
this. For a large array, the end will get very high which has its own 
problems, or you need to break up the array into smaller pieces with 
more controller expenses.

I am stuck with the following solar panel mount 


 https://www.youtube.com/watch?v=SJ-DbQwTO-c 

It moves from east to west. It has a horizontal axis. I can not do equatorial. All I wanted to know that this solar panel setup can not do azimuth and zenith at all. It can only follow elevation. 

What are your thoughts about " Back Tracking" as sown in the following link 


 https://www.youtube.com/watch?v=SJ-DbQwTO-c 


Any suggestions on avoiding the shadow casting of one panel on another! Any suggestion on the algorithm that I can use to solve this problem. 

On Fri, 18 Dec 2015 10:58:04 -0800 (PST),
lasselangwadtchristensen@gmail.com wrote:

>Den fredag den 18. december 2015 kl. 13.14.18 UTC+1 skrev Jessica Shaw:
>> Hi, 
>> 
>> I am controlling a DC motor via micro. DC motor draws 2A at full load and requires 12V. Motor needs to move 30 degrees after every hour. Total required rotation is 180 degrees. Motor starts from zero degree, moves 30 degrees every hour reaches 180 degree and then travels back to 180 degree without stopping and then repeats, 30 degree every hour.  I am using 12 V 4AH Lead acid battery, 
>> 
>> 
>> Motor moves six times in 6 hours . Each time motor moves 30 degrees, it draws 2A. But it moves for a very little time. How can I calculate that time? 
>> Plus what would be current draw for the entire cycle? 
>> How long the batteries will last without charging? 
>> 
>> jess
>
>not enough info, the naive upper limit is 4AH/2A  = 2 hours of motor run time
>you need to find out how long each 30 degree move takes and how much the motor is loaded
>
>-Lasse

The OP is clearly a troll. The task looks like some university
homework.

In any civilized country (I do not know about the USA), persons with
so little mathematical and physics knowledge would be admitted to
study.
.

Any suggestions on avoiding the shadow casting of one panel on another! 

Any suggestion on the algorithm that I can use to solve this problem.  I found the following link 

http://www.lauritzen.biz/static/solutions/backtracking.pdf

On 12/24/15 10:37 AM, Jessica Shaw wrote:
> I am stuck with the following solar panel mount
>
>
> https://www.youtube.com/watch?v=SJ-DbQwTO-c
>
> It moves from east to west. It has a horizontal axis. I can not do
> equatorial. All I wanted to know that this solar panel setup can not
> do azimuth and zenith at all. It can only follow elevation.
>
zenith is measuring angle from vertical, elevation is measuring angle 
from horizontal, so they are just different ways of talking about the 
same thing. The angles you quoted where 0 straight up, which is a zenith 
angle (it may be that the manufacturer is using the wrong word in their 
description, giving you the wrong idea).

Note that the system listed can do a limited form of equatorial, as they 
allow a 15 degree tip of the array. Depending on where you are, that 
might help some (or depending on how big, it might get things too high, 
which is why they talk about for south facing hillsides).

> What are your thoughts about " Back Tracking" as sown in the
> following link
>
>
> https://www.youtube.com/watch?v=SJ-DbQwTO-c
>
>
> Any suggestions on avoiding the shadow casting of one panel on
> another! Any suggestion on the algorithm that I can use to solve this
> problem.
>

It is basically simple math once you can compute the suns position. You 
limit the angle of the arrays so that the ray from the sun that just 
hits the back edge of the first panel also just hits the front edge of 
the second panel.

i suspect it helps as the efficiency of a panel is best when it is 
uniformly illuminated (not shadowed).

Thanks for the reply! Can you give me the formula or Do you know a website or a simple paper where I can find the formula for back tracking. I looked as much as I could but was unable to find one. I found some papers but the math was too complicated. 

On 12/24/15 1:47 PM, Jessica Shaw wrote:
> Thanks for the reply! Can you give me the formula or Do you know a
> website or a simple paper where I can find the formula for back
> tracking. I looked as much as I could but was unable to find one. I
> found some papers but the math was too complicated.
>

I haven't had to work out the formula, so don't have it handy. The most 
complicated part is working out the Sun angle (projected onto your 
panels), but you needed that before.

For back tracking, it is simple Geometry using the spacing between rows 
of panels, the size of the panels, and the angle of the sun to figure 
out what angle to place the panels so they are just on the verge of 
shadowing each other. (There are two possible solutions when you want to 
use backtracking, but you want the 'flatter' one)

On 12/24/2015 12:29 PM, Jessica Shaw wrote:
>
>
> Any suggestions on avoiding the shadow casting of one panel on another!
>
> Any suggestion on the algorithm that I can use to solve this problem.  I found the following link
>
> http://www.lauritzen.biz/static/solutions/backtracking.pdf
>

I don't see how the back tracking shown in your link has much advantage. 
  The panels intercept the same amount of sun when backtracking... no, 
they intercept less sun.  If you keep the panels aimed as closely to the 
sun as possible, they will receive more sun along the edges which don't 
overlap.

The solution to shadow casting is to space the panels further apart. 
That's pretty simple, no?

-- 

Rick

On 12/24/2015 3:40 PM, Richard Damon wrote:
> On 12/24/15 1:47 PM, Jessica Shaw wrote:
>> Thanks for the reply! Can you give me the formula or Do you know a
>> website or a simple paper where I can find the formula for back
>> tracking. I looked as much as I could but was unable to find one. I
>> found some papers but the math was too complicated.
>>
>
> I haven't had to work out the formula, so don't have it handy. The most
> complicated part is working out the Sun angle (projected onto your
> panels), but you needed that before.
>
> For back tracking, it is simple Geometry using the spacing between rows
> of panels, the size of the panels, and the angle of the sun to figure
> out what angle to place the panels so they are just on the verge of
> shadowing each other. (There are two possible solutions when you want to
> use backtracking, but you want the 'flatter' one)

Why would you want to use backtracking?  I think it results in less 
sunlight being collected by the panels.

-- 

Rick