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1
Introduce Yourself / From Alsace with love
« Last post by Tommy_Lee on November 29, 2016, 08:27:57 AM »
Hi,

i want to build an heliostat from a long time but never found time for this. Maybe this time will be the good one ;)

2
Heliostat Projects / Re: The easiest and cheapest heliostat project in the world :-)
« Last post by luiklodwig on November 28, 2016, 10:55:41 AM »
Hi

I made some progress!

The heliostat is made from components from servocity. (servo gearbox and tilt mechanism controlled by servo) They are very solid and work fine.

I use a watercut Mirror made from polished v2a steel. (currently 25cm in diameter, will move up to 40)

The camera is the openmv cam. The people behind this helped me a lot with the code for this project. By adding a visibly opaque Kodak Wratten 87C IR pass filter (The lens is fitted already with an IR cutoff filter) I managed to get the camera to detect only the reflectance of the sun as the spot of interest (although other strong IR sources such as a conventional light bulb might cause problems when they show up in the frame of the camera)

In the current setup, the camera observes the target area and stops the heliostat (which is moving around systematically as long as the target was not "hit") when the bright spot is in the center of the frame. Previously I tried to track the sun by letting the camera observe the sky through the heliostat mirror, but that did not work as good because of lensflares and other bright objects that where mistaken for the sun.

while this is certainly not the cheapest option for a working heliostat it is  still sort of easy way to do it because all the components are quasi off the shelf. It is also possible to use cheaper hardware for the two axis heliostat.
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Heliostat Projects / Wi-Fi Controlled Heliostat
« Last post by apurva.acpce on October 12, 2016, 09:57:44 PM »
Hello All,

I am working on Wi-Fi Controlled Heliostat project. the idea is to transfer elevation and azimuth angle values to the receiver modules using XBee WiFi.

I guess I have achieved 50% of the code (Transmitter). I am able to transit
1 = ? (angle values) \\ (Elevation)
2 = ? (angle values) \\ (azimuth)

I want your help for coding the receiver side. please help me with the receiver code. 1 should drive the elevation servo and 2 should drive the azimuth servo connected to arduino Uno and receiver Xbee.


Thank You.


attached is my transmitter code and snapshot of what i am receiving at the receiver end with the help of XBee Wi-Fi.
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Heliostat Projects / Re: The easiest and cheapest heliostat project in the world :-)
« Last post by Gabriel on October 06, 2016, 05:03:48 PM »
Hi luiklodwig,

Those openmv microcontrollers look really cool! This isn't something I've tried before, so I'm not sure what's the best way to do this, but I think you might have to see if anyone has any example code for finding how "bright" the individual pixels are and then moving the motors according to that pixel's location in relation to the center. It's just a thought, but overall you're probably going to have to rely on whatever someone else has already started if you don't want to spend your whole life coding. :)

I think that you could get by without much math really if you can find a library to get you started.

Let us know how it goes.

Thanks!
Gabriel
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Hi everybody.

I like the idea of a camera controlled heliostat. I have a similar idea of  realizing my own. I just ordered openmv.  It is a camera with a microcontroller and some preconfigured basic machine vision functions. I hope I can use this to track the sun.

this is how i would try to set it up:
The camera and the mirror would be mounted  on a 2 axis servo mount in a similar fashion to instructables.com/id/Sunlight-Director/ (exchange lightmeter with cameraboard). Then I would try (this will be the hardest part, I guess) to tell the camera to keep the sun at the center of the frame. If it starts to move outside, adjust the servos accordingly.

Do you guys think could be working? I hope to accomplish my heliostat project without gps and extensive mathematics and coding...

thanks!!
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Sun Tracking / Heliostat Program Discussion Board / Re: heliostat
« Last post by Gabriel on September 23, 2016, 05:06:52 AM »
I'm not sure why it's not showing up. Sometimes you have to click the file in the folder directly. I guess I could have just posted the code in the first place though. :)

The code basically just turns the sun and target's altitude and azimuth into a vector, calculates the half way point between them, and then turns the resulting vector back into altitude and azimuth measurements.

Code: [Select]
//This code calculates the angles for the heliostat (returnaltaz = 1 will return alt, 2 returns az)
void FindHeliostatAltAndAz(float SunsAltitude, float SunsAzimuth, float targetalt, float targetaz, float &machinealt, float &machineaz){

  float x,y,z,z1,z2,x1,x2,y1,y2,hyp,dist;
 
  z1 = sin(to_rad(SunsAltitude));
  hyp = cos(to_rad(SunsAltitude));
  x1 = hyp*cos(to_rad(SunsAzimuth*-1));
  y1 = hyp*sin(to_rad(SunsAzimuth*-1));

  z2 = sin(to_rad(targetalt));
  hyp = cos(to_rad(targetalt));
  x2 = hyp*cos(to_rad(targetaz*-1));
  y2 = hyp*sin(to_rad(targetaz*-1)); 
 
  x=(x1-x2)/2+x2;
  y=(y1-y2)/2+y2;
  z=(z1-z2)/2+z2;
 
  dist=sqrt(x*x+y*y+z*z);
  if ((dist>-0.0001) && (dist <0.0001)){
  dist=0.0001;
  }

  machinealt=to_deg(asin(z/dist));
  machineaz=to_deg(atan2(y*-1,x));

}

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Sun Tracking / Heliostat Program Discussion Board / Re: heliostat
« Last post by mary pascaline on September 22, 2016, 02:26:19 AM »
sorry for the late reply yes that's what i wanted but i search in the arduino IDE i see nothing i can have the link please.
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Hi Boerekos,

I remember you posted a while back. :) Things have been a bit quiet on my end as I haven't had a lot of spare time recently, but have had the chance recently to work on some things.

I have been working on a design that can be printed with a 3D printer. It seems to be going alright, but I still have a ways to go. Plastic is OK for prototyping and playing around, but once I get the design down I think I'll try to make it out of metal. There is actually a place near me that has a laser cutter that I might try getting parts made at.

1) I have played around with a GPS as someone requested the feature for one of their projects. They basically bought me a GPS and I figured out the code. The fact that they keep track of time is definitely an advantage. It's not actually that hard to add as there is example code, but I haven't done anything official yet.

2) Like you mentioned, I'm not aware of an electronic compass that is especially accurate, probably more so with the cheap ones. I actually align mine the same way.

3) I haven't done much for wind protection aside from having a mode where it parks horizontal. There is no automation there. It would be worth adding, but I wonder what it would take to build one that is sturdy enough to hold up to very high winds.

I have built (attempted mostly) heliostats where I was able to focus the reflected light by angling the mirrors. I think I've pretty much decided that it is less work, and possibly even less money, to just rip a hole in the wall and put in a bigger window than it is to try and build a single heliostat that has mirrors that are adjustable. 

I think I'm going to focus on smaller sized heliostats for that reason. :)
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Hi Gabriel,
I am very interested in your project.
I've built my own Heliostat with the help of Mark, from http://heliostaat.nl/.
I bought dual axis gearboxes and Stepper as well as DC motors in the beginning (From China).
I struggled really hard to find someone to build the electronics, although I was prepared to pay a lot of money. The electronic engineers I approached, just did not seem interested, although I was going to pay for their time.

I designed my own hardware bits on Autocad in 3D. I had all the aluminium parts cut out on a waterjet cutter. That was quite interesting how accurate those machines are, and their power. Something like 1900 bar of water mixed with grit. Able to cut through 4 inches or more of solid steel. 
My heliostat is not 100% finished yet, but its been working for a few years. I still need to put the electronic switches for the horizontal and vertical stops in place, so that the motos wont run past certain points.

Unfortunately most of my fun stopped when I got divorced, and now I am renting my property out in S-Africa where the heliostat is, while I am living in Austria.
I had many trails done, and have sent my electronic parts back to Holland several times, so that Mark could make some changes as I wanted it.
My total costs were big, as I also mounted my heliostat on a long lamp post of steel, so that the sun could go into my bedroom on the second storey. Most of the pole is hidden, as it is inside/between the branches of trees. I've spent 1000's (yes, converted to Dollars)

For your project, just my thoughts:

1) GPS is a definite advantage for position AND time, and that was one of my requirements, as Mark only used a DCF time signal, which do not cover South Africa.

2) As I work offshore, and alongside ROV's (Remote operating vehicles) crew, which use fluxgate Compasses: I know that they are not that accurate, like the fibre optic Gyros we sometimes use. I am not sure about the Arduino unit's accuracy.
Point is, you dont need to calibrate the heliostat that often, so that it knows where 0 is. Mark has a simple way of calibrating: You put a cylinder (Tall empty spraypaint/beer can) on top of a piece of paper on the mirror's surface, aim the mirror electronically at the sun, until there is no shadow from the cylinder/can. When there is no shadow, you tell the electronics that "this is the sun's position"
 
3) I have some heavy winds in my area during Winter, and during my first Winter, I had to put my Heliostat to rest a lot of times, so that it wont blow away.. Rest position as you know is horizontal. The heliostat will restart its normal cycle the next morning at sunrise. I had to send my electronic parts back to Mark again, so that he could build an interface for an anemometer. It doesn't measure windspeed, but rotations, but I cant remember at which RPM it triggers the rest command.

I used to like it to get the sun on my bed at the exact sunrise time, or even to wake up, hearing my DC motors waking up.
Same for when the days get shorter. Every day you hear the motors start up in fast mode, to go to the sleep position.

Another nice feature I have, is my remote control, which I can select 3 targets, as well as a target straight to the sun, if you have solar panels.

I do like the idea of Ben, to be able to track the Moon as well :)

I am still looking to change my setup, so that I can set my mirror's angles individually, as I lose a lot of sunlight on the wall next to my windows.
Also, just for interest. Hope that all the fanatics wont drool too much. I saw some solar trackers in Austria. Have a look here:

https://www.smartflower.com/en
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Sun Tracking / Heliostat Program Discussion Board / Re: heliostat
« Last post by Gabriel on August 23, 2016, 05:11:51 PM »
Hi Marie,

I'm not sure if I understand what you are asking, but I don't think the calculations are really posted anywhere on the site. They are in the program though, so you might be able to work them out from the programming syntax.

If you go to the "Functions" tab in the Arduino IDE and then find the "FindHeliostatAltAndAz" function, you will find where the calculations are for calculating the heliostat coordinates. It basically inputs the sun's altitude and azimuth and the desired target altitude and azimuth and outputs the altitude and azimuth direction for the heliostat.

Is that what you are looking for?
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