Author Topic: Sun Tracking / Heliostat Program Update  (Read 43485 times)

Gabriel

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Re: Sun Tracking / Heliostat Program Update
« Reply #105 on: February 23, 2013, 09:20:31 AM »
I also forgot to mention that the "Using the Arduino Sun Tracking / Heliostat Program" documentation page is now finished.
http://www.cerebralmeltdown.com/using-the-arduino-sun-tracking-heliostat-program/


lamineoriska

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Re: Sun Tracking / Heliostat Program Update
« Reply #106 on: May 27, 2015, 07:50:19 AM »
hi gabriel i made a solar tracker but i'm not familiar with arduino programming
i use two stepper motors one 1.8deg/step and the other 7.5deg/step with ULN2803 and RTC DS 1302 with a gearbox for each one the ratio for azimuth stepper motor gear is 3.6
i want to know if i can use your program and what sections i need to change it.
 


Gabriel

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Re: Sun Tracking / Heliostat Program Update
« Reply #107 on: May 28, 2015, 07:32:29 PM »
Hi lamineoriska,

I replied to your PM which has the answer to this question there.

solardude

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Re: Sun Tracking / Heliostat Program Update
« Reply #108 on: August 28, 2015, 02:01:08 PM »
Hi Gabriel!

I'm just now finding your Sun Trackng Arduino Libarary after trying some others in the past.

It seems like you have it up and running now and probably pretty good.

I'm curious how well the code is tracking on a daily basis over a 30 day time frame.  I plan on jumping in and testing also just excited to find what you have going on here. Tracking the sun for peak solar harvest is pretty cool.

Gabriel

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Re: Sun Tracking / Heliostat Program Update
« Reply #109 on: August 29, 2015, 07:09:33 PM »
Hi solardude,

I don't know if you've poked through some of the projects that other people have done, but I think Sid has had his machines up and running the longest, several years now I think. He hasn't mentioned any issue to me since the initial beta testing. There are a few bugs that I have found that I haven't had the time to fix, but it's nothing that should affect the tracking.

Honestly, if you can get the tracker to track well for a couple of hours, it should be fine from then on. One thing to keep in mind is that the time on the RTC will drift, so that at least will need to be updated every so often.

I checked out your site (or at least I assume its your site) by the way. That stuff is really cool. I was actually just looking into portable solar power. I have been considering mounting some small panels to the roof of my car to keep a set of batteries full when camping. Sure a car is more then capable of powering a laptop or smartphone, but if you take into account the fact that you would have to run the car for several hours to recharge the battery on a typical smartphone, it doesn't seem very logical to try.


solardude

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Re: Sun Tracking / Heliostat Program Update
« Reply #110 on: August 31, 2015, 12:15:12 AM »
Thanks for the reply Gabriel! Good to see your still around here and available for discussion.

Yes the website www.PortableSolarPower.Biz is my website and I built all the systems you see on there. Let me know if there is anything I can help you out with as far as your camper setup goes.

 Building really lightweight portable dual axis solar tracker using non glass portable solar panels is something I've been working towards for some time now so I'm happy to see you have the code pretty much nailed down already.

I think eliminating the GPS receiver is a big plus considering how hard it can be to get a good GPS fix. Plus I sell to many people preparing for natural disasters and government collapse where the GPS system may be shut down for civilian use.

I really want to put your code to good use in a few different projects, one of the projects would be a system that can fit into your pocket that will have enough solar panel to charge a cellphone or iPad. Using your code instead of a GPS receiver will cut down on cost significantly.

I'll be sure to look up Sid's project and try to get him to provide some feedback on how everything has been working for him over the long haul.

Can you tell me quickly about the RTC clock drift your experiencing? What is the RTC drift specs for the setup your using Uno or MEGA?

I plan using the Teensy 3.1 micro controller and it has a built in RTC but there is a add on RTC module that self corrects based on temp sensors and it stays in < 2 ppm accuracy. If that's not good enough over time then maybe using a GPS module to update time and the actual GPS location is not a bad idea. Just only use data from it once it has a 3D position lock and then update the location and time then. That would be best of both worlds kinda.

As long as the Time is correct how far out into the future will the Mega version of your tracking code remain dead on accurate as far as the sun's position goes? I've seen other code that has been cut down for the Uno that will only remain accurate for a few years before getting out of wack.

Looking forward to testing this out in the real world.

Gabriel

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Re: Sun Tracking / Heliostat Program Update
« Reply #111 on: September 02, 2015, 07:30:37 AM »
"I think eliminating the GPS receiver is a big plus considering how hard it can be to get a good GPS fix. Plus I sell to many people preparing for natural disasters and government collapse where the GPS system may be shut down for civilian use. "
Yeah that's been my thinking exactly. That's not to say that adding a GPS would hard, but in some ways it's just one more thing to go wrong. Plus adding GPS also adds a lot of cost. It has been awhile since I've looked but I remember that adding GPS would add about $80 to the price. Considering that it only takes a few minutes to set the position manually, it just didn't seem worth it.

I would still like to add a GPS option to the code though. There are situations where it would be cool to have it. When traveling for example. If you search for the username Bob101 on this forum, you'll find a guy who set up a small solar panel that was designed to be mounted on top of an RV and automatically track the sun based on GPS and compass orientation.


According to the datasheet, the RTC's accuracy is:
Accuracy 2ppm from 0C to +40C
Accuracy 3.5ppm from -40C to +85C
Here is the datasheet if you are interested. http://www.mouser.com/ds/2/256/DS3231-102175.pdf

I haven't tested super in depth for drift because, but it seems like they will go for a year or more. There is a certain amount of random chance though when it comes to RTC drift, so it's hard to test unless you have a huge number of RTCs to test. I typically say that the time should be checked at least once a year.

Having high accuracy isn't strictly necessary for sun tracking, so it's not a huge deal if the time is off a bit. This is a somewhat rough comparison, but if you figure that the amount of the sun's energy that is intercepted is modeled by the Cos(degrees pointed away from sun) then you'll find that you can be 8 degrees off and still collect about 99% of the sun's energy.
cos(8 degrees) = 0.990268069 --> 99.0268% of energy is intercepted.

Since the sun moves about 0.25 degrees per minute, we find that the time could be 32 minutes off and and still be intercepting 99% of the sun's energy!

"As long as the Time is correct how far out into the future will the Mega version of your tracking code remain dead on accurate as far as the sun's position goes? " I'm actually not sure. I got the calculations from the book Astronomical Algorithms from Meeus and it doesn't come out and directly say how far you can go with the sun calculations. Or at least, it doesn't say it in any obvious location that I can find. I seriously doubt that anyone living today would need to worry about it becoming inaccurate within their lifetime though.

Gabriel

solardude

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Re: Sun Tracking / Heliostat Program Update
« Reply #112 on: September 02, 2015, 03:01:56 PM »
Quote
Yeah that's been my thinking exactly. That's not to say that adding a GPS would hard, but in some ways it's just one more thing to go wrong. Plus adding GPS also adds a lot of cost. It has been awhile since I've looked but I remember that adding GPS would add about $80 to the price. Considering that it only takes a few minutes to set the position manually, it just didn't seem worth it.

I would still like to add a GPS option to the code though. There are situations where it would be cool to have it. When traveling for example. If you search for the username Bob101 on this forum, you'll find a guy who set up a small solar panel that was designed to be mounted on top of an RV and automatically track the sun based on GPS and compass orientation.


Yea I say add the GPS feature to the code since it does not add to the cost. I'm testing different code that use a GPS receiver output and I like it but the this particular code I'm testing is not accurate. I'm using Adafruits Ultimate GPS receiver and it's cost is $44 for their breakout module.

I know most people would rather just place the tracker outside and wait for the GPS fix to set the coordinates and then once that happens the tracker will start tracking. If the GPS module does not work then they can manually enter the coordinates manually via a few push buttons and a LCD screen.

If GPS does down having a backup manual entry method would be perfect. Like if the world goes to shit and the GPS is cut off to regular civilians, the preppers want their solar generator to keep working when they need it most.



Quote
According to the datasheet, the RTC's accuracy is:
Accuracy 2ppm from 0C to +40C
Accuracy 3.5ppm from -40C to +85C
Here is the datasheet if you are interested. http://www.mouser.com/ds/2/256/DS3231-102175.pdf

I haven't tested super in depth for drift because, but it seems like they will go for a year or more. There is a certain amount of random chance though when it comes to RTC drift, so it's hard to test unless you have a huge number of RTCs to test. I typically say that the time should be checked at least once a year.

Having high accuracy isn't strictly necessary for sun tracking, so it's not a huge deal if the time is off a bit. This is a somewhat rough comparison, but if you figure that the amount of the sun's energy that is intercepted is modeled by the Cos(degrees pointed away from sun) then you'll find that you can be 8 degrees off and still collect about 99% of the sun's energy.
cos(8 degrees) = 0.990268069 --> 99.0268% of energy is intercepted.

Since the sun moves about 0.25 degrees per minute, we find that the time could be 32 minutes off and and still be intercepting 99% of the sun's energy!


That's good news! Your info about collecting 99% of the energy as long as its within 8 degrees of the sun is something I have never heard before. Thanks for that.


Quote
"As long as the Time is correct how far out into the future will the Mega version of your tracking code remain dead on accurate as far as the sun's position goes? " I'm actually not sure. I got the calculations from the book Astronomical Algorithms from Meeus and it doesn't come out and directly say how far you can go with the sun calculations. Or at least, it doesn't say it in any obvious location that I can find. I seriously doubt that anyone living today would need to worry about it becoming inaccurate within their lifetime though.


1-5% accuracy, 100 years out would be great and easily acceptable.