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Messages - solardude

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Sun Tracking Projects / Friction Drives For Solar Tracker Movement ?
« on: October 23, 2015, 01:05:12 PM »
I was excited to see Gabrial post up a sun tracking setup by Nova Solar that is using a friction drive & encoder.

This setup and look is exactly what I'm shooting for so I'm very interested in learning all I can about friction drives and how they work since they may be a better choice than the 12v motors & worm gear drives I'm working with now.

Has anybody else tried using or building a Friction drive before?

Dave with Nova Solar if your out there please chime in if your free! Your set up looks awesome.


I have experimented some with the GPS and Compass code, but it looks like it is probably a bit too complicated to learn to code for it without actually owning the devices. I still need to take another stab at it though.

Give me your address and I'll ship over a Adafruit Ultimate GPS Module + good digital compass for you to play with. I'll also include a Teensy 3.1 micro controller so we will have the same setup to work with for testing into the future.

Here is some code I have been testing that uses the GPS & Compass to track the sun. There may be something in there that you can easily use.


How hard is it to use your current code to power 2 separate worm gear driven 12v motors?


Hey Gabriel  :)

Below are my comments on your reply.

I know your a busy man like the rest of us so I say lets work on adding one new feature at a time and see how that goes. I know others have had the main code up and running for 2 years now with no problems so we know the base sun tracking code is working just fine.

I say forget about any Iphone & Android apps for now since I think your right about it probably driving you nuts when it comes to trying to get it working on all devices and software versions without issues. Plus as Alobo says Blynk is a software platform that has already created a Iphone and Android app that allows you to connect to Arduino boards as long as your Arduino is wirelessly connected to the net which is probably unlikely for a sun tracker but still it worth checking out.

I plan on just adding a low power Sharp Memory LCD to the tracker with a simple button interface that will allow you to enter the GPS coordinates which you can source from a phone, gps tracker, or the internet or a built in GPS receiver. I see no real big benefit of having a custom application for entering GPS coordinates when setting up the tracker but that's just my personal opinion.

What do you think?

Add code for GPS support.  -
I honestly have never even used a GPS with an Arduino, but I suspect that it would probably only take maybe 10 minutes to add the code for it, so why not have it? The code may only exist as something that needs to be uncommented to work, but that would at least be good enough for some rough experimenting. Actually, if anyone has a GPS wired up maybe you can help me test the code.

I have a Adafruit Ultimate GPS receiver that I can use to help test your code. If it's really easy to add support for a GPS Receivers Data Output then lets add it for quick, automatic system GPS coordinate population.

I plan on making portable units that are not permanent so having automatic location entry via GPS would be really nice. Having the option to also enter it manually via a LCD screen and a couple capacities touch buttons is a good backup for the unlikely event that the GPS system fails. A lot preppers buy our systems just to be prepared for the collapse of the financial system, government, or electricity grid, and any of those situations could cause the loss of the GPS system for civilian use should the government want to shut it down. These situations would make renewable energy production even more valuable and important.

If you add GPS support to the code I can and will test it for you and provide detailed testing data for you to review. Let me know what you think.

Add code for Compass support.   -     
Realistically, there is a good chance this will never happen, but like the GPS code I might just stick it in the code commented out so that people can play around with it if they feel like it. It would definitely be cool, but I'm not sure if the compass modules are reliable enough or not.

I've been testing a digital compass with a different solar tracking setup and it can be tricky when you have them close to DC motor magnets since they will throw off the compass readings.

But what I find interesting is that they are using these digital compass chips in quad copters to provide the direction of the travel accuratly even though the compass is surround  by 4 heavy duty DC motors no more than 12 inches apart that are running at high RPM while the quad copter is flying around. So I think there is a digital compass solution that will probably work but more testing is required to find the right digital compass chip for the job.

I have been using a old Honeywell compass and its OK but have a newer compass on hand that I have not had the time to test yet. I picked this compass because guys are successfully using them in their custom quadcopter builds without problems. Here is the compass I have on hand along with a few Adafruit Ultimate GPS modules:

If you add the code for compass support I will do testing on this also and provide detailed testing reports.   


I'm using worm gear drive motors for the dual axis movement and they are very nice because they only require power when the motor is moving and zero power when stopped. This setup has tons of power and holding power when not moving. I see no backlash from my little testing.

I have attached some images of the prototype motor setup I'm testing and happy with so far.


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.

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.

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.

"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.

I'm so happy to see you still working on improving the code :D

I'll be digging in really soon and help with testing the latest version of the code.

Looking at your list of possible upgrades I'll list the ones that I think are most important for my goal of creating a really nice portable lightweight solar tracking device that is easy to use and as automatic as possible by the regular every day person.

Here is what I think is most important, with a person comment next to each one:

Add simultaneous movement to the stepper motors instead of having them take turns. - Code not jamming up is of most important, if this feature has the possibility to cause a MicroController to lock up then leave it out. The solar tracker is going to move minimally anyways. I do think the biggest benefit of having both motors move at the same time is that it would look cooler.

Add better support for machines close to the equator. (Altitude angles greater than 90 degrees perhaps?).  - As somebody who wants to build a low cost easy to use portable tracker I'm very interested in having the code and design work anywhere in the world. Needing altitudes greater than 90 degrees is something I never knew was needed but if it is then I think adding support for this would be beneficial.

Add code for GPS support.  -  Ideally I would like to not use a GPS receiver due to the cost of adding it and the fact that I'm looking to keep the cost to manufactuer as low as possible but I see a real benefit of having a GPS receiver on board to auto populate the GPS position. So maybe only use the GPS location data once it shows you have a 3D location fix. So adding GPS support that can or can not be used would be perfect.

Add code for Compass support.   -      Does the code right now not rely on a digital compass sensor? If not does the solar array have to be aligned manually to noon sun or what?  I have been using a different library with GPS & digital compass for position tracking but I have to admit that the digital compass can be easily thrown off by motor magnets or large metal objects.

Write Android app that sends lat, long, and time to Sun Harvester program using phone's GPS and time. (maybe)    -  I have also thought about this when it comes to making it easier to set the location coordinates. Everybody has a smartphone these days it seems and it would be a easy way to eliminate the need for a on board GPS sensor. My other thought was to just add a LCD screen and a couple cap touch buttons to make entering the GPS coordinates into the tracker. I figured that most people would use their smart phone to look up the coordinates anyways. Have you made a Android app before? I know its getting easier to do these days.

Try and get the program to play well with 32-bit Arduinos.  -   My micro processor of choice right now is the Teensy 3.1 which is a 32 bit ARM . I'm pretty sure it will run your current Arduino code but if running it at 32 bit is beneficial then I think adding that support would be good. Does 32 bit math allow more accurate tracking?

Just my 2 cents. I know not everybody is using this for solar panels but heliostats which is another great use of solar energy.

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.

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.

Heliostat Projects / Re: Mechanical Design
« on: August 28, 2015, 01:51:44 PM »
I just found this website and have been playing around with a Arduino based solar tracking program on and off for about  a year now.

I have a motor setup that I was working on that is small and compact just like Jim's except it was using motors with a worm gear drive to hold position.

I'm just curious how stable Gabriel has the code working now with Jim's tiny motor setup?

I'm looking at building out a low cost commercial version of this to go along with some portable solar generator systems we build and sell all over the world.

Keep up the good work guys!

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