Are the details on the bearing for where the vertical pole and horizontal plate meet available?  Also would like information on the motor used with the chain and sprocket (azimuth positioning) if possible.  Thanks.

Hi, there! I'm writing from Mongolia. We're interested in your project, especially the optimization for developing country-angle, so we wanted to give it a go. I have been able to see the cache of your webpage polyideas through the Wayback Machine, but I couldn't recover the photos. Is there any way you could share those with us?

We've ordered most of the parts you mentioned from the US and the UK, and are excited to try it out. The box, the battery, and the tripod will be sourced locally. I initially thought we had the linear actuator locally, but I was mistaken. I guess we'll have to order it from Pololu.

HelloJay!   

Just a note to let you know that we have been able to

use your solarrobot program in Python3.  We just finished
last night finally figuring out some errors and the only
thing that seems to still be happening is that we haven't
initialized the rrtool database and don't see any code of
yours where that happens.  We get six errors where it
seems to want to write to the database and can't find it.

    We have also been using a 12V 1Amp DC motor to move
our parabola.  It has worked just fine be we see that you
have chosen other type of motor and were wondering if we
should switch to this type of motor (i think it is of the
"step" type) or whether the dcmotor program will work with
our DC motor.  We don't have anything connected yet
because we've been looking for someone here in Mexicali
with a little more soldering experience with small joints
than what we have.
    Thought you'd like the update.
    Have a great afternoon!
    With warmest greetings,
    fred

P.S.  You're email address do not seem to be active any more.

Where did you get the sun position algorithm from? NREL? PSA?

And the comments about trig lookup tables and fixed-point math are spot-on. The Atmels have plenty of power if you are clever about the way you do the trig functions - you do not need FP hardware.

As mentioned in the project details above, I am using the Pysolar library.  Keep in mind that as also mentioned above and below, fixed tables would require recalculating them and reprogramming them every time you want to take it somewhere else.  This configuration needs only a device with wifi and a web browser to reprogram, allowing the use of tablets and phones.  As mentioned in the blog post, I've already done this with Arduino- and although it's novel to reduce the build cost by $20 by using a cheap Arduino instead of a $25 A+, you lose too much functionality, flexibility, and capability by doing that.  Arduino web servers are quite poor compared with an Apache2 server, which the A+ does well and at no additional cost.  

If you're interested in pre-programming solar positions for every major city for the next 50 years and sharing those tables, I'd love to see it.

I don't know about the Pysolar library. the two I mentioned, esp the
PSA only need the current (local standard) time and the lat/lon. The
fixed tables are for trig functions. So, I do not understand your
statement, other than you are assuming you need to create the table
exclusively for the specific location. These algorithms will give you
the zenith/azimuth quickly. The PSA runs 20x of the NREL and is easier
to use. (PSA runs 5 milliSec vs SPA/NREL 100 milliSec on an AVR32 w/ 12
MHz clock). Even if it takes 30 seconds to execute, that is good enough
for this kind of app.


Also - for ethernet - look at the
Wiznet chips. Sparkfun has the Wiznet 5100 mounted on a board with an
RJ45 connector for about $25. Sparkfun has an adapter for mounting it on
a Teensy 2.0++


YMMV

www (dot) psa (dot) es (slash) sdg (slash) sunpos (dot) htm (C++, easy to convert to C)
for the paper. google 10022519534118276 (dot) pdf

So sad you're not going to be able to continue with this.  We've been trying to build a solar hot water heater for some 3 years now.  We've got one that works, but all of a sudden (maybe it's the time of the year???) are having problems with our LEDs getting confused by the parabolic trough reflection, so we've been looking for "another way".  We were thinking about putting a compu on this anyway in order to feed the before and after temps to the "clients" - lol via the internet, so we have been looking for just a one-axis tracking system with the GPS coordinates and time of day.  Since we don't do programming, much less engineering, we've just been scanning the forums for someone else to come up with the answer.  

The other problem/challenge we would have is that the Raspi whatever only holds up to 40 degree Celius and we get some days of 50 or 51 - very infrequently - but we'd hate to loose the equipment.  (Hmmmmm... maybe it doesn' t have to be mounted on the collector itself, but could be mounted inside somewhere close. - lol - always thinkin' )

Here's a link to our OpenSource ... http://www.appropedia.org/Parabolic_Solar_Hot_Water_Heater

Maybe something there will be of use.

I'm not deleting the work I've done, but I have to be realistic about the time and resources I have to put into it.   The Python that I've done isn't terribly complicated, and should be easy to modify to what you need it to do.  As for the temps, I would add a fan and vents to the enclosure for the summer months.  There's nothing that says the Pi, motor controller, battery and charge controller need to be on the chassis- only the IMU.

Thanks, Jay, for supporting and adding to OpenSource and helping to build a better future for all of us.

Cold weather application begs for a composite worm drive to turn the entire support mast East-West. Aiming is not crucial, and can be performed using lookup values for three positions AM-NOON-PM. I see the shaft-actuated positioners freezing after condensation accrues despite weep holes, and new grease. Water gets into the grease in droplets. Composite worm drive turning across teeth localizes the problem to the gearbox portion of the motor.

I will admit that I've focused on warm weather areas so far- the panning motor is an area for improvement, but there's significant cost in going with a weatherproof worm drive.  I'd be interested in any suggestions you have that would be cost-effective.

I did a photocell based tracker back in 1991 using discrete logic. We never field tried it as we'd not bothered to calculate the loads on the motors and as a result they were under powered.

Hi, this is an awesome project, I would like to try it on few open wifi hotspots what would work with solar energy only. I still don't get how mechanics work for two axis. Can you please go into detail of how mechanic works, show which motors are needed and all other details. I agree Rpi is great choice, my second choice would be TP-LINK WR703 with 8MB of flash so it can run Python.

Thanks!

I will be adding the motor and other details in the coming two weeks.  Keep in mind you also need a motor controller that can handle high current, so the TP-LINK may be excluded here.  From a 2-axis standpoint, the Pysolar provides a heading and elevation for the position of the sun relative to the position of the tracker.  Using an IMU, I turn until I get to the proper heading, then tilt until I get to the proper elevation.

Hey, in the old days, we used tables of sin/cos/tan and just looked up the values....also we did fixed point math, instead of floating, were able to make some really good video games back with a 6502/Z80 with no multiply (tables of logs adding is multiplying :-)

That sounds cool- with the Raspberry Pi A+ I'm planning for the next version, we're bringing costs down considerably, very close to what a microcontroller with lots of memory has.  The other challenge with building tables manually like you mention is that we'd have to load them for the entire world- this device is meant to be used globally.

why not to use 3 tilted photo resistors and sense which is getting more light? then an arduino controls a servo to move to the best position.

Hi and thanks for the comment! There are several reasons:

1.) Arduinos can't reliably handle the math required since it requires extensive floating point math, something Arduinos handle poorly.

2.) Photo sensors can be fooled by shade, clouds and other interruptions.

3.) Photo sensors need to be kept clean.

4.) Adding photo sensors to the project would actually add cost to the project rather than reduce it, since there currently are no sensors of that kind on the project.

I wouldn't rule out floating point math on an arduino.  My latest project is doing voltage/current monitoring, and the arduino is taking 16x samples of 8 analog channels, averaging all 16 values and then doing floating point scaling and adjustment.  All of the math for all 8 channels, plus another 10 or so derived floating point parameters (power, amp-hours, runtime etc), takes less than 2ms to execute.

Secondly, the low power consumption of an arduino would give you even better efficiency on this project.

Thanks for your reply!  The issue is one of using tan,cosin, atan and other math functions.  It's not a question of doing *some* floating point, but it's the ability to precisely measure the location of the sun.  I actually started out with an Arduino on this project:

http://www.polyideas.com/blog/2014/3/27/building-a-2-axis-solar-tracking-robot-aka-solarbot

For the current project I chose a Raspberry Pi 2 for a proof of concept, but in the log you can see I am using an A+ for power efficiency.  The A+ also gets me a full Linux OS, so I can implement a web browser with authentication, access control, web control over variables, and especially SSL.  

Additionally, the compute unit isn't drawing very much power- it's the high current motors that eat most of the juice.  I'm open to using a different motor controller, but the two different models I have are actually lasting all day on a fairly small battery.

for web wifi control you may be interested about the new nodemcu boards, which have a programmable ESP8266 onboard. However they still don't beat a Raspberry pi A as a web server, but draw less current.

I mean photoresistors, which are really small and cheap, 2dollars for 100.Solar panels too need to be cleaned, and some of them may sense if there's clouds,  estimate light and find if something is blocking sun.

You could do an Arduino one with photoresistors, but that's a different project.  Since I am using math to calculate the position of the sun, there are no sensors to clean- plus adding analog circuits onto the A+ adds components and cost- I am going for barebones here.

I am always on the lookout for ways to set the time, latitude and longitude with switches or knobs, but it turns out that's a ton of switches when you can log in with a smartphone and change as you want that way.