2 Axis Solar Tracker (The evolution of an idea)

Yes, cap on each pin: Vcc, AVcc, Aref. Aref is cap only, do not connect to 5V.

Here are three ways to drive a relay coil. Keep the inductor spike off the arduino pin.

  1. mind the total current through 328p when all relays on, better use the transistors for switching the relays.
  2. I would not use the tracking with those optical homing sensors - add simply an RTC and you can calculate the SUN's position with GREAT precision even at night :slight_smile:
    p.

pito:

  1. mind the total current through 328p when all relays on, better use the transistors for switching the relays.
  2. I would not use the tracking with those optical homing sensors - add simply an RTC and you can calculate the SUN's position with GREAT precision even at night :slight_smile:
    p.

As the software is programmed now only 1 relay will ever be on at any given time.
But I will be measuring the current through the relay just for curiosity now. :wink:

RTC (Real Time Clock?)
Incorporating a clock into the system will add a layer of complexity I am not familiar with at this time.
It may be a better alternative/solution but I don’t have that knowledge in my tool bag.
The three photoresistors, as I originally configured them, were more accurate than was necessary.
I would also think that using an absolute type of positioning system would mean I have to position the system in a particular manner at a particular time.

If you have a good example of using the RTC in a solar tracker I would like to look at it.

Your post also made me realize the photoresistors are probably sensitive enough to track the moon.
Possibly wasting energy throughout the night. Hmmmm :~

Updated the schematic at the top of the thread.
Added caps to pins 7, 20, and 21.
Also added blocking diode to the solar panel(s).

@dsmith5167: the average number of sunny days in your state is 49-53% based on city. So in half of days your optical tracker might have troubles. An RTC based Sun's position prediction could be used as a backup then.. :slight_smile:
BTW the best results I've got in past was with 5mm ultra-violet LED as the detector - it had a quite narrow radiation diagram (+/- few degrees) and among other LED's colours gave the biggest photo current when positioned precisely to the Sun..

@Pito
Excellent observations and insights. (Thanks)

Some time ago I took some measurements on a handful of LED’s I have.
Using a consistent light source I measured the output voltage.

I want to avoid doing a calibration process so the actual output voltage is not as critical as finding 3 LED’s that give the same measurement under the same lighting conditions. Alternatively if you are going to calibrate the sensors it won’t matter as the various outputs will be converted to an equal min max scale.

LED as Light Sensor Output Voltage (mV)
Transparent Red 112.9
Clear Red 73.1
Opaque Red 34.6
Clear Green 78.1
Clear Green (Mini) 1 56.8
Clear Green (Mini) 2 46.4
Clear Green (Mini) 3 57.6
Clear Green (Mini) 4 47.7
Clear Green (Mini) 5 34.8
Clear Green (Mini) 6 28.6
Clear Green (Mini) 7 51.5
Opaque Green 45.3
Clear Yellow 158.7
Opaque Yellow 70.8

Water clear ultraviolet LED 5mm gave 2.4Volt on 1Meg resistor (photo voltage, voltmeter's R=10Meg), clean sky (June24th, at high noon). The other colours (all water clear 5mm) did between 1.5V - 2.0V.
PS:
uv 2.36V
white 2.12V
yellow 1.69V
red 1.51V
green 0.02V ??
It seems the Sun is not green enough.. :slight_smile:

So with an high impedance buffer (an opamp) you are exactly in the ADC range. Mind the LED's radiation diagrams might be VERY narrow, so it was not easy to find the maximum voltage while measuring..

Looks very interesting.
And also looks to be following some similar ideas to my Arduino Dual Axis Tracker.

I've nicked one or two of your ideas...so only fair I offer some of mine - http://www.binaryorbit.org

Nice to see development in this area.

Now I am doing much the same, except that my project incorporates the complete monitoring and control for both solar panel array as well as a micro-hydro system.
I intend also to install a tracking system on the solar array, and am digging big hole in ground as we speak for a 8 metre or for you usa folks a 4x6' triangle mast tower.

Now what i noticed with your design that did strike me with some concern is potential problems with wind loading.
With using pulleys and such, I tend to think that one good gust of wind and your belts would be snapped or slipped and your nice panel will then likely be a lovely weather cock.
I am wondering, is this something you have thought about, or is the total surface area of your panels so small that it would not e effected by such a strong gust?

I will be using a good solid ram drive, similar to what is used for satellite dish positioning, welded steel frame and suitable bearings.

Also, someone mention using a RTC as a backup, that is a good idea.
The system I am designing will not use light sensors for directional operation, but using NTP, network time protocol as my system is connected to the internet anyhow.

You have obviously spent a great deal of time making fantastic CAD drawings which makes it far easier to see and visualise your design.
Looking forward to hearing of your results.

rockwallaby

Wind loading can be a huge force, I would have a real good look at that.

Speaking of having a good look, anyone doing this sort of thing should check out this thread on the Aussie electronics forum

http://www.ozelecforum.com/viewtopic.php?f=33&t=108

As for the second axis, I think most people reckon it's not worth automating, just go out every 2-3 months and adjust them.


Rob

i have worked on my own dual axis sun tracking system. It is menu driven and all the parameters can be set using 6-key keypad and LCD. Saving the parameters in EEPROM is added.

Nice Khalid, interesting blogs as well.


Rob

Rob,
Thank you. This blog happen just with the help of nice helpful guys like youl
Regards

Hi,

I suggest to use following methods

  1. SPA algorithm code that gives you the exact position of sun.
  2. use Inclinometre to measure the inclination for reference input
    3)use suitable linear actuator and motor drive , that can drive the load
  3. use gps sensor for getting date and time
  4. real time clock has been used to provide back up incase GPS fails

Hi AMPS,
The bad thing about the stepper and servo is:
1- The whole system got too much costly
2- You have always keep energize the system ( In case of stepper if you remove the power it will loose holding torque and accuracy may suffer)

When you have a low cost approach then why to complicate the things?

@KHALID.

ITS MY OPINION , Main agenda is to provide track the sun . To measure the sun angle accurately for many years with 0.0003 deg.
2) for that time and date has to be accurate , so i suggested GPS and real time clock for keeping time accurate.
3) in ordered to measure the usually u can use potentiometer ckt after few year it will loss its accuracy, So i refereed Inclinometre
4) The person who are going to design the tracking system , He has to take care of the drive and driver unit. I suggested linear actuator and linear actuator drive for that assuming the tracking system for home or residental.

Even we are in to solar tracking system we are successfully running with arduino from past 3 years.

@AMPS
Actually if you use LEDs or LDRs then you have no worries of degradation. Both have long life.. In Solar Panel you no need that much accuracy. Question is why?
If you move the panels at 0.003 degree interval, then you have to move each second the panel. This will at the end of the day consumes lot of Motor, its drivers and controllers energy.
I am also running the solar panels for past year and i find the good accuracy in positioning of panels.

@khalid

1)It all depend on programming technique, you can save power whenever motor is not being used
2) LDR are sensitive dust. When Some dust fall on it . it might not work. It need periodic maintenance
3) 0.003 deg mentioned is not per degree to moved in everyday. I mentioned because if we use simple code using LDR after year if you reading 30deg for particular time , U might degrade to + or - 5 degree after year on same time, If we calculate for long period track will be out of position.

i made this project using bearings and mechanics of an old hard disk.....
nice idea!