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Hi John;
That is a horrible circuit for a solar tracker for several reasons:
1. It uses CdS photo resistive light sensors. These are highly non linear and age badly in sunlight.
2. Its overly complicated using comparators and requires careful of adjustment of the pots.
3. It uses relays to drive the motors. Relays have a relatively short lifetime in DC applications or the good ones are very expensive.
1. You should use LEDs as the sensors connected in the anti parallel configuration. This is very sensitive to angle. And has a built in dead band. No adjustments required except for aiming.
2. Use a solid state motor driver so it won't wear out.
3. Use high gear ratio drives, I usually recommend a total gear ratio of 100,000/1 or more. Here is a nice cheap motor: http://www.surpluscenter.com/item.asp?item=5-1763
Or a new design of mine: http://www.redrok.com/electron.htm#led555
For larger motors.
I have been testing this for a couple of months and it works very nicely.
Build the first one on a plugboard to workout the timing parameters for your application. This has a PWM variable speed motor drive.
The simple transistor output can do over 300mA. But with larger Darlington transistors it can easily do 1 amp.
With the MOSFET output the sky is the limit.
If all your doing is tracking the sun then all you need is a round cardboard tube, solar cell and a low RPM motor. Mount the solar cell at the bottom of a 2 ft long tube. Connect the solar cell so it will power the motor. When the sun light goes down the tube the low speed motor rotates the tube away from the sun. When the tube moves out of the sun the solar cell stops making electricity and the motor stops running. In few minutes the sun moves and light goes down the tube again the solar cell makes electricity again and the motor runs long enough to move the tube then the motor stops. Every time the sun moves the motor starts and moves the tube over and over and over all day long. Every time light goes down the tube the motor rotates the tube out of the sun. At the end of the day a timer circuit returns the tube to its starting position and it waits for the sun to come up the next morning.
If all your doing is tracking the sun then all you need is a round cardboard tube, solar cell and a low RPM motor. Mount the solar cell at the bottom of a 2 ft long tube. Connect the solar cell so it will power the motor. When the sun light goes down the tube the low speed motor rotates the tube away from the sun. When the tube moves out of the sun the solar cell stops making electricity and the motor stops running. In few minutes the sun moves and light goes down the tube again the solar cell makes electricity again and the motor runs long enough to move the tube then the motor stops. Every time the sun moves the motor starts and moves the tube over and over and over all day long. Every time light goes down the tube the motor rotates the tube out of the sun. At the end of the day a timer circuit returns the tube to its starting position and it waits for the sun to come up the next morning.
That might be good for a few days a year...but...the sun changes elevation throughout the year. With a 2' long "tube", you would soon lose the sun entirely.
Here is another Supper simple solar tracker based on timing circuits: **broken link removed**
And an in depth explanation of how it works. http://www.redrok.com/electron.htm#led555
BTW, if you want to use CDS cells this circuit can accommodate them too.
Duane
I made that post quick and simple I did not want to make it to complicated spending a lot of time and detail typing if your not really interested. You change the 2" tube to a 2" wide funnel. The sun can go from 90 degrees to 1 degree and it still works. It works great, tested and proven to work year round at my geographical location in middle TN.
REDROK,
Is there any chance you could recommend a dual axis tracking circuit for me. I'm thinking of doing it for my final year project in college. I searched the web, but there so many and so little time! and it looks like your in the know how when it comes to solar tracking.
Thanks allot!
S
If you're looking to make a "Solar Heater", try making a parabolic reflector with a couple pipes, using vegetable oil being pumped throught the system. Mounted horzontally it will work all day without movement. 6" to 8" polished aluminum or stainless pipe cut in half lengthwise as the reflector. Two pipes ( one inside the other, preferably centered, outer pipe capped ) are mounted in the center, where the sun reflects onto it and oil is pumped into the center one, and returned in the outer one. An old design that has heated vegetable oil to almost 800 degrees where it was used for cooking - instead of the electrical burners on the stove. Oil units were used in the same stove, in the oven to cook a turkey and a ham roast. There is more to the system, but that is the "heat gathering" portion of it.
Are you sure about that? It's a zener, if I'm correct, not a nor normal diode - it has nothing to do with making sure it doesn't start shifting east? It must be there for a reason...
I have read this specific thread with great interest as I am an avid solar photographer using White light and Halpha filters in my Observatory.
My name is Rainer and I live in Mexico.
Now the presented circuit after having read a lot seems to satisfy my needs with the difference that instead of dricing a motor I just need to pull down some TTL outputs to ground in order to activate what we call in astronomy an Auto GUide port. Normally this ports have 1 common ground and 4 lines ehich when pulled down to ground activates a corresponding movement of the RA or DEC axis, be it forward or backward.
I am talking of German equatorial mounts where normally the only motor in movement is the RA motor following be it the Stars, Moon or Sun. For Autoduigin at night there are many solutions which work perfectly as one takes juts a star and the software calculates its center and when there is a deviation it actvates the corresponding movements.
I have tried similar solutions wioth the Sun building a Sol guider scope but the software is not able to digest the Suns intensity as a stars and it looses the center and so the Autoguding get crazy.
The last mentioned circuit in this thread seem to be interesting but I have a few questions about it.
I do not need to drive directly a motor. I thiink that is the simplest solition by just using tha LM339 comparators output as a switch and close the TTL output.
How accurate is the measuring of the Suns intensity eg how fine do the opposite situated LEDs react to minimal angle changes if the incoming Sun collimated rays do excite the LEDs, in order to create a voltage difference and activate the corresponding comparator output.
Yesterday I started to experiment with a simple circuit in order to understand how the LM339 works. First by using 2 voltage splitters on theinput of the comparator and then substitutin one pot for a led and turning the remaining pot and I manged to get a ON and OFF switching if an indicator LED connected to the output of the comparator.
I then tried with 2 LEDs but nothing happened as I assumed that every LED reacts different to incoming light and thought it would switch. OK, I have to admit I had no direct SUnlight and maybe there was the problem.
Using just the comparator with a positive V+ input voltage I assume makes the whole tracker more dificult as I need one reference voltage for each lead, so after reading this with the opposite placed LEDs makes it much easier.
Another problem I have is that I have no negative voltage supplies in the observatory. We do work all Positive be it 5V and 12V.
If possible I would like to discuss this here and try to make a suitable circuit for testing it when I have full sun light and the necessary parts.
Sorry for the long introducing message and appreciate any help to get going the project using the presented circuit-
Since PV panels are wide angle view , the solar tracking is not that critical but you can gain 25% on average with a latitude tracker if you adjust the azimuth manually each season, and less if you dont. and with no solar tracking you lose on average 29%, but during peak hours more than 50% and during cloudy periods 0 gain over a fixed vertical angle.
When it is cloudy the solar power is significantly reduced and widespread , so tracking is not required. unless you want to wast time power clouds.
You create a sunset detector using a comparator with hysteresis for sunset using the same LED as photo-sensor. Since you may not have power in the morning to move the array, sunset is the best time, then use a timer or a another photos sensor to detect the sunrise position with an LED shining in the sunrise position that is less bright than sunrise but brighter than sunset.
You may want to put heatshrink tubing around the LED so it does not pik up stray light from headlights or street lights, so that it reaches slightly beyond the tip of the LED.
The algorithm of the tracker ought to be defined.
e.g. if the West/East differential voltage is X% brighter then move and after x seconds of moving stop or until the threshold of difference drops to Y% above noise levels.
If there is inertia in the motor, it will coast past the stop point, which may be ok, but if the threshold is too low , it will oscillate.
Corrections should not be done less than T minute intervals, because the motor loss in Watt-hrs will exceed the gain in solar energy in Watt-hrs.
T has to be determined by your motor and PV panel specs, but I suspect the motor power to PV power ratio may be large to manage the torque, so the net gain is improved by less frequent corrections. A 10deg correction might only improve power 5%, but you can plot in excel.
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