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Forum Index : Solar : picaxe sun/solar/tracker
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| windman1000 Regular Member  Joined: 21/06/2009 Location: United StatesPosts: 91 |
Hi Georgen my opinion would be to face all panels to 12:00pm for none tracking systems , that is where i face mine while im working on it and it seems to get the best wattage overall. but that is my opinion with out alot of testing. Hi Warpspeed i agree with Downwind , keep it simple and less cost for the average do it your self guy. |
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Tinker Guru  Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
Hi Windman, I have another challenge for you  . Instead of the photo diodes why not use maximum solar panel power tracking?
What I suggest is to fit a small solar panel, ~10W, attached to your main tracking panel frame so its pointing in exactly the same direction. Now, connect a suitable resistor to this panel that is capable of dissipating its entire output without getting hot. No battery is connected to this. Then monitor the current flowing through this resistor, it will be highest when the panel array points at a place in the sky where the most solar energy comes from. You then have your program move the panel manipulator a small amount at a chosen time interval, if there is an increase in power keep going in that direction until a reduction occurs, then back off a little. You should get the best sun/wattage there is to be had with this  . Klaus |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
With a gearbox it certainly would be. Remember, one revolution in 24 hours is pretty slow, and you can run a mighty big gear reduction. Complexity ? Not really, if you do it all with a microcontroller. The whole thing is entirely digital on/off and up/down counting, very simple software. Cheers, Tony. |
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| windman1000 Regular Member Joined: 21/06/2009 Location: United StatesPosts: 91 |
That was one of my ideas but i think the tracker would go kinda crazy on partly cloudy days, yes i know i could put time frames in the program so after it stops it need to wait 30 sec before tracking again but i think it would waste power from the tracking motors looking up/down / east/west on those partly cloudy days |
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Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
Humm, why use a stepper motor, a small DC motor with a 6 rpm output driving into larger gear reduction boxes is all that is needed (Used several of them already)this keeps it simple and low cost. A run time of 10-30 seconds every so often will do nicely, time over gear ratio is more than accurate enough. Steppers become hard to operate for a not so savy electronic minded person, where a geared DC motor can be easy controlled by a couple of relays for forward and reverse. Here is a solar tracker controller i built for Amack, he constructed all the other hardware, its been in operation for a few years now. 
Sometimes it just works |
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fillm Guru Joined: 10/02/2007 Location: AustraliaPosts: 730 |
Another nice build Pete , after dark can you use it as a phone?  PhillM ...Oz Wind Engineering..Wind Turbine Kits 500W - 5000W ~ F&P Dual Kits ~ GOE222Blades- Voltage Control Parts ------- Tower kits |
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yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
I like this design for a positioner very low geared and the reed switch will count the same number of pulses for the angle right across the sky. It would need a counterweight and heavier bushes for panels. The standard linear actuator gets a bit scary when it is fully extended and there is a wind from the back, this is far more robust. 
I'm confused, no wait... maybe I'm not... |
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| Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
Not sure if i would trust it with 1kw of panels hanging off it. 
Other designs i have seen vary from using propane and the differential difference in pressure between a cylinder in the sun and one in the shade with a ram in the middle, as the panels move it shades the cylinder in the sun, as the sun moves around the panels it exposes the cylinder to warmth which expands the gas and moves the panels to shade the cylinder again. [quote] after dark can you use it as a phone? [/quote] Only if you are ET with reverse charge calls. What would Telstra charge for intergalactic calls?  Not sure if it would fit into a "Long Distance call" discription.Sometimes it just works |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Simply because it steps, and each step is an exact precise known angle of of rotation. For example, a 64 steps per rev stepper will step EXACTLY ten turns and stop after 640 steps, regardless of mechanical load. If you fitted a 1,000:1 gearbox to it (in this example) it would require 64,000 steps to make one EXACT revolution. There are 86,400 seconds in 24 hours (60 x 60 x 24) It is not difficult to juggle gear ratios, and digital frequency dividers to get one revolution in 24 hours from a quartz oscillator. For an easy example, how about 64 steps, a 1,350:1 gearbox and 1Hz ? You can get exactly 1Hz from a standard 32Khz watch crystal. Or 64 steps and a 13,500:1 gearbox and 10Hz ? A mains (or quartz) powered clock works exactly like this, 50 Hz from the mains drives a synchronous motor, which then drives a high reduction gearbox that operates the hour, minute, and second sweep hands. And it will keep EXACT time forever, as long as the 50Hz driving it is long term accurate. There are some very powerful stepper motors available, but even a small wimpy one with the torque multiplied by several thousands would be able to move and hold an impressive load. Cheers, Tony. |
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| Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
Warpspeed, You missed my point, yes you can use a stepper motor, but its just over complicating a simple application, where a simple DC (or AC) motor will do fine. I have built CNC machines and other linear tracking machines using stepper motors and do know how they work and the accuracy of degree stepping. A 1000:1 ratio is a little high and if using a stepper it would take a month of Sundays to do the arc, 400:1 ratio is about correct for a reasonable slow rotation speed with ample holding power. I guess it all depends on what one is building here, is it a toy for a small solar panel or a tracker to take 1-2Kw of panels, as there is a huge difference in the application of a tracker to suit. All the trackers i have built use a car diff modified and stood up vertical for the rotary drive, strong and robust to weather the elements of mother nature, then a 400:1 gearbox coupled to the diff input. These take 1-2 Kw of panels mounted onto them without a problem. Pete. Sometimes it just works |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Pete, how do you get a simple dc motor to track accurately without any sun or positional feedback? The biggest advantage of a stepper is you know exactly where it is by just counting steps, completely independent of mechanical loading. And exactly as you say, this is a huge advantage of any digitally controlled positioning application. Stepper motors and mirocontrollers are a perfect match for any positioning application. Why not also for solar tracking ? All the astronomical telescope drives use steppers, and they are doing exactly the same thing we are doing, but with much higher required accuracy. You say a 1,000 to one gearbox is overkill, but it is only 0.69rpm at the motor for one revolution in 24 hours. A dc motor running at 690 rpm would require a 1,000,000 gearbox reduction!! And a more typical small 6,900 rpm dc motor might require a ten million to one reduction gearbox. I don't see that torque output limitation is going to ever be a problem with such a slow output drive requirement. You say a 400:1 gearbox ???? There are 1,440 minutes in 24 hours. Do you really run your dc drive motor at only 0.278 rpm, or one revolution each 3.6 seconds? I have never been able to get a brush type dc motor to even run at such a low speed. Cheers, Tony. |
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| JOSHY777 Newbie  Joined: 13/10/2012 Location: AustraliaPosts: 2 |
G'day windman1000 Just wondering if i could measure voltages and currents of a solar panel instead of wind turbine. Also what is the reed switch apart of, is it an anemometer or what. Last thing, just wondering why in your diagram there are 6 photodiodes instead of 5 which are used. sorry for all the questions, just curious and willing to learn :) cheers, Josh |
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AMACK Senior Member  Joined: 31/05/2009 Location: AustraliaPosts: 184 |
Hi Warpspeed and others, I have had a look at what you are doing and I think you may be overthinking the job. The tracker I have working, and now for sometime is working very well with 6 X 250 watt panels on it and I live in a wind tunnel. I have a 60rpm 12 volt motor turning a 10.5:1 box which turns a 25:1 and it run runs the diff 2.77:1 
The motor is not running all the time mine from memory comes on about every 38 min for about 8 seconds. I just worked out the ark and the time and did a bit of math. Now the days are longer I just told (DS-1307) to turn to start at 6:15 not 7:00. It is not an exact sicence as the sun is very big and the panels dont have to be perfect 100% of the time. The best thing I can tell you is DO NOT TRUST LIMIT SWITCHES. I did have a very good limit switch given to me and it is worth the money to get a real good one. I also use a section of rubber hose from the motor to the first box incase something goes wrong it just twists it off not the $2000 worth of panels it is carring. I know Mobi another member lost a panel to a run away tracker.
Amack *Note to self 1. Make it thick 2.Make it heavy. 3.Make it stronger than it should be. 4. Don't rush the first job as the second job will cost more and take mor |
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| Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
Hmmm? Im sure i have seen that drive in screen before?? i just dont remember her....Err the name.
Pete. Sometimes it just works |
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| fillm Guru Joined: 10/02/2007 Location: AustraliaPosts: 730 |
If That can handle the wind at your place .... Its a winner!!!! PhillM ...Oz Wind Engineering..Wind Turbine Kits 500W - 5000W ~ F&P Dual Kits ~ GOE222Blades- Voltage Control Parts ------- Tower kits |
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| Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
There are more ways to tackle the wind. I too have 6 solar similar sized panels but they are mounted on 3 separate trackers, two panels on each. They are located on my shed roof, some 4m above the ground and so far had no problem with 40 knot wind gusts. It also gave me three times the fun in building them from scratch , us retiree's must be kept occupied Klaus |
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| Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
us retiree's must be kept occupied
Gee best not let your wife hear you say that, she will have a list for you as long as the grocery shopping docket.  Sometimes it just works |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
This is a very important point. Some kind of very simple fail safe system should be thought out. A few ideas include a shear pin or something that slips as suggested above. Another way would be to physically break the electrical connection to the motor by pulling out a plug or snapping a thin wire link (mechanical fuse). Cheers, Tony. |
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| AMACK Senior Member Joined: 31/05/2009 Location: AustraliaPosts: 184 |
Tinker, I am not that old I can't retire yet so I need projects to work so I over build them to with stand mother nature. Where I live the wind sits at 40kots on a good day, and then get strong. Tony, The system I run is 24 volt but finding a motor in 24 with the revs I needed was hard. I used a voltage step-down to give me a bigger selection of motors. You don't need a big strong motor to drive the boxes if you have the reduction right. I can turn mine in a strong wind with my fingers. I use a section of 1/2" sprayer hose between the motor and box.1. as a safety. Pete thinks it is a bit agricultual but it works well. I have a system on the roof of 1710 and 1500 on the tracker and I was getting 740 watts from the tracker and the system on the roof was in sleep mode. I think if you have the space and time to make a tracker the returns are well worth it.
Amack *Note to self 1. Make it thick 2.Make it heavy. 3.Make it stronger than it should be. 4. Don't rush the first job as the second job will cost more and take mor |
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