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diy solar

Making a Dual Axis Tracker

How did you manage to break the north/southlinear activator?

In my zeal to "balance" my tracker it slipped and sort of thudded. What I didn't notice is that when it slipped, the entire E/W shifted about 5 inches south.
That took the E/W actuator out of alignment with its push/pull origin and its insertion points.
I didn't notice this until the next day when the panel stopped tracking E/W about 10:30 AM.
That afternoon I was "fixing" more on the contraption and noticed the off-ness of the tracker.
The internal connection of the linear actuator snaped at the exact spot where the internal gears turn the long screw. Unfixable. :( These 12V actuators are actually pretty nice internals with all-metal gears, however, even the nicest things don't like to be used wrong.
On the bright side, I ordered 6000N actuators to replace these 1200/1500N actuators. 6000N actuators use a worm gear vs the lighter duty actuators with in-plane gears.
Now I have a one-axis tracker for a few days.
 
Here's a thought.... by monitoring current drawn by the linear activator, if it would bind/stop, a simple latch would trip and turn off the current to the activator. It won't reset, and yet it will shut things down to keep from twisting parts apart. A Cd4011 could be easily configured as a set/reset latch.
 
Here's a thought.... by monitoring current drawn by the linear activator, if it would bind/stop, a simple latch would trip and turn off the current to the activator. It won't reset, and yet it will shut things down to keep from twisting parts apart. A Cd4011 could be easily configured as a set/reset latch.
Very good idea, any idea to have something that I don't have to learn how to program? Something like a window stop switch, or maybe like a garage door interrupts. I had one incident where the E/W was pushing W and it gout squished on something, I could hear the motor straining, and see the voltage on the charge controller dropping off.

I just stopped by my local metal yard. Lots of goodies I am about to get to make a proper mount. All sold by weight, $2.80/lb for the aluminum and $2.00/lb for the hardware.
 

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I'M old school, and I don't have a middle school kid near by that can write the C++ code needed.

Analog world....

A shunt in the low side of the power supply, would be monitored and amplified by a rail-to-rail op amp. The amplified voltage (from the shunt) would go to a second op-amp that would switch states when the input from the shunt exceeded the reference voltage (adjustable!!) on its second input. Then when the op-amp switches, it would reset a R/S latch. That latch would control either a relay or power MOSFET to stop the current to the motor. Since the R/S latch does exactly what the name implies, you would have to 'reset' the latch anytime an over current even occurred.

Digital world

If a shunt would be used, again, its output would need to be amplified so it is of a sufficient level the A/D converter in let's say an Ardunio could read. Or you could use a Hall effect sensor, and once more feed that into the A/D converter of an Ardunio. An Ardunio sketch would need to be written to convert the input from the Hall sensor into something usable, then code the reset of the sketch to switch an output (either low to high or high to low) and once more use a power MOSFET or rely to control the current to the drive motor. The sketch would of course need to be coded so you can reset the digital latch.
 
I'M old school, and I don't have a middle school kid near by that can write the C++ code needed.

Analog world....

A shunt in the low side of the power supply, would be monitored and amplified by a rail-to-rail op amp. The amplified voltage (from the shunt) would go to a second op-amp that would switch states when the input from the shunt exceeded the reference voltage (adjustable!!) on its second input. Then when the op-amp switches, it would reset a R/S latch. That latch would control either a relay or power MOSFET to stop the current to the motor. Since the R/S latch does exactly what the name implies, you would have to 'reset' the latch anytime an over current even occurred.

Digital world

If a shunt would be used, again, its output would need to be amplified so it is of a sufficient level the A/D converter in let's say an Ardunio could read. Or you could use a Hall effect sensor, and once more feed that into the A/D converter of an Ardunio. An Ardunio sketch would need to be written to convert the input from the Hall sensor into something usable, then code the reset of the sketch to switch an output (either low to high or high to low) and once more use a power MOSFET or rely to control the current to the drive motor. The sketch would of course need to be coded so you can reset the digital latch.
You sure had a lot of words for "Overload protector"
 
You sure had a lot of words for "Overload protector"
Those work great for all the stuff he talks about in the video, and he's talking about ac powered induction motors. You need to monitor stall current in a small dc motor. I guess the simplest method would be to simply use a fuse. But do you want to replace a fuse every time a stiff wind hits the array when it's moving?
 
PTC fuse?

If overloaded (excessive current) it will go high resistance, probably not reset until the servo turns off at night so long as servo keeps trying to operate.
But it may not prevent excessive force because it is slow-blow.

I observed that the 0.5A (spec'd output) of my Sunny Island with PTC fuse (not sure exact value) is able to drive 5A long enough to close a relay. That's 10 ohm coil resistance at 48VDC nominal battery voltage. (once closed, a switch opens and a higher resistance coil provide holding current.)

You can get self-resetting mechanical circuit breakers as well.
 
I fixed the actuator with a much better actuator. I'll replace the E/W actuator tomorrow with the other 6 kN actuator. They are way smoother. These 6 kN duty linear actuators are used in furniture and things like that. I also got a few stop limit switches that I'm going to experiment with. As it turns out I can't figure out a proper N/S mount to get the actuator mounted to. If I put it too low, it will angle itself into a negative angle and it's like when you "double joint" your finger, then try to un double joint your finger but you only make it much much worse.

The smaller (and less expensive) are all metal gears and work great. But the 6kN actuators have the motor perpendicular and use worm gears.

I also figured out a better spot for the anemometer, but it was fixed after dark. I'll show a picture or two tomorrow. :)

Now that I think I have the "design" figured out. I'm going to go get some stock and rebuild the entire platform with much less pricey aluminum stock.

 
Nice setup ya got there, was fun seeing the videos in succession with your progress :) Good inspiration for me as well !
 
I had a single axis tracker set up, and was manually adjusting for the N/S every couple of weeks.
I was using another linear actuator that I had here to do it, and got to thinking about designing/building my own dual axis sensor/controller.
I am pleased to report that as of sunset yesterday, it was functional.
I will get a video of it this coming weekend.
 
Some tweaks

260 Wh for the fixed panel
610 Wh for the dual-axis tracker.
Same panels, same inverters, same location.



 
PTC fuses:


But I think they are better at keeping the motor from burning out than limiting torque.
Some tweaks

260 Wh for the fixed panel
610 Wh for the dual-axis tracker.
Same panels, same inverters, same location.



> 2x the power output?
That sounds like more than we expect from tracking time of day.
Is the fixed panel at a very poor orientation for the season? If show, how about a manual adjustment of seasonal tilt? Just 2 different angles throughout the year, adjusted spring/fall.
 
PTC fuses:


But I think they are better at keeping the motor from burning out than limiting torque.

> 2x the power output?
That sounds like more than we expect from tracking time of day.
Is the fixed panel at a very poor orientation for the season? If show, how about a manual adjustment of seasonal tilt? Just 2 different angles throughout the year, adjusted spring/fall.
Watch the video, you can see the panel leaning against the house, it is angled about perfect for this time of year south.
End of today numbers

Dual Axis: 680 Wh
Fixed: 310 Wh

Ahhhhmazing!

Another neat feature with the BN-Link and "Smart Home App" is the Automations.
At Sunrise the BN-Link switches turn on, and at Sunset they turn off.

These are the switches - https://www.amazon.com/dp/B07CX5KLXN/ref=cm_sw_em_r_mt_dp_Ev.1FbNVDCKT8

1607988462471.png

 
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My plan for the next stage:
2020-12-15.png 2020-12-15 (1).png

The "Dual Axis Tracker.zip" is the SketchUp drawing.
 

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How about making that a gimbal mount, with X and Y axis passing through each other. As close to CG as possible.
Right now you have the two axis several inches apart and several inches from CG.

Flipping the top pillow blocks upside down would let the two axis lie in the same plane.

Goal is to approach balanced, so little force is required to tilt against gravity without need for counterbalance.

Add a pair of legs from near top of post (but low enough to clear mechanism). They could spread out North West and South West to form a tripod. That will make it much more resistant to winds forces and swaying.
 
How about making that a gimbal mount, with X and Y axis passing through each other. As close to CG as possible.
Right now you have the two axis several inches apart and several inches from CG.

Flipping the top pillow blocks upside down would let the two axis lie in the same plane.

Goal is to approach balanced, so little force is required to tilt against gravity without need for counterbalance.

Add a pair of legs from near top of post (but low enough to clear mechanism). They could spread out North West and South West to form a tripod. That will make it much more resistant to winds forces and swaying.
Lots good ideas, draw up something and let's see it.
 
How about making that a gimbal mount, with X and Y axis passing through each other. As close to CG as possible.
Right now you have the two axis several inches apart and several inches from CG.

Flipping the top pillow blocks upside down would let the two axis lie in the same plane.

Goal is to approach balanced, so little force is required to tilt against gravity without need for counterbalance.

Add a pair of legs from near top of post (but low enough to clear mechanism). They could spread out North West and South West to form a tripod. That will make it much more resistant to winds forces and swaying.
Now with everything "hanging" by bolts, that lowered everything about nine inches!

2020-12-17 (3).png 2020-12-17 (4).png
2020-12-17 (8).png

Now everything is C channel-1x3x1/8, no "studs-1x3x1/8".
 

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The single pillow block on top of the post would have to resist an forces trying to tilt the array up and down.
It only needs to allow about 47 degrees motion to follow seasons, << 180 degrees.
As second pillow block in line with it, on an offshoot from the post, would fix that. Having that cross one of the structural members will ensure it never gets shoved through the panel.
(So long as you're further North than 24 degrees from the equator, so panel only has to slope to varying angles South, never North. If so, axis of these two pillow blocks could be tilted off horizontal.)

The actuator for North/South tilt could be mounted on the post rather than that arm, if it gets a gimbal or ball joint rather than just a pivot at the panel end. I think this eliminates need for the second pillow block mentioned earlier, because tilt force is no longer transmitted through the first one.


I would brace the post (with 2x4 or the like) for greater strength.
By rotating the post 45 degrees, two 2x4 could provide diagonal braces going NE and NW.
 
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