Author Topic: Trackers between the tropics  (Read 1226 times)

tradewinds

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Trackers between the tropics
« on: January 29, 2015, 04:13:34 PM »
Hello Gabriel,
.      I haven't written since December of 2013. Attached are updates on my tracker build that I finally found some time to do more on. Have some questions but will post them later.
« Last Edit: January 30, 2015, 11:23:17 AM by tradewinds »


tradewinds

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Re: medium sized tracker
« Reply #1 on: January 30, 2015, 11:03:44 AM »
Hello again Gabriel,
     
     You may or may not recall I was discussing the differences between tracking the sun outside the tropics vs. within the tropics. I'll recap it briefly. Within the tropics we enter a period between bi yearly sub solar events and when tracking during that time frame within the Northern hemisphere in the tropics the sun will remain to our North until the second sub solar event occurs and the Sun returns to our South.

I considered using a slip ring to allow the tracker to have unlimited 360 vertical axis rotation but omitted it due to concerns with servicing issues. So the tracker has limited vertical axis rotation but could conceivably rotate 720 degrees without breaking its internally run wiring. The horizontal axis is limited to around +83 degrees to -25 degrees relative to pointing straight up at 0 degrees.

With above in mind. Would it be possible to program in a boolean factor that would ignore the vertical axis limit switch for one breach when entering the sub solar event while automatically switching to southern hemisphere mode, etc?


Gabriel

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Re: Trackers between the tropics
« Reply #2 on: February 02, 2015, 08:09:42 PM »
Wow! That looks awesome! That's definitely one of the most impressive DIY trackers I've seen. You should definitely consider sharing your design files if you have them.

I also did away with the slip ring in my heliostat design. Mine was just for the altitude limit switch, but it made assembly enough of a pain that I decided to get rid of it. I might add it back in later, but for now I'm not going to worry about it.

I will have to tweak the program a bit for your machine since by default it assumes that the zero altitude points at the horizon.

The limit switches are actually only used as homing switches, so once the machine resets they are automatically ignored. In your case, I would recommend that you add some type of hardware limits so that you don't ruin your wires.

I'm actually currently working on the Arduino program and plan on adding more support for different types of machines. Part of the update includes a 3D simulation so that I can visually check that the program is moving the machines correctly. In your case, this will be very helpful since it can be hard to visualize how the machine will behave during different times of  the year and different places on the planet. Hopefully I will have something interesting up and running within the next couple of weeks.

What is your approximate latitude by the way? Are you ready for the updated program now, or do you still have to add motors and things to the system?


tradewinds

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Re: Trackers between the tropics
« Reply #3 on: February 13, 2015, 04:01:15 PM »
Hello Gabriel,
      Sorry I didn't reply sooner, I've been distracted by other projects lately. Thanks for the compliment on the tracker. I'm not in a hurry to get this finished as it currently serves it's purpose delivering peak 4500 watts per hour faithfully from its stationary position. This summer I hope to have the slewing drives mated to their stepper motors (machining work) and I'll be ready to wire up the controller hardware etc. by then also. All of which is still collecting dust on a shelf. The design I drafted up is on ISMI Turbo Cad 3d solid modeler so it wouldn't be of much use as I didn't draft up any 2d drawings from the model as I could simply pull up the solid model and check my dimensions from it.
I might be able to draft up something later, though some of the dimensions are customized to the panel dimensions and would need to be altered by someone wanting to replicate the build style for their own panels. The custom sizing is with respect to webbing position on the truss and the obvious over all frame seating dimensions but also the counter weight calculations would need to be altered also. There's a great deal of welding, plasma & band saw cutting and drilling involved. Not something I care to build again anytime soon. ;)

      My latitude is approximately 19.4946 N.

Thanks again Gabriel.

So others may understand what's up when reading all this. My latitude which is only around 4 degrees within the tropics still tallies up to reverse hemisphere tracking between summer sub solar events.

      To sum it up for others reading this not yet up to speed on this aspect... as soon as the sun crosses that 90 degrees straight overhead within the tropics, the horizontal track then must work oppositely to your physical hemisphere tracking local. If at the equator that means half the year is northerly tracking and the other half the year is then southerly tracking. Most people on this forum won't encounter this issue because they live outside the tropics but for those who are located between the tropic of Cancer and Capricorn and want to track the sun... here's your heads up. No matter what type of system you decide to use for sun tracking, the cross over at 90 degrees straight up (sub solar event) will create a tracking issue unless the system is design specifically to accommodate for sub solar event tracking reversal. This would also be inclusive of the light chaser type trackers.