Author Topic: Heliostat Project  (Read 33615 times)

Gabriel

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Re: Heliostat Project
« Reply #15 on: May 28, 2009, 06:37:00 AM »
Here are a couple of pictures of the new heliostat that I'm working on. I still have to connect the motors, which I hope to have time to do today.

This is just the first prototype. I eventually want to find a way to make an array of mirrors all controlled with two stepper motors and an Arduino.



Davetech

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Re: Heliostat Project
« Reply #16 on: June 08, 2009, 05:32:53 PM »
Hey, looking good there.   I haven't even gotten to the point of building my mirror mounts yet.


I haven't given up.  I've just been delayed a bit by some other garbage. Wish I could find a job.
Anyway, I finally got some ABS plastic pipe. Had to special order it from a local plumbing company. They told me that ABS is on its way out.

I just have a toaster oven to heat it up in, but for the size piece I was using it worked fine. It went soft and pliable at 260 degrees F according to my infrared thermometer. Then I squashed it flat with a board and a concrete block and let it cool. I used 4" pipe and it has pretty thick walls so it makes for a very sturdy mounting platform for projects.

I cheated and used Gorilla Glue to mount the stuff up. That stuff is tough as nails but it needs getting used to. It foams up while curing and expands about 5 times its size so you just squeeze out a tiny amount.






I have connected it to my Picaxe micro-controller and a breadboarded controller circuit and I wrote a little program that runs it.  The controller circuit is pretty simple. Just two Darlington amp circuits and a double pole - double throw relay. It is cleverly wired (I can't claim credit for it) so that when the relay is relaxed, the motor runs in one direction and when the relay is energized, the motor will run in the other direction.  One of the Darlington circuits controls the relay coil. The other Darlington circuit supplies the motor power that goes through the relay contacts, so I can turn the motor on and off with one output of the picaxe.

Of course this will just run the PAN. I'll have to add a little more circuitry and another relay to run another actuator to do the TILT.  But the Picaxe 18X can handle it all. I still have lots of unused inputs and outputs. I'm thinking one input will be used for a sensor to tell if there is enough sun for the heliostat to bother searching if it has lost its lock on the sun.

One of the delays has been the circuit board.  I've etched my own boards for small projects for years, but this board is going to be way too complicated for me to do by hand and my eyesight ain't what it used to be. So I got a dirt cheap old laser printer off eBay and am trying to do the iron-on-the-toner procedure, but so far it comes out too spotty.  I think this printer does not deposit enough toner on the printout even though I have the contrast all the way up and it is set on "transparency". I've checked out the pre-sensitized boards that you expose to UV but that needs transparencies and developer and all that stuff is expensive. So I'm a bit stuck on how to etch complex boards. 

Now that the sun is getting higher I see that the spot I wanted to place the mirrors is shaded in the afternoon. Guess I'm going to have to make some firewood.

« Last Edit: June 10, 2009, 10:29:17 AM by Davetech »


Davetech

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Re: Heliostat Project
« Reply #17 on: June 10, 2009, 10:21:48 AM »
Well, it seems I've embarrassed myself again.  Almost as much as I embarrassed myself when I joined and I thought G-code was run on a picaxe.  :-\

I've just been using a bookmark to this thread and had not explored the rest of your site until this morning. I see now that you, Gabriel, are well versed in CNC. Wow! That's a fine looking machine you have built there!


Gabriel

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Re: Heliostat Project
« Reply #18 on: June 10, 2009, 07:46:39 PM »
Yeah, I've been meaning to update the link back to the site so that it would be more obvious. I kind of figured that it would be easy to miss.

I've always liked that particular CNC design you're using. It seems like it would be pretty easy to put together. It's also conveniently portable, so you could even experiment on your kitchen table if you wanted to.

Mine looks good in the pictures, but there is still a lot that I could do to make it more accurate. I can't really do any fine detail work until I finally commit a few afternoons to work out the bugs. It does what I want it to do though, so I don't worry about it. :)

I've mostly been working on my heliostat lately. I bought an Arduino and tried programming it to run the heliostat but ran into some snags. There is just too much precise math involved for a micro controller to handle.

I bought a coprocessor that I hope will be able to do all the floating point math. Programming it is a serious headache though. It's not very intuitive at all. (The coprocessor, not the Arduino. The Arduino is pretty awesome actually.)

I think that I should be able to figure it out eventually though (famous last words)  :)

Take Care
Gabriel
   

Davetech

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Re: Heliostat Project
« Reply #19 on: June 19, 2009, 04:45:39 PM »
I moved my last couple of posts here over to the CNC section because I felt like I had hijacked the thread when I got sidetracked to building a pcb milling machine to make control boards for my heliostat. I'll post more here when I make heliostat progress!  ;D


Gabriel

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Re: Heliostat Project
« Reply #20 on: June 19, 2009, 07:05:39 PM »
I've pretty much given up trying to control my heliostat with an Arduino, for now at least. I actually got side tracked when I finally learned how to write software to control stepper motors through the parallel port.

After obsessing over this program for the last week, I finally have it very nearly finished.
This program will:
1. Allow an individual to control up to two heliostats with a PC.

2. Up to 10 targets can  be programmed into it for each heliostat. Simply click on which target you want to reflect the light towards, and it will automatically adjust to the correct angles.

3.  Pin outputs can be changed so multiple different driver boards can be used.

4.  Inputs for gear ratios and steps per revolution are also available.

5. The sun can be chosen as a target for either heliostat turning it into a sun tracking machine. This would be useful for either solar panels or a solar concentrator.

6. The position of the heliostats is automatically saved, so you don't have to go out and readjust them if your computer loses power or when you turn off the program.

This is what I have so far. What I want to add next is the ability to click a button and have it automatically seek out homing switches to reset itself. That way, if the program crashes or the heliostat loses steps for some reason, all you have to do is push a button and it will fix itself. There are also a few other things that I need to do to tidy things up before I can release it.

It's still just a Beta program, but it seems to be working really well. I hope to have it released sometime next week. It would be sooner, but I'm going out of town for awhile.

I've attached a couple pictures of the program.

Anyway, I guess I've babbled on long enough.

Take Care
Gabriel

Davetech

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Re: Heliostat Project
« Reply #21 on: June 19, 2009, 07:26:46 PM »
When I read that "ten targets" I immediately thought of all the mirrors that could be employed for direct lighting and heating through windows in the winter. Could be very beneficial to your heating bill!

The lady at the recycling center called me yesterday and told me she had two "huge" mirrors for me. I went straight over there and... she wasn't kidding!  One of them was just 32" x 38", but the other one was 42"x72"!   I thought it was a 4' x 8' until I measured it. It is in perfect condition and weighs.... a lot!
She charged me a total of $7 for them :o        I tipped her.  ;)

I've made progress on my cnc mill and was going to post about it but the pictures didn't turn out so good so I'll try again tomorrow.


Good job on the tracking program!  Looks nice and straight forward.
« Last Edit: June 19, 2009, 07:31:44 PM by Davetech »

Gabriel

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Re: Heliostat Project
« Reply #22 on: June 20, 2009, 04:37:07 PM »
Yeah, I've been collecting mirrors myself. I'm surprised at how easy it is to find them. I've been picking up mirrors that would be at least $50 new for just a few bucks. I even managed to find a gigantic mirror of my own for free.

The only problem though is that none of them are the same size, so I would have to adapt my heliostat design for each mirror.

Earlier today I was trying to see how vinyl siding holds up to the heat by reflecting the light from five mirrors onto a piece of scrap. As I suspected, it started to warp some after maybe ten minutes. I could put my hand on the siding without burning it, but it wasn't especially comfortable. The temperature felt like it was somewhere between walking on hot sand and putting your hand on the hood of a car on a hot day.

I went down to three mirrors, and the siding did better. It would be a shame to have the heliostat malfunction and end up ruining the siding across the side of my house. I guess it won't be such a big deal in the winter, but it is something that I will need to keep my eye on.

If only I had a house made of brick.  ::)

Davetech

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Re: Heliostat Project
« Reply #23 on: June 21, 2009, 04:15:03 AM »
The air in the collector box on my system hits 170 F with just two medium sized mirrors pointed at it. I've got vinyl siding too.

 I hope to someday sell this property and move to Colorado or New Mexico and put 3 or 4 shipping containers together, finish them out inside and surround them with straw bale and adobe or cob. With a super-insulated dwelling like that, I think I could live comfortably off-grid. 


VidarKristiansen

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Re: Heliostat Project
« Reply #24 on: July 03, 2009, 03:57:20 AM »

There is actually a heliostat program that I found fairly that is already in Basic. The link is http://www.green-life-innovators.org/tiki-index.php?page=Sunalign

I haven't tried it myself, but it might work well for you.



We actually also have a C and a Perl version of the same program available at the same address, as well as explanations about how the program works. All the code and other information on the site is available under "Creative Commons attribution share alike" The original program is developed by David Williams, Toronto Canada, by the way.

Kind regards
Vidar Kristiansen, Green Life Innovators
"Green Tech the Open Source way"
www.green-life-innovators.org

Gabriel

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Re: Heliostat Project
« Reply #25 on: July 03, 2009, 06:59:07 AM »
Hey Thanks!

One day I want to see if I can get that program to work on an Arduino. I tried getting my own to work, but the algorithms it uses to calculate the position of the sun involve a lot of floating point numbers. The Arduino can only handle so much.

If I'm able to do it, I will have to send it your way.

Take Care
Gabriel

Davetech

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Re: Heliostat Project
« Reply #26 on: July 03, 2009, 03:31:52 PM »
I'm afraid that the sophistication of my Picaxe program will amount to: "Duh... the light is on...push the button!   The light is off... let go of the button!   Hey, it got dark... go to the morning position!"

But so goes the KISS principle.


The further into the season we get, the fewer choices I have on where to place my heliostat. Before I go chopping down a huge tree, I need to get the system working. So I'm building the heliostat to be portable at the moment.

At one time I embedded a steel post in concrete in a tire for my kid and his friends to bat a ball around on. Forget what its called. Anyway, they managed to destroy it (no sweat for them!) and the concrete filled tire has been an edge-of-yard decoration for years. Now I'm going to use it as a heavy base.

I may need to secure the bottom board to the tire better but right now there is just a good gob of Gorilla Glue holding it on. There is a 3" lazy susan bearing (rated at 200 lbs) sandwiched between the two bottom boards. I can blow on it and it will rotate.

The pivoting Z-axis rod is a 40" piece of galvanized conduit. I probably should come up with some kind of bearings for it but it rotates pretty easily. I'm mounting the mirror horizontally to keep a lower center of balance. Plus the cast reflection fits my collector box better.



Had to stop there until I get to the store to buy some conduit clamps to attach the mirror mounting frame.

It won't be portable as in staying in the cart... that was just to haul that very heavy tire to my work area and lets me work on it at a comfortable height.


While I'm showing off my junk, here's my Poor Man's Table Saw.

The aluminum sheet has not been secured yet but I've been using it like it is. If it wern't dangerous it wouldn't be as much fun, now would it?  I do use push sticks when needed. I thought the sheet was galvanized steel until I started cutting it with a metal cutting blade and was surprised! It is probably worth a bit of money.




It is just a skill saw (used - eBay) mounted upside down with a small piece of pvc pipe wedged in the trigger. At present it is turned on and off by plugging it into the extension cord, but I've bought a double electrical box to mount a switch and receptacle in. Maybe I'll do that today. Dunno what I'll do for a fence, but it would be nice to have.





Speaking of a bit of money, I put that huge mirror up on Craigslist. Hope it sells.

Well, guess I'm out of junk to show for now. Mo' later.


Gabriel

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Re: Heliostat Project
« Reply #27 on: July 04, 2009, 03:30:19 PM »
Looking good there davetech.

I've managed to make some progress on my own heliostat today, which has been redesigned because I couldn't come up with an easy way to make worm gears without a CNC. It now uses lead screws to move the mirror to the correct orientation. I'm trying to keep things simple so anyone who wants to build their own heliostat can get the parts for it out of their local hardware store.

Attaching the lead screws to the heliostat was fairly straight forward. Rewriting parts of the heliostat program I wrote, however, was a pain. The math for a lever arm is more complicated than the math for a worm gear. Of course, it wasn't really the math that gave me trouble so much as working through all of the bugs that popped up once I started making changes. (Why are you moving down when I told you to move up? Why did you just move 50 degrees when I only told you to move 1 degree? ARRRGH)

I think?? I finally got it worked out though, so life can return back to normal. I'll have to test out the program more thoroughly later to be certain every thing works the way it is supposed to before I can release the upgraded version.

Anyway, I guess I've made some progress today.

Gabriel

Davetech

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Re: Heliostat Project
« Reply #28 on: July 07, 2009, 03:28:27 PM »
A problem occurred to me about my plan to aim multiple mirrors at my collector box.

I plan to put sensors above and to the side of the collector box which, when illuminated by the mirror's reflection, will tell the motor controller that the reflection is drifting off the box and adjustment needs to be made. That should work for one mirror. But what about multiple mirrors?

So I decided "Well, I'll just get around that by mechanically linking the mirrors."  What a simple statement.  I found that linking the mirrors on the horizontal axis should be easy, but linking the vertical axis as well, while the horizontal rotates, is another story.

After looking at many, many online patents and other people's ideas on websites, most of all which you'd need a machine shop to fabricate all the parts for the convoluted contraptions, I sat back in bewilderment. But then I had my own idea. At least I have not seen it anywhere else but I'm sure I'm not the first to think of it.

The vertical tilt should describe an arc that could be followed by a roller bearing on a curved piece of ~something~. I don't know if it would be a parabola, a semicircle or something in between, but it would follow the same path everyday (barring orbital disruption of the Earth which doesn't happen often.) Gabriel, you know more about that path than I do, I'm sure.

I guess I need to put a piece of poster board behind the heliostat and once an hour center the reflection on the collector box and mark the position of the counter-balance on the poster board.

I know that the elevation of the arc will change from day to day, but I don't think it will be enough to require adjustment but maybe every week or more. So the curved piece of something (I'll call it a ramp) can be made adjustable.

That would cut out half of the required control electronics and one motor!  I'd just need to pull the heliostat around on the horizontal axis and let the ramp control the tilt! 

Whuddaya think, Gaib?  Will it work?



The counterbalance sticks straight out behind the mirror. It is not touching the mounting base like the picture might make it look.  Those two small blocks of wood were all the extra weight it needed to be balanced.

Actually, if the ramp were placed just above the counterbalance, without the blocks the forward tilt of the mirror could hold the bearing on the ramp.



Gabriel

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Re: Heliostat Project
« Reply #29 on: July 07, 2009, 08:07:25 PM »
Yeah, linking multiple mirrors is something that I had to put a lot of thought into. I went with a gimbal design because I think that it should make the process fairly easy. I hope to be able to try it soon to be certain.

That's definitely interesting idea you have about your "ramp". You might have just ruined my good nights sleep though because I'm going to be up all night thinking about it. :D Sleepless night are always when I come up with my best ideas though, so it works out well.

I guess you could probably find a way to make it work. I don't know how much effort it will take, but it is worth a shot.

I might actually be able to help some with figuring out the ramp. I've attached a couple of pictures of the sun's path in my particular area. One for just today's date and another for the next 182 days (half a year).

I did this by loading the G-code generated from my "Heliostat G-code Program" into CamBam. To get it to load, you need to rename the file extension from .ngc to .nc

I could say more, but I should go to bed. I will think about it more while I sleep. :)

Take Care
Gabriel