The Cerebral Forum

Solar Projects => Heliostat Projects => Topic started by: Gabriel on January 31, 2009, 05:35:16 PM

Title: Heliostat Project
Post by: Gabriel on January 31, 2009, 05:35:16 PM
Here is a heliostat that I have been working on over the past few weeks. So far it seems to be going pretty well. I just got it set up for the first time, and it seems to be working. I was only able to try it out for about an hour and a half before the sun went behind the trees because it was late in the day. I will have to set it up early next morning to get a good run out of it.

I have a couple of picture attached to this post. If you look at the first one, you can kind of see the sun in the upper left corner. You can also see the reflection from the mirror on the cooler.

For now, I only have a small mirror attached for testing, but I will be putting a much bigger one on later.

The heliostat is designed in such a way that I should be able to attach more of them together in a row. So it will only take two stepper motors to control several heliostats.

I will continue to update this thread periodically as I get more finished.

Thanks for reading!
Gabriel
Title: Re: Heliostat Project
Post by: d2day on February 13, 2009, 12:28:04 PM
Nice job Gabriel...I am impressed with what you have accomplished.  :) :)

I have been looking into trying to track the sun in the same way you are doing it. I have a PRT Shopbot CNC, and am wondering if after I use the G code converter in Shopbot's control software to get your code converted, that the SBot control software would work for a sun tracker. I noticed that you have an interface worked out but that it requires Linix to run; I am trying to eliminate another learning curve. 

 I appreciate any help you may be able to offer, also not sure how SBot may react to use of their software for non Bot projects; even though it is for personal use.

digitize2day
Title: Re: Heliostat Project
Post by: Gabriel on February 13, 2009, 06:06:30 PM
Yeah, I've been working on this project a lot lately trying to get it finished so I can start experimenting with it. I swear though, Murphy had this project in mind when he made his law.

I've redesigned the heliostat since I took the picture because, along with several other reasons, that version didn't seem stable enough.

I've gotten the new version put together and was able to test it out some earlier today. It's working fairly well, but I need to make some adjustments to the program because it's not quite keeping up with the sun like I'd hoped. It takes several hours before that starts to really be a problem though.


I tried out the Sbot control software that you mentioned to see if I could figure out how it might work. I've never used it before, but it seems pretty straight forward.

I had a problem converting the g-code to shop bot code. For some reason, it didn't convert the pauses correctly. What I did to fix it was change the program so that it would output shopbot code instead of G-code, which fixed the translation problem.

 When I run it in the shopbot program though, it doesn't stop to pause like it is supposed to. I think this is just because I don't have a shopbot plugged into my computer. I have attached the file I attempted to run for you to try. If it pauses for 60 seconds like it should, your half way there.

-- I also attached a test program which outputs the shopbot code for you to play around with if you want. Please note that this program doesn't track the sun like the one I have on my site but instead reflects it towards a single spot. If you get it to work and need the other one, let me know -- Program removed because it has been replaced by a newer version


The next thing you need to do is to see if there is a way to change either the gear ratio or maybe the lead screw's TPI in the shopbot program. If you can do that, you should be able to "trick" the program to make one inch instead represent one degree.  I tried to locate it myself but couldn't find it anywhere. Maybe you know where it is?

Using the shopbot program like this is pretty neat. You'll have to let my know if you can get it to work.

If you have any more questions, let me know.
Thanks
Gabriel
Title: Re: Heliostat Project
Post by: d2day on February 15, 2009, 11:09:44 AM
Hey Gabriel,

The code looks good that you generated, I have run it in "preview mode" and I have the same indication you do. The preview mode is ignoring the pauses, I believe that is normal and you are right about the code needing to be run on a live machine. I appreciate the modification in the .rb file to convert the code to .sbp that will make the process much simpler.

Shopbot does have a way to "calibrate" the amount of movement, it is found in the "Values" under "UV". Shopbots indexer for rotary "stuff" can be set in degrees but not the xy or z axis. Not sure but it sounds like that "calibration" of the units that it outputs to the motors is the problem with your controller EMC2. I updated my system and had a very similar problem with it at that time. It would run a small part file with no issues but larger more complex part files lost steps. Shopbot eventually worked out the issue. SInce the total movement is so great the potential to loose "steps" becomes an issue. It may help to install bearings on all the movement points to help with binding. I plan to use a 8 foot sat dish and make my own mount like you have. I am not as far along with with my project as you are, I had struggled with the actual code to convert the sun position. (No code no need); I believe you have that part right and I am going to proceed on to the the actual building of the mount for my dish now.

Sorry I can't run a  file to check the entire code "movement" out because my machine bed is 4'x8' and some parts of the code would cause movement that would "crash" my machine. I have had the machine for a long time though and know the code will work on the controller. I will check to make sure it does the "pause" and let you know how it does.

I do need to get code that will track the sun...if that is not too much trouble.

Thank You very much for your help, I had almost given up being able to accomplish what you have done already. If there is any way I can help please e-mail me with your comments. I check e-mail a couple of times a day. ;D

d2day
Title: Re: Heliostat Project
Post by: Gabriel on February 15, 2009, 08:56:08 PM
Hey d2day,

I'm glad that I've been able to help. I know that it was about eight months ago that I first started looking into this whole sun tracking business. I couldn't find what I was looking for, so I had to start from scratch, which was a lot of work. I decided to start this website so that other people wouldn't have to do the same. Knowing that I've helped at least one person makes it all seem worthwhile.  :)

You may be right about EMC2 losing steps. I'll have try and rig Mach3 to see if that fixes it. Although, I've used EMC2 before and I don't think that I was losing any steps, but it's hard to remember because it was so long ago and I didn't really know what I was doing at the time.

 I've actually changed the design of my heliostat again yesterday because the design I was using made it really difficult to calibrate EMC2 so that moving it one inch would equal exactly one degree, which also made it difficult to troubleshoot the problems I was having. With a heliostat, accurate movements are pretty crucial. It's not a big deal to be half a degree behind when you're pointing something directly at the sun, but ,when you're reflecting the sun to hit a spot say thirty feet away, half a degree makes a pretty big difference.  :o

Anyway, I've attached the changed ruby files. Everything seems to be in working order. I'm not sure how the shopbot software will like the pauses for the restofweek and restofyear because they are some pretty long numbers. (For example PAUSE 59.9339710834736) I ran it on my end though, and it seemed like it was working. Those two ruby files are still pretty experimental because I haven't had a chance to run them for more than a day with a sun tracking machine hooked up. You might just want to leave those alone for now until I can test them more thoroughly.

I know I've said this else where, but be careful with the sun tracking programs. There are a lot of equations in the code which have the potential to give an answer which ,mathematically, is technically correct , but completely wrong for our purposes. It's hard to catch all of these anomalies because the time is always changing and also because people live in different locations. I only bring that up because you are making solar concentrator AKA "Death Ray".  ;D


I hope everything goes well with this project.
When you get it finished, I most definitely would like to see a picture.

If you need anything else, just let me know.

Take Care
Gabriel

Attached Program has been removed because a newer better version is available.

Title: Re: Heliostat Project
Post by: d2day on February 16, 2009, 05:55:36 AM
Thanks Gabriel.. I will post some info and pictures when I have them.
Title: Re: Heliostat Project
Post by: Gabriel on March 02, 2009, 04:58:43 PM
I have completely rewritten the sun tracking program with much better calculations over the last week. It is for this reason that I haven't updated the site in awhile as I have been working on the program rather obsessively. It is a straight forward enough process, but the book I used as a reference, Astronomical Algorithms by Jean Meeus, is meant for astronomers, and I don't know much about astronomy. I got stuck in several places and had to do a lot of research on the subject to figure it all out.

Another thing that caused some confusion was the fact that the internet sites I used to double check the output  are WRONG. Arrrrrrrrrg!   ???  :)

Suffice it to say that it's a long story, but it all worked out.

The program isn't quite finished, but I figured that I would upload what I have so far just so I can say I've gotten something done today. I still want to add in compensation for light refraction in the atmosphere  and I haven't yet added in adjustment for the time it takes the stepper motors to move from sunrise to sunset yet. Plus, I want to do some more double checking.

And I need to write the documentation for it

And I still haven't gotten the heliostat working yet. (Turns out I've been trying to do it wrong the entire time. There isn't a straight forward way to do it with the current program. Also, ignore all picture of my previous designs. They are wrong!)

And I want to make a GUI for the program

And (one day) I want to make it possible for the program to run the stepper motors directly instead of through a machine controller.

And I want it up so it can point at different windows automatically when one room gets too hot.


Anyway, if anybody wants to take a peek at the new sun tracking program you can. It will output the G-code, but there is no adjustment for the time it takes the stepper motors to move back and forth, so the machine itself will slowly fall behind. It will probably take a day(/week??) or two before that happens though depending on the design of your sun tracking machine, so you can still try it out.

I'll try and get it finished soon, but I've fallen behind in other areas of life and need to do some catching up. It might be awhile.

Thanks!
Gabriel
Title: Re: Heliostat Project
Post by: d2day on April 18, 2009, 09:29:56 PM
Hey Gabriel,

Sorry I haven't been on the forum for a while but I have been busy picking up the parts I needed to complete my project and working on the everyday things that get in the way of the fun stuff. I have most of the mechanics of the dish mount complete and have found a suitable power supply, the motor drives/gear boxes. I am still struggling with the final gear ratio but I believe that I will proceed on with my best "wag" at it.  More to come later with photos.

D2day
Title: Re: Heliostat Project
Post by: Gabriel on April 19, 2009, 05:06:24 AM
Hey D2day what's up

Glad to here that you're making progress with your project.

I've attached the new sun program modified to output shopbot code.
If you have any trouble with it, let me know and I'll try to fix it.

Take care,
Gabriel
Title: Re: Heliostat Project
Post by: Davetech on April 22, 2009, 11:52:53 PM
Greetings Gentlemen,

I too am interested in this project. I have an electric tankless water heater which I wanted to preheat water for. I installed a holding tank and built and plumbed a "hot box" solar collector. Circumstances dictated that the best place to mount the collector was in an area that is shaded half the day; however, I have mirrors. The system is now working, with manual aiming of the mirrors.

I wanted to find a way to build a heliostat that would not require the use of a computer or even a microprocessor. I have seen a good sun tracker that uses green LED's as sensors and thought I could modify it to act as part of a heliostat.

I spent last night breadboarding a simple circuit that uses an LM339 dual comparitor and two potentiometers. I figured if the sun tracker turned one pot, the comparitor would be out of balance, turn on a motor and turn the mirror and the other pot until the pots were in balance again and the motor would turn off.  I hoped that with the proper gear ratios I would be able to keep the mirror reflection stationary.

I got it to work, sort of. But hysteresis in the circuit seemed to make it take more and more movement on the second pot to get them back in balance. I'm not even sure if the pots were linear or logarithmic, I just dug them out of the junkbox and saw they had the same resistance value.

By then it dawned on me that this was only going to be the first of many snags I would run into by trying to do it this way. I decided to go ahead and learn to use a picaxe.

I've done a bit of simple programming in Basic years ago, but my total experience with the picaxe and gcode consists of a few hours of reading here and there. I got on eBay tonight and ordered a board/kit from England which has a picaxe and motor H-bridge on it. So it will be a while before I can get my grubby hands on it.

So in the mean time I thought I would see if there was any gcode heliostat programs available on the net... I googled +gcode +heliostat and there wern't too many choices that popped up. But this forum was right at the top so here I am!

I'm surprised that there seems to be so many people building sun trackers (judging from youtube, instructables, etc) and yet so few tackling the heliostat. Anyway, this is my all consuming state of mind now and the thing that keeps me awake at night with all the little wheels turning, and I'll probably be checking in fairly often.

Davetech
Title: Re: Heliostat Project
Post by: Gabriel on April 23, 2009, 07:01:44 PM
Hello Davetech and Welcome to the Cerebral Forum

Sounds like you've done quite a bit of work already. I'm not overly familiar with electronics, but I think I understand what you were trying to do with the LED's. From what I've read on the net, it is indeed difficult to get it to work correctly with that method.

I've also been interested in setting up a microcontroller to take the place of the computer simply because it uses a lot less power. That, and it can be placed directly on the heliostat. Right now though, I've been trying to get a larger heliostat design put together first so that I will have a decent amount of sun power to play around with.

I have attached the heliostat program. I haven't actually released it on the site yet because I haven't had much of a chance to test it, but you are welcome to check it out. Do be careful though.
UPDATE: Attached Program has been removed as it is now out of date. Follow the link for the most recent version. http://www.cerebralmeltdown.com/projects/heliostatprogram/default.htm (http://www.cerebralmeltdown.com/projects/heliostatprogram/default.htm)

So, are you going to try and translate it into Basic for the picaxe, or were you just looking for this out of curiosity?
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 (http://www.green-life-innovators.org/tiki-index.php?page=Sunalign)

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

Anyway, I have to go. Which is probably a good thing because I have a tendency to ramble.  :)

Keep up the good work
Gabriel
Title: Re: Heliostat Project
Post by: Davetech on May 07, 2009, 09:05:31 AM
Well, I've made some progress.  I built a mock-up sun tracker that uses LED's as sensors. I used gears and a dc motor out of a junked printer and breadboarded a control circuit using a single BA6209. it is capable of driving the motor either direction depending on which pin goes high. It will follow my LED flashlight around the room and will track the sun. Bright sunlight has enough ambient light reflected that it makes the motor chatter all the time, so I'll either solve that with a hood or might need to interface it with a component with a threshold. I think if the sensors are mounted on the mirror assembly, it should work fine but I'd need a second one to control the Z axis. Getting tons of rain down here now though.

My Picaxe 18x w/ motor control kit arrived yesterday. I've assembled it, built a diy serial download cable, programmed it and have it working flashing LED's. Now it is just a matter of interfacing it to do something useful. Myriads of possibilities! 

I've downloaded PCB Artist (freeware) and gotten used to using it. Its autorouting is a great timesaver! Laid out and etched a board with two PBL3717A's on it that I think will control the X,Y and Z axis. The Picaxe will control this board. The RKeducation board came with an L293D on it but this board I made will be beefier I think.

So I'm making progress on two fronts.
Title: Re: Heliostat Project
Post by: Gabriel on May 07, 2009, 07:24:34 PM
Yeah, it's raining here too, and it is most certainly slowing things down as far as building heliostats goes.

Sounds like you're definitely making good progress. When you get it finished, you should put it on your site to show it off. (Assuming that you haven't already and I just missed it.)



Gabriel
Title: Re: Heliostat Project
Post by: Davetech on May 10, 2009, 06:25:38 PM
Although I've been successful at driving stepper motors with the picaxe, the KISS principle dictates that I just use regular 12vdc motors for this (especially since I have a box full of them from junked VCR's). I also have several quad pole, double throw relays (military grade!). A single one of these relays can reverse the directions of the motor using only a single output from the picaxe if ya know how to wire it.

Its gotten down to mechanical construction now and I have gathered volunteers from my junk box. The pics are of dead VCR gears, motor, head cylinder assembly (good bearing) and a threaded rod with 2 nuts brazed to a straight copper fitting. The flat belt and gears will slow down the rpm's and the threaded rod assembly will be my linear actuator.

(http://davetech23.tripod.com/motor_and_gears_01.jpg)

(http://davetech23.tripod.com/motor_and_gears02.jpg)


Now I need to make a housing to mount the stuff on and to make bearing ends for the threaded rod (after I remove the end threads). I decided to fire up the foundry and make some aluminum/zinc alloy sheet metal. I've done it in the past when I poured molten aluminum on a thick steel I-beam. Then I just cut it into sheets. Thin but strong.  Well, 2 attempts and 2 failures today. The first time the metal bubbled. I had forgotten to heat the steel up to remove any trace of moisture from its surface. The second pour resulted in too thick a puddle, which cracked upon cooling due to shrinkage. Then I remembered that I should have tilted the I-beam a bit so the metal would run down it, producing a thinner sheet.  Lessons learned.  Well, I had gotten enough smoke in my eyes for today and decided to leave attempt number 3 for another day.


Title: Re: Heliostat Project
Post by: Gabriel on May 19, 2009, 08:10:49 PM
Wow, you're really moving along. I'm going to have to raid a few of the old/broken VCRs that I have lying around the next time I need some DC motors.

I also like how you attached the threaded rod, which is something that I can rarely get right.

And sorry it took me a couple of days to reply. I had some work I needed to take care of.

Thanks for the pictures and I can't wait to see what comes next!
Gabriel
Title: Re: Heliostat Project
Post by: Gabriel 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.

Title: Re: Heliostat Project
Post by: Davetech 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.

(http://davetech23.tripod.com/linear_actuator_1.jpg)

(http://davetech23.tripod.com/linear_actuator_2.jpg)


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.

Title: Re: Heliostat Project
Post by: Davetech 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!

Title: Re: Heliostat Project
Post by: Gabriel 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
   
Title: Re: Heliostat Project
Post by: Davetech 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
Title: Re: Heliostat Project
Post by: Gabriel 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
Title: Re: Heliostat Project
Post by: Davetech 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.
Title: Re: Heliostat Project
Post by: Gabriel 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.  ::)
Title: Re: Heliostat Project
Post by: Davetech 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. 

Title: Re: Heliostat Project
Post by: VidarKristiansen 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 [url]http://www.green-life-innovators.org/tiki-index.php?page=Sunalign[/url] ([url]http://www.green-life-innovators.org/tiki-index.php?page=Sunalign[/url])

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
Title: Re: Heliostat Project
Post by: Gabriel 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
Title: Re: Heliostat Project
Post by: Davetech 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.

(http://davetech23.tripod.com/porta-heliostatbase01.jpg)

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.

(http://davetech23.tripod.com/poor_mans_tablesaw01.jpg)


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.


(http://davetech23.tripod.com/poor_mans_tablesaw02.jpg)


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.

Title: Re: Heliostat Project
Post by: Gabriel 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
Title: Re: Heliostat Project
Post by: Davetech 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?

(http://davetech23.tripod.com/porta-heliostatbase03.jpg)

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.


Title: Re: Heliostat Project
Post by: Gabriel 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

Title: Re: Heliostat Project
Post by: Davetech on July 07, 2009, 10:59:17 PM
"You might have just ruined my good nights sleep though because I'm going to be up all night thinking about it."

Heh... you and me both!

Your half year path representation tells me that the ramp's dimensions might have to change with the season. Unless I can figure a way to make it "seem" to change without actually changing it.  I tried to think what the effect of moving the ramp further away from the vertical axis would be, but it is late and it made my head spin. Guess I need to cut a piece of wood and try it.  Of course the ramp not only needs to be curved vertically but also curved horizontally. Got any curved boards laying around?  :-\

 
________________________________________________

Hmmm... I might have just thought of a way to use a straight board... yep, sleepless night ahead!

Title: Re: Heliostat Project
Post by: Davetech on July 29, 2009, 03:41:49 PM
Well, I haven't posted here for 3 weeks because I've been busy with my cnc project.  Now it is on hold until I receive some thick copper clad board that I think (hope) will be thick enough my machine won't cut through it.

Today my eBay wireless doorbells arrived. I've already explored the electronics and found a point that jumps from zero volts to 1.3 volts when the remote button is pushed. That should save me from having to run wires from the collector box to the heliostat.  Now I can keep busy for a little while hacking the remote to be triggered by light hitting LED sensors.

I've checked and each remote will only trigger the sound module it came with, so I'll have two channel capability. I didn't see any dip switches to change the coding. But, what did I expect for $1 plus $4 shipping?  :D




Title: Re: Heliostat Project
Post by: Davetech on July 30, 2009, 02:04:10 AM
Here's a little more about the wireless doorbell. I'm kind of excited about this because it could have lots of remote control applications and was really easy to do.

(http://davetech23.tripod.com/sensor01.jpg)

Here's the transmitter and receiver opened up and bareing all on my train wreck of a worktable. The receiver/ringer part runs on two AA's. That would be 3 volts with standard batteries but I used NiMH so it was only seeing 2.4 volts... and working.  Since it will be mounted along side the heliostat control board which has the micro on it which needs 5 volts, I wanted to know if it could run at 5.  So I ran the receiver at 5 volts from the bench supply. It was quite happy. The Simpson is set to 15ma full scale. With 5 volts Vcc, the receiver draws a mere 2.5ma  :o   A regular LED draws about 20 to 30ma!  When activated, the current jumps to 5 ma for just a moment and then drops back to 2.5ma.  Clearly, a couple of alkalines would run this thing a long time. Or a small pv panel could run it.  It might have drawn a bit more current had I not disconnected the little speaker. I could have my choice of 24 melodies to listen to every time the heliostat made a correction, but I opted out on that.

As I said in the above post, I found a point in the receiver circuitry that goes high when it receives a signal from the transmitter. With 5 volts Vcc, this point goes to 2.6 volts. It will be a simple matter to run that through an 10k resistor to an input on the micro.



(http://davetech23.tripod.com/sensor03.jpg)

The transmitter runs on 12 volts. The $1 price tag included a 23A 12 volt Alkaline which came with the unit. The transmitter draws zero current on standby and here too, only a very few milliamps when the button is pressed.

Here's the transmitter hacked to be triggered by three water clear gallium phosphate (green) LED's. I have soldered their leads in series and glued them together with a gob of gorilla glue (kind of hard to make out in the picture, but that's what you are looking at). In strong light, they generate .7 volt, enough to forward bias the 2SC945 NPN transistor which then turns on the 2SD837 high gain NPN Darlington transistor. The 2SD837 is a high current device and was overkill, but it was handy and it worked.

This thing is set up so that the battery is disconnected until the button is pressed. The button presses on a micro lever switch, which connects the battery to the circuit, so it was simple to let the Darlington supply the circuit.

I was planning to make a little circuit board for the sensor components, but since it turned out to require so few parts, I just soldered their leads together and will probably mount them in a tube and pot them in resin or epoxy. I'd just gob hot glue all over them if they wern't going to be in the sun. The tube will extend out as a hood and help keep ambient light from affecting the LED's. That's the plan, anyway.

The seller claims the unit will work up to 70 meters.  With NiMH batteries in the receiver, my unit was getting about 100 feet. I think the voltage in the transmitter would have a much larger effect on range. But 100 feet is plenty for what I want (to keep from having to run wires from my solar collector hot box to my heliostat controller).

So. Now you know more than you ever wanted to know about wireless doorbells. Put your thinking cap on and I'll bet you can find a use for it in your project.



Title: Re: Heliostat Project
Post by: Jon on July 30, 2009, 02:40:49 PM
Thats looks like some good off the shelf material for wireless.  My wife got a solar powered garden light at Family Dollar today, and it switches on/off with the light level on the solar panel (some other units/types have another photo-sensor device near the panel).  That or its parts could be used for sensors, but it's not wireless.

[UPDATE Aug. 5, 09  OOPS , yes it is wireless, a laser, but it's "very narrow" coverage as compared to common radio-wave wireless  :) - I guess thats what I was thinking when I wrote this. ]

Title: Re: Heliostat Project
Post by: Gabriel on July 30, 2009, 06:06:46 PM
That's a really cool hack of a wireless doorbell. It makes me want to sit down and learn more about electronics so I can do that sort of thing myself.
Title: Re: Heliostat Project
Post by: Jon on July 31, 2009, 12:29:05 PM
Another option to go wireless is with a laser pointer.  From the sensors, it can "send" a signal to the heliostat that light/no light has been sensed, but it would require more "alignment" than a wireless method, and is prone to some interferences such as people or birds interrupting the light signal, etc.

I guess for any "feedback" aiming system, the light sensors will also have to sense when the Sun changes direction after the afternoon....that is, when it starts to go down or lower in the sky.   A motor will be required to change the direction of the heliostat; probably reverse the direction of the vertical adjust stepper motor.  It might take some kind of "logic gate/electronics" such as a logic chip (maby AND perhaps) or transistors to collect and then signal this condition.
Title: Re: Heliostat Project
Post by: Jon on July 31, 2009, 09:05:07 PM
Looks like Gabriel's mechanically ganged heliostats can illuminate multiple targets/receivers, and even possibly increase the energy per unit area of any single target/receiver if they reflect all the solar energy to that one spot.

I was also thinking of a way to increase the energy per unit area without any ganged heliostats.  Maby I'm wrong but I'll try to explain.  Given one heliostat, the right side of the mirror will effectively illuminate the right side of the receiver, and the left side of the mirror will effectively illuminate the left side of the receiver.  If the mirror is cut in half, the left side mirror can be adjusted so that its reflected light will overlap the right side light on the receiver.  Hence the illumination or energy there has doubled.   I still need to make a basic experiment of this using two mirrors on a piece of wood, when the Sun ever comes back out, and see if it is possible.
Title: Re: Heliostat Project
Post by: Davetech on August 01, 2009, 04:21:27 AM

"Another option to go wireless is with a laser pointer."

I tried that.  A couple of months ago I ordered a laser pointer for that very purpose. It puts out red light and is quite powerful. I could clearly see its spot on the trees across the highway in front of my house at night. That's over 150 feet away I'd guess. But I couldn't get any led's to produce electricity from the light. Wrong wavelength I guess. Besides, the laser spot was so small that I couldn't illuminate more than one led at a time unless the group of three was a long way off.    I also tried an infrared receiver from the front panel of a junked vcr, but no joy.  A regular tv remote control might be useful but I had the feeling it might be susceptible to stray infrared.

---

I mounted the sensor components in a tube today and took the whole bread-boarded sensor/transmitter assembly outside and set it atop my solar collector box. I adjusted a mirror to shine on and off the tube and it worked great... for a little while.   Then it quit working. To make a long story short, I finally discovered that the supplied A23 12volt battery was pretty much dead.  Now I think I know why the units were being sold so cheaply. They probably sat in a warehouse for too long (years) and the alkaline batteries bundled with them ran out of shelf life. It was easier and cheaper to just get rid of them on eBay. 

I didn't have any good A23 batteries so I just dug a 12vdc wall wart out of the junk box and will power the the thing with that for testing until I get new batteries. I think a good battery will power the thing for years and I won't have a lossy wall wart wasting electricity in the form of heat 24/7.

---

"I guess for any "feedback" aiming system, the light sensors will also have to sense when the Sun changes direction after the afternoon....that is, when it starts to go down or lower in the sky.   A motor will be required to change the direction of the heliostat; probably reverse the direction of the vertical adjust stepper motor.  It might take some kind of "logic gate/electronics" such as a logic chip (maby AND perhaps) or transistors to collect and then signal this condition."

The little actuator I've built uses a regular pm motor instead of steppers. I've got a whole box of them from scrapped vcr's. And the circuit I've designed is capable of reversing the motor direction. It probably would not be too difficult to do the basic control with some TTL logic but a picaxe micro with its software can be so versatile. In addition, it is dirt cheap. So the plan, at present, is to let a picaxe do the controlling and it can know when and where to go back to the morning position, and maybe through software I can teach it to do an occasional search if the sun is playing hide and seek. But that's further into the future than the end of my nose, so I haven't given it any deep thought.  I tend to learn by doing and I can't do that part yet.



Title: Re: Heliostat Project
Post by: Jon on August 01, 2009, 09:33:36 AM
I guess laser light would have its problems, but it can be sensed reasonably well with a light dependent resistor (LDR) - sometimes known as a photo-resistor, and maby a photocell also.  I have a vid. on my youtube channel with a laser and LDR.  Thing is also, when I used the LDR, I think there is some "grey areas" of on and off conditions when a simple transistor is used to amplify the light/electric signal received, so someday I'd like to make a voltage comparator circuit or something similar so that the condition of on or off is solid with no grey areas.    Using a microprocessor chip might also not have the problems just described due to its digital nature, rather than analog.  When I get a good burst of energy in me, I begin to make something, until then it's just a dream.


Update of using multiple mirrors:  I did a quick test using two small mirrors, one test in the house with the lightbulbs, and one test outside with the Sun.  The target was just a wall, and I did not test long enough for the Sun to make reasonable changes in its position.  I "focused" the light from each mirror onto the same spot/target, and then moved both the mirrrors a bit together and the lightbeams stayed together (but not at the same target/location for this quick experiment), but I can tell that for this system, once the mirrors are set, that the target cannot change; or at least must be the same distance away if it does,  otherwise the "light beams" won't intersect at the target/receiver.

Update: Aug 4, 09:  A short vid of this concept:  An Understanding Of Some Heliostat Concepts (http://www.youtube.com/watch?v=HP3ZWTkkNTU#lq-lq2-hq-vhq)




Title: Re: Heliostat Project
Post by: Davetech on August 15, 2009, 09:58:12 PM
My first attempt using led's as sensors used an LM339 dual comparitor and I bumped into the same problems with "grey areas".  Perhaps if the comparitor were followed by a flip-flop...   but, yes, a micro does make the whole system a lot more versatile and easier to configure.



I've gotten a little more done on my project.

Back when I saw it was going to take weeks to get the engraving bits to make my control board, I ordered a picaxe project board. I hate perf- boarding but it is better than nothing. Well, it arrived the other day and I built the controller on it and wired up the door bell receiver to it. I've installed the mechanism and the electronics in an enclosure along with a motorcycle battery and have taken it outside and attached it to my mirror assembly.

The wireless door bell receiver output goes high for about 2 seconds when it is triggered and I thought that was going to be a problem because the mirror would move too far in 2 seconds, but I found that the picaxe could easily handle the problem by just telling the motor to run for 250 milliseconds and then pause for 2000 milliseconds, then check to see if the sensor pin was still high. It works great, with the motor just bumping the mirror about a degree at a time.

Today I tried to learn something about my ramp idea. I took hourly notes on the position my mirror assembly was in to reflect on the collector box and then I cut a piece of wood in a semicircle that I thought was close to what the ramp needed to be like. I needed about six arms to hold everything in place and was having a difficult time with it. Part of the problem was the heat. I can only work a for a while in this heat and then I start feeling my pulse in my temple and my vision whites out in the center. My peripheral vision stays okay, but what I'm looking at is just a big white spot. Then I have to go inside and cool off. So I didn't get near as much done today as I had hoped.

In retrospect, building the electronics on the picaxe project board is probably a good thing because it is something "Everyman" has access to since they are available on eBay. And my goal is to present something that anyone handy with tools and who knows at least how to assemble an electronic kit would be able to build this system for themselves.
Title: Re: Heliostat Project
Post by: redrok on September 14, 2009, 10:41:09 PM

Hi Davetech;

You asked about using light sensors to track heliostats.
Here are some concepts for you to ponder:

1. There are 2 basic heliostat mounts.
   A. The "Vertical Axis" heliostat mount, Like Gabriel's.
      Alternate names are ALTitude/AZimuth or Pan and Tilt.

     The tracker for these, and others, are the "Inline"
     dual axis trackers. See:
     http://www.redrok.com/neat.htm#US4276872 (http://www.redrok.com/neat.htm#US4276872)
     See Leo Gerst's heliostats:
     http://www.heliostat.us/ (http://www.heliostat.us/)
     This tracker is positioned between the mirror and
     receiver and sees the sun back through the mirror.
     It control the motors so the sun is positioned in
     the center.

     There is a problem though. There is another stable
     mirror orientation where the sun is located at the
     edge of the mirror.

    B. The "Receiver Axis" heliostat mount.
      Alternate names are Target Axis.

       This heliostat mount is a bit different. See:
      http://www.redrok.com/heliolighting.htm#receiveraxis (http://www.redrok.com/heliolighting.htm#receiveraxis)
      The main axis, or Receiver Axis, is aimed at the
      receiver. The secondary axis is tilted from the main.

      The dual axis tracker is mounted on a mechanism that
      allows it to aim directly at the sun. The mechanism
      allows the mirror to be aimed in the half angle
      direction. In this case its made with a pair of
      gears. See:
      http://www.redrok.com/heliolighting.htm#recaxgear1 (http://www.redrok.com/heliolighting.htm#recaxgear1)
       Cables or pantographs can also do this.
       
      Here is another one:
      http://www.heliotrack.com/ (http://www.heliotrack.com/)

      The tracker for this is not confused by alternate
      orientations as it's always aimed directly at the
      sun. The mirror is kind of dragged along.

An advantage of these types is no computing is required
for operation.

Duane
                                      Receiver
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Title: Re: Heliostat Project
Post by: Jon on October 06, 2009, 11:01:05 AM
This is about the feedback method where the light sensors are downrange near the collector/receiver.  Perhaps if the sensors are brought closer, maby a few feet away or so from the mirror, then a wireless sysem might not be needed.   It might affect the accuracy slightly, but it should still work right if it's not to hard to implement.  The light sensors still are to "side" of the reflected light to the target.  When the Sun appears to change position, the reflected light will illuminate the sensors which will turn the motors on to adjust the mirror back into position.  I guess the sensors have to be positioned exactly where needed since a degree off here could mean a foot or two off at the receiver/target.  Downrange, I believe the light from the mirror gets "fuzzy" at the edges so it could be good to have the sensors closer to the mirror.   I think it is also possible to have the light sensors in the reflected light.

One thing to remember about this "heliostat feedback system" is that it is supposed to be/in theory a non cpu/micorprocessor controlled type thing, except for some optional simple logic circuits/ic chips if needed.  Or in short/otherwords there is no timing/guidance method with this system, it simply positions itself with light sensors as things happen.
Title: Re: Heliostat Project
Post by: xqp on November 14, 2009, 05:16:40 PM
A regular tv remote control might [...] be susceptible to stray infrared.

They will pick up stray infra red, but it's not a problem because the handset transmits a short fast sequence of pulses (a different sequence for each button) and the receiver only reacts to those pulses. The "stray" changes in IR level are very slow so they're easy to filter out. I wouldn't expect it to work too well outside because (on a sunny day) the IR levels are going to be pretty high and the receiver will probably saturate (ie "overload").
Title: Re: Heliostat Project
Post by: helpmonkey on November 18, 2009, 05:32:00 PM
Hello Davetech ... helpmonkey from greenwatts... long time ... hope all is well ... sent you a youtube message ... this is a nice thread on heliostats ... very impressed to see Duane from Redrok post here ... I have been trying to make the canuckle into a heliostat for a long time and I have a circuit that I think can do it.. it converts the targets (sun and whatever your aiming at) into voltages and then simply devides the resultant.. I havnt made the final circuit as I am still working on making a single axis work using resistance and I sure could use some help... I will post a link to a schematic if any of you guys are interested or would have some input...
Title: Re: Heliostat Project
Post by: helpmonkey on November 26, 2009, 09:39:53 AM
here is a link to the first circuit which is a single axis solar tracker ... I think I have the circuit worked out but would welcome any comments and help to improve it. Basically the same circuit will be used for the heliostat but I want to make sure I have the basics covered.
http://www.greenwatts.info/index.php?page=cds-tracker (http://www.greenwatts.info/index.php?page=cds-tracker)
Title: Re: Heliostat Project
Post by: Gabriel on November 27, 2009, 07:29:44 AM
Hello helpmonkey, and welcome to the forums.

I don't know enough about electronics to be of any help there, but I have seen a couple of other people who have done something similar to what you are trying to do.

You might have already seen these, but, if not, here they are.
http://www.foundry.ray-vin.com/fusion/fusionstory.htm]
[url]http://www.foundry.ray-vin.com/fusion/fusionstory.htm (http://[url)[/url]

http://www.heliostat.us/howitworks.htm (http://www.heliostat.us/howitworks.htm)


Both of those sites use a two axes system instead of a single axis.  Are you planning on making two single axis trackers for your heliostat? I think that would add a lot more capability. A single axis system would only really work well when the heliostat is aligned a specific way using a Polar Tracker setup. (Here's a Wikipedia link which explains the polar tracker some (scroll down). http://en.wikipedia.org/wiki/Solar_tracker (http://en.wikipedia.org/wiki/Solar_tracker))

A single axis system would work, but a couple downsides are that the target must be situated directly in front of the heliostat (in line with the tracker's axis) and that the heliostat's declination would have to be changed manually as the sun get's either higher or lower as the seasons change.

You might have already known all that, but I figured that I would say it anyway in case someone else is interested.

By the way, is the Greenwatts site yours?


Title: Re: Heliostat Project
Post by: J. Garcia on June 12, 2013, 01:08:53 AM
Well, I've made some progress.  I built a mock-up sun tracker that uses LED's as sensors. I used gears and a dc motor out of a junked printer and breadboarded a control circuit using a single BA6209. it is capable of driving the motor either direction depending on which pin goes high. It will follow my LED flashlight ([url]http://www.robustbuy.com/led-lighting-gadgets-led-flashlights-c-505_1027_730.html[/url]) around the room and will track the sun. Bright sunlight has enough ambient light reflected that it makes the motor chatter all the time, so I'll either solve that with a hood or might need to interface it with a component with a threshold. I think if the sensors are mounted on the mirror assembly, it should work fine but I'd need a second one to control the Z axis. Getting tons of rain down here now though.

My Picaxe 18x w/ motor control kit arrived yesterday. I've assembled it, built a diy serial download cable, programmed it and have it working flashing LED's. Now it is just a matter of interfacing it to do something useful. Myriads of possibilities! 

I've downloaded PCB Artist (freeware) and gotten used to using it. Its autorouting is a great timesaver! Laid out and etched a board with two PBL3717A's on it that I think will control the X,Y and Z axis. The Picaxe will control this board. The RKeducation board came with an L293D on it but this board I made will be beefier I think.

So I'm making progress on two fronts.



I have made a 180 degree rotators and that is with some not used parts in the house.. It needed only one motor quite amusing thing..
Title: Re: Heliostat Project
Post by: Brendan on June 18, 2013, 06:25:42 AM
Hi J,

I'm working on a single motor design also -- hope to release it to the wild in a month or two.  The goal is cost reduction but it comes at the price of a little complexity.  Good luck on your work.

Brendan
Title: Re: Heliostat Project
Post by: Gabriel on June 25, 2013, 07:53:36 AM
This topic is waaay old. It is safe to assume that everything I posted here is completely wrong and doesn't work.

I'm now marking it as closed so that it doesn't get bumped up to the top of the forum as new information.