My first step in the right direction...

[Madscientist267]

 

Hello all!

Well, today marks a decent day for me in the quest to start using RE rather than the grid, and while it is minimal, it definitely works very well for what it is, and I feel that 'addiction' setting in that I keep reading about...

The setup is very simple at this point:

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Solar Panel:

20V OTV, 8W peak (just over 0.4A Isc, measured @ high noon summer solstice; that's how they're measured right?)

Primary Storage:

12V 5AH SLA

Secondary Storage:

3.7V 2100mAH LiPo (several)

Power Conversion:

6-40V input drawing 190mA @ 13.8V, with 4.20V 480mA output

Based on the 34063A DC-DC controller chip in bucking configuration

Lighting:

A modified 24 x White LED 'UFO' camping light fixture from Wally-World @ $4.97 (really good source of cheap, bright white LEDs, all packaged up ready for use!)

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It turns out the key to this whole operation's success is the bucking converter that converts surplus voltage into more useful current for charging the LiPo cells.

Before the converter, I was trying to charge them via dropping resistor, which I knew was a waste, but didn't realize how much until I incorporated the booster. It was taking several hours to charge one off of the SLA, and the panel was having trouble recovering even what it took to charge just one LiPo that was about 50% discharged! I would have to wait a whole day for the SLA to charge back up with no load on it just to recover the losses!

When I did a comparison of the old method vs. new, I found that the old method was something like 24% efficient - sad. Using the buck converter, the number is in excess of 75%! Niiice! Now I can charge 3 (discharged by about 50%) in one day easily, and still have a little bit of time at the end of daily insolation to recover most of the charge in the SLA that was lost from passing cloud cover and such. I'm sure this number will increase when summer rolls back around; guess I'll have to come up with a better surplus dumping scheme, eh?

So, most of the time, there is a surplus from the panel. To deal with this (without being wasteful), I am currently dumping any surplus from the panel via blocking diode to a small bank of four 12V 12AH SLA wired in parallel. This ensures the primary battery gets full charge, and prevents overcharge by diverting the excess (at intentional potential loss thru the diode) to the larger bank. Anything left over after that is well, just lost, but the panel doesn't quite have enough juice to get the 48AH bank going into OC, so all is good.

The panel isn't permanently mounted, and actually sits on top of a tripod that was included with this cheapy telescope I picked up from Rite-Aid a while back. Works great, just have to adjust it every hour or so to keep it pointing in the optimal direction. I'm working on a tracking mechanism (powered by it's own independent panel), using the gutted remains of a tray type CD changer's carousel, and a cute little circuit using CdS cells I picked up on the web a little while back. We'll see how that goes.

In the mean time, I use the lights nightly, and even though temptation (and habit) make me reach for the light switches on the walls, I make a concerted effort to use the UFO lights whenever I think of it.

It's not much just yet, but I'm having fun and learning a lot, isn't that what's important?

Pics to come as soon as I get them out of the camera.

Steve

 

[DamonHD]

Sounds good!

You're definitely getting hooked: you think that you can give it up any time you like I know, but just you try!

B^>

Rgds

Damon

[Norm]

Do you know how much Ma. the fixture uses?

For example I have a 4LED lamp push button

that uses about 32 Ma. adequate for a reading

lamp or 'nite lite' but I prefer 6 volt 4watt.

fluorescent fixture for $5.95

8 12volt 5amp/hr NiCad packs and 3 lVW panels

Aluminum plastic web lawn chairs to position

each of the VW panels.

Winter sucks for panels....but good for little

stepper windmills.

Sounds like you're having as much fun as I....

Terrifficc !

[Madscientist267]

Norm -

Unfortunately, I never did any actual readings on the original design, and you posted just after I modified the other 3 UFOs I had! I can however give you the details of what was inside; maybe you can get a ball park figure from that...

In the OEM version, there are 24 LEDs, cut into 8 sets of 3, with a 30 ohm dropping resistor feeding each trio from a 6V rail (4xAA).

Combine that info with the specs that are known for the modified version:

Instead of 8 sets, they are now cut into 4 sets of 6, with a 10 ohm resistor per set, being fed from the LiPo battery. The voltage drop across any single LED is approx 3.2V and the entire fixture draws about 300mA with close to a full charge in the battery (terminal voltage under load is approx 4.1V).

Hopefully this answered your question...

While I'm at it, I'd like to add that this proves to add a bit of difficulty however when calculating an accurate 'lifetime' draw for WH calculation, since the current declines significantly as the battery discharges. I haven't done a graph yet to get a good picture, but I know for sure that its not straightforward...

They will run for over 8 hours before the battery starts dipping to dangerous voltage levels (must be monitored manually - there is no low-end cutoff). The cells are a couple of years old, and were used when I got them (power for hand held computers). They are currently performing at somewhere between 1/2 and 2/3 their rated capacity. Didn't bother me - I got a decent stash for a nice price - FREE!

Doing minimal math, 8H x .3A = 2400mAH isnt possible even with a NEW cell (2100mAH), and with the prorate applied (~1050 - 1400mAH), you can see that there is a complex equation going on here.

Also, I just finished a 36 LED lamp, that is a mix of 24 of the 'cold' white LEDs from the wally world fixture, and 12 warm white from a lamp I picked up at home depot some time back. This was borne out of complaints from the wife that the light was "institutional" in appearance, and she hated using them because of this. The new lamp puts off beautiful, what appears to be close to full spectrum white now. De Beers should consider this thing for providing display light - I think I just had my first true experience with a diamond.

The drawback is that it is hungry - I pushed the LEDs a bit harder this time around and when I measured the current, I figured I should put a limiter in there so I can get more than a couple hours total use out of it. There are 3 power settings: night light (1mA), Mood (50mA), and OMFG the sun is back out (750mA).

Steve

[zap]

I'm still waiting for the pics.

"Pics to come as soon as I get them out of the camera."

Are they refusing to come out on their own?

[Madscientist267]

Ok, here they are. Zap is right, I've been neglecting my duties as an experimenter, and not posting the pictures. So without further adieu:

From top to bottom, left to right:

The 12V 5AH SLA is primary storage

The battery 'interface' (aftermarket 12V power port set, mainly for it's terminal posts and fuseholder)

Main power tap (size M coax, everything is!)

xV->4.2V buck converter for charging the LiPos. Usually I do this from the SLA, but it works just fine directly from the panel as well. Charge Time? 4 hours per LiPo if they are exhausted (3.2 OTV).

The 3 'UFO' 24 LED wally-world specials with the one on the right flipped over to show the power connection. Runtime? 8+ hours without dipping into the dreaded 'danger zone'.

The 4 LiPo 2100mAH batteries for secondary storage.

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This is the solar panel. 33 cell kickin' out a whole 8 watts (OTV x Isc method):

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And my latest pride and joy, a 36 LED table lamp that is 1/3 home depot, 2/3 wally-world, 100% modified, and definitely sweet!

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A peek down into the top of it, showing the lampshade mount mod with the coax power connector as the 'hub', and that almost spark-plug feel the mate has going into it. It also now 'floats', meaning that if you hit the shade, it doesn't cause the lamp to tip over - my biggest gripe about the original design, by far!

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With the shade removed, a look up from below reveals the array of LEDs:

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And last but not least, with the lamp powered on in 'mood' mode. Here you can see the difference in color between the 24 'cold' white and 12 'warm' white LEDs. The camera didn't do that great a job of capturing the warmth, as I had to turn on the overhead light and kill the flash, but the chill that the wife complained about sure shows up in that outer ring! This combo is an excellent balance between light output and color. The wife is happy now, and will actually use it!





The lamp has 3 modes:

Night Light mode draws just 1mA and is just enough to keep the 'pitch' out of black in a radius of better than 15 feet.

Mood mode draws 50mA and is perfect for just say, laying in bed chatting with the wife.

High power mode draws 750mA and is more than enough to read with, but sucks hard on the battery (another 2100mAH LiPo). I can get a couple solid hours out of it before I begin to get paranoid with voltage levels and want to drop it down a notch.

The battery is not yet changeable with the others; I tried to keep the aesthetic mods down as much as possible. Charging is done through a miniature (Nokia-like) coax connector that plugs in by the switch), but function is going to definitely outweigh form i believe on this one - I think I'm gonna drill out a hole in the backside of it and put another 'size M' coax back there so that the batteries can be changed out!

I'm also seeing if the original panel that sat atop this thing can still be considered effective enough for daily use, so we'll wait for the coax mod until I get this data back.

And there you have it. Sola-Minima at all of well less than $100!

[zap]

Nice work Steve.  Certainly well disguised once it's in the lamp.

What was the solar panel from?

I've never seen those ufo lights at my walmart but then I've never really searched.

I'm working on a tracker, it will be nice to see what you come up with.

[Madscientist267]

Thanks, it was fun re-creating it.

The panel is from an old style sunroof vent for a car, I picked it up several years ago when I was working at a tint shop. The exhaust scoops are still on the right side in the picture. It serves well for the purpose, not all that much power, and older technology leaves it in the less-than-efficient category, but it works.

The walmart UFO lights were in the camping section, as they are intended for use as a tent light, complete with a 'hook' and 'beaner for hanging it up. I haven't looked to see if they are still stocked; you know how wally world can be, something shows up, dies off, and is never seen again. Knowing this, I bought the entire shelf stock in like 2 trips so I'd have them in the future for stuff like this. A kickin' deal at $4.97 a pop, considering they have 24 LEDs and even come with a starter-kit set of AA's.

As for trackers, thats gonna be fun. I haven't exactly worked out the details, but I'm leaning toward a CdS based system, something like http://www.redrok.com/electron.htm#led3x (about 2/3 of the way down the page, 'Jeremiah Chace's Analog Solar Tracker Schematic'). The hard part is finding one that doesn't draw so much when idle to make it impractical; though it will be on it's own supply and panel. Much more research to do on this before I get where I'm going.

Steve

[zap]

Yes... Walmart's stock sometimes seem to change completely overnight.  If you're there at the right time you can hit real pay dirt if they're closing something out.

I saw this tracker on youtube.  Super simple if I can get it to work.  I have the panels, I need to dig out a suitable motor.

 

[spinningmagnets]

Yes, I have read many places that Wally World constantly grinds down on their suppliers. The initial contracts are so huge in volume it is hard to turn down, especially if your small factory might close down soon anyhow.

Might as well jump on the merry-go-round for a couple turns, even if you know ahead of time you are volunteering to be the next 3-legged pig (that pig is so good, we just couldn't kill him all at once!)

Everywhere around the country people are not buying anywhere near as much Christmas stuff as usual. There is always an "after Christmas sale", and if you've been wanting to buy some white LED lights, that may be the time to keep an eye on them...

[Madscientist267]

Very interesting, and definitely provoked some thought - enough to start playing with it.

I gutted that old CD player and got the tray mechanism out (had a nice little dance with a black widow in the process heheh), lubed it up, and doing some basic testing for proof of concept. It's the first day I've been able to really put it out there and let it do it's thing. That east coast storm sucked all the juice out of the experimentation for a few days.

I like the idea of powering the tracker directly from solar. Hadn't really thought about it that way, but it's much more efficient for tracking the smaller panels for sure, although I'm sure for larger panels it wouldn't be practical (or should I say economical). The beauty of this method tho is not wasting any main battery power to track the panel, and no standby losses. Definitely factors for a panel as small as mine!

I havent taken any pics yet, but the basics of it are the carousel tray (5 disc flat) turned upside down (so that the motor moves with the panels to avoid as much parasitic torque as possible due to wiring) and a set of 3 panels from those 'plop-em-in-the-yard' lights, just like in the video.

They are arranged vertically in relation to one another for the moment, with a piece of cardboard taped up on the side of one of them, perpendicular to the panel. The cardboard casts a shadow on the one panel, reducing current flow enough that the motor stops spinning until the sun's position is such as to defeat the cardboard, and make the whole thing move over a bit.

It's arranged in such a way that if cloud cover keeps it from moving, it will fire up and go until it finds the shadow again, assuming it hasn't been cloudy for several hours. This of course could put the sun at too much of an angle to break startup friction. I'm not worried about it, if it's cloudy for that long during the day, I call it a 'solar loss' anyway.

It handles what I have sitting on top of it weight-wise for the moment, but I wonder about it's abilities to turn when I go to mount the main panel on it. We will see.

I haven't gotten very far in thinking about the return system yet, but one of those cheapy mechanical alarm clocks with the switch for the alarm and a AA battery mixed in with a limit switch comes to mind. I'd have to set it to like 8 o'clock for it to work properly, since there's no differentiation between AM and PM. Maybe a dollar tree digital version would have just enough to do it... ?

Whatcha think? I'll get a pic of it up soon to give you a better idea.

Steve

[zap]

The cd changer sounds like a nice start.

I tried some small motors that will take off with one of the garden light panels powered up with a 100 watt bulb.  I doubt the small motors will handle the job of turning too much weight but I do have a few of the panels I can throw at it plus I have a few of the Harbor Freight $10 battery minder panels I could try.  I was hoping to keep the whole thing small though.

I have quite a few bearings sitting around but to get the torque out of the motors I would need them geared up so for now I'm messing around with a small bike wheel as my turntable and using it's rim as a giant gear.  I don't think you need the speed that the guy in the video has.

You've gone further than I have but I'm still working on it.

The comments in the video about a mirror for the return is interesting but I haven't made it that far yet.  Dollar Tree has so many possibilities for so many things... I wish my brain worked better to be able to utilize them.

Good work so far!

[Madscientist267]

Yup, weight (and subsequently friction) are the enemies here. Torque is definitely one of the more difficult things to come by with the small amounts of power we're using.

My test run today ran reasonably well, until the angle of the sun got low enough that I had to 'help' it along a little bit by giving it a nudge to get past the startup friction. This of course is unacceptable, so I'm looking into another possibility for gearing and the like.

Fortunately, as you said, speed is wasted here. I don't care if the motor has to go 10,000 revolutions just to move the panels a quarter inch. If it is capable of going faster than the earth is spinning, we're good.

I think you're on to something there with the bike wheel - Might not be a bad idea to drive the wheel using a fairly small hand crafted pulley off of the cd changer? Making a belt out of innertube rubber and going around the rim, etc. The bike wheel would be stronger too, and won't crap out from fatigue or parasitic friction as easily, since it has ball bearings.

At some point, dual axis might be plausible, but at the moment, I don't have any more panels to throw at it. What kinda specs are we talking about on the harbor freight panels, and are they still available?

Steve

 

[zap]

I cobbled one together out of a a 16" bike wheel and cardboard... It worked.  I should have known the motor wasn't the best choice, it was off of an old CD-ROM or CD player, but it had a very long axle so I had a lot of free play for mounting.  Being out of a CD it's wound for speed so even with the small output of the tiny panels it zips right along.  Plus the two panels aren't matched up very well at all.

I put some wire insulation on the axle for better grip but found that adding some electric tape to the rim worked even better.

My tests were done using the 100 watt light, no sun test yet.

I have a 26" wheel I can try if none of the motors I have are slow enough for the 16".

I would think dual axis would be possible but I could see weight balance being very critcal unless you find a nice geared up motor.

The HF panels are listed at 1.5 watts but I don't think mine have ever put that much power out.

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=44768

I'm not sure what the sale price is any more, for quite a while you could get them for $9.99 and before that I remember seeing them at $7.99 on sale but don't quote me on that.

What fun!

[Madscientist267]

Sounds like a plan. Let me know how it works out... I got to thinking though about one possible negative side effect of the bike wheel - flyweight. I noticed today on mine that it would have a tendency to overshoot a bit; thinking that added flyweight will increase that. It'll be interesting to see...

I'm gonna get mine up and out early tomorrow... Weatherman says its supposed to be sunny all day. I have a couple of minor mods I'm gonna do in the early morning to see if they have any better effect, and go from there. Still won't have the main panel mounted to it yet, but if it will stick to the sun from morning to night, I will be pleased.

Alpha 1 Revision B mods are planned as follows:

I'm going to take out the blocking diode from when I was charging LiPo's with them (was too lazy today - it was quick and dirty to get the concept running). Might be able to go from marginal in early/late day sun to sufficient power to get that last swing out of it before dusk.

Also going to turn the 'switching' panel 90 degrees so that instead of partially blocking all 4 cells in one panel, I can just block one. My theory there is that I will get better resolution out of it.

The third is I'm going to extend my shadow mask a bit, so that the shadow is taller and moves faster across the surface of the panel. Should also help with resolution.

HF solar panel:

1.5 watts you say, eh? Is this of the ~20V OTV variety? I'm assuming since it's designed to keep 12V topped. Also appears to be of the amorphous type (?). The other question is (doesnt seem to be anywhere on the site) is how big are they physically?

Steve

[Madscientist267]

Working beautifully so far this morning!

It adjusts by only a few degrees at a time now, moving several times an hour.

Also replaced the cardboard shadow mask with a 6" long or so piece of aluminum - no influence from the wind wagging the mask around making it false trigger.

I'm going to take some pics, and post them by this evening some time.

Steve

[zap]

That's cool Steve, I'm glad it's working well.

Here's the pdf for the panel at HF.  There's usually a little green box you can click below the listing for the pdf.

http://www.harborfreight.com/manuals/44000-44999/44768.pdf

Yes, they are amorphous.  I don't have any sun to test mine but they are the 20-21vdc variety.  The actual glass is about 11 3/4" X 3 3/4".

Last night I soldered 2 old 'garden light' cells together and tested the setup with those, it worked much better.

I didn't know whether to join them serial or parallel so I joined them parallel since it was easier.  It will now follow the lamp very well.  It's still made out of cardboard and not anywhere close to ready for prime time but it definitely proves the concept.

I should take a pic.  As it's set up right now, the wheel is stationary(no momentum from a spinning wheel although it still moves very fast so there is some overshoot) with the motor running against the wheel rim.  The motor is mounted on the cardboard which is mounted to the wheels axle.  The solar panels sit on the cardboard.

With more power from the panels I can now run a bigger motor and I have an idea for a more geared approach.  If I get the time today I may give it a whirl.

[Madscientist267]

Ok here it is... My first attempt at a tracker.

Most of the details have been discussed in the above posts, this is primarily to give everyone an idea of what it looks like. Thanks Zap for establishing the link between easy, cheap, and self-powered. Right now, it's not doing anything useful, but it makes the kids point and giggle when it moves. I'll make it actually do something of purpose in the near future.

The original concept in my mind looks something like this. Ironically, according to the wife, it's also an accurate image of what the inside of my mind looks like. <shakes head> . . . Primitive human... >X-D

Down and dirty, 10 minutes of actual building, primitive self powered solar tracker. Three 'plop-em' panels, wired in series, connected directly to the motor.

What can I say, it worked. It was rather sloppy since even the smallest breeze would send the cardboard shadow mask into a quivering frenzy, and screw with it's perception of the sun's location. Also, turns out that trying to partially block sets of cells on a panel wasn't the best way to stop it tracking. It would sit and be late for a move, then jump and go 15 or 20 degrees (as is apparent by the shadow in the picture).

The tracking plane is (audio folks don't cringe too much hahaha) - A Pioneer 5 Disc tray type CD changer tray, turned upside down so the wires and motor would move with the panels. Ripped it out of a working player. Yep thats right. A working player. It had minor front panel damage and the top cover didn't fit right. It had been sitting in storage for 2 years, and under a bed for a few before that. Time to reincarnate it, MadScientist style. Besides, who listens to CDs anymore?!

A back side view with a better look at the motor. Ignore the board behind the solar plane - it does nothing other than prop the panels up at a decent angle:

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So, this morning, I made some quick mods. Swapped out the cardboard for aluminum, turned the panels 90 degrees so that the mask would hit only one cell of the 'sensing' panel, and bypassed the blocking diode previously in place for battery charging:

Ahh, thats better. Got it out there early enough to let it run a full sky's range of light, about 100 degrees or so of tracking. Now works much more the way I originally had in my mind. It does something of the order of 2 or 3 degrees per jump, evident by the shadow that is now visible in this picture.

It passed the 'cloud' test too (even though there was never a cloud in the sky all day). There is a good size tree across the street from my house that the light has to pass through from about 10AM until 11 or so. It didn't move at all during this time, then all of a sudden... zzzzt! Pointing right back at the sun in one quick turn.

Tomorrow, I may get froggy and try to work out exactly how the main panel should be mounted on this thing.

Until next time . . .

Steve

[zap]

Good job Steve... now you'll need to do a time lapse video

I'm not sure I understand the panel setup.

Only 3 panels powering it?  Does the aluminum "shadow mask" keep enough power from the motor to keep is from spinning till it's time to align with the sun?

I found a geared motor that might work on mine... a worm gear affair out of a printer or scanner.  It will be awhile before I can test mine outside.  2.5°F right now, snowing and blowing at a good clip.

[Madscientist267]

Yeah I thought about the time lapse thing while I was watching it do it's thing yesterday. That's gonna be a little bit more difficult with what I have laying around. I have some cameras laying around that might be able to come up with something if I toy with some software...

As for panels, yep just the 3, wired in series. In full light (right now in winter) they're good for something like a total of about 6V OTV and ~100mA Isc, slightly more current in summer. It's just enough power to get the motor going.

The key is that in order for a series panel to produce power, all of the cells must be exposed to light. If even one cell gets blocked (or even just a good part of one cell), the entire array is rendered more or less useless. Think of it like the whole 'weakest link in the chain' thing. The total current through the entire array is only as high as what can flow through the weakest cell.

I am exploiting this by having the shadow mask cast the shadow on only the last cell. There's only a couple of degrees of difference between full and no (ok, unusable) power, so I get good resolution out of it.

The worm gear seems to be the ideal way to go for this, as it helps lock the turntable where the panels put it. And, it provides a torque boost in exchange for speed, which isn't needed anyway. I could easily gear this one down some more and still outrun the sun.

Also, you're probably going to find that your real-world results are much different from what you're seeing with the 100 watt bulb. Mine won't even think about moving with a 100 watt bulb right up on top of the cells, but moves along rather well in full sun. I hear ya with the snowstorms out there - I've lived in Aurora, Golden, and Missouri Lakes (just northwest of Blackhawk) - many years ago, but the memories still live on!

Let me know how it goes.

Steve

[zap]

If you have the right model Cannon and don't already know about it, I can point you toward some very fine software that can "temporarily hack" your firmware and give a time lapse option.(depending on what model Cannon)

How you've explained the 3 panels is pretty much how I figured you had it setup.  The "return to east" portion will be the tough part.  Maybe a few limit switches and using extra juice from the panels stored in a rechargeable AA or 2?

I did have a chance to test it outside Saturday before the weather got nasty and it did seem to move much faster.  I just held it in my hands and turned this way and that and it kept pointing at the sun without any problem.

With the friction drive as it is now, the bike wheel needs to be darn near perfectly level or it doesn't work at all and I can see any amount of wind at all blowing it all over the place.  I didn't want to tear the motor I have apart because it has what looks to be some sort of optical drive control hooked to the other end.  I'll probably tear it apart today.

Yeah, if you lived here... you know what I'm talking about.  I guess we broke a record on Sunday from 1901 of -14°, it was -15°.  Today we broke a record from '51 of -6°, it was -18°!  A change of seasons it always nice but.......I can do without this *rap!

[Madscientist267]

Unfortunately, naa, its an Olympus. I have a capture card set up on a box, I could set that up to record a day's worth of video at a low resolution, then go back and lapse it. Haven't done much as far as editing video other than cutting and splicing for commercials etc. I think I saw a feature in Kino that might do it... I'll check to see what I can come up with.

The return issue is definitely perplexing, considering that its powered live on the fly. I gave some thought to an onboard battery, but then I realized that the very thing that makes it work would keep the battery from ever charging... sigh. Thought about 'cheating' a bit, using a single alkaline for the return, maybe with a CdS cell to detect darkness, and initiate the return. I haven't done much experimenting on what the motor's minimum requirements are to move yet, so I'm not sure how thats going to work.

Maybe the 2 panels that are never shaded charging up 2 NiMH like you said, but would need a polarity reversal system that is simple. Things are starting to sound complicated heheh. I honestly didn't envision breaking out the breadboard for this, but it may go that way... shrug

Sounds like the Colorado I remember... Temperamental and unpredictable in the winter. Definitely a force to be reckoned with! I moved to VA in '88 and remember them shutting down the schools when there was 1/4 inch of snow on the ground. They're kidding right? LOL They don't know what snow IS! HAHAHA

Steve

[zap]

I think I came up with a good plan for the return.

So far the panels I'm using came from old solar garden lights... most had quit working a while ago.  I noticed one would work if you wiggled 1 of the 2 transistors around so I re soldered the transistors and it works.

I figured I could hook it's 2 nicd cells to the motor and instead of, or along with, turning the led on when it's dark, it will power the motor back to the east.  It's own solar panel should keep it charged up for the return at dark.  A diode on one of the power lines going to the motor will keep it from stealing any charge during the day and a limit switch will cut off the current once it's been sent back to the east.

I don't think this is complicated at all but I might be missing a detail or 2.

I got the worm drive motor hooked up and it works great... tons of torque.  Once I get the thing past the cardboard stage and get the return working I'll probably post a story.  What a blast!

Ha... a 1/4 inch of snow... except they do get ice storms there right?  I'd sooner have snow than ice.

I don't think we ever got above zero here today... rather odd weather for these parts.

[Madscientist267]

Sweet... Sounds like a plan. The only thing I'm seeing as a possible caveat is the polarity reversal to drive the motor the other way. Might not even be an issue. Have to try it and see.

As for the ice, its very rare but happens. Even the snow is rare, but once in a while we get a good one. The best part (or worst, depending on spectator/participator status LOL) is people trying to drive in it. You should see after the roads freeze up after a mild daytime thaw. VA doesn't have the resources to deal with it because its so rare. They get major highways and some of the larger roads, and thats it. Everywhere else is Russian roulette.

One year we had about 6 inches, and there were record wrecks all over the side of the roads. There used to be a catwalk down the street from my house; now THATS entertainment! I got to where if it snows here at all, I refuse to go out until its gone. Lost a car once and watched it happen as a guy came up behind me like a hockey puck. They have no concept here at all.  

[Madscientist267]

I got a response back from mowerofdoom today on the specs for the tracker on the video.

He says that they are the same panels (yard light), and are wired backward to each other and connected to the motor. When the light striking both panels is equal, the net output is zero, and the motor stops. Found this once again applicable to what we're talking here with the return, maybe a modification to the design on the video; If a set of panels were used on each side instead of a single panel, so that they were all at slightly different angles to the sun, maybe it would return east every morning as soon as it saw sun.

One problem with me testing this idea is I am out of panels. I would need at least a total of 6 to do it with my current setup, and I only have the 3. So, it might be a while before this happens out my way but I figured I'd throw it out here in case you have more panels laying around.

He also said the motor is a low-voltage low-current gear motor so that it moves with small imbalances.

Steve

[ghurd]

I think you guys are slowly working toward reinventing Amanda's idea?

Two series panels. Slightly inverted V toward the sun.

Measure the voltage at the end and middle or whatever.

The one facing the sun has a lot more voltage than the one 5 derees away from the sun.

Could do it with a pair of the red 1.5W $10 on-sale HF panels.

http://www.fieldlines.com/story/2008/1/13/61741/0871

G-

[Madscientist267]

Nope. Wired in parallel opposing each other, and directly powering the motor. The idea is to stay away from logic and comparators as much as possible. We're not setting up to move large panels, so we don't want to use anything other than a self powered tracker.

[zap]

Hey G, once I saw the youtube video, I knew this would be a cheap and easy way toward a tracker.  The the beauty of it is it's simplicity and fairly low cost.  I don't have to build any type of complicated circuit.

I always thought the redrok was great and really wanted to try it but I didn't have the motors.

I think the motor drive is one of the biggest obstacles and I'm also testing different drives in hopes of finding something that anyone can find, build, or buy (hopefullly cheaper than buying motors and the redrok controller).

I've tested a CD-ROM's drawer opening mechanism and the panels operated it perfectly well but there's not a ton of torque and it's small amount of travel would hinder it's usefulness.

The one I've cobbled together will forward track with about a 3° accuracy(so far just a guess) and will back track with about a 10-20° accuracy(also still a guess), although I don't know how much of a need there is for back tracking (cloud shadow over your site with the sun reflecting off of another cloud?)  I still need some better weather before I can try some sort of mirror set up for a self return feature.

I did try the 2 AA batteries from one complete yard light for return to east (RTE) and there was plenty of power for that.  The beauty of using the yard light for RTE is, again, simplicity.  I have yet to "insert" the RTE yard light into the tracker setup but I should be able to get that done today.  I think it will work fine but we'll see.

One problem I can see with the yard light RTE is a dark enough condition during the day (big thunderstorm) where it causes the yard light to RTE and once the storm has passed the 'west' panel is now too far out of position for it to do it's job and bring the system back to a tracking position.

Steve, I set mine up from the beginning with the positive and negative leads of the panels "crossed" after reading the comments on the youtube site.  I found it to be a positively brilliant idea... one of those "why didn't I think of that!!!" moments.

The way you have your's setup is a close approximation although with your setup you will have a constant voltage into motor but it's small enough that I doubt it will matter.  You could try using 2 of the panels together and cross wiring the third.  It would do basically the same thing as your 'mask' does now... just cancel out enough power to keep the system from moving forward.

The only difference between your setup and mine is that mine will back track but like I said, I'm not sure back tracking is all that important.

[Madscientist267]

I'm taking a slightly different approach, to keep as much silicon out of the driver as possible. I've drawn up a schematic. Its primitive, yes, and has 2 (pretty major) caveats, but is a start. It's still only on paper, and likely won't be built as it sits in pencil, but gave me a better visualization to work from.

I'll get the diagram posted as soon as I get a chance, but the basics are as follows:

Two of the panels are exposed 'all of the time', so I tapped them with a diode to get juice to charge 2 AA NiMH cells, and then put a DPDT toggle in that would be tripped by stops at either end of the run.

In tracking mode, the switch connects the motor to all 3 panels, as they are now.

In RTE mode, it reverses the polarity, and connects the one leg of the motor to the batteries instead of the panels, returning the carousel to the start point, with no help from the panels.

The switch then gets flipped back by the east stop, and the process repeats.

The 2 caveats that I see at the moment are:

1. - If there is cloud cover before the switch can trigger at the end of the day, the carousel will remain where it is until at least the following day. Result, lost input.
   
2. - Even in ideal conditions, upon reaching the west stop, the RTE triggers immediately, causing the panel to go home while there is still usable sunlight left in the west. Again, lost input. Not as much per day as an RTE failure, but should be considered cumulative, so still significant over time.
   
   

Not perfect, but its keeping with the theme here of ultra-simple, and self powered. I'm sure at some point I'm going to have to concede to a transistor or two. Sensing darkness sounds the easiest, but like you said, a dark enough day, and it may get confused. I suppose worst case there would be one 'missed' day of solar. We'll see how the paper evolves, and then I'll go from there.

Steve

[Madscientist267]

Here's the schematic -

[zap]

Steve that certainly is simple.  The schematic helped me sort out how the DPDT was going to work.  How did you draw it?

I didn't get the RTE portion of mine hooked up yet, hopefully today or tonight.

[zap]

Steve, I found some sw for the schematic AND got the RTE gear put in.  Seems to work ok so far.  I'll try and post a story tonight.

[Madscientist267]

Nice dude... I've been looking for a decent all-in-one (w/ SPICE modeling) for a while now, just haven't found anything that really does what I want it to. As for the ones I've been posting, they are done the hard way. I found myself in the car with the wife a few weeks ago with a laptop that had nothing on it to manipulate anything with except GIMP and after I made up some templates, it's not that bad actually. Kinda stuck with me.

Anyhow, here's the latest and greatest. I figured out how to nuke caveat 2 (immediate RTE) with minimal parts. Took some hunting to find a suitable MOSFET that would do it at these voltages. Everyday (IRF510 etc) wont cut it; can't quite trigger the gate at 2.4V.

Turns out there was a gold mine of low voltage MOSFETs right under my nose - LiPo battery controllers use them as interrupt switches. Perfect! It took some delicate soldering to use an SMT package with pigtails, but I've done it. Probably just going to pot it in epoxy.

The RTE portion of this is bench tested, and works beautifully, although I am considering experimenting with the 470K a bit (maybe a 220K?). The higher the value, the darker it needs to get before it triggers. It has a fairly sharp response, although I haven't measured what parasitic draw is up to the point that motor stall is overcome. Shouldn't be a big deal; the NiMH are 2000mAH.

Also, I have no idea what the exact specs are on the phototransistor, it was part of a sensor for the original carousel (it's like it was made to do this!)... In virtual darkness, there's about 750K of resistance, <1K under a 60W light bulb. I'm patiently waiting for actual sun; it has been overcast here for 3 days straight now!

Anyway, here it is: