h a l f b a k e r yVeni, vedi, fish velocipede
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So after 'like four freakin' years of obsession, my brother and I
finally
have a giant solar powered coffee roaster up and running. We use
it
to roast all the coffee for our coffee shop & we are just starting to
get our coffee into stores, etc. Our problem is one of refinement,
or
lack
thereof~ right now we track the solar concentrator by hand
using a viewing scope & switches you flip by hand. Kind of lame,
actually!
I've been reading about different ideas for easily tracking the sun
&
there are a lot of different things out there. It's got to be
accurate,
though. I haven't made up my mind to build something using the
A.)
Robotic, timer-based approach, or B.) the Sensors & feedback
based
approach.
I keep thinking there should be some kind of system that is a mix
between the two.. senses when it is cloudy, so it can stop
tracking,
but knows exactly where it is in some absolute sense when the sun
IS
out. Some sort of hybrid between timer and sensor-based.
(??) solar coffee roasting machine, sans tracker
http://solarroast.c...nge.html#No2_anchor
...pages from a contest Im hosting on the subject of sun tracking. [Bleep!Plif, Feb 12 2009]
commercial passive solar tracker
http://www.wholesal...r.com/trackers.html
[colorclocks, Feb 13 2009]
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[edit] a $50 entry fee?, gee what a bargain. |
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Easy. A flat sheet, horizontal, photosensor either side;
outputs go to noninverting and inverting sides of an op amp,
drive the vertical motor through power transistors. Same
thing on its side drives the
horizontal motor. If you don't want to track the sun when
it's dim or cloudy, put a trigger in each circuit that will only
operate when the signal is above or below a certain
threshold. |
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Easier, a 1ft wide tube synched parallel to the mirror array allows a 1ft wide sunspot to shine on a 2ft wide platform which can tilt a cm or so in any direction; said tilting controls the horizontal and vertical azimuth of the mirror-array. |
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Place an open tin of catfood near the platform in the pre-dawn hours. |
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//Place an open tin of catfood near the platform in the pre-dawn hours// |
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Maybe I'm a little slow today, but I'm really struggling to fill in the gaps in the rube-goldberg procession of events that goes from this to that hyper-expensive cat-sh^t coffee. |
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Care to fill in the gaps, [toaster]? |
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Is the sun really a sensible way to roast coffee? Even wood fired roasters seem pretty marginal to me. I mean consistency is everything here, right? An errant cloud and suddenly four hours of roasting and pounds of beans are wasted. I hope you can make it work, but don't ask me to subscribe. |
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The cat jumps onto the platform since it's there, close to food and looks like a good place for a nap. The cat notices the sunlit spot in the middle and lays down for a catnap. |
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The sun moves across the sky and the warm spot starts to travel towards the edge of the platform. The cat moves towards the warm spot which tilts the platform which moves the mirror-array to face the sun dead on and moves the warm spot back to the middle of the platform which causes the cat to move back to the middle and stop the traverse... until the next time the warm spot moves away far enough to irritate the cat, again. |
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How the cat-shit ends up roasted I think [Bleep] has that covered already. |
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What [FlyingToaster] said first; $50 for the chance to help you with your business! How I wish I could find more people who want me to pay to provide them an engineering consultation. And the task is being massively overcomplicated. The location of the sun is known at all times through just three simple equations. Hence, the motion is entirely predictable once calibrated. A beige box PC, a data card, several transistors, possibly a relay array and about two hours of programming are all that is required. |
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... a scissor car jack and a paper and pencil... for the less McGyverly inclined, a calculator... but you still need the scissor-jack. |
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Bimorph. NASA has some work on bimetallic
benders that keep solar panels on satellites aimed
at the sun. I think you could do reasonably well
with a metal/plastic bimorph. It's not powerful,
but it has a greater range of motion than a
bimetal, because plastic has a greater thermal
expansion coefficient. |
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I actually built one of these, but it failed because I
didn't get a good bond between metal and plastic. |
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Also note that there are commercial passive solar
panel trackers (see link) that work on the principle
of a warmed fluid expanding and running from one
reservoir to another. |
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a glass orb, a matte glass behind that, a webcam behind _that_, image recognition, -> actuators; Steampunk looks included. |
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