Half a croissant, on a plate, with a sign in front of it saying '50c'
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Solar Coffee Sun Tracker

Designing a solar tracker for my solar coffee roaster...
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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.

Bleep!Plif, Feb 12 2009

(??) 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.
FlyingToaster, Feb 12 2009
  

       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.
MaxwellBuchanan, Feb 12 2009
  

       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.   

       Place an open tin of catfood near the platform in the pre-dawn hours.
FlyingToaster, Feb 12 2009
  

       //Place an open tin of catfood near the platform in the pre-dawn hours//   

       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.   

       Care to fill in the gaps, [toaster]?
Custardguts, Feb 13 2009
  

       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.
WcW, Feb 13 2009
  

       //gaps//
  

       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.   

       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.   

       How the cat-shit ends up roasted I think [Bleep] has that covered already.
FlyingToaster, Feb 13 2009
  

       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.
vincevincevince, Feb 13 2009
  

       ... a scissor car jack and a paper and pencil... for the less McGyverly inclined, a calculator... but you still need the scissor-jack.
FlyingToaster, Feb 13 2009
  

       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.   

       I actually built one of these, but it failed because I didn't get a good bond between metal and plastic.   

       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.
colorclocks, Feb 13 2009
  

       a glass orb, a matte glass behind that, a webcam behind _that_, image recognition, -> actuators; Steampunk looks included.
loonquawl, Feb 13 2009
  


 

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