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April 10, 2015

Welcome the Sun Dragon

   At long last I now have a computer that is solar powered.  After placing the solar panel and running the solar panel wires on the roof yesterday, I completed running the wire into the house today.  It quickly hooked up to the battery charger and battery.  I then wired Odroid into this setup, and it transformed into the Sun Dragon.
   Almost as soon as I had the setup connected, a storm moved in and the daylight dropped from over 100k lux to 5k lux.  Using an ammeter I was able to see the current going to/from the battery.  This would tell me if the battery was charging or discharging.  If charging, the current would be positive as energy would be flowing from the solar panel into the battery.  That means the Sun Dragon is running purely from solar power.  If the current is negative, that means the solar panel isn't producing enough power to run the Sun Dragon by itself, and the battery is supplementing.  Since a storm was overcasting the sky I was actually able to see this cutoff point.  Right about 6,000 lux there is enough light to idle the Sun Dragon with no current going in or coming out of the battery.  If the Sun Dragon begins do any work, however, this is no longer the case.  Running a heavy CPU load on the Sun Dragon requires about 13k lux.  Everything above that is energy in the bank.
   Right now the Sun Dragon's battery has a full charge.  I am going to allow this setup to run without the switch-over relay circuitry (it isn't finished) just to see how that goes.  There has been plenty of sunlight lately so I shouldn't need it, and this will be a good first test for the system.

April 09, 2015

Solar Panel Goes to Roof

   My power cable for the solar panel come today, but I didn't have a lot of time to work with it as I had a meeting in the evening.  At long last I placed the solar panel on the roof.  It is secured to the chimney but otherwise just lays flat on the roof surface.  Once the solar panel was placed I began to run the 10 awg wire.  It way it was wound made this rather painful as it tangled up pretty bad.  I did better with the second wire than the first.  Once the wire was routed off the roof it began to rain.  By this time it was getting close to when I had to leave, so I called the project a day.

April 08, 2015

   At our biweekly swim we have company again.  The past month we had been enjoying a mostly empty pool as no one had reserved it for classes, and it was really nice.  That has ended, but so far the deep end by the diving boards (they call it the Well) has been open and all the classes finish at or before 8:30 pm.  Xen has hit an new milestone and is now able to swim the length of the Well (between 10-15 yards) in a single breath.  This is due to both his increase in speed and lung capacity.  His swimming in general has greatly improved and he can move pretty quick now.  I was swimming with him under water to observe his leg technique and actually had to put a fair amount of effort into keeping up.  As for my own progress, I've decided I want to try the challenge of swimming 700 yards in 12 minutes.  That is 28 laps and each lap taking no longer than 25.7 seconds.  My front crawl is only good for about 1.5 laps before I can't keep it up, so I did my initial run using a breast stroke.  The 700 yards took over 14 minutes, and I was going about as fast as I could manage.  This comes out to an average of 30 seconds/lap.  Clearly this challenge is going to require work.

April 05, 2015

Daylight Observations from Operation Lux

   The last few days have been very good for sunlight hitting the roof of Elmwood Park.  In fact, ππ took for the first time measurements that jumped off the 120k lux scale.  Several days had power levels of over 4,000 Wh/m2.  This bodes well for solar power.
   The peak light happens about 1:30 pm with a climb from around 50k lux at 1:00 pm to over 100k lux.  Prior to this time the light is quite variable, presumably from the trees blocking the incoming light.  From the peak there is a steady decrease from >100k lux down to around 55k lux from 1:30 pm to 4:30 pm.  Right around 4:30 pm the sun ducks back behind the tree line and there is a sharp drop to around 30k lux.  By 5:00 pm the light is around 15k lux, and about 6:15 pm it's down to 5k lux.

April 04, 2015

6 polyhedrons

6 polyhedrons

   My roommate James got me hooked on drawing polyhedrons.  He asked for two shapes he is considering for a project, and needs models for a 3d printing.  I pulled out Sketchup and went to work.  Some of the shapes, like cuboctahedron where really easy because they had 90 degree angles.  My first difficult polyhedron was the icosidodecahedron.  I found I could use the Dihedral Angle if I could get it to several decimal places, and all the polyhedrons I drew had the dihedral angle worked out.  The last shape I draw was the truncated-icosidodecahedron for by which time I found an easy secret.  Once past the initial angle, all the shapes could be rotated in reference to a stationary shape.  In all I draw 6 shapes (I had been requested only to draw 2).  They are (from left to right, top to bottom): cuboctahedron icosidodecahedron, rhombicosidodecahedron, rhombitruncated-cuboctahedron, truncated-icosahedron, and truncated-icosidodecahedron.

April 02, 2015

Andrew Que in the lab, April 2015

Andrew Que in the lab, April 2015

   So we at the house have been keeping track of our weight since shortly after the new year.  Since then I have successfully lost 20 pounds, and last month my weight averaged 146.2±3.345 pounds (66.3±1.517 kg).  Despite the fact I've tried to level off, I actually averaged a loss of 3/4 lbs/week in the month of March.  Looking at my calorie intake, it is clear why.  I should be taking about 2,200 calories/day to maintain body weight, but I averaged only 1,900.  In addition, I haven't been making up the calories I've burned during swimming.  While I don't mind this additional drop, it wasn't my goal.  If I plan to maintain weight, I can't keep losing it.
   I have also managed to stick with doing a set of push-ups every hour in front of the computer.  I started at 15 push-ups, quickly moved that to 20, then 25 and now I'm doing 30 each hour.  If nothing else, the push-ups every hour does put into prospective how long operations take because I can't ignore the passage of time like I usually do.  Maybe it will help me better predict how long projects should take—something I'm actually pretty weak at doing.

April 01, 2015

Rethinking Solar Power Web Server Location

Wyvern's Haunt, April 2015

Wyvern's Haunt, April 2015

   I got on the roof today to measure the distance from the solar panel to the basement.  My initial design for the solar powered web server was to keep the battery and computer on the roof next to the solar panel.  The reason is that the solar panel is 12 VDC, and that there would be a significant voltage drop from the roof to anywhere else.  However, the design issues with locating the server on the roof were becoming a larger issue.  Rather than create a custom housing to hold the Odroid, I will simply keep the setup in the basement and take the power loss. 
   My measurements show I need about 100 feet of wire.  Using 10 awg wire this will result in a 7% loss in power if all 50 watts are produced (which won't happen).  Still, this greatly simplifies the setup.  Worse case, I can add a second solar panel in series, produce 24 VDC, and both increase power production and decrease total losses.
   The initial reason I was so reluctant to do this was I wanted a 100% solar powered server if I could get it.  Now that I see the numbers from Operation Lux, I just don't think that is likely in the winter months.  Keeping the server inside has a lot of other benefits as well.  We want to replace the house router with an Odroid, and have this be the gateway for house services.  The web server can handle this additional task without difficulty.