Friday, December 2, 2011

My Router has a bad case of S.A.D.*

In the last post I blathered on quite a bit about sizing solar panels for routers.  As it turns out, the theoretical and the empirical don't match up so well.  Instead of running 24h/day, the Farm School solar nodes are currently running more on the order of 6h.  I suspect this has mostly to do with the fact that the sun is so low for much of the day in this part of the world that it's behind trees, but it's also possible the new charge controllers aren't as efficient as billed.  Whatever the reason, I'm about 18h/day short of the full monte (translate: waaaaay short), which has me thinking about power optimization.

In laptops, a very common way to save juice is to adjust the clock speed down when the device is idle, and it seems someone has built a package to control CPU clock for the RouterStation.  It would be a great project for someone to wrap this with a script that measures load and adjusts speed accordingly.  Anyone interested??

*S.A.D. stands for Seasonal Affective Disorder

EDIT:  I took a few minutes to try manually switching the clock speed with the above package.  A few Results:

  • Changing speed requires a reboot (the package is simply a command line tool for rewriting the bootloader)
  • The overall reduction in power going from 680Mhz to 200Mhz is only abvout .25W at idle
  • Running a RouterStation at 200Mhz makes it boot waaaaay slower




9 comments:

  1. Hi this is Patrick i can offer assistant on the power system side by sizing a system that can manage the power consumption.
    how many appliances and their consumption rating.
    and where in the part of the world do you want to put the system with that i can help.
    Also you might consider a hybrid for both solar and wind turbine
    regards
    patrick
    pkaraini@gmail.com

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  2. Patrick,

    As i mentioned in the previous post, I'm powering a single device that is likely using about 8W. If used heavily, it might get as high as 10W. The location is Athol, Massachusetts USA. The tricky part is that there's no way to mount the panels so that the sun is unobstructed for the entire day. I'd be interested in seeing what you come up with.

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  3. Any way to increase the amount of AH storage (add more batteries)?

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  4. Yes, by adding more batteries... Current batteries will run the system for nearly two days on a full charge, but they aren't getting enough sun to charge all the way.

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  5. Wow... That is a huge drop-off. Have you adjusted the angle of the panels for the location? I know that will greatly effect the power output. Unless you have a solar tracker to maintain the ideal angle they need to be changed, often. This can be accomplished with a simple geared motor that adjust the angle of the panels as the sun moves east to west. That will probably help a bit as if they are stationary you will only have peak power generation for a relatively short period of time.

    The better systems actually use a solar detector and angles the panels as such. But, the "dumb" ones are easier and simpler to make.

    I found two links:

    http://hackaday.com/2011/06/17/a-simple-diy-solar-tracker/

    http://www.solardiy.info/?p=50

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  6. To:electronbee, Your links helps me alot, thanks.

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  7. Also you can achieve significant power savings by using half and quarter width channels for your backhaul/mesh links during off peak hours or always if the users are not to hungry for bits.

    This also greatly increases range and resilience agianst multipath delay spread.

    Check out http://src.acm.org/raghavendra/raghavendra.html for details as well as this HAM'ers blog for nitty gritties

    kb9mwr.blogspot.com

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