h a l f b a k e r yThe phrase 'crumpled heap' comes to mind.
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What you have here is a room with benches around the edge. On the benches are 8 sets of monitors, keyboards, and mice. All of them are hooked into a single machine that operates as a server. EVERYTHING runs from 12v batteries (NOT upping to 240 volts at any stage) that are charged from photovoltaic
panels mounted on the roof.
This kit could be used to educate the millions of people that have no access to PCs or mains power.
A 12V switch
http://www.netgear....tail=Specifications
//(no 12v switches available though). // [coprocephalous, Jun 22 2009]
[link]
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Failing to see how a computer lab, in particular, is good for the Third World, in particular. This sounds like a more general solution than that. |
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And, frankly, couldn't you just string together 8 solar-powered laptops with peer-to-peer networking? |
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Yes, I'm not sure what the point is here. Is the idea to
provide computer access by solar power? Or is there
something special about the 12v that I'm missing? What's the
advantage over having a solar collector charging batteries
(which I presume is the norm in remote areas), and then an
inverter to give regular mains voltage to power normal
computers? Probably not quite as efficient, but a lot simpler
all round. And what's the reason for having one server as
opposed to (as DrCurry suggested) a bunch of laptops or even
desktop machines? |
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We consider the potential difference of choice shoudl be 24V. |
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24V kit is readily available. Many trucks use 24V systems. |
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The maximum rail voltages in personal computers are +12 and -12; with careful planning, and a virtual earth, no stepdown needed. |
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A +24V DC rail would be fine for powering an 18/20/22V LiIon battery as found in many notebooks, via na efficient switching regulator. |
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Taken altogether, not a bad plan for using locally-harvested opportunistic environmental energy. |
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We consider that 24V truck systems come from two 12V batteries.
Computers use +/- 12V merely for RS 232 compatibility, which will work perfectly well from +/- 5V. |
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[ Failing to see how a computer lab, in particular, is good for the Third World, in particular.] When I say 'lab' I mean a computer suite for a rural school with no mains. |
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[What's the advantage over having a solar collector charging batteries (which I presume is the norm in remote areas), and then an inverter to give regular mains voltage to power normal computers? ] |
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The batteries would drain too quickly. |
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[And what's the reason for having one server as opposed to (as DrCurry suggested) a bunch of laptops or even desktop machines?] |
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Less power required for one machine. I was hoping to be able to link 8 work stations via a switch (no 12v switches available though). |
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Thanks for the other suggestions. |
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The lack of stepping up is widely baked in photovoltaic (stand-alone) installations. With modern hardware (OLPC2-goal is one Watt), there is no need for a server (low-cost solar cells will provide ~50W/m2). Actually, coating a OLPC2 (~200cm2->1W) with solar cells should suffice for a few hours daily use |
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// Computers use +/- 12V merely for RS 232 compatibility // |
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We think you'll find that the +12V rail does rather more than just power the Rs232 bus drivers..... the odd trivial device like large hard disk drives are quite fond of 12v. Many modern motherboards don't even use the +12V for the serial port, they use a device such as the MAX232 integrated serial buffer/driver to synthesise the levels from the +5V rail. |
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-12 V is what's no longer needed. +12 V is still needed in
normal
computers (including for the CPU), but that's easy, and
specified in
the idea. You can easily run a whole regular desktop
computer on
only +12 V, too, using a picoPSU. |
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If you wanted to, you could design a computer to run on
1.8 V
only. |
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// no 12v switches available though // |
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Are you sure? I feel like 12 V has always been the most
common voltage for consumer switches to take. |
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For this idea, though, just get some Raspberry Pis? They
run on 5 V
(3.3 V internally). You can also get a 5 V network switch
these
days, I bet. But you might need a higher voltage for the
monitors. |
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