Geoff:<br><br>Point noted, am getting the Grob Basic electronics and also the mathematics for basic electronics book....<br><br>Any recommendations for some good electronic kits that anyone may have encountered or any reference to the top of the line electronics groups if any exist?<br>
<br><div class="gmail_quote">On Mon, Dec 15, 2008 at 7:46 AM, Geoff Jacobs <span dir="ltr"><<a href="mailto:gdjacobs@gmail.com">gdjacobs@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<div class="Ih2E3d">Robert G. Brown wrote:<br>
> On Sat, 13 Dec 2008, arjuna wrote:<br>
><br>
>> A simple question though...Aluminum plates are used because aluminum<br>
>> is does<br>
>> not conduct electricity. Is this correct?<br>
><br>
> Aluminum is an EXCELLENT conductor of electricity, one of the best!<br>
> Basically all metals conduct electricity. When you mount the<br>
> motherboards you MUST take care to use spacers in the right places<br>
> (under the holes for mounting screws on the motherboards, usually) to<br>
> keep the solder traces of the motherboard from shorting out!<br>
><br>
> Your question makes me very worried on your behalf. Electricity is<br>
> quite dangerous, and in general messing with it should be avoided by<br>
> anyone that does not already know things like this. In India, with 240<br>
> VAC as standard power, this is especially true. True, the power<br>
> supplied to the motherboards is in several voltages 12V and under, but<br>
> believe it or not you can kill yourself with 12V, and starting a fire<br>
> with 12V is even easier.<br>
<br>
</div>You can actually do a good job of TIG welding with 12V.<br>
<div class="Ih2E3d"><br>
> I would >>strongly<< suggest that you find a friend with some electrical<br>
> engineering experience, or read extensively on electricity and<br>
> electrical safety before attempting any sort of motherboard mount.<br>
> Mark's suggestion of hot melt glue, for example, is predicated on your<br>
> PRESUMED knowledge that cookie sheets or aluminum sheets are<br>
> conductors, that the motherboard has many traces carrying current, and<br>
> that when you mount the motherboard you must take great care to ensure<br>
> that current-carrying traces CANNOT come in contact with metal.<br>
><br>
> The reasons aluminum plates are suggested are a) it's cheap; b) it's<br>
> easily drilled/tapped for screws; c) it's fireproof AS LONG AS YOU DON'T<br>
> GET IT TOO HOT (heaven help you if you ever do start it on fire, as it<br>
> then burns like thermite -- oh wait, thermite IS aluminum plus iron<br>
> oxide); d) it reflects/traps EM radiation.<br>
<br>
</div>Ask the Royal Navy about fireproof aluminum.<br>
<div class="Ih2E3d"><br>
> Wood would be just as good except for the fireproof bit (a big one,<br>
> though -- don't use wood) and the EM reflecting part.<br>
><br>
> The aluminum plates should probably all be grounded back to a common<br>
> ground. The common ground should NOT be a current carrying neutral --<br>
> I'm not an expert on 240 VAC as distributed in India and hesitate to<br>
> advise you on where/how to safely ground them. You should probably read<br>
> about "ground loops" before you mess with any of this.<br>
<br>
</div>Commodity ATX power supplies will have a grounded frame. Mounting the<br>
power supply to the pan will work quite well.<br>
<div class="Ih2E3d"><br>
> Seriously, this is dangerous and you can hurt yourself or others if you<br>
> don't know what you are doing. You need to take the time to learn to<br>
> the point where you KNOW how electricity works and what a conductor is<br>
> vs an insulator and what electrical codes are and WHY they are what they<br>
> are before you attempt to work with bare motherboards and power<br>
> supplies. It is possible to kill yourself with a nine volt transistor<br>
> radio battery (believe it or not) although you have to work a bit to do<br>
> so. It is a lot easier with 12V, and even if you don't start a fire,<br>
> you will almost certainly blow your motherboard/CPU/memory and power<br>
> supply if you short out 12V in the wrong place.<br>
<br>
</div>Yes, it is possible to kill yourself with low voltage. You have to<br>
really work at it and/or be unlucky, but it can be done. A DC resistance<br>
from leg to arm of 100 ohms or so is hard to achieve. Stabbing oneself<br>
with electrified needles, for starters.<br>
<div><div></div><div class="Wj3C7c"><br>
>> Also for future reference, I saw a reference to dc-dc converters for<br>
>> power<br>
>> supply. Is it possible to use motherboards that do not guzzle electricity<br>
>> and generate a lot of heat and are yet powerful. It seems that not<br>
>> much more<br>
>> is needed that motherboards, CPUs, memory, harddrives and an ethernet<br>
>> card.<br>
>> For a low energy system, has any one explored ultra low energy<br>
>> consuming and<br>
>> heat generating power solutions that maybe use low wattage DC?<br>
><br>
> The minimum power requirements are dictated by your choice of<br>
> motherboard, CPU, memory, and peripherals. Period. They require<br>
> several voltages to be delivered into standardized connectors from a<br>
> supply capable of providing sufficient power at those voltages. Again,<br>
> it is clear from your question that you don't understand what power is<br>
> or the thermodynamics of supplying it, and you should work on learning<br>
> this (where GIYF). As I noted in a previous reply, typical motherboard<br>
> draws are going to be in the 100W to 300+W loaded, and either you<br>
> provide this or the system fails to work. To provide 100W to the<br>
> motherboard, your power supply will need to draw 20-40% more than this,<br>
> lost in the conversion from 120 VAC or 240 VAC to the power provided to<br>
> the motherboard and peripherals. Again, you have no choice here.<br>
><br>
> The places you do have a choice are:<br>
><br>
> a) Buying motherboards etc with lower power requirements. If you are<br>
> using recycled systems, you use what you've got, but when you buy in the<br>
> future you have some choice here. However, you need to be aware of what<br>
> you are optimizing! One way to save power is to run at lower clock, for<br>
> example -- there is a tradeoff between power drawn and speed. But<br>
> slower systems just mean you draw lower power for longer, and you may<br>
> well pay about the same for the net energy required for a computation!<br>
> You need to optimize average draw under load times the time required to<br>
> complete a computation, not just "power", weighted with how fast you<br>
> want your computations to complete and your budget.<br>
><br>
> b) You have a LIMITED amount of choice in power supplies. That's the<br>
> 20-40% indicated above. A cheap power supply or one that is incorrectly<br>
> sized relative to the load is more likely to waste a lot of power as<br>
> heat operating at baseline and be on the high end of the power draw<br>
> required to operate a motherboard (relatively inefficient). A more<br>
> expensive one (correctly sized for the application) will waste less<br>
> energy as heat providing the NECESSARY power for your system.<br>
><br>
> That is, you don't have a lot of choice when getting started -- you're<br>
> probably best off just taking the power supplies out of the tower cases<br>
> of your existing systems and using them (or better, just using a small<br>
> stack of towers without remounting them until you see how clustering<br>
> works for you, which is safe AND effective). When you have done some<br>
> more research and learned about electricity, power supplies, and so on<br>
> using a mix of Google/web, books, and maybe a friend who works with<br>
> electricity and is familiar with power distribution and code<br>
> requirements (if any) in New Delhi, THEN on your SECOND pass you can<br>
> move on to a racked cluster with custom power supplies matched to<br>
> specific "efficient" motherboards.<br>
><br>
> rgb<br>
<br>
</div></div>Although this list is quite liberal, we should be fair to Donald Becker<br>
and Co. in pointing out that most of the questions you have, here, are<br>
general computer hardware/electrical questions. They are best dealt with<br>
aside from this list. However, we'll make sure you have a good place to<br>
start.<br>
<br>
Buff up on basic electronics, both theoretical and practical. Start with<br>
a good textbook like Grob, "Basic Electronics" and something like an<br>
electronics projects kit. We used to be able to buy them at Radio Shack.<br>
<br>
If you just want to cut to the chase and assemble some computers, GIYF.<br>
Look for "build your own computer". For example, I have included one of<br>
the first links available. It appears to be fairly thorough.<br>
<a href="http://www.pcmech.com/byopc/" target="_blank">http://www.pcmech.com/byopc/</a><br>
<br>
Once you're at the stage where you are comfortable with computer<br>
hardware, at least, and perhaps electronics in general, then you will be<br>
prepared to build a Beowulf. We will be happy to help with any questions<br>
at this stage, buy please check google first always, as sometimes the<br>
answer is already out there.<br>
<font color="#888888"><br>
--<br>
Geoffrey D. Jacobs<br>
</font></blockquote></div><br><br clear="all"><br>-- <br>Best regards,<br>arjuna<br><a href="http://www.brahmaforces.com">http://www.brahmaforces.com</a><br>
<br />--
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