Brian Rankin wrote: > On Sun, 5 Dec 1999, Mark Willis wrote: > > The thing that has to be happening here is huge inductive surges on > > power-up. BAD news for computer hardware! I've seen XT/286/386/486 > > class machines run off a 12V golf cart battery with some voltage > > regulation and DC-DC voltage converters, for robotics and/or car MP3 > > usage (You might look around for the MP3 players, to give that a > > thought. If you cannot find some, ask & I'll pass you URLs, I'm good > > with search engines.) Can you get Golf Cart batteries, or other deep > > cycle lead-acid batteries, in Ghana for reasonable prices? (Marine > > Trolling motors are the same thing, only lots more pricey than Golf Cart > > batteries, you would want deep-cycle batteries, definitely, here.) Or > > could get them here & ship there. > > Deep-cycle batteries are available in Ghana -- that is not a problem. > Based on my experience in Ghana, simplicity is the key to success with > computer technology. So: if we could build computers that use electricity > from deep-cycle batteries charged with wall power -- that would be the > simplist, most cost-effective solution. Great! That makes some things much simpler. I'll go find you some MP3 player power supply schematics (for the Battery-to-Computer end of things), if you want (I could set up and make PC boards for these probably, if you're not in a huge hurry - when's the target date for your next trip overseas?) I think deep-cycle from AC power should be good, maybe add solar charging as you get a chance if and as budget allows. A deep cycle battery acts as a short circuit to noise coming in off the power buss, so if a surge comes in, the computers should be pretty safe, at least. > > Is there an amateur radio service in Ghana? Could do some kind of > > amateur satellite, we're talking lots of money here though, I think? > > Don't know -- though I can find out. Wonder if you could get a grant for that sort of thing? European comm sats are in an orbit close to what you want, should be able to arrange something, I hope! > > > Maybe we could begin by working on the specs for the computers to be > > > built. I saw an earlier post indicating that using a Linux interface might > > > be an alternative to Win95. I think that Linux would be fine, as long as > > > we can make it easy for the children to use (Staroffice instead of MS > > > Office, computer games, etc). > > > > That could be a good answer. Need a list of components, and to know > > what way you want to proceed, what the needed resources for each > > computer are, etc.? What sort of way makes the most sense - you know > > what is needed better than we do! > > I'd suggest coming up with a simple computer design that uses minimal > electricity from a deep-cycle battery. Each computer should have > vga and i/o for mouse,kbd,floppy,hd. Hd's can be in an external box. > Ram not <16MB per computer. If you go with a plywood sheet "tower" design, the HDD's could sit on the plywood, too. (Forgot to mention earlier, the plywood sheets could just be angled for "natural" ventilation, if fan power cost's a consideration; Might be good for your situation!) > > Spare components and "clusters" of identical machines are good, here; > > What else is needed? Tie a Linux guru to each machine or something? > > <G> (I've been joking about "kidnapping" one local guy to help me with > > a Linux problem, inside joke I guess. I'll get him to go willingly > > <G>) I'd guess voltmeters are available at that school, crimp tools for > > Coax for Ethernet (or for 10BaseT?), spare hubs might be good, etc.? > > The school has a 16-port hub, and another 8 porter on the way. They have > crimping tools and a spool of Cat5. I can get spare hubs, etc. None of > that is an issue. The key here is designing the hardware so that > components can easily be swapped-out, and so that machines are identical. > Regarding Linux: based on my own experience with RedHat, they may not need > a Linux guru if it is solid enough. Or, we could go with Win95 as the lab > tech on-site is experienced with that, has training/books, etc. Linux is pretty rock solid, if it breaks, you've done something wrong, usually. (I use WFW 3.11 here a lot, as it's pretty much the same way. Now if only Netscape was more so <G>) > > A good question for me to ask, too: What's Ghanan power set for? > > 110VAC, 220VAC? 50Hz, 60 Hz? <G> > > 230VAC, 50Hz Aah. We want chargers that can cope, then <G> Hmmm, set up the chargers for self-disconnect and line voltage monitoring, anyone want to take that on, or am I "it" on that? <G> Seems a current limiting resistor in series with the AC power, with a bypass relay across the resistor, could solve this problem with a minimum of trouble, maybe. What we want is a "soft start" as opposed to an explosive start <G> Say 1000V surge, 1A limit, so a 1000 ohm, 1KW (peak! not continuous!) resistor would perhaps do, doubt that'll be an SMT part <VBG> > > Would it help if they can e-mail someone in the US who can answer > > questions, and/or hunt down spares and ship them there, as needed, > > perhaps? I'm not super rich now, but can try to help somewhat. > > They do have email. I'm currently providing support, but we could > certainly form a support listserv they could send their questions to. That'd be do-able, maybe have someone over here Admin it (I could assist when you're overseas, among others <G> I am pretty used to L-Soft ListServ commands.) > So: I would say that we should begin by speccing-out the computer design. > I'm not familiar with PC104/sbc options, best practices, etc. Any > thoughts? PC104 boards? Hmmm. They're more pricey than baby AT motherboards, certainly, usually. May want adapters to Desktop style HDD's, as laptop HDD's have shorter lifespans usually. You could make these into "cartridge computers", put the PC104 board on a metal plate, screw the HDD/FDD onto the plate, and you're in a small form factor. Still need power conversion, PC104 machines are a little more energy efficient than desktop momboards though! You know, folks, EIO still has those $40 or so 486 embedded machines, Timeline only wants $79 or so for their Epson 486 POS machines, and there are lots of $30 486sx25 "pizza boxes" around, add some RAM and those would do pretty well, would that be a better answer than everything else? They're smaller and most everythings' already there... And I found a PC/104 board for $40ish, want to get one before they sell them all off <G> > Sincerely, > > Brian Rankin Mark -- I re-ship for small US & overseas businesses, world-wide. 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