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Protecting Hardware on Unstable Power Sources?
psuedo_samurai asks: "Later this year, I will be returning for a visit to a small 3rd world country in Africa. I was lucky enough to travel to the country before, and the last time that I went I was able to bring four fully functional computers that I donated to a local high school, to provide a small computer network for teaching purposes. I had loaded Red Hat Linux with Open Office and a multitude of free goodies onto the systems and everything was working well. The equipment I brought back with me survived for about 12 months, but eventually fell victim to power surges, brownouts, blackouts, and so forth. On my return, I will be better prepared and am planning on setting up 8 computers, this time around. However, I am still stuck on how to best provide either a battery backup (aside from lugging UPS's along with me) with automatic shutdown and/or AVR on the cheap. Does anyone have any good references, experience, or suggestions on how to over come the challenge of running a computer network in a country where the power fluctuates wildly and multiple outages in week are not unusual occurrences?"
I will be returning for a visit to a small 3rd world country in Africa.
I hope this doesn't have anything to do with an advance fee scam someone sent to your e-mail, does it?
What you need is known as an off-line UPS, which is nothing more than a battery charger, a battery, and an inverter.
The charger charges the battery, the inverter runs from the battery - if the line voltage spikes, the battery charger takes the hit. If the line voltage sags, the inverter draws power from the battery until power is restored.
You can take along just the inverter if you can count upon getting batteries and chargers for them at your location.
The charger MUST be able to put out more current than the inverter will draw - so for a 400W computer system your charger will need to be able to put out about 40 amps at 12VDC.
The other advantage to this approach is the ability to run off a battery string charged by photovoltaic panels.
Lastly, if you can find somebody with the skill, you can get a replacement power supply for the computer that will take 12VDC to make the voltages for the computer (usually 5VDC, 12VDC, and 3.3VDC) - this will eliminate the inverter (at the downside of using a non-standard power supply for the computers.)
www.eFax.com are spammers
The off-the-shelf system that doesn't need a reliable power source is an old-fashioned laptop. You can buy obsolete laptops very cheap. Many are too big and bulky by todays standards, but will fill in nicely for a desktop system when power comes and goes.
Another idea might be to roll your own. This would involve buying a large-capacity 12V power supply capable of running from whatever voltage/frequency combination you'll have in Africa and a high-capacity inverter here in the US, shipping them to Africa, and using them to create a UPS together with car batteries purchased locally. If you have some hardware and driver experience, you could probably create an automatic shutdown system without much trouble, and might even be able to create an automated battery-maintenance system which delivers a slightly higher charge every few months to prevent sulfation (discussed in the linked article). This setup has the advantage of being a true UPS: it will provide power filtering and protection up to the point where either the battery goes dead or the battery chargers take one for the team and catch on fire. Also, it's incredibly scalable; with enough batteries, you could run a computer room for weeks without power.
That's it. I'm no longer part of Team Sanity.
Google is your friend. Just put the UPS in the PC.
Error: PANTS NOT FOUND. Press <F1> to continue.
During the day, the solar cells and power from outside charge the deep cycle batteries. if the power from the grid sags (brownout) the inverter starts adding power from the battery bank, or the solar arrays. (depending on time of day, not much solar power at 3am) Many of these inverters have serial ports, and tell you the status of what is going on (brownouts, battery life left, etc). You can setup a computer to poll this, and if the thresholds get too low, have that one system force the others to shut down.
This is probably the most reliable way to setup a power system to have clean power, in the US, or in africa. Depending on how far you are from your trip, you could start hitting BP solar (or someone else, like GE, or phillips) for donations. They might jump at the chance to send you a couple of PV arrays.
What are we going to do tonight Brain?
Get a pedal cycle and a dynamo. You should be able to produce 150W+ with that for a short while (an hour or two). If you can't get a bike try a Concept 2 rowing machine - I've pulled 400W on one of those (until I reached VO2 max and fell off).
Sigs. We don't need no steenking sigs.
Install a file server that is protected with an UPS. Configure automatic shutdown of it.
Put the client PCs behind a surge protector (but not on an UPS). Make them boot from the file server drives.
That way the storage/filesystem is reasonably protected and is not smashed everytime there is a brownout. And you don't have to spend the money for a large UPS for the client PCs.
(1) Get some really heavy duty surge suppressors.
(2) Buy 2-3 APC UPSes, each 700VA or so.
(3) Take the batteries out of the UPSes and sell them or discard them.
(4) Go to Africa.
(5) Get 2-3 car batteries.
(6) Drill some vent holes in a large metal box. Put the car batteries inside. Wire one car battery to each UPS. Put the whole shebang in an area with good ventilation.
(7) Plug the surge suppressors into your AC supply. Plug the UPSes into the surge suppressors. Plug the computers into the UPSes.
Spend about $75, get an AC isolation transformer -- 450 VA or 450 W minimum -- from eBay. Don't try to get one of this capacity new, you'll spend way too much. Then get an inexpensive UPS new. You'll either have to get both these items compatible with the wall-voltage of your destination (not much more difficult) or run an adaptor that can handle 500W. Once you have it all there, plug the isolation transformer into the wall, plug the UPS into the transformer, and plug the PC into the UPS. The transformer will protect both UPS and PC from spikes, and do it very well; the UPS will protect the PC from power failures.
I have been running an isolation transformer on my home PC for years, and would not have it any other way. I used to get hit by spikes, have not been since the transformer went in. This eBay item would be perfect:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&cate gory=4665&item=7504750488&rd=1
This one is questionable. It looks right, but I would have to verify that 13 "AAC" is really 13 amps A.C.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&cate gory=4665&item=7504750488&rd=1
J.E.B.
Joshua Corps
There is a company who is developing computers specifically for developing countries:
http://www.explan.co.uk/solo/index.shtml/
I would look in to getting some laptops with really good power supplies, I had an old twinhead laptop for a while that would run off 60 to 300 volts which would probably be more than enough.
Really though the safest bet would probably be your own generator since from what I understand the power goes off in Africa in places for hours at a time. I doubt you'll find a UPS or many laptops that'll make it. Used generaters can be had for a couple hundred from a pawn shop, and will be worth something when you get back if you want to sell it(unlike your computers).
I would also possible recommend looking at some more industrial/military type of solutions. I've seen a lot that weren't much more expensive than normal computer equipment. Most computer equipment(and electronics) simply isn't made to operate at much higher than room temperature, not to mention what humidity could possibly do(I'm not sure on this one but I doubt it's good). I think the upper ranges are around 90-100 degrees. That could actually be what cause the problem instead of brownouts/power surges.
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UPS only filter LARGE power disturbances. AVR on APC UPS only filters if the voltage goes outside a 30v range. (12% below or 12% above nominal).
AVR is really useless, because APC UPS can switch to battery on stricter basis than that.
On the other hand, a UPS to filter big disturbances and a very high quality PSU to filter smaller stuff is not a bad combination.
From my experience on an island in Thailand without government electricity, a UPS is hopeless. The range of voltage is only marginally suitable for driving incandescent lightbulbs. If you need to use local power (no solar option), you have limited options.
An AVR helps, but is usually only good in the +/-15% range. A laptop is the ideal solution, with an input range of 240-100V, but that will go in time as well with enough surges. An old battery will usually still give you a couple minutes of run-time, which will at least get you through the sags.
If you have to work with a desktop, the only solution I found that actually kept the surges away was to make a small M-G set-- couple a two motors on a common shaft with a flywheel, and connect a UPS to the output of that. All the little hits will be taken by the flywheel (as will the overvoltages), and the UPS will deal with actual outages. If you want to increase the life of the UPS batteries, put an Automatic Voltage Regulator in front of the UPS.
As for UPS systems, an off-line UPS won't do you much good. You will need a good double-conversion system to condition incoming power.
I don't think APC makes one of their "Delta Conversion" systems in that small of a size, but that could give you the best of both worlds; very good voltage regulation with buck/boost capability, and the best efficiency.
Good luck... it's an uphill battle.
suggestions on how to over come the challenge of running a computer network in a country where the power fluctuates wildly and multiple outages in week are not unusual occurrences?
Save now and save often.
Bzzzzrt!
Now, good psus nowadays can easily handle a brownout or a surge. For example, the antec neopower power supply can survive with only 60 volts (i tested this) and up to 220 volts, (that's what it says, probably more than this.)
remember, good powersupplies can survive little brownouts and surges, but i recommend a surge protector just in case.
I know that this is a little off-topic, but why do all of the 120 volt conversion when you can run directly off of low power? The display and keyboard sizes may pose a problem for you, but there has to be a solution somewhere. If I was going to a remote location then the last thing that I'd want to be thinking about is dragging along a heavy transformer/UPS and car battery.
If you don't want crime to pay, let the government run it.
1. You might not really want to use UPSs. Unless the grounding is good they really won't help much with spikes and surges. They will also cost an arm and a leg to ship. If you choose to use UPSs anyway, check to see if APC or one of the other decent UPS makers will sponsor you. I know APC likes to run success stories in their newsletter and this sounds like it might make for a good story. Also consider using 1 or 2 large high quality UPSs rather than a bunch of small/cheap ones.
2. Laptops. Someone else mentioned this option and it's a good one. Even though they cost more than desktops you'll save in shipping and you won't have to factor in the cost of UPSs. Most used laptops have something or other wrong with them (dead battery, flakey CD drive etc.) so factor in $100 or so per laptop for repairs/upgrades. Stick with IBM since spare parts and especially repair info is more easily available than others. I wonder if IBM might help you out with a good price on some off-lease laptops for a good cause?
3. CD based Distros. Seriously consider Knoppix or one of the other CD based Distros. If disk corruption was a major problem last time then this will avoid most of that problem.
Good luck.
As other posters have mentioned, get the best power supply you can afford for your system. This is the single biggest factor. If you can, consider a notebook you can run off of low voltage DC. The solution could be as simple as running the computer always offline, and swapping batteries out of a charger on the fly.
:)
The power requirement would be low enough that looking at absorbing the one time shipping cost of a solar panel might not be out of the question.
Next you need to take care of large spikes and voltage outages. This is where a decent APC UPS comes in. You can find them very cheap on ebay. They are also very trivially modified if you want to run them from large deep cycle batteries - make sure to consider a model that has built in fans (1400+) if you want to do this. If you need to ask how to do this, you probably shouldn't go that way.
If you don't need a large reserve capacity, a smaller cheapie UPS might be enough.
I'd seriously evaluate how badly you need a full-fledged PC in an environment like that though. A notebook would be much better; if you have connectivity, perhaps you could do your heavy lifting in another location?
..don't panic
"Avoid employing unlucky people - throw half of the pile of CVs in the bin without reading them." -- David Brent
On the assumption that most of your problems were caused by data becoming corrupted, why not use Knoppix (or some similar CD-based distro of your choice)? Throw in some decent surge supressors for the worst of the fluctuations. You won't have to worry about the cost of getting UPS's going, and your core OS will be good. No reason students can't save data to a hard drive on it.
"It is a miracle that curiosity survives formal education." -Albert Einstein
I suppose this will be seen as a plug, but so far as I know, the best surge suppressors available are to be had from the brick wall folks. Kind of expensive though, even after quantity discount, but still less expensive than replacing the equipment it protrects.
Then I plug my relatively ordinary UPS into the surge protector.
You're out in the bush.
1) It's a royal PITA to get parts.
You know which parts are most likely to fail as you've BTDT so bring spares of these!
2) Gather info on acceptable mains input to your equipment. Apply a cheap firewall in the form of a sensor to detect excursions likely to be unacceptable. This controls a hard disconnect (relay) from the mains. If you use a UPS then you've only it's input to worry about. Suggest a UPS that will work with locally available batteries so you don't have to lug them around the world.
Simple as that.
From a social POV. Structure your curriculum to handle outages. This way the students won't be discouraged. I liked he pedal power suggestion. The restless kids can burn off energy making power for the studious kids. So, setting up one or two computers to run on pedal power alternative might make for a big gain in holding students interest. It's also a great demo for the physics, science, and maths teachers.
Of course you could all go out for a bit of football or field hocky to burn off frustration priot to cracking books after the power disappears. I've a bit of teaching experience in 'developing' countries and guarantee that a bit of recess is paramount to holding successful lessons. esp. when things aren't going well.
Isolate as much as possible - cheap UPS's won't do that for you.
i ewItem&rd=1&item=4538880150&category=50073
or
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?Vi ewItem&rd=1&item=4538380600&category=26444
) connected to one or more car batteries. Coming off the car batteries, you hang a cheap inverter - 400 watt 12V->120V inverters (enough for a computer and monitor) are in the $30 range. Hang a voltmeter across the batteries, draw a red line at 12V or so, and teach the kids that when the needle is below the liine, you can't run the computers (deals with most issues associated with deep cycling the batteries).
/frank
Here's a thought. For each computer (or, possibly, group of two or three computers), run 120/240V power into an RV or Marine battery charger (something like http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?V
This gives you an inexpensive, reasonably isolated, double-conversion system. It might even work!
And the worms ate into his brain.
Seems like the power source is the real problem. Perhaps you could fix that problem.
Where law ends, tyranny begins -- William Pitt
I'm not sure if you're talking about equipment that has been donated to you or if you're talking about buying equipment that you are going to donate. If the later, you might consider Telco equipment designed to run on -48V DC power. It's going to be more expensive than a cheap Dell, but they're built to more demanding standards. A quick Google turned up a couple of links:
w are/tour/briefs/telco_server.html
x -48v-dc/
http://www.angstrom.com/products/viper.htm
http://www-1.ibm.com/servers/eserver/pseries/hard
Or just a -48V power supply.
http://www.zantech.com.au/zantech/power-supply-at
Alternatively, you could look at products geared for automotive use. Look at what people are using for in car computers running directly off of a 12V supply. They should also be pretty robust, although I think the Telco standards are probably more demanding (though buying NEBS3 certified equipment will really cost you.)
By running off a DC battery directly you provide a buffer against the flaky AC power distribution while saving the complexity of a UPS doing AC-DC-AC.
My grandfather used this system to charge batteries at his radio shop so many years ago I hesitate to guess. The 'kids' have stories about it so it's at least 60 years old.
... POP.. POP . POP POP POP .... then quiet again :)
You apparently could always hear the single stroke motor come on when the flywheel would slow down... a very lound POP
Layer 1
http://www.zerosurge.com/ for a surge-suppressor that'll protect your UPS, make it one of the wide-spectrum jobbers ( these things don't use MOV's which fade, so you can TRUST 'em, and no I don't work for ZS )
Layer 2
line-conditioner
Layer 3
UPS, with add-on battery capability, and BIG batteries added on, in parallel ( absorbed-glass-mat or starved-electrolyte, same-thing, are the standard for putting in UPSs, but if you're going to be doing this for extended-no-grid-use, then probably going with a bunch of big normal-lead ones might make more cost-sense. . . )
Alternative layer 2+3
get a big line-interactive UPS ( line-interactive is more efficient than the offline ones: it's using a line-conditioner instead of battery for sags etc. ) & add big batteries in parallel.
Layer 4
add solar to trickle-charge the batteries to keep 'em very topped-up & help make the hit milder, when having to rely on battery.
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