Atomic I/O letters column #149
Originally published 2013, in PC & Tech Authority(in which Atomic magazine is now a section)
Reprinted here June 20, 2014 Last modified 24-Nov-2018.
Computer-furniture stress testing
I was cruising eBay looking for large used UPSes, preferably with no batteries so I can hook up to one or more car batteries as you've written about in the past. I see some serious "enterprise" units going cheap from time to time, within pick-up distance of my house or work.
I mean, really cheap. Like, under $AU200 for something that listed for at least $AU2000.
Could I use one of those huge things at home? Would I need a computer with Windows Enterprise Fortune 500 x128 Fifty Thousand Dollar Version just to make it work?
Mason
Behold: My least stealable piece of technology.
Answer:
There are a lot of different heavy-duty UPSes out there, but any that can be transported
in a civilian automobile should do the same basic stuff as home and small-office units,
without needing to be hooked up to a management machine. (You can usually download a
PDF manual to reassure you about this. An ordinary Windows box or Macintosh should be
able to control all of them via USB, too.)
There are other reasons why you might not want one, though.
First, if you think ordinary UPSes with a couple of sealed-lead-acid bricks in them are heavy, you ain't seen nothing yet. Big UPSes can be astonishingly heavy, even without the batteries.
My current main UPS is an APC Smart-UPS 3000 XL, the shipping weight for which is fifty-four kilograms. The battery cartridge, containing eight standard-sized seven-amp-hour sealed-lead-acid bricks, is more than 23 kilos by itself.
Remove the latter from the former and the UPS now feels like a dresser drawer filled with housebricks on only one side. The "two person lift!" stickers are still not kidding, but I managed to move it solo without injuring myself. Lift with your legs.
I am not in the habit of recreationally tossing cabers and/or towing jumbo jets with my teeth, though, so I wouldn't want to have to move anything much higher-spec than the 3000.
(Note that larger commercial UPSes may run from rather high-voltage battery packs, with a lot of batteries in series. There's nothing stopping you making your own pack of 16 batteries in series to run a 192V-input UPS, of course, but there is obviously some electric-shock risk involved, and if you're building a battery module from cheap car batteries, sixteen of 'em will take up rather a lot of room.)
The 3000 XL is also loud. It has intake and exhaust fans, and it, like many other big UPSes, likes to run them all the time. And all UPSes draw some extra power on top of the draw of whatever you have plugged into them, but the 3000 draws more than seventy watts non-stop, all by itself, even when it's not charging its batteries.
(This is actually rather less than my giant old power conditioner.)
In a server room, none of this matters much. The 3000 XL's commercial-grade power filtering and large current capacity (and ability to actually deliver that much current for a long time without overheating...) are much more important. It's a bit too industrial for the typical home office, though.
(I'm working on a silencer for mine.)
If it's stupid, but it works...
I feel like a genius but want to check that I really am.
I was on a business trip in a motel and for boring reasons needed to read a DVD-ROM on my little ThinkPad with no optical drive. But I had an old 3.5-inch external USB drive, and the motel had a broken PC with a DVD drive in it, so I got permission to remove the drive from the dead PC, and I took my external drive apart too, and I plugged the little cables in the drive box into the DVD drive, and it worked!
I'm now wondering, one, just out of interest would this work with a DC/DVD burner as well, and, two, am I likely to blow up the external box's power supply or something? Are optical drives and hard drives really that similar?
Eligio
Answer:
Yes, this'll work, and it'll work with a burner too, and nothing should blow up.
Writing that sentence hurt me a little, because there are a ton of niggles and caveats. Different flavours of USB-to-ATA bridge hardware have, for instance, different documented or bug-related limitations on what device types they support, and the biggest capacity they can handle. Capacity isn't going to be a problem if you're only talking CDs and DVDs and your USB bridge hardware isn't 15 years old, and modern bridge hardware is also very likely to be fine with any device you can physically connect, but I can't give you a guarantee.
Even the obvious point, that an external box that takes a modern Serial ATA (SATA) drive will not be able to connect to an older Parallel ATA (PATA) optical drive, is not totally straightforward. Use a second bridge adapter to turn the PATA device into a SATA one, and that may actually work too! Or not!
The power supply will probably be OK, too, but again I can't be certain. An optical drive writing a disk at high speed can easily consume twice as much power as a 7200RPM desktop hard drive working hard, but the power supply probably has more than enough headroom. Or perhaps it doesn't.
Optical drives are more than just physically different from SATA and PATA drives. Even SATA optical drives still use the ATA Packet Interface (ATAPI) extensions to the AT Attachment (ATA, also known as IDE) interface that essentially squish Small Computer System Interface (SCSI, pronounced "scuzzy", and the most satisfying thing it is possible to say in a Sean Connery accent) commands into the older, hard-drive-only standard. Again, there are a forest of different canonical versions and incorrect interpretations and lord knows what else all over the place. In the olden days it was easy to find USB bridge hardware that didn't work with optical drives, or that only worked for reading, not writing. And everything can be driver-dependent, adding yet another variable; all USB mass storage devices do not use the same driver.
These days, though, pretty much anything that can physically connect will work. I'm a big fan of super-cheap ATA-to-USB adapter leads, which can get you out of all sorts of problems when, say, a laptop dies but its drive is still OK. You can get a USB adapter lead with connectors for 3.5 and 2.5 inch PATA drives, in addition to any SATA drive, for less than five bucks delivered on eBay.
You still need to power the drives, but you can do that by connecting them to leads pulled out of a working PC, or with a spare PC power supply. (Connect pin 14, the only green wire on the ATX motherboard power plug, to any black-wire ground, to get the PSU to power up when it's not connected to the motherboard.) Or you can pay a bit more for a USB adapter kit that comes with its own little power supply, and power-plug adapters for all kinds of ATA.
The reason why I mentioned an old PC PSU before mentioning kits with their own power supply is that the kit power supplies are pretty questionable. I've only had one of them pop the moment I plugged it in, though!
Did you say, "Simon says, boot"?
I've downloaded a Linux LiveCD and mounted it in Daemon Tools, but when I copy it to an actual CD-R it doesn't end up bootable. I can boot from other CDs and DVDs, so it's not a BIOS setup boot order thing, just this one disc doesn't work.
Help!
Joel
Answer:
Actually, what you've done should have worked, but you didn't need to do it. To burn
a CD image to a disc, you don't have to mount it and make it appear as a disc in a virtual
"drive" on your computer; you just use software that'll burn the image directly to a
disc. (Perhaps the software you used is just file-copying the contents of the virtual
disc to the real CD-R, without
making it
bootable? I dunno.)
Every half-decent disc-burning application can burn an image file directly, and there are several free options. On Windows, try "ImgBurn".
Fishing for Internet
Is it legal to set up your own mobile phone signal amplifier?
My house has flaky ADSL internet (forest, plus phone lines, equals...), so I just tether my Samsung Galaxy S3 for Web browsing when the normal internet is out. But my house is also in a VALLEY, and the phone connection is flaky too. When I was installing a better TV antenna the other day I took my phone and found it got OK reception while I was on the roof, so can I mount an antenna up there and use an amplifier and another antenna down in the house to solve the problem?
Layla
Answer:
Yes, this can be done. It can even be done legally, in theory at least.
It's quite easy to find pretty inexpensive antennas and repeater amplifiers that work on your local mobile-phone-network frequencies, including those here in Australia. There are various dealers that claim to be Australian and also claim complete 100% gold-plated you-beaut legality.
Using these repeaters probably violates your contract with your phone company. It probably also breaks the law, because the gear hasn't been approved by the Australian Communications and Media Authority, and/or you don't have a license to use it, or direct personal permission from some body (like your phone company) that does have a license to use it.
There's another option, though: A "passive repeater".
A passive repeater is just two antennas connected by a wire. No active electronics, no amplifier, possibly still some kind of technical rule violation, I Am Not A Lawyer, et cetera. But since it's almost impossible to mess up the network with a passive repeater, and nobody cares as long as you aren't messing up the network, I wouldn't worry at all.
The antennas for a passive repeater can be any kind you like that works at the appropriate frequencies. So you can have a directional one on the roof aimed at whatever tower it is that your phone can see up there, and an omnidirectional one down in the middle of the area where you want your phone Internet to work. Because there's no amplifier there's inescapable signal loss even if you use the minimum possible length of the fanciest possible cable, but this setup really can cure the kind of marginal-signal problem that you have.
(You can also have a passive-repeater system with a directional bottom antenna, and only use your phone right on top of that antenna. If you're tethering it for Internet access then you're not going to want to move the phone around anyway, and this setup guarantees you'll get as much as possible of the feeble un-amplified signal.)
And then there's yet a third option: A better antenna connected directly to the phone.
Some phones have docking-cradle pins that allow you to connect a better antenna via such a dock, generally for using the phone in the car. Other phones have a charge-and-data connector with pins that let you connect an antenna directly. And even more phones, including I think all of the Galaxy S models, have a tiny antenna connector on the circuit board inside. The only way to use that is by dismantling the phone every time you want to plug the antenna in, or by putting a hole in the case and dangling a pigtail out. But then, a small directional antenna pointing out an appropriate window may solve your problem, perfectly legally.
(If you don't want to tie up a phone semi-permanently for Internet access, there are also inexpensive "portable access point" products that combine the guts of a mobile phone and a Wi-Fi access point, without the expensive extra parts of a phone, like the screen. Some of them are one-box devices where you just install a SIM card and you're away; others, including all the very cheapest ones, are a two-part deal where you have a mobile-phone-system "modem" that connects to the access point via USB.)
