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Low-powerered Ethernet Hard Drive?
WotPeed asks: "The company I work for builds extremely sensitive electric and magnetic field sensors. The project I'm just starting needs to use a hard drive to store the digitized data for long-term measurements (no more than 20GB). Unfortunately the hard drive has to be external to the sensor because it generates too much magnetic interference (hard drive needs to be at least 20 feet away). I'm therefore building an ethernet link into the sensor so that it can connect to a remote hard drive. Wireless is an option for a later revision but we're going with wired ethernet at first to keep things simple. There are plenty of network attached storage devices out there but they all assume they will be used in an office environment, and therefore consume a LOT of power. I'm looking for an ethernet hard drive that consumes less than 10W (this system will be used outdoors and runs on 12V batteries). Does Slashdot have any suggestions before I roll my own? I don't need any of the fancy features found in most NAS solutions...I just want a hard drive I can FTP to."
I imagine that MicroDrives consume very little power due to their small size and the fact that they can be powered by a PCMCIA slot.
I'm sure the hard drives used in many MP3 players such as iPods also consume very little power. . .
How do you propose to do wireless without EM interference? Sound waves? Gravity waves?
I'd think you'd have to roll your own. That said, it shouldn't be too hard to do. Just take a laptop drive, interface it to a microcontroller (search Google and you can find code and such to interface PICs, Amtels, HC11s, and others to HDs). Add ethernet (either a ethernet chip, you can find info on interfacing those with the same microcontrollers) or just use a reliable ISA card (3c509s are very well documented) and connect that to the microcontroller (also easy to do).
Comment forecast: Bits of genius surrounded by a sea of mediocrity.
Nowadays I'd recommend an external USB/FW HDD. Maximum cable length will be suffcient and power consumption should be reasonable - at least the models which use notebook HDDs. And you can watch the prices dropping...
The slowest Seagate 20GB drive i found consumes 24 watts. You'll still need an interface - cpu, memory, network... /." help. If it's a power availability problem - spacecraft maybe?... you're not looking for a COTS solution... there would be none. If it's a power DENSITY problem... consolidate all the drive needs in a server away from the environment you're measuring.
You're talking about NAS. So far, as you note, that's always been an office thing. They're made with ready power and heat dissipation taken for granted. I can't imagine a company with a real need for such a specialized requirement (as in, you're about the only case it's ever been needed) needing "ask
Incidentally, just so you don't embarrass yourself in front of your boss... wireless, at least in the most-commonly used sense, uses both electric and magnetic fields, most commonly at 2.4 or 5 GHz. Hell, conventional ethernet is something like DC-UHF, but mostly contained in the cable... perhaps something optical might be better-suited to your needs?
Frankly, I think I'd take the DC outputs of the sensors and route them as the center conductors of good-quality coax, and bring them all to a bank of A/D converters somewhere away from the environment being measured.... can you give some kind of detail about the environment?
Anyway, when you roll your own, you'll have to use something like a Hitachi microdrive. The 1GB drive consumes 8-1/4 watts on write. Maybe a transmeta-based motherboard won't break the rest of the budget.
I'd be glad to work on it. I need a job.
I'm interfacing MMCs (could just as well be SD cards in non-secure mode) via SPI to a microcontroller right now for data logging....if ~128-512Mb is sufficient for your application, this is an excellent alternative to rotating storage.
-psy
As others have said, why have you not looked into the 2.5" form-factor laptop hard drives? They're exactly what you want (low power, moderate size, shock resistent) in addition to being a standardized/commodity item. The interface is pretty much the same as any other hard drive (ATAPI), so I don't understand the problem. Or were you just hoping for free product development or something?
Of course, you'd need to add USB capabilities to your sensor(s) and you wouldn't really FTP to the drive (I don't believe), but this would be a fairly cheap and modular way to solve your problem.
But, if you do roll your own HDD that can be dropped into any network with just a Cat5 connection, let us know! ;)
"1984" was ment to be a warning, not a guidebook. You hear that Kim Jong-il!? BushCo?!
You might consider using compact flash or a similar medium instead of a HDD. That'll be low power. Otherwise, you might power the device over some of the spare pairs in the ethernet cable. Some telco stuff is implemented that way.
Assembly is the reverse of disassembly.
Assuming it is average and you are doing long term measurements, the average data rate must be pretty low (relative to hard disk transfer rates). So, I would add RAM to the sensor end controller and cache information there until you hit lets say 80% cache full, then fire up the hard disk and do the writes.
I would use USB 1.1 for the link, controllers are easy to find and cheap, the power requirements are much lower then ethernet+microcontroller+drive interface.
If your power requirements are peak, then put a lion battery on the hard disk end, charge it from the USB power and operate the drive from that.
If cost it not a huge issue, you might consider 10 2GB compactflash cards. That would eliminate the need to implement the remote data link.
I must say I'm impressessed by the quality of /. spell-checking. Now, even the titles are misspelled. I presume the next step will be to change the character set, so they can make typos in the letters themselves *sigh*...
Xenu brings order!
If you're power sensitive, perhaps ethernet isn't the best technology for you. Ethernet is designed for long distances, and is hardly low power relative to other interconnects. If it's in the budget, maybe you should consider optical fibre channel. Then you would have essentially the power requirements of the disk and the tranciever. Another option would be firewire. It's lower power than ethernet and it has the added benefit of being able to power the drive over the interconnect cable.
Ever heard of Near-End-Atenuation? No? Its the electo-magnetic interferance suffered by telecomm gear when lots a wires draw near each other at the switch. Well, thats the snow-ball effect. No single rain-drop thinks it is the cause of the flood! Anyways, if this sensor gear is so sensitive, then ethernet might be too noisy, electro-magneticly speaking! I would sugest a fiber-optic linkage with a low-powered led that is significantly less noisy, in relative terms comparied to a wire. In an ideal situation the sesor would be away from the data collectors anyways. Oh, and BTW - wireless would in theory trip the sensor too! Seems as if optics is the only real true solution, in my mind anyways. ;)
It isn't a lie if you belive it.
Many modern IDE drives have a low-speed setting that reduces the spin rate. It also reduces power consumption and is used in some power-saving modes on some PCs. The only question is, how to get the mini-server to toggle that setting...
If that's the case, you've made the usual "Ask Slashdot" mistake of phrasing the question in terms of specific and non-essential technology. Instead of an Ethernet port, your device should have an old-fashioned RS-232 port. If your serial hardware meets the spec it will reach 25 feet. (Most RS-232 hardware drastically exceeds the spec and will reach at leat 100 feet.) At the other end of the cable, put some computer system that's low-powered enough to run off its own solar panel. If you scan EBay, you'll find a gazillion laptops and PDAs that fill the bill.
the problem with laptop HDD's is that since they grab their power from the same power connectors as the data transmit chip does, they can not do long distances like they want. You would need some form of repeater to use a Laptop HDD, and also due to the small ammounts of casing etc... on a laptop HDD, they have a high magnetic interferance (sp?) rating... This also makes them weak to magnetic interferance which might be bad in this situation. As far as data transmition etc goes... an optical transmision will be the best source... even heavily shielded ethernet will have some UHF interferance and wireless will provide plenty of RFI to throw the sensors off... Optical does have it's downsides though.
Erutangis ym si siht.
If EM interference is an issue, your cabling may cause a problem too... They're a bit pricier, but what about a FibreChannel drive? You've got an optical data path -- no EM interference. Yeah, the adapters cost more, but consider the overall cost for the lab, and the potential EM worries avoided.
Fascism starts when the efficiency of the government becomes more important than the rights of the people.
I guess it's still in the prototype phase, but you might be able to work with Intel to get what you need from them. I don't know how likely that is - probably not very - but you never know. The skeptics seem to be wondering what the point of a "pocket server" is, maybe you could help give Intel a concrete example to provide to them.
Sure, but once you specify FTP you then need TCP, which means you need IP, and an FTP server, and a filesystem, and Ethernet, and ... you've just specified a NAS.
But the problem didn't require a NAS. Your problem was "too much interference so need the hard drive 20 feet away". You could solve this problem with Fibre Channel.
Investigate an external disk enclosure with fibre channel and a DC power supply. I know Sun was selling these just 2 months ago for desktop external disks.
There are plenty of bus-powered USB drives for use with laptops. That's the lowest-powered external drive you are likely going to find.
Don't bother with Ethernet-attached storage; those are not usually designed with low power in mind.
buy an old laptop for $300 on ebay and replace its ~4gb hdd with a new 20gb hdd. run your favorite bsd or linux distro on it.
The personal server is not an actual product. Just an interesting concept.
what about the terrapin mine at thinkgeek its got ethernet and USB. Seems ver flexible. only 10gigs though but you maybe able to drop a 20 or bigger into with minor hacking...
Incredibly sensitive equipment can't be that cheap.
So why not just use an old laptop?
get one that will throttle back the prossesor and get all the extra batteries you can.
should last quite a while, is upgradable to wireless and easy to set an FTP server on.
It can also have capabilityt added if your needs change.
Wow, sent an e-mail as suggested when clicking on "use classic" banner, and got a fast response that addressed my msg
take one usb laptop drive. replace cable with laser link.
problem solved.
unless you can't provide adequent line-of-sight, that is.
-I like my women like I like my tea: green-
have a look at the latest iSCSI stuff. It may be what you need. Sure you'll have to write a driver but at least you'll have stock parts available.
Also why can't you put the HD in a faraday cage? Or doesn't that block magnetic fields?
http://www.everythinglinux.com.au/item/ELS18032 v, 30GB, onboard ethernet, supported by linux. Just enclose it in a secure waterproof enclosure..
e ms/thin clients
1
Barebones on this page:
http://www.everythinglinux.com.au/cat/syst
Cheaper than NAS.
But what about a USB external harddrive?
Just buy enough USB extensions to put it 20 feet away, and your done. I'm not sure how much power they use, though.
OK, this is *completely* off the shelf; no soldering or anything (well, maybe a little for the power arrangement). All you need is a USB HDD and a USB to Ethernet adapter (about $20-$30). Put all this in an environment proof box with some batteries for powering the USB device, link the Ethernet with your monitoring kit and off you go!
UNIX? They're not even circumcised! Savages!
Would it be possible to add a firewire or usb2 controller to your computer?
Technically USB1 would even work but it would be slow.
Get a $80 bridge-board for an IDE harddrive and a 20+ foot cable.
www.fwdepot.com has bridgeboards, cables, enclosures (if needed) for both firewire and usb.
Why does the sensor need to be on the end of an ethernet cable? Couldn't you use something simpler to connect the sensor to the controller board, and keep the controller and the drive close together?
just continuing on with another posters idea of using firewire, why not use an apple iPod. It comes with its own built-in battery and add on batteries are on the way for the new models. Apple states a 10 hour battery life (although it will probably be less if you have to spin the drive all the time).
As for the distance factor I use a six foot firewire cable with my iPod but I have seen 10 foot cables before, as for 20 foot ??? they might be possible but you might have to build them yourself. I get the impression you know you way around electronics so this shouldn't be a problem. I would check to see what the cable lenght limit is on firewire first though.
Most people have suggested USB/FW/FC hard drives instead of ethernet. The 2 problems I can see with this solution are:
1) The 20 feet distance I mentioned in the original submission is a minimum value. It may have to be further away than that. I'll look into what the real distance limitations of these technologies are. Obviously FibreChannel still stands as a possible option over longer distances.
2) One of the reasons I chose ethernet was that it gives me the option of putting something else besides a dumb storage device at the end of the wire (i.e. laptop). The laptop can do double-duty as a storage device and a display so that an operator can look at the data in real time. I guess it's possible to have the same functionality if the sensor is a Firewire device, but not that many laptops come with Firewire ports yet. Ethernet is far more universal.
Granted, ethernet's not the lowest power transport mechanism out there, but it suits our needs pretty well. ANOTHER detail I left out is that this sensor will eventually be attached to a generic data acquisition system made by another company. We haven't settled on an interface mechanism yet but I'd bet they'll prefer ethernet to USB/FW.
It looks like I'll be rolling my own. I'll probably use a single board computer running embedded linux and a 2.5" hard drive. Other than some packaging there's not much design to do, other than maybe writing some software if I want to do something more sophisticated than acting as an FTP server.
iPaq with a dual PCMCIA expansion pack, standard ethernet card and a microdrive comes very close to your requirements.
A fully loaded iPaq consumes less than 18W
BB.
The Linux Kernel supports importing Block Devices over the Network, so it would be really nice to have a harddisk, which can speak NBD over Network. More info about NBD on http://nbd.sf.net/. So if someone is going to develop a Ethernet Harddisk, please consider using NBD as your protocol.
You could with out too much effort create an ide->Network interface using an AVR or Zilog MPU. what type of transfer speed do you need?
Maybe I'm stupid but it seems like you could just enclose a laptop HD in a farraday cage, or some custom made shielding specific to your application. What's harder - developing some hardware control mechanism or using off-the-shelf parts and a thick metal box with a little shielded exit port for an IDE cable? Surely being in the business of desiging high precision sensors you know a thing or two about shield design...
For $200 or so you can get a 1GB compact flash card, no magnetic field, no moving parts, size of a matchbook, get rid of that ethernet cable. You can get PCMCIA flash cards up to 4 GB or so but it starts getting pricy after a while.
if you urse firewire you could hook a mightly little ipod up to it....20 gigs of storage right there....somewhat low powerconsumption
What you can do is use an iPaq. Then get the Dual PC Card Expansion Sleeve. Then add one PC card for a network card and one PC card for a Toshiba PC Card Hard Drive (2 and 5 gig PCMCIA card drives available). I am keeping this simple, because the aforementioned will work and iPaq drivers are available. However, any pcmcia card will work provided an iPaq driver exists, so you may be able to add a usb cardbus adapter and then add a usb storage drive.
. ht m
You can see the sleeve at this url:
http://www.pdabuyersguide.com/tips/ipaq_sleeves
The benefits to this approach:
- Completely off the shelf
- Meets technical requirements specified
- The iPaq is useful for other applications
- Low power use
- small, portable
The only disadvantage is the cost.