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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."
Actually the Ipod uses a non-cheap, not-so-mass-produced 1.8" hard drive - that's why it's so small. Apart from this, yes, I fully agree.
:-)
I recently replaced the hdd in my laptop with a 40GB one, which eats 2.2 Watt and cost me less than 100 Euro.
How you're gonna hook it up a fastethernet without a PC in between is another story
(but I think such interfaces do exist).
Another option could be a Firewire or USB2 enclosure - they allow fairly long cables - up to 20 metres (sorry no body parts used for measurements on this side of the pond) for firewire on sale at the 1394 store. Linux and Windows have no problem using them.
Just my 0.02
Vacuum cleaners suck. Kings rule.
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
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.
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.
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.
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...
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.