Low Power Ethernet Hubs? 24
mike.851 asks: "I'm an engineer working in the embedded systems field. For the past few years, I've been using RS-232 to interconnect various modules into the embedded systems that I build. Lately, I've found that RS-232 simply isn't flexible enough for my growing needs. I need to switch to something else, and I don't think that USB is really an option for me. I've been looking into embedded ethernet as an alternative. I've found several great low-power platforms for hardware development including several of the uClinux kits as well as products from Rabbitsemiconductor. However, I'm having trouble finding ethernet hubs that meet my power requirements (my goal is 2W or better for the hub). So far I've found Ctrlink and W-linx, and I've considered replacing the power supplies in commodity hubs with switching regulators. Does anyone have experience with these products? Does anyone know of other low-power hubs? Thanks."
well... (Score:1)
Re:well... (Score:2)
Re:well... (Score:1, Offtopic)
At any rate, wireless power exists everywhere, even before Tesla. It's in T-storms with their lightning. It's in the water. It's in the wind. It's in the earth, the sun, and all atoms. And that's just the stuff we can get at right now! Wait until someone makes a Dyson sphere!
Re:well... (Score:1)
=)
And yes, it's already done. Sorry to spell it out for you. Depending on the technology in question, it might even be an appropiate system, such as, say, in smartchips for passcodes.
Re:well... (Score:2)
But, if that's the case, then every transformer on the planet is using "wireless power". You see, you're making the definition broader than most EEs would agree with, but my whole point was that it is shortsighted to say that the only power is that which we have already gotten into our wires. Everybody already knows about what you're saying, and you add nothing to the discussion.
I should have just left it at that, but you corrected me, and your comment was based on a poor reading of my comment. It's just annoying when people do that. Have a nice day.
Re:well... (Score:1, Offtopic)
Tesla coils (haha, funny joke) were groundbreaking because they managed to place electricity in a usable form that didn't require a wire. Blowing wind across a room doesn't count either - you'd need a generator to convert it then. BTW Joe... exactly what is it that you accelerated into? It appears to have had an impact on your logic. (yeah, a pun, no kidding)
Re:well... (Score:2)
And when we play Quake 3, I'll hang on to the lightning gun, and you can just have the gauntlet.
I think you're pissed that your version of wireless power has wires, while mine doesn't. You seem to believe that electrical power is the only kind of power, but I still bet you'd run to the storm cellar during a tornado! I guess you could say that I accelerated into slashdot with my Mega-Cool low User ID, and yes, hanging around here that long might have a lasting impact on my brain functionality. Duh! Oh well, at least you got in within the first 200000 users!Re:well... (Score:2)
Sure, my UID is not the lowest, but at the least I've made an effort to contribute in a positive manner along with my smart-ass remarks.
FireWire (IEEE 1394)? (Score:2)
How about decentrailized ethernet? (Score:4, Insightful)
You could always take a step back in time and use 10base-2. Yeah, coaxial cable sucks and you're limited to 10 Mbps.
Also, I have no idea if any embedded ethernet controllers support BNC connectors, but this would allow to you take one device out of the power consumption equation.
Starting references: here [wown.com] and here [tldp.org].
Re:How about decentrailized ethernet? (Score:2, Informative)
Ethernet uses alot of power - Options (Score:2)
Sixnet industrial ethernet switches (Score:3, Informative)
I ran into a similar perdicament last year where I needed a low power ethernet switch/hub to connect two wireless units on a tower where the cable lengths to the ground were too long.
We ended up using industrial ethernet switches from Sixnet. The price wasn't _too_ bad, I seem to recall $500 for a 5 port switch. Their site is: here
Taking a look at the specifications located here [sixnetio.com] they have units in the 2W Range.
I hope this helps. BTW, we've had no problems with the unit, even after a lightning strike that nuked two of the connected radios.
Lots of choices.... (Score:3, Informative)
Some of the things you left out were the ability to survive in harsh environments, dirty power tolerance, price considerations, distance, etc.
There are a number of other bus systems that have made a few trade offs in these areas vs. total speed. Many of them are derived from work for the aerospace and automotive markets.
A few systems you might consider are:
LIN - very very low cost, but probably not fast enough for you.
CAN - up to 1 mb/Sec, lots of low cost off the shelf parts available, developed mostly by Bosch.
Flexray - faster yet, parts are more expensive, but it is faster
MOST - very fast, but targeted at moving multi-media data.
TTCAN - a modification of CAN for real time.
Most of these will support power on connects/disconnects, and are very fault tolerent.
Places to go:
www.flexray.com
www.can.bosch.com
www.ami-c.org/downloads1.htm
These are automotive focused (I'm NOT a "Car guy"), but that is because the industry is very cost aware and very big into reliability. What they tend to use is 10 year old technology that has been beat to death, has all the bugs worked out, has bunches of development tools, and all the hard parts (chips, in this case) are commodity items.
Re:Lots of choices.... (Score:1)
> I'm NOT a "Car guy"
hrm. With a name and sig like that, we'd be forgiven for making that assumption
A crossover cable (Score:1)
Re:A crossover cable -- not a joke. (Score:2)
Power-over-Ethernet solutions (Score:2)
ArcNet? (Score:1, Informative)
stay away from 100Mb (Score:3, Informative)
The Altima AC205 [altimacom.com] is an "ultra low power" part that may be used in the hub you want. It is 100Mb, but to use the power hungry 100Mb mode, both sides have to be 100Mb.
I2C? (Score:2)
The same I2C protocol used in PCs for environmental monitoring and whatnot is useful for embedded too. You can string several devices on a two-wire bus, you get 2Mbps of speed (I think, it's been a while), and I've seen embeeded systems boards as well as devices like lcd display units that support this protocol for generic communication. There's also the I2C-variant "SMBus", not really sure what the difference is between the two.
PCI-NIC+Hubs? (Score:1, Informative)
It's probably not applicable for your use, but there are at least 4 manufacturers out there producing a combined PCI NIC (rtl8139) and 5 port 100Mb switch or 10Mb hub.
One port is used internally for the NIC and the PC presents 4 ports out the back, with one having a rollover switch for uplinking.
My own experience with small external hubs is that there's more power dissipated in the wall-wart transformer than in the hub itself. This also applies to modems. Most of the wall warts are pretty ineficiently designed and produce about 9-10W worth of heat.
(This is significant when you have 70 modems in a cabinet. As a small ISP, we converted the modem pool to one big-ass transformer and a bus feed, which dropped power consumption by 600W and the AC bills by a few dollars a month.)
If every mW counts, consider clipping the leds.
Have you actually measured the current consumption of a DC hub to see how much they're chewing?
Most of the DC hubs(*) I've encountered are being fed from 9VDC/250mA PSUs, so can't be exceeding 3 watts in the first place.
(*)AC-fed ones are more common, usually with 9-12V 250mA PSUs feeding them, so the power consumption stacks up to much the same thing.
Roll your own? (Score:1)