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Constructing A Low-Power 2U Wireless Rack-Box
adelayde writes "Recently we decided to build ourselves a custom rack-mountable box that we could use as a web and DNS caching proxy and which would offer flexible wireless networking facilities and have an uniterruptible power supply. The result was a 2U rack-box with dual wireless networks built upon a low-power Via EPIA MiniITX motherboard. The box has two wireless networks built in with external antenna connectors, locking switches on the front to avoid tampering, a battery to give at least 20 mins of autonomous operation, a low wattage power supply and most importantly lots of blue LEDs :)"
1. Sell these
2. Profit
No ??? needed!
Seriously...
--TheOrangeSquid Is it any wonder things seem so awry? We swim in a sea of confusion and don't have to think to survive
Yay LEDs, they're the wave of the future because they're all blue and such. It reminds me of those old Flash Gordon episodes where everything was polished chrome and looked like it could kill you if someone flicked a switch somewhere.
Oh yeah, and I already can't reach the site. *laugh*
----- Wtcher Dragon, UDIC
Let's see how long she lasts ...
...and most importantly lots of blue LEDs
You may have meant that as a joke, but blue LEDs suck quite a lot more power than red or green ones.
When you care about power consumption, rather than coolness, come back and ask again.
(I was going to post a link to an article/long thread where a bunch of people bitched about blue LEDs, but I can't find it at the moment... Damn.)
http://mirror.us.psand.net/plinth/
"MCT7806CT 6V Regulator 1.5A Out ...
Capacitor 25Vdc 2200uF 324-5212 0.93 each
Capacitor 35Vdc, 0.1uF 221-8584 0.13 each
Capacitor 35V, 1uF ...
2 x Resistor, 0.5W, 5%, 100"
Anybody with a minor background in electrical engineering could tell you that the above equipment isn't about to get along well together. I hope they don't kill themselves.
Whats wrong with wires? :)
i 3 mini-itx
good thing it's not a chick that made this thing, or I could get in a lot of trouble for say this....
"Hey, Nice Rack!!"
Do you actually get decent performance out of mini-itx computers?
I've been toying with the idea of making a HTPC-ish box, but the performance questions stop me from buying anything.
Then how about a mirror?
http://hackish.org/~rufus/flakey.info/plinth/
Looking at the pics on the page, it looks like they could have easily built the thing inside a 1U chasis of they used the proper power supply and heatsink. All of the other parts should fit within 1U.
That being said, they could have simply used an ultraportable laptop with the screen unplugged and unnecessary parts removed/disabled.
You'd be amazed as to how little there really is inside a laptop. Think about it -- the drives and batteries take up about 75% of the chasis. Leave about another 10% for the power supply and heatsinking, and you've got a REALLY small PCB.
If space, not power, was their main concern, they could have also used one of the Shuttle cube boxes. They pack an incredibly strong punch for their size, and are usually on par with their desktop equivilants. Hell... they've even got an opteron box. The performance on the EPIA boards is horrific. What were they thinking designing a processor without a FPU? That being said, they're pretty cool because they're small, low-power, and widely availible (which laptop MBs strangely aren't). Still, they're pretty expensive considering that you're getting a PC which would have been considered pretty slow 4 years ago.
-- If you try to fail and succeed, which have you done? - Uli's moose
Incase it is needed: http://fluky.org/slashdot/flakey.info/plinth/index .html
Their site seems to be slowing quite fast:)
I'm a college degreed Electrical Engineer with over 30 years of experience, including teaching electronics at the college level for three years. That regulator circuit looks quite familiar. As long as the heatsink is sufficient for the heat dissipation in the LM317, there should be no problem. Since this is powering only the wireless bridge, the current drain at 7 volts should be modest and it only needs to drop 5 volts across the regulator IC. The total power dissipation spread across both of the 1/2 watt resistors is only 85 milliwatts so no trouble there either.
If you are referring to the capacitor voltage ratings, the only requirement there is that the voltage rating of the cap be more than the voltage actually applied to it. For example a 35 volt cap is just fine with 6 volts across it. It could even be a 1,000 volt rated cap with no ill effects.
"Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain
"Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain
Personally, I found their antenna designs much more interesting.
Actually, I've been planning on getting one of these little things for a a while now (the pcmcia model). I want it to replace my current PII 233 bulky router. The only drawback is the price of it I think. Size is really small, it's fast, and really quiet. The space where my servers are is very limited, and I'd rather not have it all used up by a router...
There has to be something special or unusual about this setup, but damn it all I can't see it.
Sure, they integrated a wireless bridge into it, but with all that room, it doesn't look like anything special... So where's the nifty part that makes this thing "News For Nerds"?
Looking for hardware (Currently need: Large Etch-a-Sketch) Have one? See my journal!
1. Go to ebay.
2. Find and buy cheap notebook.
3. Get into argument with seller over shipping.
4. Wait for notebook to arive.
5. Pick up hammer.
6. Open notebook.
7. Hit notebook screen with hammer until it comes off.
8. Stick some WiFi cards in notebook and put it on shelf.
"Have you ever thought about just turning off the TV, sitting down with your kids, and hitting them?"
Depending on what's required it would save a fair bit of power and boot time in the event of a reset to use solid state for the storage.
If the device doesn't need more than say 512MB of storage which is plenty for a small copy of Linux there are some great Compact Flash cards out there for the cheap.
Too boot and operate from these speedy low power little guys you can use an adaptor from http://www.acscontrol.com/
It's a dirt cheap solution if you only need 128MB for small applications.
Amazon always had great deals on CF cards and the adaptors are only $20 or so and their fully bootable.
Mirror here - and this is kind of a neat looking project. Do they have any plans to make any more? From the looks of it, they want to be able to take these things out in public to create a WiFi network.
Maybe they can hook up with the Huge Ass WiFi Backpack Guy from the other day?
Link: Soekris
42
I'm curious as to what their definition of "low power" is. Low, compared to a power-sucking P4 or Athlon, maybe, but probably not very low by low power standards.
I've just set up a similar system as an home file server (no wireless, though, and I've added a cheap DVDROM drive), and my box is sucking up around 55-60W, idle. That's measured via an actual wattmeter connected to the power cord, and not by multiplying V*A.
On second thought, maybe a soekris board and a 2.5" disk drive might have been a better solution (less RAM and CPU, which would probably be fine for an home fileserver, but the power usage would probably be in the 10-20W range).
How fast a CPU do you really need? Years ago I popped open a 3COM Ethernet bridge/router and found a Motorola 68020, running at 25 MHz if I remember correctly. It was fast enough to handle two fully loaded 10-megabit Ethernet segments.
Mea navis aericumbens anguillis abundat
The most important lessons these guys learned from this project are: * Blue LEDs are strangely attractive to technical people and * Sticky-back plastic is cool.
Have you metaroderated recently?
He may have built this for remote locations
or heat filled rooms/closets. In those cases
you want decent space and decent airflow INSIDE
the box.
Laptops have neither, and tend to suffer heat
related problems easily enough.
Its good already that he went low power and
low thermal, and put it in a good solid spacious
chassis.
If dollars were a concern, going down to 1U
isn't bad, but no further for real applications.
So, he writes up some stuff about his new box, and then posts it on Slashdot to stress-test the thing? Clever, clever...
Hey, you try to find an open nick these days!
The human eye is especially sensitive at wavelength of 550nm, that is Green light and that's why for the same power output (watt), the green LED appears much brighter and has a much higher luminous intensity (unit in cd or mcd) than blue or red LED.
"To be fair, I saw 1 intelligent post."
Too bad it wasn't yours.
I know this is going to be modded as flamebait, and I'm not trying to be insulting, but maybe instead of criticizing things, you should help improve things by posting something truly worthy of "Insightful"?
I find that UPS battery being too naked next to the powersupply... It rather be protected by itself in a cage because battery's can do strange things sometimes (I can tell :S)
..
...
if that thing explodes in your rack you can throw away the hard drive, maybe the mainboard and wireless bridge
so far for a rendundant/autonome system
although a beowolf cluster of blue leds? hmmmmz...
--- I am known for the ones who want to find me on the net. Is that a privacy risk or a privilege? One might wonder..
I dunno what all the fuss is about wireless. Yeah I have it in my house so I can use the notebook in the kitchen or whatever but at work? Running cable isn't that hard and if your network is large enough to make running cable a pain then it's too large for wireless unless it's all spread out then it's too large physicaly. Bah WiFi has limited applications and most of them are stupid gee-wiz stuff. I think WiFi sells well because 1/2 the techs out there are too scared or stupid to crimp their own cables. Sure they can configure a gee wiz wifi routomadealy but they can't figure out where the GWA goes.
U can actually fit 2 of these boards + 2 hd in a 1 u box
Looking at this page, and a bunch of their other pages, I think cost was their main concern. They found a 2U box for only GBP29, while the 1U box mentioned in another post by jjshoe runs GBP149. The wireless access bridge "was just laying around".
Most of their projects are of the "cheap and green" variety. They have built pedal powered repeaters, solar powered satellite receivers and the like.
I'm a bit appalled by their lack of engineering knowlege on some of their projects. But I do admire their "slap it together cheap" attitude. They are not building reliable, production level kit, they are tweaking items they found in the spare parts bin and making useful one-off projects.
the AC
Hemos is like...sci-fi fans;he thinks technology is cool, but he hasn't bothered to understand the science it's based on
For those of you interested in applying this sort of thing in the real world, we'll be taking this box out into the field along with the rest of our kit in a couple of weeks in an event taking place simultaneously in Tarifa, Spain and Tangiers, Morocco, as well as elsewhere in the world.
Transacciones / Fadaiat
It's partly insane government taxes, and partly reduced competition because a lot of companies either won't ship overseas or charge much higher rates. Plus currency differences make it easier for companies to play games with the prices. Plus an extra premium to pay for all the goods lost in transit to the pirates that plague the English Channel.
I'm making another post that should never have been submitted. Sorry, but I'm a horrible person with nothing better to do.
What operating system is he running on it?
I'm still looking for a mini-itx rack case that isn't so deep. Maybe 20cm or so. (For a musician's rack setup.)
here
lets think this through, a rack is metal on all four sides, and both the top and bottom. this does not sound like the optimal location for radio emissions. slashdot delivers another grade A plan.
* You can run linux on them
... although I understand status lights and the fact that the LED lights use VERY little power, why include them? Any power saved in a low power consumption setup is good
... can you REALLY trust your own setup vs a commercially tested system?
* You can reduce the power consumption in the same way (hard drives etc)
* They are quite powerful
One thing I didn't understand
For the $1250 that this thing cost to build you could have a much better tested and reliable system. The thing with "homebrews" is
Yell & scream & rant & rave... it's no use... you need a shaaaave ~ Bugs Bunny
The milliamp rating of the part bears no direct relationship to the need for heatsinking. The heatsink requirements are related to the amount of power that the regulator IC needs to dissipate to stay within rated operating temperature limits. The power dissipation is given by Pd=(Vin-Vout)*I. Where I is the current drawn through the regulator. For example, in this case being discussed, the voltage drop is roughly 5 volts across the IC and if the current was 1 amp, then the power being dissipated would be 5 watts. Given, from the data sheet, that the junction to ambient thermal resistance is 50 degrees C per watt, the junction temp rise above ambient for 5 watts would be 250 degrees C which is far in excess of the junction maximum operating temp of 125 degrees C. So in that example a heatsink, which reduces the junction to ambient thermal resistance, is clearly a necessity. See LM317 data sheet
Don't feel bad, though, it's a common misconception that has caused a lot of burned fingers. You are right that the heatsink can't hurt, even if not required, since lower temperatures are ralated to lower MTBF (Mean TIme Between Failures.)
"Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain
"Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain
This is all fine and dandy but wouldn't anyone who actually needs this complicated of a system to run wireless off of probably need more access points than the 2 this thing's going to hide back in the server room?
my sig's at the bottom of the page.
when I got a patent on them for my corporate employer in the 70's using all discrete parts - no IC's. It's pretty easy today to build a small one with relatively few parts, but you have to look out for the noise that they produce. Here's a link to an application note for one that would work in this case: LM2575 ap note (warning, 26 page pdf) I still like linear regulators for a lot of applications unless efficiency is paramount.
"Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain
"Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain
The hand nibbler tool from Radio Shack is great for cutting square holes, provided the sheet metal you are cutting is thin enough. (Surely must exist in the UK too) Or, an air-powered nibbler. That's the next toy I want to get.
Also why use a switch for a hard drive? Just use hdparm to turn it on and off; I doubt the electronics on the drive take a lot of power in "sleep" mode. Besides, powering it on with a switch might be able to cause transient pulses that could be harmful to the IDE controller, maybe.
FWIW don't forget that CF cards make wonderful "hard drives" for embedded systems, but you can't get 30 gig ones yet. Still not bad for a root filesystem, and just power-up and mount big media-storage filesystems when necessary.
Would using flash instead of a hard drive save power?
This is not flamebait! Okay, the last statement could be rephrased, but I think it's a valid question.
Whoever calls an LM78xx/LM317/etc. a linear supply, try leaving off the little 0.1u capacitor near the input terminals and move the larger, typically electrolytic filter cap some distance away. They may classify technically as "linear" because they don't involve a chopper/PWM driving a transformer, but there is still a current-hungry transistor at the input being switched rapidly on and off...
Caveat Emptor is not a business model.