The proper cased education model for schools was due out last September, but everything seems to have gone quiet on that. I think they may be realising that the Pi is more or less useless in schools and that its strengths are in the Hacker/Maker/Gadgeteering market.
Ian
On Sat, 10 Aug 2013 14:04:28 +0100, The Natural Philosopher declaimed the following:
Well... My TV has a 1A USB port meant to power a disk drive for slide-shows (and maybe video)... Since USB is 5V that makes 5W (max) for a drive... If an R-Pi is drawing 3.5W without any such peripheral, one may be back to 8.5 to 9W needed.
--
Wulfraed Dennis Lee Bieber AF6VN
wlfraed@ix.netcom.com HTTP://wlfraed.home.netcom.com/
Which is sort of what I meant. An atom MB bare is not much different from a pi with similarperipheral drivers added.
If you want a low power board that hase.g. video and disk drivers comparable with a PC, the atom is simply a simpler place to start and very little difference in power.
And has the advantage that cases and power supplies to fit it are stock items.
-- Ineptocracy (in-ep-toc?-ra-cy) ? a system of government where the least capable to lead are elected by the least capable of producing, and where the members of society least likely to sustain themselves or succeed, are rewarded with goods and services paid for by the confiscated wealth of a diminishing number of producers.
I can't believe that it is useless in schools, but can believe that it is useless to most teachers in schools. Not all, of course, but I think most who were raised on a diet of Chimneys will be averse to the radical change to Unix. I base that on my own reaction to a new OS or new editor, which instantly reduces me to infuriating incompetence. That would surely be much worse for a school teacher.
India has a reputation for mathematics, has many very poor districts, many power cuts, and lots of sunshine with which to power Pis. Might that be a good market? (Though surely it must be time for someone to produce a 12" LCD display which uses ambient light instead of a power-hungry cold cathode tube.)
-- Windmill, TiltNot@NoneHome.com Use t m i l l J.R.R. Tolkien:- @ S c o t s h o m e . c o m All that is gold does not glister / Not all who wander are lost
On what do you base this sweeping statement?
And it's called a powered USB hub.
Well, most of it is!
James
For a more generally useful mega-gizmo:
- some sort of RAIDed NAS box (HP microserver?)
- an Ethernet switch (connects NAS box, RPIs, printer(s) and provides connectivity for thin clients etc)
- a powered USB hub (power for the RPIs)
The would you to add headless RPis pretty much as needed.
-- martin@ | Martin Gregorie gregorie. | Essex, UK org |
There are lots of nice-to-have features but they might not have a big enough market to make them viable as products. I was thinking for schools that there might be sufficient demand for a limited base station in part to protect the Pi from physical damage and theft, and to allow leads to remain connected.
If children were to provide their own Pis maybe they could simply plug them in to the base station to get the school's network, USB, HDMI, power and sound... though the arrangement of ports on the Pi would not make that easy as they are arranged around all four sides!
James
True. Its a pity that you can't use POE with the model B: this would allow headless operation with a single cable. It also looks as though shifting the mounting hole alongside the USB socket stack would have let them put the micro-USB socket there instead, thus making it a lot easier to make cases with access to the SD card from the outside.
-- martin@ | Martin Gregorie gregorie. | Essex, UK org |
Well, there would have to extra circuitry to handle POE which would increase the cost over the target price.
Also, the so-called "mounting holes" weren't there on the original version and the USB fuses F1 & F2 were where the hole next to the USB sockets is.
Instead of POE, try POUSB! For late model B, a powered USB hub that leaks power down the client line works. Earlier model B needs a wire soldering from the USB+ to the TEST+. I don't use the front ?USB anymore.
It would be trivial to make a pseudo-dumb-PoE cable by connecting the unused pairs in a length of Cat5 to USB plugs at each end (or you can get injector/splitter plug/sockets on eBay for a couple of quid, to which you'd need to attach USB plugs). Obviously voltage drop would be more of a problem than with the ~48V that PoE uses. The cable should be fine for the current drawn by a R-Pi with a camera module.
I worry about this sort of pseudo-POE, because of the risk of confusion. Attaching a pseudo-POE client to a real POE switch is likely to inject 48 volts into the 5V pins.
Alan
-- Alan Adams, from Northamptonshire alan@adamshome.org.uk http://www.nckc.org.uk/
Shouldn't do. The PSE (Power Sourcing Equipment) looks for a 19 to
26.5 k ohm resistance between the power pairs first. If it doesn't see that it does nothing. If it does see the resistance it applies a low voltage to power just the PoE chip at the far end and has a conversation with it to set power levels etc before the full 48 V is applied. The PD (Powered Device) has to keep drawing power above a certain amount and at least every so often to remain powered.-- Cheers Dave.
Real PoE is smart enough not to do that - that's why I called the above arrangement "dumb". With proper PoE the power supplying end interrogates the power consumimg end to decide how much current it's allowed to draw. If it gets no reply it will default to not powering that port.
That would work with mine (512MB model B) but (me being picky) that's two cables instead of one.
I see what you mean about extra components: I expected the POE voltage would be 12v or 5v, not "minimum 44V".
-- martin@ | Martin Gregorie gregorie. | Essex, UK org |
48V is standard telco power stuff. They have already debugged the building codes and such.
-- These are my opinions. I hate spam.
And if the kit is running at 5 V you only need to send 1/10th the current (plus conversion and line losses) down the ethernet cable. Simple ohms law: V = I^2 * R shows that reducing current dramatically reduces voltage drop across a given value of R.
-- Cheers Dave.
Well, maybe where you live, but over here in the Netherlands we have V=I*R (without the square) so the voltage loss is less ;-). However, our power loss P=I^2*R matches your voltage loss, so we still agree that there are advantages to higher voltages and smaller currents ;-).
Best regards,
Peter
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.