1. vis-a-vis de huburile cu alimentare: asta este concluzia tuturor utilizatorilor. acum, caut hub-ul cel mai stabil. exista undeva, o lista cu dispozitivele testate si compatibile cu acest microPC. trebuie s-o gasesc si voi posta link-ul.
2. in mod cert, acest microPC este un pionier in domeniu! asteptam "concurenta" si deschiderea competitiei.
vorba lu' taica-miu: pana si filtrul de cafea va avea posibilitatea sa ruleze linux, la un moment dat! :cool2:
succesuri! :drinks:
---------- Post added at 12:53 ---------- Previous post was at 12:50 ----------
articol preluat de aici: http://elinux.org/RPi_Hardware
PowerThe board takes fixed 5V input, (with the 1V2 core voltage generated directly from the input using the internal switch-mode supply on the BCM2835 die). This permits adoption of the micro USB form factor, which, in turn, prevents the user from inadvertently plugging in out-of-range power inputs; that would be dangerous, since the 5V would go straight to HDMI and output USB ports, even though the problem should be mitigated by some protections applied to the input power: The board provides a polarity protection diode, a voltage clamp, and a self-resetting semiconductor fuse.
Premier Farnell recommend the following power supplies:
Model A: 5V dc, 500-700mA
Model B: 5V dc, 700-1200mA
Power consumption of the Raspberry Pi device is
Board A: 5V, 500 mA (2.5W) without any devices connected (e.g. USB, Ethernet, HDMI)
Board B: 5V, 700 mA (3.5W) without any devices connected (e.g. USB, Ethernet, HDMI) (Is this correct? These [1] (http://www.raspberrypi.org/forum/troubleshooting/usb-hub-sending-power-to-raspberry-pi-through-usb-port/#p68382) links [2] (http://www.raspberrypi.org/forum/general-discussion/raspberry-pi-power-requirements/page-2/#p68224) suggest that the 700mA is only required if "using networking and high-current USB peripherals" [3] (http://www.raspberrypi.org/archives/260).)
You will need to provide a power supply that can provide enough current to power the device plus any connected peripherals, and taking into account inefficiencies of the supply itself and the cable between the power supply and Raspberry Pi. The community advises opting for a power supply that can supply at least 1A if using USB peripherals or Pi plates that draw more than a few tens of milliamps of current.
As the 5V rail is brought out in the GPIO pins (http://elinux.org/Rpi_Low-level_peripherals), you can power the Rpi from there too. You should mind however, that those are behind the power protection circuitry, so you should provide your own.
It is possible to power the Rpi from a powered USB hub the Rpi controls, but only on 'dumb' devices, that allow the port to supply the full current without waiting for the usb device to ask for it[4] (http://www.raspberrypi.org/forum/general-discussion/power-pi-from-usb-hub-connected-to-pi). As the power input of the Rpi doesn't have its data leads connected, there is no chance for a communication loop of some sorts.
POE (power over ethernet (http://nl.wikipedia.org/wiki/Power_over_Ethernet)) is currently not available for the Rpi (but nobody stops you from taking your soldering iron and doing it yourself - mind though that the Ethernet jack on the board is a 'magjack' -http://www.sparkfun.com/datasheets/Prototyping/MagJack.pdf - which means that the usual 'dumb or passive PoE' power pins 47 and 78 are *not* wired through to the board. So this is not an entirely trivial exercise).
Power Supply ProblemsThere have been a number of problems reported that seem to be caused by inadequate power, this is an attempt to explain what is needed and the consequences of not having enough power.
The power required by the Pi will vary depending on how busy it is and what peripherals are connected.
Running a GUI will take more power.
The USB devices and Ethernet connection will take power.
Running the GPU will take extra power.
This means that it's difficult to say exactly how much power is needed. People have reported current requirements of between 300mA and 550mA. But it could in reality take more, especially for short periods. A simple multimeter will not show short surges on the power requirement. A surge in the power requirement for a few milliseconds will not be detectable by a meter but will be enough to cause problems. If the board does not get enough power the voltage will drop. If it drops enough parts of the system will run unreliably because data can get corrupted. The USB IC runs on 5V and handles the USB and Ethernet ports so it's likely that this will be the first thing to fail. Problems seen are unreliable Ethernet connection and unreliable operation of the Keyboard and/or mouse.
Each of the two USB ports on the Pi has a polyfuse rated at 140 mA, so any connected USB devices should draw less than this amount of current. In addition the polyfuse will cause a significant voltage drop, so that USB devices get less voltage than is available on the RPI itself, sometimes up to half a volt less (maybe more if the fuse has recently been hot). For regular "low power" USB devices this doesn't cause a problem as they are designed to work with voltages as low as 4.4 Volt. This isn't the case however with some USB devices such as WiFi dongles which may need 4.75 Volt, and are also known to draw more than 150 mA when configured and active.
The microUSB input port also has a 1.1 A polyfuse (700mA "hold current") which may also have enough resistance (although much smaller than the 140mA fuses) to cause a significant voltage drop on the board, even below its 1.1 A total current.
A extended explanation of the consequences of the use of these polyfuses can be found here Polyfuses explained (http://elinux.org/Polyfuses_explained)
There are several reasons why the power to the board may be inadequate:
The PSU may not deliver enough power. Although the maximum power requirement is said to be 700mA, that is with no peripherals connected (USB, Ethernet etc), so a 1000mA PSU should be regarded as a minimum. This allows some leeway in case the power supply cannot deliver its full power without the voltage dropping.
The PSU is not regulated.
The cable connecting the PSU to the Pi may not be good. People have reported cables with 4 ohms resistance on the power connections. At 500mA drain this would reduce a 5V supply to 3V.
How Can I tell if the power supply is inadequate?Common symptoms of an inadequate power supply are
Unreliable Ethernet or keyboard operation, especially if it's OK at first but not when the GUI is started.
SD card errors at start up seems to be another symptom of poor power.
If you think you have a problem with your power supply, it is a good idea to check the actual voltage on the Raspberry Pi circuit board. Two test points labelled TP1 and TP2 are provided on the circuit board to facilitate voltage measurements.
Use a multimeter which is set to the range 20 volts DC (or 20v =). You should see a voltage between 4.75 and 5.25 volts. Anything outside this range indicates that you have a problem with your power supply or your power cable. Anything inside, but close to the limits, of this range may indicate a problem.
http://elinux.org/images/thumb/d/d1/RPI_Test_Points.JPG/400px-RPI_Test_Points.JPG (http://elinux.org/File:RPI_Test_Points.JPG) http://elinux.org/images/thumb/8/8c/Voltmeter.JPG/250px-Voltmeter.JPG (http://elinux.org/File:Voltmeter.JPG)
It has been reported by a number of users that Apple iPhone and iPad USB power supplies are inadequate for powering the R-Pi. ([5] (http://www.youtube.com/watch?v=XX3kiRUf7mg)).
Things that can cause problems
A USB connection on a TV or PC. The USB power supply specification is for up to 500mA and if the TV implements this then it can cause problems. The system may work initially but be unreliable because as it becomes more active the power requirement increases.
A single supply from a powered hub. Most hubs seem to deliver more than the specified current but there's no guarantee. Check the power supply rating, it must be enough to supply everything that's connected to the hub.
A power supply that is rated for less than 700mA may work some of the time.
Adding a USB hard disk drive. A HDD will take quite a lot of power as it starts, maybe an amp or more. It the power supply for this also supplies the Pi then this could overload things and cause trouble.
Some complex keyboards have been reported to take a considerable amount of power, maybe up to 500mA. The Pi cannot deliver this amount of power. Simpler budget keyboards may be better. If the system works with no keyboard attached but not with a keyboard then it's worth trying a different, simpler, keyboard.
Summary
If you are having unreliable operation the first thing to do is check your power supply.
Start with a good quality regulated power supply that is rated to provide 5V and at least 1A (1000mA).
Use a good quality micro USB cable. Cables are notorious for giving trouble so be prepared to swap for another one.
Not all power supplies will deliver what they claim.
Capacitor C6Behind the microUSB power connector on the Model B is a metallic grey component called a capacitor, marked as C6. This capacitor helps stabilise the DC power on the board, but for some it has also become a place for their thumb when removing the RPI's power lead; unfortunately, this can result in the capacitor breaking off! It has been stated in the forums that the type of capacitor used for C6 will be changed on later RPi models for one with sturdier leads. If you do break off your C6 capacitor, it's highly likely that your RPi will still work properly, unless you have a particularly unstable power supply, but the general advice is to not use C6 as a leverage point when removing the power connector and also take care when storing or transporting your RPi if it's not fitted in a case - try not to stow the board where C6 could be knocked by other items - for example in a laptop carry case or in amongst some books.
http://elinux.org/images/0/04/Rpic6.jpg (http://elinux.org/File:Rpic6.jpg)
http://elinux.org/skins/common/images/magnify-clip.png (http://elinux.org/File:Rpic6.jpg)
Capacitor C6 (ringed)
It's unlikely that replacing a broken off C6 capacitor will be covered under warranty, but fortunately they are easy to replace if you have average soldering skills (http://www.raspberrypi.org/archives/1494), but remember that reworking your RPi will void its warranty too. C6 is a surface mount electrolytic capacitor with a capacitance of 220 microfarad (μF) and a voltage rating of 16 volt (V). The capacitor is polarised and so must be fitted the right way round - notice the black marking on one side in the picture above. A replacement capacitor can be purchased from numerous sources - for example:
Farnell (http://uk.farnell.com/jsp/search/browse.jsp?N=202457+110114112+110119850+110141127+110200576&No=0&getResults=true&appliedparametrics=true&locale=en_UK&divisionLocale=en_UK&catalogId=&skipManufacturer=false&skipParametricAttributeId=&prevNValues=202457+110114112+110119850+110141127&mm=1000002|110114112|110114112,1001880|110119850|110119850,1002520||,1002063||,1002999||,&filtersHidden=false&appliedHidden=false&autoApply=true&originalQueryURL=%2Fjsp%2Fsearch%2Fbrowse.jsp%3FN%3D202457%26No%3D0%26getResults%3Dtrue%26appliedpar ametrics%3Dtrue%26locale%3Den_UK%26divisionLocale%3Den_UK%26catalogId%3D%26skipManufacturer%3Dfalse% 26skipParametricAttributeId%3D%26prevNValues%3D202457)
Rapid Electronics (http://www.rapidonline.com/Electronic-Components/220uf-16v-85deg-Smd-Electro-Capacitor-11-2264)
RS Components (http://uk.rs-online.com/web/c/passives/capacitors/aluminium/?sort-by=default&sort-order=default&applied-dimensions=4294884868,%204294884170,%204294672278,4294885140&lastAttributeSelectedBlock=4294955811)
If you prefer to make your own PSU - see: Power Supply construction - HowTo (http://elinux.org/RPi_5V_PSU_construction)
---------- Post added at 12:54 ---------- Previous post was at 12:53 ----------
A 5V power supply for the Raspberry Pi - Construction How ToDue to various problems with the power supply for the RaspberryPi, a home made PSU might be a solution for some of you. You will need some experience with construction of electronic circuits, appropriate tools and a multimeter.
I have had problems with a cheap 5V/1A adapter from Ebay too (freezing, no LAN, etc.) ... The adapter could not provide enough power. It had 5.0xV unloaded, but with RaspberryPi connected I've measured 4.78V and less - dropping to 4.5V on TP1 and TP2, and that's not good. The voltage drop might be partially caused by the cable, but I've used a branded Nokia cable that looks pretty solid. Anyway, we have to compensate for that too. Also there is some voltage drop on the polyfuse F3, hence don't expect to get >=5.0V on TP1-TP2...
http://elinux.org/images/thumb/9/98/Ebay_cheap_5V_adaptor1.jpg/120px-Ebay_cheap_5V_adaptor1.jpg (http://elinux.org/File:Ebay_cheap_5V_adaptor1.jpg)
Cheap PSU
http://elinux.org/images/thumb/f/f5/Ebay_cheap_5V_adaptor2.jpg/120px-Ebay_cheap_5V_adaptor2.jpg (http://elinux.org/File:Ebay_cheap_5V_adaptor2.jpg)
Cheap PSU - inside
So instead of looking for another PSU (or cell phone charger), I decided to make my own PSU with the popular 7805 - 5V/1A regulator.
The basic idea is shown on this schematic:
http://elinux.org/images/d/d7/PSU_7805_v01.jpg (http://elinux.org/File:PSU_7805_v01.jpg)
The resistors R1 and R2 serve as adjustment of the output voltage. The formula is: V out = V fixed + { R2 [ (V fixed/R1) + I standby] }, where V fixed=5V and I standby=2.5mA (for 7805). I calculated for resistors that I had at home, but for best results R1 should be about 470ohm to 1k. Remember that resistors have some tolerance, so results may vary slightly, always measure. Value of C3 is not critical, I recommend 100-470uF. Same for C4, where for every 1A drawn, use 1000uF of capacity (and add some reserve). Don't forget to put C1 and C2 as close as possible to the regulator. And a heatsink for the regulator is necessary too.
I've used an old 9.5V/1500mA power supply from an printer as the source for this regulator, so no transformer and rectifier etc. was needed in my case. And it works just fine :)
Here is a schematic of a complete PSU including all components:
(a suggestion, with better filtering and protection)
http://elinux.org/images/6/6f/PSU_7805_v02.jpg (http://elinux.org/File:PSU_7805_v02.jpg)
Starting from left, we have a transformer (protected by a fuse - F1) supplying about 7-12V AC at 2A (use what you have at home or what is cheaper to buy). Next is a rectifier (or 4 diodes / >1A) with caps (C7-C10, for filtering). Now we should have approx. <AC voltage> x 1.41 - so if we have a 9V transformer, it will be about 12.69V. The 7805 needs at least 2V (depending on type/manufacturer) more on the input than on the output (I prefer using a little more, >3V to be sure) for stable regulation, and it can be up to 35V (but a big difference between input and output voltage means "a lot work" for the regulator and a lot heating). In this case, 8-9V DC measured after the rectifier would be optimal. Main filtering is ensured by C4 (use at least 1000uF for each 1A drawn), another filtering after the regulator is C3 (100-470uF). C1-C6 serve the 7805 for stable function and HF filtering. R1 and R2 adjust the voltage to 5.25V, as described before. D1 and D2 are for protection. A transil is used for over-voltage (peaks) protection on the output, a 5V8 type should be fine (5.8V reverse standoff voltage and approx. 6.2V breakdown voltage) - use P6KE6.8A or BZW06-5V8. For operation signaling (device on) a LED coupled with R3 is used. You may use another fuse on the output - F2.
This is a rather fancy circuit, you may simplify it if you like - by leaving out C7-C10, C5, C6, D1, D2, LED and R3, F2 (and the transil, if you don't want any protection). Or leave just some of them. Your choice ;)
Also if you prefer to fine-tune the output voltage, you may replace R2 with a small pot (trimmer) as shown here:
http://elinux.org/images/7/72/PSU_7805_v03.jpg (http://elinux.org/File:PSU_7805_v03.jpg)
With this values (R1=1k, R2=100) adjustment from 5V to approx. 5.75V is possible.
Resources on 7805For more info about the 7805 regulator, google the datasheet (http://www.google.com/search?q=7805+datasheet) and see the following resources.
Resource links:
The Adjustable Voltage Regulator (http://www.rason.org/Projects/regulator/regulator.htm),
Variable power supply using 7805 (http://www.circuitstoday.com/variable-power-supply-using-7805),
or google more (http://www.google.com/search?q=7805+regulator)
The testing prototypeThis is my testing prototype of this PSU, based on the first schematic. It's made of "what was found in the drawer". I've used an old 7805 regulator in TO3 package, C3 was taken from some broken mainboard, C4 is left out (it's not necessary, because the circuit is powered by a stable power supply from some old printer). The PSU provides stable 5.25V and i have 4.82V on TP1-TP2. My RaspberryPi works OK now :)