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by Johannes
Mon Oct 24, 2011 4:55 pm
Forum: General discussion
Topic: Power supply news!
Replies: 176
Views: 22464

Re: Power supply news!

<t>I am by no means an electronics expert, but here\'s the way I think the protection circuit may work: A fuse directly after the connector, a diode between the circuit-side of the fuse and the other pole of the connector to \"short-circuit\" wrong polarity and a voltage clamp anti-parallel to the d...
by Johannes
Mon Oct 24, 2011 4:24 pm
Forum: General discussion
Topic: Power supply news!
Replies: 176
Views: 22464

Re: Power supply news!

<r>[quote]<B><s>[b]</s>Quote from Lob0426 on October 24, 2011, 13:21<e>[/b]</e></B><br/> A sub \"C\" NiCad or NiMh cell can deliver up to 70amps of continuos current until the cell has been depleted.[/quote]<br/> <br/> If there are cells that can deliver that much current, they\'re top notch with a ...
by Johannes
Thu Oct 20, 2011 10:24 pm
Forum: General discussion
Topic: Power supply news!
Replies: 176
Views: 22464

Re: Power supply news!

Thanks for the clarification. I was misled by this: \"Unlike coaxial jacks, we know that we’ll be receiving 5V over this connector, which we can pass on unregulated to HDMI and USB devices.\"
by Johannes
Thu Oct 20, 2011 10:18 pm
Forum: General discussion
Topic: Power supply news!
Replies: 176
Views: 22464

Re: Power supply news!

<t>This puts a big damper on the hopes of many people who envisioned \"alternatively powered\" applications. Any battery / solar / dynamo / PoE powered system will need an external voltage regulator now and flaws in that part will not only lead to fried Raspberry Pis but also fried peripherals as th...
by Johannes
Sun Oct 16, 2011 11:22 pm
Forum: General discussion
Topic: what will you name your pis?
Replies: 104
Views: 16503

Re: what will you name your pis?

Bob, Dave, Jerry, Kevin, Mark, Phil, Stuart and Tim.
My computers aren\'t gods, they\'re minions.
by Johannes
Sun Oct 16, 2011 2:47 pm
Forum: General discussion
Topic: Why not VGA port on the Rpi ?
Replies: 25
Views: 5284

Re: Why not VGA port on the Rpi ?

<t>Rasz, no, that is not an empty box. It is a passive adapter for devices which accept HDMI signals on a VGA port.<br/> <br/> The Raspberry Pi can not deliver a VGA signal and cheap VGA-only monitors can not accept a digital signal on their VGA ports. While there are (few) device combinations which...
by Johannes
Sun Oct 16, 2011 7:32 am
Forum: General discussion
Topic: Why not VGA port on the Rpi ?
Replies: 25
Views: 5284

Re: Why not VGA port on the Rpi ?

<r>Then you have an HDMI TV that uses a VGA connector for HDMI input, for whatever reason the twisted minds of its inventors could fathom. It certainly wasn\'t the cheapest TV on offer, was it? That\'s what people are hoping for though: To buy a very low end monitor with just VGA-in and then use a c...
by Johannes
Sat Oct 15, 2011 9:44 pm
Forum: General discussion
Topic: Why not VGA port on the Rpi ?
Replies: 25
Views: 5284

Re: Why not VGA port on the Rpi ?

<t>The current design does not allow for a simple cable connection from the Raspberry Pi to a VGA monitor. This has been discussed at length in other threads and there is no need to post more \"solutions\" that don\'t involve an HDMI receiver chip and a DAC. A cable or simple discrete electronics ar...
by Johannes
Tue Oct 11, 2011 11:46 am
Forum: General discussion
Topic: Which interface will be easiest to access (GPIO, SPI, I2C, UART)
Replies: 24
Views: 3828

Re: Which interface will be easiest to access (GPIO, SPI, I2C, UART)

<t>I guess the difference is the endpoint. A \"true UART\" is an endpoint that can be accessed from the OS, whereas a debugging interface only lets you talk to a specific part of the device (in this case the GPU), which may not even be exposed to the OS through documented interfaces and could be imp...
by Johannes
Sun Oct 09, 2011 8:22 pm
Forum: General discussion
Topic: A cheap LCD screen to go with the Raspberry Pi ?
Replies: 7
Views: 3206

Re: A cheap LCD screen to go with the Raspberry Pi ?

<t>The obvious answer is, don\'t skimp on the screen. I\'d say 70% of the perceived quality of a computer is in the screen. A nice 1920x1080 screen with DVI input can be had for about 100€. I don\'t see anything below 70€ new. The extra resolution is definitely worth 30€. The screen will last longer...
by Johannes
Thu Oct 06, 2011 4:31 pm
Forum: General discussion
Topic: Fitting Energy Saving Monitor?
Replies: 7
Views: 1716

Re: Fitting Energy Saving Monitor?

<t>Due to the way LCDs work, the amount of energy required for the backlight is more than meets the eye (pun intended). Even white pixels absorb most of the light: The first polarizer takes half the light away, the liquid crystals and the second polarizer absorb a small percentage and the color filt...
by Johannes
Wed Oct 05, 2011 7:57 am
Forum: General discussion
Topic: Power consumption?
Replies: 60
Views: 11486

Re: Power consumption?

I for one am disappointed to see that you insist on a connector. I was hoping for wireless power.
by Johannes
Wed Oct 05, 2011 12:13 am
Forum: General discussion
Topic: Power consumption?
Replies: 60
Views: 11486

Re: Power consumption?

<r><URL url="http://www.sparkfun.com/products/10287">http://www.sparkfun.com/products/10287</URL><br/> <URL url="http://www.reichelt.de/?ARTICLE=112278">http://www.reichelt.de/?ARTICLE=112278</URL><br/> <URL url="http://www.amazon.com/GTMax-Po.....004Q43WVK/">http://www.amazon.com/GTMax-Po.....004Q4...
by Johannes
Thu Sep 29, 2011 3:59 pm
Forum: General discussion
Topic: Coburns take on powering the Raspberry Pi via batteries
Replies: 69
Views: 12993

Re: Coburns take on powering the Raspberry Pi via batteries

7.4V*2.6Ah=18.72Wh. Divide by the average power consumption to get the running time in hours. (This assumes that the onboard regulator is a switching regulator, not a linear regulator.)
by Johannes
Thu Sep 29, 2011 3:26 pm
Forum: General discussion
Topic: Coburns take on powering the Raspberry Pi via batteries
Replies: 69
Views: 12993

Re: Coburns take on powering the Raspberry Pi via batteries

<t>@kme<br/> <br/> You can charge a supercapacitor in seconds, but you need a power source which can deliver the necessary current to the capacitor. If you want to charge a capacitor with the power to run a 2W device for 3 hours and you only want to take 60 seconds to do so, then you need a 2W*10800...
by Johannes
Thu Sep 29, 2011 1:27 pm
Forum: General discussion
Topic: Coburns take on powering the Raspberry Pi via batteries
Replies: 69
Views: 12993

Re: Coburns take on powering the Raspberry Pi via batteries

Unless there's a regenerative braking USB accessory that I don't know of, where are you going to get the current to charge a supercapacitor much faster than a set a of AA batteries?
by Johannes
Thu Sep 29, 2011 11:59 am
Forum: General discussion
Topic: Coburns take on powering the Raspberry Pi via batteries
Replies: 69
Views: 12993

Re: Coburns take on powering the Raspberry Pi via batteries

<t>Physics time: The voltage over a capacitor is linearly dependent on the charge and reciprocal on the capacitance, or the other way around, Q=V*C, charge equals voltage times capacitance. Charge is measured in coulombs, capacitance is measured in farads. A 1F capacitor charged to 1 coulomb will me...
by Johannes
Fri Sep 16, 2011 8:22 pm
Forum: General discussion
Topic: What software will run on the Raspberry Pi
Replies: 9
Views: 2210

Re: What software will run on the Raspberry Pi

<t>WINE is one of those recursive acronyms. It means "WINE is not an emulator". It provides the Windows API on top of a Unix OS, but it does not include a processor emulator. Software for the Windows API tends to be compiled for the x86 and x64 processors, so it won't run on ARM, even if the API is ...
by Johannes
Fri Sep 16, 2011 7:59 pm
Forum: General discussion
Topic: What software will run on the Raspberry Pi
Replies: 9
Views: 2210

Re: What software will run on the Raspberry Pi

<r>Debian lists package availability by distribution and architecture. For example, here's the list of packages for the armel architecture in Squeeze (stable):<br/> <URL url="http://packages.debian.org/en/.....eze/armel/">http://packages.debian.org/en/.....eze/armel/</URL><br/> <br/> That software, ...
by Johannes
Tue Sep 13, 2011 9:24 pm
Forum: General discussion
Topic: truecrypt usb drives shared over network
Replies: 9
Views: 3748

Re: truecrypt usb drives shared over network

<t>What's the point in attaching disks through Ethernet when the Ethernet port uses the same limited bandwidth as the USB port? Besides, in absence of hardware accelerated AES, you shouldn't expect more than single-digit MB/s with Truecrypt. Also, the network interface is only 100Mbps, so you can ex...
by Johannes
Tue Sep 13, 2011 1:36 pm
Forum: General discussion
Topic: Should I be able to boot off a 16GB SDHC?
Replies: 20
Views: 3348

Re: Should I be able to boot off a 16GB SDHC?

Is the boot loader in the GPU something that can be changed? If so, how is it protected against accidental changes, and is there a recovery mechanism?
by Johannes
Tue Sep 13, 2011 10:23 am
Forum: General discussion
Topic: Sizing?
Replies: 5
Views: 1374

Re: Sizing?

<t>Josh mentioned 5x3 centimeters, probably in reference to the very early prototype board that is still shown on the "media" page, and Obarthelemy responded that the final version will be much smaller, probably in reference to the current boards. I think you could avoid much confusion if you remove...
by Johannes
Tue Sep 13, 2011 7:35 am
Forum: General discussion
Topic: Coburns take on powering the Raspberry Pi via batteries
Replies: 69
Views: 12993

Re: Coburns take on powering the Raspberry Pi via batteries

Charging lithium batteries is simple in principle (Don't exceed the maximum cell voltage, don't exceed the maximum charging current), but if you do it wrong, you can end up with a battery violently catching on fire.
by Johannes
Mon Sep 12, 2011 9:14 pm
Forum: General discussion
Topic: Streaming video
Replies: 10
Views: 2321

Re: Streaming video

<t>Unless the DSP or the GPU can be used, encoding video will be very slow.<br/> <br/> Wild guesstimates from my experience with a Sheevaplug-like device: The Raspberry Pi will encode less than 5 frames (640x480) per second to H.264 if it can use VFP with the hardfp ABI. Softfp with VFP will be slow...
by Johannes
Mon Sep 12, 2011 7:59 pm
Forum: General discussion
Topic: External Battery
Replies: 1
Views: 2693

Re: External Battery

<t>As far as we (ordinary forum people) know from what the developers have told us, the Raspberry Pi will accept voltages from 6V to 20V and Model A will use about 1W under load without supplying power to attached devices. The USB hub and the Ethernet port will add to that and attached devices which...

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