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by MrEngman
Tue May 22, 2012 9:38 am
Forum: Beginners
Topic: Automatic setup for RTL8188CUS based wifi adapters
Replies: 1147
Views: 622281

Re: Automatic setup for RTL8188CUS based wifi adapters

ScoobyDoo wrote:Excellent work, will make setting up Wi-fi for 8188CUS users a doddle.
The script makes it very very easy to install.
I really hope so :)
by MrEngman
Tue May 22, 2012 9:01 am
Forum: Beginners
Topic: Automatic setup for RTL8188CUS based wifi adapters
Replies: 1147
Views: 622281

Re: Automatic setup for RTL8188CUS based wifi adapters

I have just uploaded a modified script to Dropbox. Now there is no need to modify any files before copying them to the Pi and installing your Wifi. Just copy the files to the SD card, plug in your Pi and run the script to install your Realtek RTL8188CUS based wifi adapter. The instructions can be do...
by MrEngman
Mon May 21, 2012 6:06 am
Forum: Beginners
Topic: Automatic setup for RTL8188CUS based wifi adapters
Replies: 1147
Views: 622281

Automatic setup for RTL8188CUS based wifi adapters

I have produced a script to allow automatic installation of the drivers for Realtek RTL8188CUS based wifi adapters and a document giving instructions on how to use it. The script is rather crude but does the job pretty well I think. All you have to do is edit the script to add your own SSID and PASS...
by MrEngman
Mon May 21, 2012 5:29 am
Forum: Troubleshooting
Topic: Trying to get an RTL8188CUS wireless USB NIC working.
Replies: 57
Views: 75898

Re: Trying to get an RTL8188CUS wireless USB NIC working.

I'm still struggling to get this working. I have a Pi running the latest Debian and I'm trying to get a MicroNEXT MN-WD552B working. "lsusb" hangs on Debian, but with ArchLinux it says: Bus 001 Device 005: ID 0bda:8176 Realtek Semiconductor Corp. RTL8188CUS 802.11n WLAN Did you install the firmware...
by MrEngman
Fri May 18, 2012 2:08 pm
Forum: Beginners
Topic: DHCP Issues
Replies: 5
Views: 1632

Re: DHCP Issues

It may seem obvious, but have you checked your power supply? http://elinux.org/R-Pi_Troubleshooting#Troubleshooting_power_problems The Ethernet NIC runs directly from the 5V rail. Therefore it will suffer from low voltage problems before they affect the CPU. 5v really? On the schematic I have I onl...
by MrEngman
Thu May 17, 2012 12:34 pm
Forum: Beginners
Topic: Backup SD
Replies: 62
Views: 82042

Re: Backup SD

I use the Windows Win32DiskImager program to read everything off my SD card and store it in a .img file. I can then write this to a different SD card, if I ever need to :D I just tried this method but it only created a 77mb image file. How do you get it to read all partitions? Update: This issue wa...
by MrEngman
Wed May 16, 2012 2:25 am
Forum: General discussion
Topic: Design flaw? Polyfuses for USB current limiting
Replies: 245
Views: 104933

Re: Design flaw? Polyfuses for USB current limiting

Though the schematic indicates F3 as 1.1A it seems 750mA has been fitted to actual boards.... ....IMO the logical solution is to stick with 140mA ( or similar ) but use low resistance fuses. Anything else has knock-on consequences, having to increase inlet fuse F3 rating or risk that tripping and c...
by MrEngman
Tue May 15, 2012 11:37 pm
Forum: General discussion
Topic: Design flaw? Polyfuses for USB current limiting
Replies: 245
Views: 104933

Re: Design flaw? Polyfuses for USB current limiting

Lets say (very conservatively) that this should be so when drawing 200mA. ( remember this is is what a simple keyboard with to USB ports for connection of a mouse uses, which is what the FAQ says is the ideal use of a R-PI USB port). What is then the maximum allowable resistance? its R=U/I = 0.1/0....
by MrEngman
Tue May 15, 2012 10:51 pm
Forum: General discussion
Topic: Design flaw? Polyfuses for USB current limiting
Replies: 245
Views: 104933

Re: Design flaw? Polyfuses for USB current limiting

Getting back to looking at the fuses I've been taking a look at some docs from Littlefuse regarding PTC's and USB. Interesting reading. http://www.littelfuse.com/data/en/Application_Notes/ec616.pdf http://www.littelfuse.com/data/en/Application_Notes/ec606.pdf http://www.littelfuse.com/data/en/Techni...
by MrEngman
Tue May 15, 2012 6:21 pm
Forum: General discussion
Topic: Design flaw? Polyfuses for USB current limiting
Replies: 245
Views: 104933

Re: Design flaw? Polyfuses for USB current limiting

A quote from the USB-2 spec section 7.2 Power Distribution "All devices default to low-power. The transition to high-power is under software control. It is the responsibility of software to ensure adequate power is available before allowing devices to consume high-power" Also all root port hubs (suc...
by MrEngman
Tue May 15, 2012 5:52 pm
Forum: General discussion
Topic: Design flaw? Polyfuses for USB current limiting
Replies: 245
Views: 104933

Re: Design flaw? Polyfuses for USB current limiting

Getting back to something useful... If your USB device doesn't work, use a powered hub. Not true;) I usually have my keyboard and mouse in the powered hub and wifi adapter plugged directly into the Pi. And it all works beautifully. Thought I'd see what happened if I plugged the wifi into the hub wi...
by MrEngman
Tue May 15, 2012 12:32 pm
Forum: General discussion
Topic: Design flaw? Polyfuses for USB current limiting
Replies: 245
Views: 104933

Re: Design flaw? Polyfuses for USB current limiting

If however a higher than normal constant voltage is supplied to the main power input the TVS will limit the voltage and in doing so will produce excessive current through the fuse and trip it. Using the breakdown voltage of the TVS, the junction to ambient thermal resistance of the package, assumin...
by MrEngman
Tue May 15, 2012 9:40 am
Forum: General discussion
Topic: Design flaw? Polyfuses for USB current limiting
Replies: 245
Views: 104933

Re: Design flaw? Polyfuses for USB current limiting

No SCSI on the Pi? well, they've got an adaptor for that :-) http://www.amazon.com/Adaptec-1856600-USBxchange-Kit/sim/B000067OHN/2 Does'nt appear to be available any longer :( However I'm not sure what my 15000rpm SCSI drives would make of it. They'd probably tend to doze off waiting for the data t...
by MrEngman
Tue May 15, 2012 8:46 am
Forum: General discussion
Topic: Design flaw? Polyfuses for USB current limiting
Replies: 245
Views: 104933

Re: Design flaw? Polyfuses for USB current limiting

Morgaine wrote:
On the bright side, isn't it fun to be an early adopter? ... Tick one: Yes: _X_, No: __ :D

Morgaine.
by MrEngman
Tue May 15, 2012 12:47 am
Forum: General discussion
Topic: Design flaw? Polyfuses for USB current limiting
Replies: 245
Views: 104933

Re: Design flaw? Polyfuses for USB current limiting

Hi Reiuyi, Before meeting the Pi I think my view of USB was pretty much how you appear to view things although I don't think I would expect the USB ports to output anywhere near 1A. Now though is has changed somewhat. Using Windows, which is what I've been used to for a long time now I can plug in ...
by MrEngman
Mon May 14, 2012 10:57 pm
Forum: General discussion
Topic: Design flaw? Polyfuses for USB current limiting
Replies: 245
Views: 104933

Re: Design flaw? Polyfuses for USB current limiting

Hi Reiuyi, Before meeting the Pi I think my view of USB was pretty much how you appear to view things although I don't think I would expect the USB ports to output anywhere near 1A. Now though is has changed somewhat. Using Windows, which is what I've been used to for a long time now I can plug in a...
by MrEngman
Mon May 14, 2012 8:21 pm
Forum: General discussion
Topic: Design flaw? Polyfuses for USB current limiting
Replies: 245
Views: 104933

Re: Design flaw? Polyfuses for USB current limiting

Bigwol wrote:My fuses measure a little differently

F1 = 7.5 Ohms
F2 = 5.0 Ohms
F3 = 0.5 Ohms
If you are using an external powered hub connect that to the top USB port (with F1) as it should not draw any current, and any other device to the lower port (using F2).
by MrEngman
Mon May 14, 2012 8:17 pm
Forum: General discussion
Topic: Design flaw? Polyfuses for USB current limiting
Replies: 245
Views: 104933

Re: Design flaw? Polyfuses for USB current limiting

These are USB-2 ports, only USB-1 ports are expected to only support low power (low speed) devices. Using Polyfuses to protect USB ports is common practice, but they are supposed to have resistances in the milli ohms, so that only a few tens of millivolt drops over them at ranges a few 100mA. The o...
by MrEngman
Mon May 14, 2012 7:49 pm
Forum: General discussion
Topic: Design flaw? Polyfuses for USB current limiting
Replies: 245
Views: 104933

Re: Design flaw? Polyfuses for USB current limiting

Hi Morgaine, I hadn't actually looked the Lo Rho devices. Nice low resistance. Using these will however need a minor change to the PCB to match the different footprints and there might be a noticable price difference. The ones I had looked at were http://www.littelfuse.com/data/en/Data_Sheets/Littel...
by MrEngman
Mon May 14, 2012 6:11 pm
Forum: General discussion
Topic: Design flaw? Polyfuses for USB current limiting
Replies: 245
Views: 104933

Re: Design flaw? Polyfuses for USB current limiting

+1 to mahjongg's last point. Which takes me back to my initial quest for fully detailed information on the electrical characteristics of these polyfuses. That brief PDF I linked is far below what is considered detailed design information in the industry. I expect parametric curves for pre-trip oper...
by MrEngman
Mon May 14, 2012 3:14 pm
Forum: General discussion
Topic: Design flaw? Polyfuses for USB current limiting
Replies: 245
Views: 104933

Re: Design flaw? Polyfuses for USB current limiting

Interesting. Personally I am not convinced that there is any design flaw as such. Using polyfuses for protecting the USB is I believe a fairly common practice. There are, however; several issues that need thinking about the PSU being a significant one, but there are also others just as relevant. I t...
by MrEngman
Mon May 14, 2012 12:38 pm
Forum: General discussion
Topic: Pi compatible WIfi adaptor
Replies: 27
Views: 36853

Re: Pi compatible WIfi adaptor

Hi Thunder__X,

If you type the command "lsusb" you should get a list of connect USB devices and it should give some idea of what your device actually is. Would be useful to know.
by MrEngman
Sun May 13, 2012 11:36 pm
Forum: General discussion
Topic: Pi compatible WIfi adaptor
Replies: 27
Views: 36853

Pi compatible WIfi adaptor

For anyone searching for a Wifi adapter to plug directly into the Pi USB port try the Micronet Wireless LAN USB Adapter SP907NS. I bought mine from Maplin, order number N47HW. I have been using one now for a couple of weeks and have seen no problems. This adapter uses a Realtek RTL8188CUS. Details f...
by MrEngman
Sun May 13, 2012 9:13 pm
Forum: Beginners
Topic: using a powered usb port to power a RPi
Replies: 7
Views: 7484

Re: using a powered usb port to power a RPi

I tried a cable from my Samsung USB powered DVD drive ~60cm long but very substantial. It also has a second USB connector for addition power but I didn't connect that. This reduced the voltage drop through the cable by 0.2 volts. I have now got my HDMI TV and connected that. With my original configu...
by MrEngman
Sat May 12, 2012 12:13 pm
Forum: Troubleshooting
Topic: Power: Micro-USB not pluggable
Replies: 6
Views: 4761

Re: Power: Micro-USB not pluggable

<r>Rabis49,<br/> <br/> The picture you are showing is a miniUSB connector. You need a cable wth a microUSB connector.<br/> <br/> Everything you need to know about USB connectors can be found here - <URL url="http://en.wikipedia.org/wiki/U.....connectors">http://en.wikipedia.org/wiki/U.....connectors...

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