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by MrEngman
Tue May 15, 2012 5:52 pm
Forum: General discussion
Topic: Design flaw? Polyfuses for USB current limiting
Replies: 245
Views: 111097

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: 111097

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: 111097

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: 111097

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: 111097

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: 111097

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: 111097

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: 111097

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: 111097

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: 111097

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: 111097

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: 37417

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: 37417

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: 7581

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: 4883

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...
by MrEngman
Thu May 10, 2012 5:43 pm
Forum: Beginners
Topic: using a powered usb port to power a RPi
Replies: 7
Views: 7581

Re: using a powered usb port to power a RPi

A quick addition to my previous post.

The wireless hub I'm using is the N150 version Maplin order code N47HW as I noticed there are a couple of Micronet wireless USB adapters available.
by MrEngman
Thu May 10, 2012 2:58 pm
Forum: Beginners
Topic: using a powered usb port to power a RPi
Replies: 7
Views: 7581

Re: using a powered usb port to power a RPi

<r>I'm currently using a Belkin 4 port F5U224 powered hub without any problems. It has been running pretty much 24hrs/day for about a week now.<br/> <br/> The hub's host port is connected to the Pi's USB port. A cheap keyboard and mouse I think I got from Asda are plugged into the hub. A Micronet Wi...
by MrEngman
Wed May 09, 2012 8:47 pm
Forum: Troubleshooting
Topic: Debian DHCP configuration
Replies: 16
Views: 35639

Re: Debian DHCP configuration

<r>Hi Error0404<br/> <br/> I've installed the two packages without any issues. No need to uninstall the old packages but I was asked whether I wanted to overwrite the /etc/dhclient.conf with the new one so I said yes and then restarted the network.<br/> <br/> All is OK. I can still contact the RPi u...
by MrEngman
Wed May 09, 2012 12:29 pm
Forum: Troubleshooting
Topic: Debian DHCP configuration
Replies: 16
Views: 35639

Re: Debian DHCP configuration

<t>bredman said: <br/> <br/> <br/> Try using<br/> <br/> send host-name `hostname`;<br/> <br/> <br/> <br/> <br/> <br/> This generates errors<br/> <br/> /etc/dhcp/dhclient.conf line 16: expecting string.<br/> send host-name `<br/> ^<br/> /etc/dhcp/dhclient.conf line 16: expecting a statement.<br/> sen...
by MrEngman
Wed May 09, 2012 11:29 am
Forum: Troubleshooting
Topic: Debian DHCP configuration
Replies: 16
Views: 35639

Re: Debian DHCP configuration

<r>error404 said: <br/> <br/> <br/> Also hopefully not insulting, but did you restart networking after changing the configuration? You will need to drop and renew your lease to have the change take effect (/etc/init.d/networking restart).<br/> <br/> <br/> Not insulting at all. A useful suggestion fo...
by MrEngman
Tue May 08, 2012 11:17 pm
Forum: Troubleshooting
Topic: Debian DHCP configuration
Replies: 16
Views: 35639

Re: Debian DHCP configuration

<t>error404 said: <br/> <br/> <br/> a) Have you set the hostname properly? (ie. does the command 'hostname' return the desired hostname)<br/> <br/> b) You don't need winbind, it is for something else<br/> <br/> c) On my system running 'unstable', the line in /etc/dhcp/dhclient.conf is 'send host-nam...
by MrEngman
Tue May 08, 2012 7:45 pm
Forum: Troubleshooting
Topic: Debian DHCP configuration
Replies: 16
Views: 35639

Re: Debian DHCP configuration

<t>Paul Webster said: <br/> <br/> <br/> I"ve not checked this with recent Debian - but old solution was: to add the following line to<br/> /etc/dhcp3/dhclient.conf<br/> <br/> send host-name "mypiname";<br/> <br/> <br/> and<br/> <br/> <br/> bredman said: <br/> <br/> <br/> I have never successfully ma...
by MrEngman
Tue May 08, 2012 4:09 pm
Forum: Troubleshooting
Topic: Debian DHCP configuration
Replies: 16
Views: 35639

Re: Debian DHCP configuration

<t>I am using the latest Debian release and I have my RPi connected to a Windows network with a Windows2003 server running as a domain controller. I have no problems with internet/network access from the RPi BUT...<br/> <br/> The Pi connects to the network OK but the W2003 server shows no hostname f...
by MrEngman
Fri Feb 03, 2012 2:53 pm
Forum: General discussion
Topic: FPGA Stuff ?
Replies: 55
Views: 18485

Re: FPGA Stuff ?

<r>Haven't seen it mentioned yet so for those interested in FPGA's try <URL url="http://opencores.org/">http://opencores.org/</URL><br/> <br/> Loads of open source FPGA projects.<br/> <br/> The OpenRISC project has several inexpensive development boards with either Altera or Actel FPGA's and there i...

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