castalla
Posts: 558
Joined: Thu Jul 19, 2012 3:46 pm

Edimax EW-7811UN wifi & power

Thu Aug 09, 2012 12:59 pm

I use the standard Kindle power adapter - 750mamp

Will this be sufficient to drive the Edimax from the onboard port?

bredman
Posts: 1415
Joined: Tue Jan 17, 2012 2:38 pm

Re: Edimax EW-7811UN wifi & power

Thu Aug 09, 2012 1:11 pm

It will probably not work in the RPi USB port.

WiFi devices normally use too much power when transmitting.

However, there is some variation in the fuses on different boards. You may be lucky, some people are. But don't depend on it.

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campi
Posts: 35
Joined: Fri Jun 01, 2012 10:45 am
Location: North Yorkshire, UK

Re: Edimax EW-7811UN wifi & power

Thu Aug 09, 2012 1:16 pm

It didn't in my Pi - I had to put it in a powered usb hub for it to work reliably.

Campi

castalla
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Joined: Thu Jul 19, 2012 3:46 pm

Re: Edimax EW-7811UN wifi & power

Thu Aug 09, 2012 1:22 pm

Okay!

Thanks for the info.

PaulCheffus
Posts: 381
Joined: Tue May 29, 2012 2:51 pm
Location: Lincolnshire UK

Re: Edimax EW-7811UN wifi & power

Thu Aug 09, 2012 3:37 pm

bredman wrote:It will probably not work in the RPi USB port.

WiFi devices normally use too much power when transmitting.

However, there is some variation in the fuses on different boards. You may be lucky, some people are. But don't depend on it.
Hi

I used this in the RPi USB port with a Blackberry Charger as power worked fine for me (I also had a keyboard attached Logitech K400 but this did have a few more repeating key issues than with the RS supplied PSU).

Cheers

Paul
Procrastination - The Thief of Time.

castalla
Posts: 558
Joined: Thu Jul 19, 2012 3:46 pm

Re: Edimax EW-7811UN wifi & power

Sat Aug 11, 2012 10:01 am

I don't understand the references to fuses.

In my simplistic world, if a fuse trips then it has to be replaced or reset.

So, what happens in the Pi?

drensber
Posts: 1
Joined: Thu Aug 30, 2012 2:03 pm

Re: Edimax EW-7811UN wifi & power

Thu Aug 30, 2012 2:10 pm

I've been using an Edimax adapter powered directly from the USB hub. It works fine, but after several days, it disappears from the USB hub altogether. If I unplug it and then plug it back in, it works fine for several more days.

Can anyone speculate as to whether this is an issue with my power supply? I'm using a 700mA Samsung supply. That theoretically provides enough power, but doesn't leave a lot of headroom... I was sort of surprised that it worked at all, but I'm even more confused as to why it would work fine for days before deciding to power itself off.

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danpeirce
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Location: Richmond & Surrey BC Canada
Contact: Website

Re: Edimax EW-7811UN wifi & power

Thu Aug 30, 2012 9:45 pm

castalla wrote:I don't understand the references to fuses.

In my simplistic world, if a fuse trips then it has to be replaced or reset.

So, what happens in the Pi?
The raspberry pi contains surface mount versions of resettable poly fuses which have some resistance even before they trip. If the current gets too high the temperature increases so the resistance increases dramatically and limits the current. They do cause some voltage drop even at room temperature. They are handy because they reset on their own as they cool down.
see http://www.te.com/content/dam/te/global ... entals.pdf

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