rahlquist
Posts: 146
Joined: Tue Jan 21, 2014 1:02 pm

USB Wifi Power Draw.

Sun Feb 08, 2015 9:29 pm

So I am one of those, "sometimes there is no substitute for seeing something to believe" types. After some of the recent power discussions here I was told that I may have a power issue. Which led to me ordering a 20awg USB cable that should be here tomorrow. Today I saw the story about the Xenon Flash issue and while I was examining to see if I had the same shiny U16 as others were reporting I saw my power led blinking on and off while the Pi was still functioning (my camera was still outputting live images). To cut back on power drain I removed the USB Wifi adpter I use (an older Belkin). The Led came on and stayed steady.

So I dug out a better wall wart (my samsung 2A charger for my phone) and a known good cable. Lo and behold the power led stayed on even with the wifi adapter plugged in. Suspecting I wasn't seeing the whole story I pulled out my hand usb meter and placed it between the Pi and my wifi adapter. The other day I was trying to get better wifi signal and thinking there may be a bit of current limiting I applied the "max_usb_current=1" setting in my config.txt. The results of using the meter was interesting, I saw current draw up to 1.62A from the wifi adapter! No wonder I have some instability every now and then. I posted some footage on youtube. sorry bout the potato quality https://www.youtube.com/watch?v=GI9FG-guMVw

So now the question is, has anyone seen any good comparisons on multiple wifi adapters and how much power they use.? I am considering the Broadcom unit but its so unattractive and I dont need the extra usb ports. I used to have a Edimax EW-7811Un and maybe I will go that route. This makes it clear though, why powered hub are almost a 100% must have.

User avatar
pluggy
Posts: 3636
Joined: Thu May 31, 2012 3:52 pm
Location: Barnoldswick, Lancashire,UK
Contact: Website

Re: USB Wifi Power Draw.

Mon Feb 09, 2015 4:36 pm

I'm running a Pi2 with a cheap RTL8188CUS wifi adaptor (same chipset as the Edimax), keyboard and mouse without a hub on a Samsung 700mA charger without issue. Maybe yours is faulty ?
Don't judge Linux by the Pi.......
I must not tread on too many sacred cows......

rahlquist
Posts: 146
Joined: Tue Jan 21, 2014 1:02 pm

Re: USB Wifi Power Draw.

Mon Feb 09, 2015 6:37 pm

pluggy wrote:I'm running a Pi2 with a cheap RTL8188CUS wifi adaptor (same chipset as the Edimax), keyboard and mouse without a hub on a Samsung 700mA charger without issue. Maybe yours is faulty ?
The Belkin is likely just a power hog, its at least 4 years old. It is a F7D1101 which is based on RTL8188SU. I guess I need to buy a new Edimax and give it a shot, my main issue with it was due to the location I us the pi there are several walls and a floor in the way and the Edimax didnt get good enough reception. Time to try again I guess.

Return to “General discussion”

Who is online

Users browsing this forum: No registered users and 45 guests