Hello,
I have had some problems with Yuns not behaving as expected with regards the wifi connectivity.
For example, one Yun has to be plugged into a USB port on my computer for the wifi to work as expected. If it is run from a 5V regulated power supply (exactly 5V), the wifi doesnt work. Usually, USB ports on computers seem to provide about 4.5 V. Is there something critical about the voltage used?
I have seen someone else mention this. Is this a common problem?
Thanks,
Nick
Use powered USB Hub, Per-port power switching one even better which allows software control individual usb port power on/off. (as well as each port indicate LED on or off. independently to power on/off)
What power supply are you using, Have heard--for the RasPI 
--that HTC supplies working good while other mobile phone supplies do not the job. But I wonder if this is really a problem because power consumption seems to be not a critical thing: Power Usage | Embedded Linux Board Comparison | Adafruit Learning System
Well I am using several different power supplies with a number of Yuns. For a couple of YUNs, I am using a powered USB hub. It is not the same one as suggested above. I am using one Yun as a wireless access point and the second Yun is connected to it as a client. In this case, the Yun acting as an access point seems to keep dropping out.
I changed the power to the access point yun to a computer USB port and it worked without dropping out. I wonder whether there is not enough power for both yuns and the wifi drops out even though the rest of the yun appears to work (at least the LEDs are on including the white one which says the device is working as an access point)
So I could imagine that this was an issue with the amount of current being drawn. However, on other occassions, I have tried to run YUns from Vin using a 5V regulator. There should be masses of current available but again the wifi didn't work so I went back to using the USB mini port and an external power block.
Nick
NickH:
::::SNIP::::
Is there something critical about the voltage used?I have seen someone else mention this. Is this a common problem?
@NickH,
The problem is people do not read specification.
Arduino Yun requires, at most, 315mA.
USB 2.0 delivers at most 500mA.
This would seem to be enough, until more items are added to the USB bus. Using a powered USB hub allows for more power (current). Generally people use a 1A or 2A power supply.
Jesse
Thank you Jesse,
I am coming to the conclusion that you are correct. I am using a powered hub but I do not know how much power it actually supplies. It is quite a small power brick but I will read the label!
What I would still like to know if whether it is expected that the wifi will simply cut out if the power is too low. I guess I though the whole Yun would simply shutdown.
Can someone confirm that a lack of power might show itself as a drop out of the wifi whilst giving the impression that the other parts of the yun (LEDs) are still working. In particular, the white LED that shows the Yun is working as an access point is still on.
Thanks,
Nick
NickH:
In particular, the white LED that shows the Yun is working as an access point is still on.
A minor clarification: the white LED simply means that Linux has reached the end of the boot process, it has nothing to do with the actual networking state.
NickH:
::::SNIP::::
Can someone confirm that a lack of power might show itself as a drop out of the wifi whilst giving the impression that the other parts of the yun (LEDs) are still working. In particular, the white LED that shows the Yun is working as an access point is still on.Thanks,
Nick
a drop in power (current) can have some components operate and other not. There is no way for the casual observer to say which will work and which will not.
On the LED portion, as SS says, it is not related. Also, there is much confusion as to the functions of the LEDs. This article should help.
Arduino Yun LEDs
http://codesnippets.altervista.org/documentation/yun/leds/leds.html
Jesse
NickH:
Can someone confirm that a lack of power might show itself as a drop out of the wifi whilst giving the impression that the other parts of the yun (LEDs) are still working.
Can not say it for the Yun and Wifi but I have some GSM modules who seems to act normal but don't. I can for example get no connection while all (LED, serial debug output) seems to be ok. Have the impression the problems in power supply can cause chaotic problems.