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Few questions about powering pi 2 and rainbow square

Posted: Fri Mar 27, 2015 4:15 pm
by userino
Hi, i am currently powering my pi(using openelec) via TV USB(powering tv powers my pi, then with my remote 1st i shutdown kodi then i power off tv and my pi powers off), and it runs smoothly pretty much, rainbow square is static in top right corner which i know means that my power supply is low. It shutdowns maybe twice in 3-4 days coz of it. I have wifi dongle and small fan that i got with my case attach to pi.

Now my question is, does it harm my pi to power it as such? What temperature is considered high for pi? Without my small fan it goes to cca 50C, with it less then 40C. So if 50+ is ok then i can unplug the fan.....

If such powering is ok, how do i remove the rainbow square?

Re: Few questions about powering pi 2 and rainbow square

Posted: Fri Mar 27, 2015 4:17 pm
by RaTTuS
remove the fan
add

max_usb_current=1
in /boot/config.txt

and reboot

Re: Few questions about powering pi 2 and rainbow square

Posted: Fri Mar 27, 2015 4:30 pm
by DougieLawson
If your temp is less than 85°C then you have NO WORRIES.

The RPi does NOT need fans or heatsinks in any environment with a comfortable (to humans) ambient temperature.

Re: Few questions about powering pi 2 and rainbow square

Posted: Fri Mar 27, 2015 4:50 pm
by userino
RaTTuS wrote:remove the fan
add

max_usb_current=1
in /boot/config.txt

and reboot

Ok iv removed the fan, now rainbow square pops out every few seconds......

max_usb_current=1, from what i gathered will put output from my pis usb to 1200mA from 600mA, and that will remove the rainbow square from flashing?
Are there any downsides from doing this?
Oh and i dont mind the square flashing, does the underpowering pi harm the hardware or something?

Re: Few questions about powering pi 2 and rainbow square

Posted: Fri Mar 27, 2015 4:57 pm
by DougieLawson
max_usb_current=1 has ZERO effect on the under voltage warning square. If anything it's more likely to appear if you run a high current USB device.

What it means is the input voltage is TOO LOW, below 4V85 and your power supply can't cope with the load. The way to fix it is two-fold
1. A better power supply
2. A better USB cable between the power supply and the RPi
If you think your power supply is good change #2 first.

Re: Few questions about powering pi 2 and rainbow square

Posted: Fri Mar 27, 2015 5:04 pm
by userino
I wanna run my pi off an tv usb....
Does it harm the pi if voltage is too low(rainbow square)?

Can i just use it regardless of the undervoltage, like i said only thing that happens is couple of restarts of pi in a few days, and i dont mind that...

Re: Few questions about powering pi 2 and rainbow square

Posted: Fri Mar 27, 2015 5:51 pm
by DougieLawson
It doesn't harm it. But you're more likely to crash and you're more likely to trash the contents of your SDCard when it crashes.

Re: Few questions about powering pi 2 and rainbow square

Posted: Fri Mar 27, 2015 6:57 pm
by solar3000
userino wrote: ..... then i power off tv and my pi powers off),
....

please clarify. You power off your pi by shutting off your tv?

Re: Few questions about powering pi 2 and rainbow square

Posted: Fri Mar 27, 2015 7:36 pm
by userino
solar3000 wrote:
userino wrote: ..... then i power off tv and my pi powers off),
....

please clarify. You power off your pi by shutting off your tv?

Yep, works great, with hdmi cec, i use my remote from tv to 1st shutdown the pi(OS openelec shuts down but pi is still powered, have to do this 1st so that sd doesnt get corupted), then few seconds after pi shutdowns i just i turn off tv and as tv turns off, there is no power coming from usb anymore so pi powers off.

Then when i turn on tv, pi powers on :)

Re: Few questions about powering pi 2 and rainbow square

Posted: Fri Mar 27, 2015 9:03 pm
by DougieLawson
Are you allowing enough time between the operating system shutdown and the time when you pull power? With a regular RPi running Raspbian the green LED winks ten times when the system halts. When that winking stops it's safe to pull the power.

Re: Few questions about powering pi 2 and rainbow square

Posted: Fri Mar 27, 2015 10:03 pm
by xoopha
Depending on your display you might even get a "Signal lost" type of message on it when the Pi shuts down completely.

Re: Few questions about powering pi 2 and rainbow square

Posted: Sat Mar 28, 2015 9:36 pm
by solar3000
userino wrote:
solar3000 wrote:
userino wrote: ..... then i power off tv and my pi powers off),
....

please clarify. You power off your pi by shutting off your tv?

Yep, works great, with hdmi cec, i use my remote from tv to 1st shutdown the pi(OS openelec shuts down but pi is still powered, have to do this 1st so that sd doesnt get corupted), then few seconds after pi shutdowns i just i turn off tv and as tv turns off, there is no power coming from usb anymore so pi powers off.

Then when i turn on tv, pi powers on :)
I feel better now. I thought you just kill the power to the pi.

Re: Few questions about powering pi 2 and rainbow square

Posted: Sat Mar 28, 2015 9:56 pm
by pluggy
Changing the USB cable from the TV to the Pi for a better one may get rid of the rainbow square. The USB cable is as least as important as the power supply itself. The shorter and the thicker the better.