KVK
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Joined: Wed May 04, 2016 6:21 am

RPI 3B Boot Issue with Power Adapter

Tue Feb 13, 2018 11:18 am

Hello,

If I attach my RPI 3B with PC (Desktop USB) supply, it perfectly boot up and working fine but when I connect it with 5V/2A power adapter, it is not booting at all.

Do I really need 5V/2.5 A adapter as I am not using WiFi, keyboard and mouse? Or is it something related to my RPI configuration?

For more information, WiFi is also not working and RPI is showing "No wireless interfaces found" if I use any of power supply.

Please guide.

pcmanbob
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Re: RPI 3B Boot Issue with Power Adapter

Tue Feb 13, 2018 11:33 am

So this 5V/2A power adapter is it a proper pi power supply or just a phone charger ?

when you use the 5V/2A power adapter do you see the red LED on the pi flashing or go out all together ?
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KVK
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Re: RPI 3B Boot Issue with Power Adapter

Thu Feb 15, 2018 10:22 am

Hi,

Thanks,

Behavior of PI is something like as below,

On Charger Insertion: RED LED turns ON.
After one second: Yellow led blink once and then it is ON, RED is ON.
After few seconds:Yellow led OFF, Red is ON.
After few seconds: Yellow led blinks few times and red led also blink once.
Last: Yellow LED is OFF and RED is ON.

Hope this will give you idea.


Thanks again.

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Imperf3kt
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Re: RPI 3B Boot Issue with Power Adapter

Thu Feb 15, 2018 10:27 am

The red light should be on all the time. If it blinks, it usually means either the power source or the USB cable you are using, is of very poor quality and unable to maintain the required voltages to run the Pi smoothly.
For argument's sake, the Pi3 should be able to run on around 500mA (What should come out of your PC USB plugs) just fine, so long as you don't plug in too many USB devices or high-drain USB accessories and don't push the Pi to it's limits. However, it is recommended to supply it at least 1A or more.

The yellow light flashing a lot is normal / expected behaviour. If you didn't see this, then it'd be time to worry about it.
Stop plugging your fan directly into the GPIO 5v
https://www.electronics-tutorials.ws/power/transient-suppression.html

KVK
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Re: RPI 3B Boot Issue with Power Adapter

Thu Feb 15, 2018 11:25 am

Updates:
I am getting same behavior of LED indication with PC supply when HDMI cable (Monitor) is not connected.

Another observation with power adapter (Yes it is phone charger 5v/2A) is as below,
Even if there is no screen on monitor, it shows some activity on Ethernet jack. Network cable is plugged.

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FTrevorGowen
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Re: RPI 3B Boot Issue with Power Adapter

Thu Feb 15, 2018 3:12 pm

KVK wrote:
Thu Feb 15, 2018 11:25 am
...
Another observation with power adapter (Yes it is phone charger 5v/2A) is as below,
...
OOC**, what make/model of 'phone charger?
Trev..
** It may be a type I've tested:
http://www.cpmspectrepi.uk/raspberry_pi ... plies.html and later ones here:
http://www.cpmspectrepi.uk/raspberry_pi ... dPSUs.html
Still running Raspbian Jessie on some older Pi's (an A, B1, B2, B+, P2B, 3xP0, P0W) but Stretch on my P3B+, P3B, B+, A+ and a B2. See: https://www.cpmspectrepi.uk/raspberry_pi/raspiidx.htm

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HawaiianPi
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Re: RPI 3B Boot Issue with Power Adapter

Thu Feb 15, 2018 6:04 pm

Charging a phone battery does not require precise 5V regulation, so some phone chargers will not maintain 5V under load. I have tested "5V/2.4A" chargers that dipped well below 5V at only a 1A load.

Another potential problem with phone chargers is the micro-USB cable used to supply power to the Pi. The USB 2.0 specification for power is 5V/500mA (0.5A) and that's all some micro-USB cables are designed to deliver. Besides a good power supply you also need a good micro-USB cable to deliver the power to your Pi3B. Look for a micro-USB cable with at least 24 AWG power wires and preferrable larger (lower number = larger wires, so 20 AWG is better than 24 AWG). Shorter cables also have less resistance, so what you want is the shortest micro-USB cable with the fattest wires you can find (or that is practical). Charging cables included with smartphones or tablets will usually be designed for higher current. Here's a post I made awhile back about some of the best micro-USB cables I have used: viewtopic.php?f=63&t=165393

You should be able to run a Pi3B off of a 5V/2A supply, as long as you don't have very power hungry USB devices attached, but the official RPF power supply, which is rated at 5.1V/2.5A with nice fat 18AWG power wires is highly recommended.
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