BritannyVole
Posts: 1
Joined: Sun May 26, 2019 8:22 pm

Solved! Problem with VNC Viewer and other apps - Low voltage?

Sun May 26, 2019 8:37 pm

I had what I thought was a strange network problem. VNC Viewer (on a Windows PC) connected to a brand new Rasp Pi 3B was being continually disconnected. Putty SSH wasn't much better. When I *could* get a VNC Viewer remoted desktop that stayed open more than a few seconds, running anything like sudo apt-get update would work for a few seconds, then hang for no apparent reason.

At the same time, another VNC Viewer session to an older Rasp Pi 2 was working fine, rock solid.

Both Pi's were connected to the same Ethernet and to the same power source. A mains socket with two built-in USB sockets.

Then a dim lightbulb came on! I'd noticed that mobile phones connected to these mains sockets (with the built-in USB) took a lot longer to charge then when connected to an individual plug and USB socket.

So I changed the Pi3B's power source to an individual plug and USB socket. Immediately the Pi3B ran much better, no network problems now.

I'm guessing the newer Pi3B must draw a bit more power than the old Pi2's?

Andyroo
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Location: Lincs U.K.

Re: Solved! Problem with VNC Viewer and other apps - Low voltage?

Mon May 27, 2019 12:23 am

They do indeed and the 3B+ is worse.

Just buy the official power supply - it’s 5v1 and 2.5A and a decent set of cables from the adapter to the Pi. The higher voltage allows for the cable loss and the supply copes with all four cores running flat out.

Your charger could drop the voltage to 4.2v or so - not good for the Pi as you have found :lol:
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HawaiianPi
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Location: Aloha, Oregon USA

Re: Solved! Problem with VNC Viewer and other apps - Low voltage?

Mon May 27, 2019 1:48 am

A phone charger is NOT a power supply. Charging phones doesn't require precise voltage control (most will charge at anything over 4.2V), so many phone chargers have poor voltage regulation that won't maintain a stable 5V under load. I used to have a charger rated for 5V/2.4A that dropped well below 5V at only a 1A load. It charged my phone fine, but it was a lousy Pi PSU.

In addition, standard micro USB cables aren't designed to supply much more than 500mA without significant voltage loss. Combine a phone charger and a standard micro USB cable and you're asking for trouble.

As Andyroo said, just buy the official Raspberry Pi Universal Power Supply. It's a proven performer, and it's usually pretty affordable (depends on where you are and who you buy it from). Buyer beware of non-official power supplies (many are just repurposed phone chargers), especially those with separate micro USB cables (even worse if they have a power switch on the micro USB cable).
BritannyVole wrote:
Sun May 26, 2019 8:37 pm
I'm guessing the newer Pi3B must draw a bit more power than the old Pi2's?
The official power supply was rated for 2A when the Pi 2B was the top model. That was bumped up to 2.5A when the Pi 3B launched.
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