Hello RobH,

RH> I have been trying to get a simple led project to work on my pi 3 using
RH> a 5 volt 6 amp power supply and a 510 ohm resistor in front of the led
RH> to reduce the current going to it. Now after trying different tutorials,
RH> my pi 3 goes off on it's own from being powered up.

RH> If I remove the power lead and restart the pi 3 the red comes on and the
RH> green led flashes as well as the ethernet port flashing green led.

RH> I ssh into the pi 3 to try and run a python program, but then the pi
RH> dies, and there are no lit up leds anywhere at all on it.

RH> Is there any way it can be fixed or should I just forget about it.

Me is told to never draw more power from your Pi than 2 Amps at a Pi 2B,
or not more then 2.5 Amps on a Pi 3B.
If you connect a 5 Vdc= 6 Amp power supply to your Pi's input power socket,
and you took more dan 2.5 Amps from it by GPIO or USB devices,
you will blow the power input fuse from your Pi 3B's input power socket.
So if you need more power then that the Pi can handle, buy an external powered
USB2 hub, or power the GPIO externally with buffers (resistors),
as others told here.
So giving your Pi a higher Amperage feeding than it can handle is potentially
dangeroues. I.e. feeding a Pi 2B with a 2.5 Amps Pi 3B power supply, or feeding
a Pi 3B with a 4, 5 or 6 Amps power supply.
So keep it at max or below 2.5 Amps for the Pi 3B and max or below 2 Amps for
all the other Pi's.
You know each USB port may only take 0.5 Amps as a max.,
but donot exceed the max. Amperage the Pi can handle, or your Pi will go down,
i.e. stops running. That can crash the software on the SDcard.

Some friends of me at ships are unpatient and donot shut down OpenCPN and
Rasbian Linux, but pull the power plug ones when they are ready vieuw ECDIS
charts. They were surprised that their Linux was broken.
I had to fill their SDcard with a complete setup, and their Pi worked again
in good condition. It happend more times with the same skipper, so he
asked me for a backup SDcard when this happened more times.
Some people do not study to handle computers the right way ;-(.
Ofcourse I will help people to go on, but at some point it has to stop.

This power in fuse is also the reason to feed in a light higher Voltage of
about 5.1 Vdc= to the Pi's power input, as the Pi does not like a too low
Voltage on its power input port. That fuse also lowers the Voltage a bit.
At ships it could be a reason to power it directly via a step down dc-dc buck
power converter from the batteries 24 Vdc= to 5.2 Vdc= to avoid problems
with the usually installed 24 Vdc= to 230 Vac~ / 50 Hz inverter,
and than use the normal 230 to 5 adapter.
Because if the 230 Vac~ inverter shuts down suddenly, your microSDcard could
get broken software on it ;-(.
With the Pi at 24 Vdc= to 5.2 Vdc=, you have time to shut down normally.
Or immediate start the generator to fill the ships battery and the inverter
will also start up again. Then the monitor at 230 Vac~ will show pictures again
but the Pi at 24 Vdc= did go on during the inverter down period.
So always make BackUps of your good working (micro-)SDcard.

My third option would be to use the Pi 3B with his own keyboard, mouse and
monitor to see how it functions. With SSH you donot see everything I think.

Hope this helps? Good luck in getting your Pi 3B working again.

My own experience:
My first Pi 3B got a totally dead USBus when I was looking at pictures on a USB
stick with clicking at a mouse to find some special photo.
When doing that my one year new Elesar USB keyboard with red function keys
(Acorn BBC Style) got defect and blowed up the Pi 3B's USB.

The mouse, USB and Micro SD card worked OK in my Pi 2B,
but my Elesar red function keys keybord had been died ;-(
It was expensive at Euro 99,00 in 2016.
The Pi 3B booted normally and I got a good window screen and programs run,
but I could not use another keyboard and mouse any more at no USB port.
Unluckily I had closed down SSH, so I could not reach my Pi 3B then.
That was because SSH is default (=your fault) allways ON,
and it is not wise when the default password is not changend ;-(.
Especially when the Pi is also connected to the outside InterNet.

I got a new Pi 3B under garantee, and the first thing I did was changing the
default password to something else, and leave SSH default ON.
I wrote down that new password in a textfile on another home computer.
Normally you hardly need it, as the Pi starts automatically.

I think it is still strange that the keyboard broke at the moment I did not use
it at all, because I was busy with the mouse.
But may be continues clicking to see the next picture generates a kind of an
USB data pulse the keyboard electronics could not handle?
But that should not happen methinks.
Both Pi 3B and (red) keyboard were stuck ;-(.
Who has seen such a (strange) behavior before?

Henri.

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