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Power and GPIO pins

Posted: Wed Jan 01, 2014 11:03 pm
by TheGMODSPAZ
Hello all,

I recently bought the Raspberry Pi and I have a few questions about the GPIO pins and power pins in general.

1. Is the voltage output TRULY 5 volts from the 5v pins? Forgive me if this is a stupid question. I hear it can vary?

2. What is the MAX current and voltage that can go back through the ground pin? Is the ground connected straight through back to the power supply?

Sorry if the questions are badly worded!
P.S feel free to move this to a different area - first post!

Thanks in advance!

Re: Power and GPIO pins

Posted: Wed Jan 01, 2014 11:44 pm
by joan
I don't think the 5V supply is regulated on the Pi so the voltage will be whatever is supplied by the power supply.

I have a memory that the tracks can take an amp or so (seems a bit low but I wouldn't want to experiment).

Re: Power and GPIO pins

Posted: Thu Jan 02, 2014 12:20 am
by TheGMODSPAZ
joan wrote:I don't think the 5V supply is regulated on the Pi so the voltage will be whatever is supplied by the power supply.

I have a memory that the tracks can take an amp or so (seems a bit low but I wouldn't want to experiment).
Thanks for the reply.

I heard the ground can take a fair bit but I'm not so sure. Any more info on this anyone?

Thanks.

Re: Power and GPIO pins

Posted: Thu Jan 02, 2014 1:25 am
by Tage
as far as I know, the layout files have not been released to the public so it is impossible to know how much current the traces can carry and how the GND pin is connected. just looking at the circuit board, it appears that the traces are fairly thin so I would think that you safely can run 1 Ampere but probably there can be some issues if you run more than 5 Amperes. the usual issues are: the trace can fuse open. the via that connects traces on different layers can fuse open.
by "fuse open" I mean that there can be enough heat so that the connection opens. if a trace that is inside the circuit board, there can be a loud bang as gas build up inside the board and suddenly escapes, but usually when a connection opens you just see some smoke.
with the Pi you should not expect a trace to burn up unless something went terribly wrong with our power supply.

Re: Power and GPIO pins

Posted: Thu Jan 02, 2014 11:01 am
by TheGMODSPAZ
Tage wrote:as far as I know, the layout files have not been released to the public so it is impossible to know how much current the traces can carry and how the GND pin is connected. just looking at the circuit board, it appears that the traces are fairly thin so I would think that you safely can run 1 Ampere but probably there can be some issues if you run more than 5 Amperes. the usual issues are: the trace can fuse open. the via that connects traces on different layers can fuse open.
by "fuse open" I mean that there can be enough heat so that the connection opens. if a trace that is inside the circuit board, there can be a loud bang as gas build up inside the board and suddenly escapes, but usually when a connection opens you just see some smoke.
with the Pi you should not expect a trace to burn up unless something went terribly wrong with our power supply.
Thanks! Spot on!