skogen
Posts: 3
Joined: Wed Jul 30, 2014 6:53 pm

Need more than two 5v GPIO outputs

Wed Jul 30, 2014 7:08 pm

I have a model B with a relay and distance measurement module connected. I also have a camera module connected (and a wifi adapter).
This have been running fine for a couple of months but suddenly I was unable to ssh into the Pi. So after hooking up a monitor I was greeted with a corrupt file system :evil:
It might be a bad power supply or powerloss...? The power supply is labeled with 2A, but it might be defunct.
So if I want to replace it, how much Ampere should the power supply be able to deliver?

I also want to connect another distance measurement module which also will require 5v but I have used both 5v outputs on the GPIO - how do I deal with that? Is it possible to split one of the 5v outputs or should i get another power supply just for that?

Skogen

Duane Degn
Posts: 55
Joined: Thu Jul 10, 2014 6:30 am
Location: Idaho, USA

Re: Need more than two 5v GPIO outputs

Wed Jul 30, 2014 7:52 pm

skogen wrote:I also want to connect another distance measurement module which also will require 5v but I have used both 5v outputs on the GPIO - how do I deal with that? Is it possible to split one of the 5v outputs or should i get another power supply just for that?
This is a big "it depends". How much current are these 5V devices drawing?

I don't think you want more than a total of 200mA (I'm not sure of the exact amount but I think 200mA is close) being used from the 5V bus.

If the three 5V devices don't draw more than the "safe" amount of current then splice one of the 5V wires.

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rpdom
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Location: Chelmsford, Essex, UK

Re: Need more than two 5v GPIO outputs

Wed Jul 30, 2014 8:14 pm

You can split the power from the pins. They are joined together on the board anyway.

But you can't take much power from the B (a bit more from the B+) because the input fuse limits the current to around 700mA for the Pi, USB and GPIO.

Especially if you are running relays you would be better off with another 5V supply to run your external circuit. Just make sure the GND/0V of the Pi and circuit are still connected, but don't connect the 5V of the circuit to the 5V of the Pi.

skogen
Posts: 3
Joined: Wed Jul 30, 2014 6:53 pm

Re: Need more than two 5v GPIO outputs

Fri Aug 01, 2014 3:57 pm

Thank you guys,
I will replace the power supply just to be sure and I will connect the two distance distance measurement modules to the two 5v GPIOs and I will supply the relay with power from a separate power supply. I think that might be the best solution.

I have also ordered an new sd card. After doing some googling I realized that the Kingston 8GB SDHC Class 4 (SD4/8GB) I have been using might cause some issues.

-Skogen-

skogen
Posts: 3
Joined: Wed Jul 30, 2014 6:53 pm

Re: Need more than two 5v GPIO outputs

Sun Aug 10, 2014 7:18 pm

rpdom wrote: Just make sure the GND/0V of the Pi and circuit are still connected, but don't connect the 5V of the circuit to the 5V of the Pi.
I am a little confused here. So...
I connect the ground from the relay circuit to one of the GPIO grounds on the Rpi.
I connect the 5v from the additional power supply to the relay circuit.
What about the ground from the additional power supply? Should it also be connected to the relay circuit or should it be connected to on of the GPIO grounds?

-Skogen-

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FLYFISH TECHNOLOGIES
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Location: Ljubljana, Slovenia
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Re: Need more than two 5v GPIO outputs

Sun Aug 10, 2014 7:49 pm

Hi,
skogen wrote:
rpdom wrote:I connect the ground from the relay circuit to one of the GPIO grounds on the Rpi.
What about the ground from the additional power supply? Should it also be connected to the relay circuit or should it be connected to on of the GPIO grounds?
Since you already connected together ground from the relay circuit to one of GPIO ground pins, there is no difference (... at first sight). However, I'd suggest you to connect it to the relay board ground.


Best wishes, Ivan Zilic.
Running out of GPIO pins and/or need to read analog values?
Solution: http://www.flyfish-tech.com/FF32

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