Raspberry Pi Forums

Hi

As part of an engineering project we're trying to run a raspberry pi b+ with the following extras

A Dagu pan tilt kit
Picam
Pibright (lighting)

We're using a 1.5a charger for the pi however we don't think that's going to be enough to power everything.

So I was wondering if anybody could help out by detailing a way of supplying the pan tilt kit and picam with external 5v power which mimicked the power usually given by the 5v gpio power pins. Mains power is available

Thanks in advance to anybody taking the time to answer this post

connect the grounds together, but not the 5V lines.

Ok, thanks for the quick reply.

But how would i get extra power to the extra things?

mpaterson wrote:Ok, thanks for the quick reply.

But how would i get extra power to the extra things?

This is only a suggestion
For your project you could use two power adapters

1, 5v 1.5 / 2amp for the Pi

2. One at the voltage & current you require for the project.

3. Use Opto isolators for the Project driving signals
from the Pi GPIO pins

The Opto isolates will isolate the different voltage levels
no need to common the 0v-, No noise feed back

This might be useful for (future I assume) engineers

http://www.elinux.org/RPi_5V_PSU_construction

hampi wrote:This might be useful for (future I assume) engineers

http://www.elinux.org/RPi_5V_PSU_construction

Only if they want to keep warm
The 7805 is a linear regulator and very inefficient. It dumps the excessive voltage as heat and will require a good heatsink to prevent it shutting down due to overheating.

Much better to just buy a decent switching power supply

Is there no way of getting another mains pi charger and somehow splitting that so it can go to the extras?

rpdom wrote:The 7805 is a linear regulator and very inefficient.

A careful reader can spot a switching mode power supply from that page too. Anyway the PSU is not that difficult and does not need similar very dense multilayer PCB like the RPi has.

I don't really understand any of what you guys are talking about unfortunately.

All I want to know is, is there any way of getting another mains pi charger and somehow splitting that so it can go to the extras?

mpaterson wrote:I don't really understand any of what you guys are talking about unfortunately.

All I want to know is, is there any way of getting another mains pi charger and somehow splitting that so it can go to the extras?

Forget the word( CHARGER )
What you want is a 5v 4amp
power supply / Adapter , Split the
lead for the project and the Pi
But remember any over current
cut out that the adapter wall have
will operate around 4amp. This
is very high with out extra current
limmiting for the Pi and project.
Advice Two adapters as I suggested
on other post,

I hope you are budding Mechanical
Engineers and not Electrical Engineers
If you fit any current limiting set the
Pi around 1.5a. Set the limiting
For the project at a safe calculated value

If your project is Mobile ( BATTERIES)
I think you can work that out

Thanks will look into this and post back later.

Yeah aerospace engineering is more my thing, but unfortunately the only scheme my school do is electronic

So I found something like this for the power supply but how would I get it to connect as its micro USB and the devices take gpio pins?

http://m.rs-online.com/h5/mobile/uk/cat ... 7263069%2F

mpaterson wrote:So I found something like this for the power supply but how would I get it to connect as its micro USB and the devices take gpio pins?

http://m.rs-online.com/h5/mobile/uk/cat ... 7263069%2F

This thread is getting out of hand
You keep changing the goal posts
The adapter you found , are you
using it to power the Pi, If so the
the micro usb plug will plug in to
the Pi micro power in/put socket.
Do you have a IT teacher at you
school, If so ask for further advice
Draw a diagram of how you want
your power feeds to the Pi and
project, then we can give better
advice, and post it on the forum

mpaterson wrote:So I found something like this for the power supply but how would I get it to connect as its micro USB and the devices take gpio pins?

http://m.rs-online.com/h5/mobile/uk/cat ... 7263069%2F

I suspect that you could do almost everything you need to by changing your existing 5v 1.5A power supply to a 5v 2A power supply, if you find this isn't enough then read on...

I didn't find anything called Pibright, just brightPi, is that what you meant?
you wish to use this as the power supply for the pan and tilt kit and the BrightPi Lighting?

The Pi-Cam cannot be fed from external power, only from the pi. a USB camera would be able to be fed from a separate power supply (with some effort).


To connect a BrightPi (as I'm assuming you are using) to an external supply you would need to connect the 5v and Gnd connections to your 5v supply (be careful to get the polarity right) and the SDA, SCA and GND connections to the pi (Yes, the GND connection has to be connected to both the external supply and the pi).

to connect the pan / tilt kit actuators to an external supply you would connect the red (+5v) and black (Gnd) cables to the 5v supply (polarity is, again, essential) and the yellow (signal) and black (Gnd) cables to the pi. yes there is only one black cable and yes it does have to connect to both the power supply and the pi.

the easiest way to connect a spliced off 5V 1A from a heavier power supply to the microUSB input of a PI, (unless you slit up a micro-USB cable) is to wire to a common USB-A connector, and from that use a short USB-A to micro-USB cable.

Read the Wikipedia page to see how to wire up the USB-A cable, then check with an ohm-meter (multimeter) if the ground (negative) input wire connect to the shells of either micro-USB connector normal USB connector, HDMI connector or even the ethernet connector (all of them have their metal outer shells connected to the PI's GND)
If you make a mistake and fed the PI -5V instead of +5V its will immediately destruct your PI, so be careful and check your wiring.