[Advice Request] Discussing Power and Raspberry Pi setup

Antoine

Hello,

I am a complete Retropie / Raspberry Newbie and I would like to create a DIY console that would be both:

a normal console (plugged for power and using HDMI)
portable (which implies a battery that can charge while serving and a screen that is on if no HDMI is plugged in

But since I am an electronics Newbie as well, I would like to ask for you advice on my conceptual setup.
I don't feel confident in buying all the components before being sure it'll work nicely.

Here is my dreamed setup:

I am using a Raspberry Pi 3 Model B (the only hardware from this list that I already have so far).

The external power supply will be connected to a power management card which will handle the battery. For example:

Adafruit PowerBoost 1000 Charger (http://www.adafruit.com/product/2465)
Adafruit Lithium Ion Battery Pack 3.7 V 6600 mA (http://www.adafruit.com/product/353)

The output of that card will be connected to a power switch handling the on/safe-off button and connected to the Raspberry Pi GPIO pins for the safe shutdown. For example:

Petroblock PowerBlock (http://blog.petroblock.com/powerblock/) -- but is it possible to power through Micro USB instead of GPIO pins?

The Power Switch will manage power through Micro USB for an LCD screen connected to the Rabsberry Pi through a DSI ribbon. For example:

Raspberry 7'' LCD screen connected to the Pi via its DSI ribbon connector (http://raspberrypi.org/documentation/hardware/display/) -- is it possible to power it through a USB to MicroUSB power cable instead of GPIO?

The Raspberry Pi will be powered by the Screen through the GPIO pins.

The Raspberry Pi will be booting from a USB drive instead of a Micro SD Card (probably a hard driver, but nothing's set in stone so far).

The Raspberry Pi will be connected to a USB hub allowing 5 USB controllers to be connected (it's actually going to be 4 USB emplacements and one built-in control using for instance a raphnet USB Game).

The Raspberry Pi Jack will be connected to a splitter to allow one Jack per player (4 emplacements)

The whole set up will be placed in a custom case that I'll 3D-print.

So what do you guys think?
Does it sound feasible?
Do the components I mentionned sound insufficient/fair/overkill to you?

I have seen several threads mentionning power hubs. I'm not exactly sure if they are necessary or how to set it up taking into account the Power Switch and the Screen...

I also wanted to compute the necessary current intensity and voltage but it is very hard to find accurate requirements for all components, especially so for the screens.

Thanks in advance for all your help and advices!
Thanks in advance!

rbaker

@antoine Wow! I applaud your ambitions. The only advice I can give is not to try and realise this dream in one go. You should setup a Pi, a power supply and a controller and have a go a configuring the device for a variety of emulators. You should try and ssh into it from a pc and make configuration changes as this will save you time. I spent about 6 months off and on tinkering around an learning a lot before starting on a system build. Reading posts on this forum is great because even if you do not have the issue described in the post, you can start to understand why those issues arise and see how to solve them. Onto your questions...

I cant comment on all your questions but I have some experience with screens. I used an 8" screen and it was powered by the usb port on the pi. As a consequence, it will not auto detect via the hdmi so you will need to edit /boot/config.txt and make sure that this line is present... hdmi_force_hotplug=1. If there is a hash symbol before it, just remove it. Once you reboot, your screen should then work.

You mention a 3.7V battery pack, you need 5.1V to reliably power the Pi at all times. Also, you need a 2.5A current rating as a minimum especially if connecting peripherals.

I don't really know what "The Raspberry Pi Jack will be connected to a splitter to allow one Jack per player (4 emplacements)" means.

You mention powering the Pi via GPIO? This is dangerous. You can supply 5V on the GPIO pin. BUT, it has no reverse protection and it was not really designed to be a 5V input pin. Typically any power pins on GPIO area are used to power extended circuits. You could fry your Pi.

caver01

@antoine You might also look at a Mausberry circuit/switch to power your Pi via micro USB. These little boards do what you want in that regard, and a lot of discussion has taken place here to improve/enhance the safe shutdown script that you would normally setup with it.

The battery power is an interesting challenge, especially since you are aiming to use a USB hard drive. The HDD seems like an unnecessary luxury and a waste of power when large SD cards are available.

I would probably start by building this project on a workbench of sorts, outside of any case at first. You can do the configuration iteratively by getting it going as a console first, then adding the built-in screen and getting that working the way you want, and finally, once you know all of your power consumption needs, start working on the battery power idea. Then, by the very end, you have some sense of the volume required and you can look at case options.

To use more than 4 USB ports on the Pi3 will require a USB hub as you mentioned. That will cost you more power.

You do contradict yourself about the power. On the one hand, you mention the Powerblock, but want it to go through micro USB not GPIO. Then you mention that the Pi will be powered by the screen via GPIO. Which is it?

The questions about powering individual components by alternate means are probably best questions asked of the folks that make them.

I would say that it all sounds technically feasible, but I would build it in stages for sure to make certain everything works the way you want it to work.

Antoine

@rbaker @caver01 Thank you for your messages!

@rbaker :
Yes, you are probably right, better taking steps and learning rather than trying it in one go. Actually I am fiddling with my raspberry pi and the Retropie / RetroArch settings in the meantime :)

About the screen, I am surprised because in the documentation for the raspberry pi 7'' screen, they wrote:

"We also recommend that you power the Model A/B via the GPIO pins using the jumper cables."
"Power the setup via the PWR IN micro-USB connector on the display board. Do not power the setup via the Pi's micro-USB port: the input polyfuse's maximum current rating will be exceeded as the display consumes approximately 400mA."

But maybe that is only applicable to their screen. Anyway, I'll trust you on this one, I'd rather not fry my pi right away!

Strangely, I don't find the exhaustive specs for the screens on the vendor websites, they almost never mention voltage or intensity...

In order to switch from portable to "normal" consoles (in French we call them "livingroom consoles" when they are not portable but I couldn't find the appropriate word in English), I would have like a way to tell the raspberry pi to use the portable screen if it is not connected to a TV.

I initially thought that if I was using a portable LCD screen, the priority would be given to the HDMI port and I would have that switch behavior without any work. But if they are both HDMI, I guess I should look for a way to tell which HDMI port is busy to tell if an external screen is plugged in.

About power, from what you wrote I understand 5.1V and 2.5A should be the minimum to aim for, especially if I plug extra USB devices.

The sentence about Jacks, I realize, is probably a a translation issue. In France we call "Jack plug" any audio jack and don't have a distinction between jack and socket, only "male jack" and "female jack". I meant that I want players to be able to plug their headphones and thus need more than one "female jacks" (I'll probably use this: http://amzn.eu/87GMzo6)

@caver01 :
The Mausberry switch looks pretty awesome, I think that's what I'll go for.

Following yours and rbaer's advice, I believe I'll start by using the SD card and without integrating a controller right away, thus not requiring the extra concern of a USB hub.

About the power through GPIO, my sentence was not very clear I have to agree. I want to avoid using the GPIO for power whenever possible. But I wanted to quote the documentation for each piece of hardware I mentionned. And the documentation went against that wish.

Thanks again for your answers!

rbaker

@antoine said in [Advice Request] Discussing Power and Raspberry Pi setup:

But maybe that is only applicable to their screen.

This is probably the case. Always do what it says in the instructions that come with the screen!

caver01

@antoine you could write a little bash script that copies configs back and forth to switch screen behavior. You could put it in a menu like ports or RetroPie menu and in emulation station, select this script when you want to switch screens. Reboot and it would use the other screen option.

Antoine

@caver01 That's true, I am also investigating udev and xrender as I was told by a friend that a rule could probably be defined to handle that behavior. Indeed, since the portable screen will be connected internally (inside the box) to the raspberry pi, we can know for certain which HDMI port is associated to the screen and therefore differentiate it from the other one which would be assumed to be an external screen.

EDIT: Actually, I realize now that contrary to USB ports, HDMI splitters only duplicate the input display to two outputs in an identical way, so I am no longer sure udev understands it is communicating with two different displays.

@caver01 @rbaker I am also investigating using a USB Power Bank as a UPS (which I read from over at http://raspi-ups.appspot.com/en/index.jsp). Some models have smart charge features and are able to serve while charging and feature two USB ports (which is useful to provide power to both the Raspberry Pi and the portable screen).

Controlling the power drop seems feasible using a voltage diviser and an analog digital converter bound to the Raspberry Pi GPIO (one reference among others: http://raspi.tv/2013/controlled-shutdown-duration-test-of-pi-model-a-with-2-cell-lipo).

A quick Amazon search provides results that I believe could do the trick (like http://amzn.eu/fAd5fRV which:

is pretty cheap (~20 bucks),
has a 16.75A capactity,
provides 5V outputs,
provides 3A max on each of its 2 ports,

I am guessing this could be used as a UPS.

Just as a side note I have seen several interesting projects providing UPS boards for the Raspberry Pi. But they seem focused on powering it through the GPIO (as far as I understand) and therefore do not seem very appropriate to me if I want to power a portable screen as well.

Another side note to say that I don't have any stakes at Amazon (and my links aren't sponsored), it just seems convenient to provide examples :)

EDIT: changed the example provided for a more suitable USB Power Bank