Play Room Media Centre: Hail the PiHub!!

In my previous post regards the development of a play room media centre, I cited one of the key goals was to attempt to build a solution that was going to be more green than other games/media centres on the market - and trying to keep the power consumption as low as possible.

Now there might just be something to help gain that all needed advantage, thanks to the pirate crew at PiMoroni - all hail the PiHub.  When I saw the post pop up about this earlier tonight, I was all set to go and buy one, damn the torpedoes!  Problem; they seem to be shipping with power packs for the UK and EU market.  Any chance that they could do one for the Australian market?

The Drawing Board
Looks like this post is therefore relegated to the drawing board.  So what was all my excitement about?  Given that I am still at the research and planning phase of my media centre project, I don't need to rush out and get a PiHub right this minute.  Well the PiHub is a powered four port USB hub built with the Raspberry Pi specifically in mind.  As you may recall from my previous post, my initial plans for a media centre incorporate USB keyboard, USB mouse, USB WiFi dongle, and USB HDD.  So that's four USB devices.  Now, if we configure the +RasberryPi so that it is drawing power from the PiHub, that means that we have just enough USB ports left on the Pi itself and the hub to cater to the four peripherals.  Great - that should then be quite tidy.

Shooting from the Hip
What we do know about the PiHub is that it's power pack supplies it with 3000mA (3A) of power.  My current Raspberry Pi power pack only supplies 1A, and consumes 36 W.  What I have not been able to discover yet is, how much power does the PiHub power pack consume?  For now, I am going to shoot from the hip and assume that since it's output is 3 times the amps of the Rasberry Pi power pack, its consumption is also 3 times greater.

If this assumption holds true, that means that the media centre project project built around a PiHub, would consume approximately 108W.  Based upon my initial research of the current media centre market makes it competitive.

From Here...
From here I need two things; to confirm the power consumption of the PiHub power pack, and to seek another edge to make my idea a worthy opponent of the current market products.

Play Room Media Centre: Keeping Ahead of the Curve

Following on from my last post, with any ideas of what we could do with a RaspberryPi in the #play_area, I need to make sure that I have some of the questions and answers squared away before introducing the ideas to my son. He's a smart, intelligent boy, with a great ability to conceivewhat could be done. But like all seven year olds, they don't necessarily handle failure and changes to plans once you start them on something. So, with any such projects, there is always going to be the necessary parental home work to be done upfront.

Play Room Functions

There are a number of needs that could be fulfilled within our son's play area. He loves watching his DVD/Video collection (my wife has an uncanny knack of finding old kids favourite videos in good condition!). He is also at an age where his musical tastes have and will continue to expand beyond the Wiggles, so playing music is also required. As all of these media can be digitised and served across our network - this all comes under the need for Wi-Fi media streaming. Though for the sake of our household Wi-Fi performance, it might be best if the majority of the children's content is available locally on the media centre.

Some of the programming that our son enjoys may be available from online/smart TV services line the ABC's iView service. However, other programs are not. Our experience is also that some smart TV devices are not compatible with the ABC's iView. So being able to watch free-to-air digital TV is desirable, but at the moment, we'll consider what hardware will be required to provision this, but not move to implement.

Games console. Don't ask how, but somehow we have existed all these years without owning a games console. No Xbox, no PS3, and no Wii. No we are not deprived and nor is our son. If anything there are times when he plays too many games already. However, as part of having a play room that provides entertainment to a small group of children when he has friends over, having a multi-controller games console would be good. Lets face it, having a group of friends huddled around one PC and a small monitor in the confines of a bedroom, whilst cosy, gets boring for those who are waiting to have a turn.

Other Requirements

All this needs to be established in such a way that it's power usage is economical, and such that it does not cost a lot - which might mean some seemingly crazy, yet innovative recycling/re-purposing of devices.

Initial Research - OS

One of the many questions to resolve here is which distro would be the most likely to achieve the greatest number of requirements - therefore providing a simpler low-risk solution and less set-up effort - and keep the focus upon conducting a successful project. Primarily I am considering one of two options - Debian 'Wheezy' and RaspBMC. Of these two offerings, RaspBMC is probably going to cover the need for the storage and streaming of digitised content. I am yet to find another distro for the Raspberry Pi that is know to be stable enough that would natively support a gaming interface such as Valve's Steam.

So, this is something that will need to be tested - is there a Raspberry Pi distro that can run steam? If not, this does not kill the project nor mean that we cannot meet the requirement. It just means that when we look for games to play, there will be a simple 'marketplace' to get them from.

Initial Research - Hardware

From the requirements that I've set, the solution is going to require the following hardware:

1. Raspberry Pi - I'd like to go with the latest, but I have an old Rev A Ver 2 that needs to be put to use.
2. Powered USB Hub - to power the Raspberry Pi and to provide device connectivity
3. Wireless keyboard/mouse replacement - For the moment, I'll have to start with just a USB mouse and keyboard.
4. USB HDD - at the moment I do have an HP 3TB unit sitting spare. I need to test it on the Pi as it is a little proprietary in its interface. It has it's own power supply which draws about 144W - so I am not entirely keen on this. A unit that is less power hungry or that could be powered through he USB hub would be nicer.
5. USB Wi-Fi dongle. I have a Netgear Wireless N dongle that's been spare for a while. It might well be too old to support the bandwidth for the media streaming.

Initial Research - Power Consumption

What are we replacing? A DVD/Video player, in which the DVD does not work (50W), a DVD player (15W), and a stereo system that I suspect runs about 45W - but given that CD's can play in the DVD player, it's consideration is negligible. There is also the as yet non-existent games console. So for now, that means that we are trying to keep power input to around the 65W mark (drawn by existing DVD and Video players combined). In terms of considering the project a success in this aspect, some consideration must also be given for replacing the need for a dedicated game console. Not currently owning one means that more detailed research of their specifications is required.

If all that is required to successfully implement this was the Raspberry Pi, a Wi-Fi dongle, and a wireless RF or Bluetooth dongle to connect to a wireless controller, that could be successfully achieved on just the power supply for the Raspberry Pi, which draws 36W.

I know from previous investigations that most powered USB hubs draw more than 60W, and the powered USB drive I have sitting handy draws 144W.

From doing some leg work and looking for the power consumption specs for game consoles online - well they sort of do not exist. That is to say, that in conducting searches it was easier to find power consumption statistics from independent sites, than from the manufacturer's themselves. Probably the most useful statistics I found compared the Wii U, the Xbox 360S, and the PS3 against one another (http://www.eurogamer.net/articles/digitalfoundry-wii-u-is-the-green-console). Definitely the Wii U runs at 30-35W by this reckoning, where as the older versions of the Xbox and PlayStation platforms were running at 65-75W. Not sure about the power drain of the Xbox One and the PS4 - the companies are all about bragging about the power usage when in stand-by or low power modes, but not about their power consumption whilst the device is actively being used.

So to keep this home-made solution green, I think that a reasonable target for success is 100W or less. At 130W or less, I think it could be considered on a par with the collection of devices that it replaces, but any result over 130W would be a fail.

Current Theorems - Am I on Track?

Perhaps my previous calculations of power consumption are too simplistic.

In researching green options, I discovered on some forums the use of a 5 port USB powered hub to deliver power to the RPi, and its peripherals, with the RPi delivering communications and data back to the hub.  I had been wondering about the concept of using one hub to power multiple RPis - would it be more efficient and greener?

Both the RPi and the hub run from their own transformers.  The RPi transformer has an input of 240V at 50-60Hz, drawing 150mA, and delivers a DC output of 1A 5VA.  To my limited knowledge of the calculations involved, this means that the input power is: 240 x 0.15 = 36 Watts, and the output is: 5 x 1 = 5 Watts.  This would imply that 31 Watts is lost to the resistance and impedance of the unit, and generates heat in the transformer.

When I look at the input and output of the USB hub's transformer, the input is: 240V at 50-60Hz, drawing 1A, therefore 240 Watts.  The output is 5V 1.5 A, therefore 7.5 Watts.

This would imply that whilst the powered hub supplied 50% more power, it draws 660% more power from the mains, and hence would not be a greener more efficient supply.

However, I know that my knowledge in this area is presently limited - am I using the right calculations and making the right deductions? Should I be calculating and comparing the power consumption of the transformers from their input or output values? Are these constant loads, or the maximum loads of each unit?

Anyone able to help?

Raspberry Pi - The Organic Way to a Green Network?

Epilogue to the Previous Post

There was life in my RPi, but not as I planned it Jim!

As a headless box, remotely operated through an SSH session, the Pi worked well - including its raspi-config tool.

But the wireless USB keyboard and mouse not working was my fault.  I didn't check the specs of the peripherals first.  If I had, I would have realised that they were not compatible with Linux.  Have since ordered a new set from Element14.

Going Green

Whilst waiting to get these goodies, I've been doing some thinking and planning.  My testing of the RPi and its abilities against other platforms is still in the planning process..  But in parallel I've had some other thoughts.

Looking at the power bills that we are getting out in a rural region - horrendous.  I'm certain that part of that excessive power usage is my small network of machines at home.  Yet I want to do more from home, with more machines.  That can only mean one thing - a bigger power bill.  Or does it?

Perhaps the RPi can come to the fore here.  Part of the problem is the machinery that I leave running most of the time.  My desktops and laptop are not so much of an issue if I shut them down overnight when not in use.  But looking at my network as it is now, and how I would like it to be, there are several spots in which I might wish to substitute in a RPi.  The list of appliances that I would like to have running 24/7 includes:

• Firewall/Proxy Server
• Dedicated Web Server
• Dedicated Web App Server
• Dedicated DB Server
• Dedicated IDS/Honeypot
• Dedicated Print Server

In considering the suitability of the RPi for any of these roles, I need to be able to compare apples to apples.  To do this from the power supply perspective, we need a way of comparing our traditional desktop power supply of 300 to 400 Watts, to the 1 Amp supply running the RPi.  To do this, we are going to make use of the equation;

          Watts = Amps x Volts

So, how many Watts does the RPi draw?  This is always going to be dependent upon the power pack used.  The power pack that I'm using currently has an output of 1 Amp at 5 VA.  But that is what it outputs to the RPi, not what it draws from the power socket.  What it draws from our power socket is 240 Volts at 150 milli-Amps.  Throwing these values into our equation;

          Watts = 0.15 x 240

          Watts = 36

But of course, I could compare this to a desktop or server with a 1KW PSU, and rave on about how much of a saving it should make, but it is not the size of the PSU that is important, but the amount of hardware that it supports.  From various sites you can utilise an online power calculator.  I went to eXtreme Outer Vision's calculator page.  Here I plugged in the values that were as close as possible to what my existing firewall machine has.  It is running a 300Watt PSU.  I calculated the power draw for it based upon a 90% CPU utilisation and it calculated that it would require a minimum of 198 Watts, but recommended 248 Watts to be sure.  For my comparison, I am going to take the conservative value of 198 Watts.  This is nearly 6 times more than the power draw of the RPi.  I think that there could be some real savings achieved.

To see how these potential solutions turn out, I have started a new page at: Raspberry Pi and Green Home Network