I’m making a little arcade machine project from a Raspberry Pi and a 9″ LCD screen

The Pi needs a 5v 1.2A dc supply and the LCD screen 12v 1A dc supply.

I am hoping to find or design a circuit where I can put a rechargeable battery in the box to power both and have a single power connector just like a laptop.

So, are you ready for the noob questions:-

Let’s say I had one of these:-

1) Would it power the screen direct or do I need to worry about the 1A, my assumption is that it is the screen that draws the amp and I have to hope that 1amp can be drawn from the pack

2) How would I step the voltage down for the PI power? Do I need a regulator like this one

http://www.rapidonline.com/Electrical-Power/Recom-International-R0-5Z-1205-DC-DC-Converter-12V-In-5V-Out-49-8185/?source=googleps&utm_source=googleps&IncVat=1&gclid=CJX5hM6HmMECFSTMtAodHCsAWQ

1) Would it power the screen direct or do I need to worry about the 1A, my assumption is that it is the screen that draws the amp and I have to hope that 1amp can be drawn from the pack

Your assumption is correct – you’d have to rely on the pack being able to supply 1A. If it can then it should work – I say should because there’s little information there about how well regulated it is (though the screen is unlikely to be that fussy).

2) How would I step the voltage down for the PI power? Do I need a regulator like this one

Yes, something like that, though that is far too low power to supply a RPi. When I power mine from batteries I use a UBEC from ebay eg http://www.ebay.co.uk/itm/Hobbywing-3A-UBEC-w-RF-Noise-Reduction-RC-Output-BEC-Switch-Mode-for-Lipo-/221521105304?pt=UK_ToysGames_RadioControlled_JN&hash=item3393afd198 – lots of power decent regulation and cheap.

The battery should be fine, you just need to check its rated for 1.5A discharge.

That converter is no good as it’s only rated for 0.5W. The easyest way to get the supply is to buy a car fag lighter adapter that has a USB port rated at 2.1A aand just solder wires into the connectors and connect to your battery. You can the just use a standard USB lead to connect the power to the pi.

God I love STW