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[spillage]

Spillage's HDTV - Beyond Advanced - Interface

Speedypancake asked a question regarding the use of one xbox connected to two different display devices in two different video formats.

What does the "Spillage HDTV Beyond Advanced Interface" do?

My little tut here allows you to connect one custom cable from your xbox to the interface, and from the interface have BOTH component and RGBCs wired at the same time althought of course they are accessable one at a time.

The reason you might need it

If you have an EU TV with conventional RGB SCART and a projector with an HDTV Component video input and want them BOTH connected to the xbox permently without unplugging the leads then this project is for you.

Disclaimer

Is it going to work? Well I have not built one nor am I going to as I don't have a component input on my display. I am confident this is completely correct and hope that someone will give it a go and let me know if it works ok. Remember you MUST power down your xbox THEN throw the YUV/RGB switch THEN power up again to change display output type. Note this mode is a simple combination of YUV and RGB thus supports normal RGBCs @ 15KHz and YUV @ 31KHz

Why is it powered?

To allow the use of ONE simple toggle switch to change output types, relays must be used. This project uses two 4PDT changeover relays, one for signal grounds, one for signal carrier. The reason for this is simple to make sure the interface is not a contributor to ground loops and/or video noise by having the grounds from two displays and the xbox all commoned together. If you build this in a metal box you MUST use insulated connectors to achieve it. If you choose to use a SCART socket, thus allowing you to make use of the common SCART to SCART, make sure PIN 21 ground is not tied to the case. For simplistity I would use RCA or BNCs'

Custom AVIP cable

This project requires the use of a custom AVIP cable. Thus you will have to modify an existing cable to provide the necassary connections.

How it works

The circuit is very simple. However wiring it correctly will be fairly fiddly as you need to use screened cable and keep the lengths as short as possible. All relays barring the NO/NO dual coil types, have a NC and aNO post. NC refers to Normally Open and NC, normally closed. This state refers to the coil of the relay NOT being energised. Thus with no power on the relays the units default is RGBCs passthrough. If you follwo the circuit you can see the all three mode selects are grounded and RGB and Cs pass straight through the relays and out throught a SCART or four RCA's. When the switch is thrown [xbox switched off before doing so] the coils in both relays are energised and the mode select 1 is open circuited. when you power up the xbox the encoder will see 11/12 ans 13/14 on the AVIP shorted which results on component (YUV). The relay contacts have changed over and now the three primaries are fed to the YUV output. Note the compsite sync connection is dropped when in component mode. Batteries are used as it is a simple method of powering it and frees up a mains socket. You can of course use the circuit with a wall wart if you wish. If you buy 5v relays then use 4 x 1.2v rechargable cells as the result will be 4.8v which is perfect for the relays. If you use 12v relays then you will need 10 x 1.2 cells to power them. So long as you remember to switch the circuit of, that is to say, leave it in RGB mode the batteries should last ages, especially if you use good hi current AA cells. You can easily buy 4 and 10 cell battery holders to make the cells safe in the case.

The build

The build is simple enough. A nice case a few holes and some soldering and you're away. This is not a step by step as I don't really think it warrants one. I would glue the relays upside down in the case and use 2700mAh AA for the supply. The diode in the relay coil circuit is simply to stop back EMF. [you can look that up (IMG:style_emoticons/default/smile.gif)]I will say take care when you are cutting open a lead to get the AVIP plug freed up for the mod and advise the use of 75 Ohm video cable at all times and keep the length short. Do not use hi power auto motive type relays as the contacts are not designed for tiny currents. I usually use medical grade relays that are tiny, use very low coil hold currents but they are generally speaking, expensive at around £6/$10 a piece. Follow the diagram, use your brain and you should be using both formats within a few hours.

(IMG:http://img.villagephotos.com/p/2003-9/392648/YUVRGB.jpg)

This post has been edited by spillage: Jul 23 2007, 11:50 PM