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Automatically turn on a TV

Some TVs can be automatically turned on from an external device. Your television must have a SCART (known also as P�ritel, EuroSCART or Euroconnector) input. Wikipedia has a good description of this connector. If you live in Europe, every TV has one.

According to the voltage on the pin 8 of scart connector, the TV will behave differently:

VoltageTV behaviour
0-0,4VTV will turn off, and stay off.
5-8VTV will turn on in 16:9 aspect ratio. The channel will be set on the scart input (usually called "AV")
9,5-12VTV will turn on in 4:3 aspect ratio. The channel will be set on the scart input (usually called "AV")

The voltage must be provided between GROUND PIN 21 and PIN 8. Only some modern televisions support this feature, and sometimes incompletely (maybe it won't turn on in 16:9 mode, or won't turn off automatically, or something else). My TV is a Thomson, and it works fine for me. I know Thomson usually supports this feature.

How to connect
I use this hack for turning on the TV when I turn on my Media Center PC (it runs GeexBox!)
I used the PC power supply as source for 12 V. I connected the PIN 8 of my scart to the +12V of PC power supply (usually the yellow cable), and PIN 21 of my scart to the ground of power supply (usually the black cable). So wen I light up the Media Center, the TV turns automatically on. When I power off the Media Center, the TV turns off.
If you're wondering how much power can take the scart from the PC power supply, it is really really small. Surely lower than 1 watt, so it doesn't really matter (the input impedance of a scart connector is about some Kohms).
No software programming is needed, it's just a matter of hardware working.

I think you might use also the +12V of some pins of the serial port (that is the RS232), but you have to check if the pin can give you enough current (usually very small), and what pins are usually set to +12V when the PC is turned on. You have to work with a multimeter.

Only a small bug, for my TV: if you switch to another TV channel while the TV is on, it won't turn off automatically when the PC is powered down. Moreover, if you turned on the TV before the Media Center, the television won't turn off automatically. It works this way for my TV, on other TVs the behaviour may be different. You have to try.

NOTE: I don't assume any responsability for damages to you or your hardware. If you don't know how to work with electric and electronic devices, give it up. This article is only a suggestion. I'm sorry but I have no time to post photos and tutorials, even though I think it is a really really simple work, if you know just a little of electronics. It's only a matter of connecting two wires from the PC power supply to the scart.

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