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Forum Index : Electronics : Connection to a TV AV input without Video

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Ray B
Senior Member

Joined: 16/02/2007
Location: Australia
Posts: 219
Posted: 08:02am 01 Mar 2012
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I thought it should be possible when away from home to connect the audio Left / Right from say a portable audio device or even a laptop into the AV input of say a hotel TV screen so I can play audio through the TV speakers. Video not required.

TV AV inputs have the usual Red / White for Audio Left / Right as well as a Yellow input socket for video but a TV won't recognise these alone.

TV normally won't recognise the audio inputs alone but seems to depend on there being a signal on the Yellow video input connector. For example I've measured approx 1 volt DC out of portable devices so maybe I could simulate this using using a single cell (1.5) and maybe voltage divider to get about 1 volt DC.

Maybe in the TVs AV input is just a transistor junction wanting to be switched on?

Before I blow something up has anyone come across a specification for connecting devices into a TV AV input or even seen a circuit in this area of a typical TV.

Cheers
RayB from Perth WA
 
vmike

Newbie

Joined: 25/05/2010
Location: United States
Posts: 2
Posted: 08:48pm 01 Mar 2012
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What the input is looking for is the composite sync signal rather than a DC/AC voltage. Probably the cheapest and easiest device for your application would be to purchase one of those single board NTSC video cameras and power it with a 9 volt battery.
I tried to contain myself, but I escaped.
 
Ray B
Senior Member

Joined: 16/02/2007
Location: Australia
Posts: 219
Posted: 12:26am 02 Mar 2012
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Suppose I could always just connect the composite video output from any portable device like a digital camera (yellow lead) into the TV to bluff it then poke what I like into the White/Red audio inputs & audio will come through speakers.

Maybe a typical TV may be smart enough to look for the composite sync signal but I thought it may just be looking for some input level. From memory composite goes up to approx 1 volt peak on full white.

Should give it a try.....
RayB from Perth WA
 
aargee
Senior Member

Joined: 21/08/2008
Location: Australia
Posts: 255
Posted: 02:31am 02 Mar 2012
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I think you'll find that the A/V input is going into an IC that detects video then passes audio and video through. That's why when you select AV on most TVs, with no video connected, the screen is blue and the audio is muted. A video source to fool the TV is the only answer.

- Rob.
For crying out loud, all I wanted to do was flash this blasted LED.
 
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