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Posted by on December 2, 2007, 12:00 am
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Hello guys,
Posted this to the sci.electronics forum as well, so some of you may
have seen it already.
I am building a medium size robot that will have up to 4 video sources
that I want to be able to control.
The best thing I have found so far has been the "X-QVC-EM" engineering
module from www.xavien.com . I have 2 questions:
1. Has anybody used this before, and if so how well does it work? The
price is really good, I have seen similar units for alot more money,
but you never know.
2. Anyone have any other ideas or recommendations? I need 4 video
inputs that are 75 ohms, I want to be able to choose which source is
displayed on the screen, and I want simple TTL control.
Thanks guys.
Carl.
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Posted by Peter Baltus on December 2, 2007, 4:20 am
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Hi Carl,
I don't have any experience with this module, but I did build a very simple
video multiplexer myself. It really depends on your requirements, but if the
only thing you require is the functionality of a switch between multiple
video sources, without the need to synchronize line & field sync etc. then
you might be able to use the same circuit as I used. It consists of emitter
followers, one per video source, with their outputs wired together. The
inputs are AC coupled to the video sources, and the DC level is controlled
through a resistor from digital control lines. There should be only digital
control high, which results in that video being transfered to the output.
The other emitter followers will have their base-emitter junction reverse
biased and are therefore reasonably well isolated. Not a high-performance
solution, and I didn't even measure the isolation, but judging from the
picture it should be at least 50dB.
I hope this explanation makes sense. If it doesn't, but you are interested
in the circuit, please let me know and I will try to give a better
explanation and/or send you a schematic. Good luck with your project!
Best regards,
Peter
> Hello guys,
>
> Posted this to the sci.electronics forum as well, so some of you may
> have seen it already.
>
> I am building a medium size robot that will have up to 4 video sources
> that I want to be able to control.
> The best thing I have found so far has been the "X-QVC-EM" engineering
> module from www.xavien.com . I have 2 questions:
>
> 1. Has anybody used this before, and if so how well does it work? The
> price is really good, I have seen similar units for alot more money,
> but you never know.
>
> 2. Anyone have any other ideas or recommendations? I need 4 video
> inputs that are 75 ohms, I want to be able to choose which source is
> displayed on the screen, and I want simple TTL control.
>
> Thanks guys.
>
> Carl.
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>
> Posted this to the sci.electronics forum as well, so some of you may
> have seen it already.
>
> I am building a medium size robot that will have up to 4 video sources
> that I want to be able to control.
> The best thing I have found so far has been the "X-QVC-EM" engineering
> module from www.xavien.com . I have 2 questions:
>
> 1. Has anybody used this before, and if so how well does it work? The
> price is really good, I have seen similar units for alot more money,
> but you never know.
>
> 2. Anyone have any other ideas or recommendations? I need 4 video
> inputs that are 75 ohms, I want to be able to choose which source is
> displayed on the screen, and I want simple TTL control.
>
> Thanks guys.
>
> Carl.