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terrastudios

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About terrastudios

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  1. Just something to add, I stumbled across the MAX4652 which is a low-on resistance (4 ohm @ 5V) 4x channel switch http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2215 Might be a better solution than using a 4066, just use a DC bias on the input and a buffer (such as one of Hartwigs excellent designs) and off you go.
  2. Hi Hartwig, Thanks for the reply - your bottom schematic looks great Do you see any problem in removing the input 75R resistor, as the other device has this already (so the input video signal will already be 1v peak to peak) - and i'll almost T-piece the video input - one will go to the op-amp buffer that you posted and the other side will continue on to an LCD monitor. Thanks again, Matt
  3. Hi Hartwig Thanks also for your reply - i did not see it before i posted the above response. The problem of course with any of these solutions is the need for dual rails unless the video has a dc bias applied to it, but the MAX4314 looks quite promising if i sit this on 0v gnd potential with a ~8v input voltage on VIN, as the maximum video input voltage is VIN - 2.5v - so with a DC bias of 2.5v and 1v p-p video signal i'd be looking at about a 3.5v input. As its an op-amp i guess it won't have any negative effect on the input video signal which goes to the other device; again i'd have to
  4. Thank you for your reply, it is appreciated! I'm thinking something like a 4066 (as it has quite a high Ron), with a 2.5v bias applied via a simple potential divider, and of course a suitable electrolytic cap on each input to stop the bias effecting the other devices connected to the video input and another electrolytic on the other side of the 4066 to remove the bias voltage as the LM1881 wants a maximum of 2v p-p. 5v-->Res (10k)--><--Res (10k)<--GND | Video input --> || +(47uf 16v) -->---------> 4066
  5. Hi all, I'm thinking of playing about with the LM1881 and an AVR but just wanted to run something by someone, hope you dont mind. I've got 4 video inputs which I want to check to make sure each has a "valid" video signal; i felt the easiest way to do this is to feed the 4 camera inputs into some form of video switch, then the output of the switch to the LM1881. Using the AVR i can then count hsync/vsync pulses to determine if i think a video signal is present. As the camera inputs go off to another device I was wondering if i should amplify/decouple each video source, i'm not really b
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