Video Processing Using LM1881

[aljroo]

Hello

I am trying to use LM1881 video sync seperator chip to analyze some signal that I get from a video source. The video format is NTSC , and I have video source which monitors a darkbox. I am trying to build a circuit that would tell me if there is something available in the darkbox such as a white small car or ball by making a noise or sound.


Could someone please help me ?

Thanks in advance and hope to hear from you soon.

 

[blueroomelectronics]

You'll need alot more than just a simple sync separator.

 

[aljroo]

Could you give me some hints or suggesntions then, please? I looked at the DATASheet for the LM1881, and I was able to get the different possible signals from the chip, but now, I am not sure how to use those signal and I dont know what kind of logarithm I need to make a use of the produced signals.

 

[blueroomelectronics]

They are simply Horz & Vert sync pulses. You still have to digitize the video data.

 

[Super_voip]

all you need is a compaator, run the video into an integrator and if the level changes then the comparator senses the change.

 

[ronsimpson]

The 1881 is a start. With it you can get H and V sync along with 'back porch'.
Many cameras use AC coupled outputs. This makes the video hard to analyze.
When the Back Porch signal is low video is black by definition. Normally the video is AC coupled and then during Back Porch it is clamped to 0 volts. This way sync is negative and video is positive.
A very simple way to test for a ‘white car’ is to use an analog comparator or peak detector. Any video greater than 0.3 volts probably indicates a ‘white car’.

 

[aljroo]

Thank you guys for the help. I think I know where my problem is.