Detect Analogue Video Signals Reliably

Thread Starter

koterod

Joined Jan 19, 2019
1
Hi!

First of all the obligatory: Long time lurker first time poster. Hope I have the thread in the right part of the forum

I'm have trouble building a switch for video signals from old game consoles. It needs to know exactly which video signals from the source is on and off.
RGB, CVBS and Y/C signals are only 0-0.7V with CVBS+CSYNC being -0.3-1.0V but I'm not certain that the channels will be entirely noise-free.
I assume the cheapest and simplest solution would be a comparator of sorts. While I do have a basic understanding of how op-amps and comparators work, unlike simple stuff such as logic gates and the 555 I have never really learned to use them correctly.

Does anyone know of a simple way to solve this?

//Kody
 

crutschow

Joined Mar 14, 2008
34,285
I would try a small Schottky diode rectifier with a capacitor filter to give a DC signal when the video is present.
You can detect the signal with a comparator.

Below is the LTspice simulation of such a circuit, shown detecting a 0-400mVpk, 3MHz sinewave.
The Ref voltage is ≈100mV which gives a signal detection threshold of about 300mV pk AC.

upload_2019-1-19_23-10-33.png
 
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