I am trying to use 1 digital pin to switch between 2 video signals, like a selector switch with only 1 camera signal going through at a time. I can make a simple NOT gate to enable only one signal at a time with a NPN transistor. Say pin 7 output to camera 1 and the NOT gate, then output of NOT gate connect to camaera 2. The question is, do I need a special transistor that can handle the frequency of the video signal? Say pin7 connected to the base of a transistor to allow signal through, can I use a general purpose NPN transistor on that?
I do not want the switch to control the power to the camera because most camera will need start up time.
I wonder if a small reed-relay with change-over contacts would work - some phase distortion due to stray impedances perhaps, but there appear to be 50ohm RF reed relays around, no idea the price though.
Ty for the reply that helps a lot, now I just have to add a negative votage part to my list
Also I have a new question:
If the output of AD8184 connected directly to the video input of a 5.8Ghz video transimitter module, do I still need a AD8009 (Op Amp) to buffer its output?
I think the AD8184 will solve my problem, it cost around <£5 which is not too bad and also allow me to add more cameras at later stage.
Say pin7 connected to the base of a transistor to allow signal through, can I use a general purpose NPN transistor on that?
If the video is analog like from simple security cams, then a typical NPN transistor can switch the video. A lot depends on your specific setup.Years ago I made a video switcher for my web cams using NPN transistors and operated it from the pc parallel port.
The camera are simple PAL/NTSC CMOS cam. I will try with NPN transistor first, and see. I have also found a DIP alternative to AD8184 available from RS.
When using transistors, care has to be taken with the grounds. I inputted a video capture card, so I let the base current thru the transistor (1ma or less) flow along with the video signal into the capture card.
As best as I remember, the video multiplex chips are not as easy to use as one would think. I also made a mechanical video/audio switcher using a rotary switch from RS and positioned it using a servo.
OK, from the AD8174ANZ datasheet the example cuits uses 50ohm and 75ohm resistor to terminate. What power rating of resistor should I use say 1/4w, 1/2w ?
OK, from the AD8174ANZ datasheet the example cuits uses 50ohm and 75ohm resistor to terminate. What power rating of resistor should I use say 1/4w, 1/2w ?
An 1/8 watt will probably do.I don't thin video signals carry much current. So you have figured out how you will supply the -5v?
