Interrupt analog signal

Hello forum members.
I am new to Arduino.
I am carrying out a project in which I have to make a very fast and very short interruption in an analog signal.
This will help me generate a flicker on a monitor, but practically invaluable to the eyes.
How could I do this?
I have seen that different types of interruptions can be made but I don't know which one runs faster.
Can you help me please?

Thank you

"very fast" - how fast?
"very short interruption" - how short?

Numbers please, adjectives are not useful here.

I have seen that different types of interruptions can be made

What types of interruption?

Could be explained (a lot) better. :roll_eyes:

Perhaps step back and explain why you might want to do this? That may help you to improve the detail so that it becomes meaningful. :sunglasses:

Thank you very much for responding so quickly and sorry for the inconvenience for my inaccuracy.

There really would be two analog signals, and I must perform the blinking on both. Like a shutter
This flickering must be synchronized, I explain, when the monitor works the camera does not work and when the camera works the monitor does not work.
The signal of the motor is 3'3V and that of the camera at 5V. I have read that arduino UNO for analog inputs can work in a range of 0-5V, so there would be no problem.

I have the problem because I don't know very well how it works, I have tried to monitor the rising and falling edges through the serial but in an analog signal there is no level 0 or 1 and I do not know if it does it internally with ADC and calculates them through from there.

As the intermittence must be synchronized, the times should be 2ms, I explain, 2ms ON 2ms OFF, I think this time would be fast enough to cut the signal so fast that the eye does not see it and generate images without lag, without reaching turn off the monitor completely, only the image flickers.

In the "Gammon" page Gammon Forum : Electronics : Microprocessors : Interrupts I have seen the attachinterrupt but I can not indicate time and had thought about using a for loop with a time.sleep at the end, but the truth is that I am Very lost and the more information I seek I realize that I am increasingly lost.

Thank you very much for the help and excuse my ignorance, it may be that the approach is even starting badly.

You can use a MOSFET to switch the signals on and off. When on, it’s like a small resistor, regardless of the actual voltage of your signal (as long as it’s within range of the MOSFET). 2 ms on/off is easy to do. Then the Arduino can control the passing (or not) of the signals.

Now actually I’m wondering if you really want an analog signal (so randomly varying voltage), instead of a digital signal: one 3.3V/0V and one 5V/0V.

And I’m also wondering whether you want to interrupt an external signal, or whether you want to produce the signal itself.

Your description does not make clear what you really want to do.

Thanks for the answer wvmarle.

The truth is that I am open to any solution since I am starting this project and there is no exact procedure to follow, I do not know how to do it.

The project we have in our hands serves to solve a problem we have with an application.
We have a camera and a projector in the same elevated position facing the table, interactions with the objects and hands of the subject are created. Here comes the problem, because it is emitted and captured at the same time, the image of the hands is delayed and the image is not clear since it is generated as a delay as if it were fed back with past entries.

I have analog signals because I take the vsync of pin 14 of the VGA and the camera we use has a minijack input, also with an analog signal. If it were digital, I think it would be easier to take advantage of the rising or falling edges or, as you say, do you mean to introduce as a synchronism signal?

This is where the solution I try to implement comes in, I want to eliminate that lag, so I want to generate 2 interrupts, one for the projector (in this case I am using a monitor to try to generate the effect) and another for the camera. That is why it is important that you record while the projector does not emit to just grasp the hands and stop recording when you issue the projector, so as not to capture the joint image of projector and hands.
This would generate a perfect application and subject interaction.

Is it better understood now?

Thank you very much

it is still a bit of a puzzle but I get the impression you are wanting to perform an interactive presentation where the person's hands can be used to manipulate the image.

I can reasonably assure you that you are approaching this in the wrong manner. Your idea appears to be to shut off the video signal for a very brief interval so that you can capture an image of the hands in uniform light with the camera during that brief interval.

There are many reasons why this is impractical. In particular, the projector cannot be blanked in that manner as it uses a "frame buffer" which holds the image while it is being drawn, so any interruption to the "drawing" process will not suppress the image. This was somewhat more practical when CRT displays were used because the image was not retained to such a great extent as the raster scanned across the screen. In fact, they could even be used as a "flying spot scanner" to actually take a picture where the reflection from the target was detected as the spot scanned across it.

Secondly, a common video camera does not necessarily implement a shutter, though digital ones may, so you would need to control the camera precisely in order to capture the image at the moment of your blanking of the projector. This is vastly more involved than just using a CMOS switch to interrupt a video stream.

Finally, the flicker in such a process as you have imagined would always be apparent. In particular, in order to take a picture, you would have to not merely blank the projector video, but flash it full white. That would always be apparent and even if happening repetitively and regularly, say at 100 Hz, it would have the effect of "washing out" and reducing the contrast of the remainder of the video.

I think you will find that the commercial systems for doing what you propose, do so either by matching the camera's image against the actual dynamic projected image and detecting differences, or else use an alternative means of locating hands and other objects near the table, such as infra-red.

Yes @Paul__B, is what you say, the project is to create a computer (program) - user interaction.

We must work with an image projector and digital camera, for example, intel realsense depth camera D415 or Kinnect Azure.

I have seen some procedures with a very brief explanation about solutions about this idea. It is known as shutter and there are two types: mechanical and electronic. In this case I have to make an electronic one.
There are people who introduce black frames into the projector signal electronically, instead of turning off the projector.
I think that if we generated a square signal with the tone function at an x ​​frequency, I could create through the flanks that it activated or one input or another, that of the projector or the rave´s camera of the trigger they have.

I do not want to be discouraged, I would like to do it since a group of people depends on this project.

Thank you

Reading all this I have the feeling you should be looking for off the shelf solutions for this. Cameras and video projectors that are designed for this very purpose.

Black frames should be quite easy to add to a video stream - as long as you have full control over the video player, that is. That video player will be running on a full size PC of course, not an Arduino, probably not even a Pi. Messing with a fully decoded analog video stream, that’s a whole different ballgame and will require a lot more horsepower even: you have to read the stream (very high data rates), figure out what it is, where to stop it for a full frame to be blocked, and start it at the next frame again.

Yes @wvmarle, I think you are right, if it is as difficult as you say working at those speeds. What you say is correct. The image comes from the PC to the projector and must be interfered with.

But I must keep looking for solutions, we can look for solutions for the projector but we cannot change the camera, since they are depth cameras and the videos we have made are adapted for those types of cameras.

I would like to be able to change all the work done and acquire another type of hardware but I must adapt to the hardware that
We have and must implement some system that achieves this interaction in the most optimal way possible.

Thank you for your time.