Hello
Ignator I spent many hours on internet searching for 3 encoders to arduino tutorial but I found tutorials only
for one encoder .
Kadora, you most likely will not find a tutorial on your wanted operation. This you will need to produce on your own, and my post was to point you in a direction of how to learn Arduino operations so you can make this system yourself. If you looked at any of the encoder tutorials, they will teach you how an encoder works with the A and B phase, which your encoder of choice produces. And how to count pulses, and produce a direction signal. The direction signal is if the count is up or down. Most of these tutorials use an integer variable to count the encoder 'clicks', and by looking at the phase of the A and B, determine if the count should be incremented or decremented.
In another tutorial, you can find out how to produce pulses to a connected stepper motor amplifier/driver, as that typically is as simple as a pulse/clock and a direction discrete output from the Arduino discretes.
I have seen tutorials that will use an encoder and then drive a stepper. This is a single channel of what you want to have triple of.
So in youtube search, I keyed in "arduino encoder stepper", which brought up many found videos, the first one being;
If you follow through the tutorial, the author shows the arduino code, and describes what it is doing. If you click on the "Show more" under the video window, the authors web page is found where the code can be down loaded. You do have to search for this specific example on his web page, as I found it on the 4 sub-page of the site.
Note all the other examples on this Brainy-bits page, even ones showing the driving of multiple steppers.
If you have an Arduino Uno, you may not have enough discretes to control the 3 channels, and this may need an Arduino Due, or Mega that has a few more. Or you need to figure out using the direction and step signal connection in parallel to the 3 stepper amplifiers, with an enable discrete unique to each of them. But all of this will require YOU to do the coding and design. This is mostly copying the code and modifying it for your specific system.
Understand, that if you post your code on this HMEN site, others will help you if you include the bugs you are experiencing.
So in a follow up post or yours, you want to integrate your existing CNC control with a manual input. That is going to require some sort of switching between the output drivers of these 2 systems. That can be a big hurtle to over come, as if you put digital output drivers fighting each other, the one with the bigger transistor will most likely burn out the other driver. So you need some way of what is called "oring" the signal, so the CNC machine, OR the Arduino is in control without have what is called "bus contention". And I'm afraid I'm getting beyond your electronics skill, if I use the term "open collector driver".
I hope this advice is of use.