Sorry for my English. I studied at school, and I've forgotten a lot.
We need your advice and, ideally, help.
We are doing a project with a friend for my house (I am too lazy) on adding water to poultry. There was a problem with long transmission lines (about 3 meters).
I already wanted to buy optocouplers, as many forums advise, but then my friend his older brother said that at his work on the basis of Arduino, a system of some control was developed (as it turned out, they have now switched to a pure atMega328 with a desoldering from China).
So, there was used uart with lines about 5 meters. There were no problems. As it was possible to find out from the taciturn man-programmer, it is necessary somehow (I said-you will understand, yeah) at the receiving part (RX) to turn on a suspender that on this port 0 volts hung.
In an old book, I have already read today that the principle used on long lines is this: the receiving part hangs 5B, and the transmitting part puts it on the ground. So, allegedly, the Soviet developments worked.
Forumchane, tell me: how can I solve the problem of long UART lines (signal fades out) without adding weight and shortening?
Your English is fine, but your rambling on about stuff that makes no sense makes it hard to find out what you are doing.
IF you are just connecting Arduino TX and RX pins together to communicate and are having problems, then get some RS-232 adapter boards and use RS-232 to communicate longer distances. That is what it was designed for so many years ago!
Yes, but I am not sure in a way that helps. I am using telephone cable (I have lots of telephone cable, see the link in my profile) with Tx and Rx on one pair, which is not the way to use a twisted pair. However, it works. I stuck my oscilloscope on the end to see how distorted the signal is and found it is only very slightly distorted. I might try some terminating resistors one day to see if they clean up the small amount of distortion there is (or make it worse!)
If your problem is that grounds are at different potentials then an opto coupler is a good approach - see how MIDI works for a good way to use opto-isolated serial. MIDI - Wikipedia
Note than many optocouplers are rather slow, MIDI gets round this by limiting the baud rate to 30k or so, rather than anything higher.