How to make communication between two arduinos ( two devices, each device has own arduino nano and can be on distance about 50 meters from each other ) to communicate and send messages ?
Which hardware I should use to solve this, it should be smaller as possible, any advice or link is welcome.
( I am very new to electronics )
Connect Rx to Tx, Tx to Rx, Gnd to Gnd.
If you use good wire, should work without anything else.
If not, add RS232 buffer to each end.
CrossRoads, the subject is "... without cable".
There are maybe 50 ways to transmit data with radio signals (RF). Some RF modules are able to transmit and receive, called transceivers.
Legal frequencies are 315MHz in the US or 433MHz in Europe, and 2.4GHz everywhere.
The 315MHz/433MHz modules are cheap, but slow and often low quality, they might not have a range of 50 meters. The XBee modules are high quality, but they are large and they need extra hardware.
Sparkfun has a nice list, the Sparkfun wireless buying guide : Wireless Buying Guide - SparkFun Electronics
You can do this with Bluetooth 4 (BLE). This is reputedly good for 100m. Tinysine make a module that is about the same size as a Nano. Check the Philippe Cantin website but note that he is referring directly to the HC-05 module that would not be up to the job. There are other wireless methods, like NRF24.