Hi,Thanks for the replay.I am investigating your suggestion.I am not 100% procent sure that I understand you solution.I will search the web for more info about RS485 and hope I will understand your post better.
I was hoping that the cat5e FTP cable will protect me from most of the noices but it seems I am wrong.I need to find cheap solution to transfer the data trought so long wires becasue may sensors should be very very cheap-becase someday I hope I will need a lot of them(1000+).If each sensor has its own arduino with enc28j60 network module or some kind of wireless module I will not have problems with the wires but I will produce too expensive sensor that I can't afford.(1pcs-ok 1000pcs-not ok)So you dont have any ideas about cheap solution?Now i Will investigate this MAX485-how it works and what I should do with this.
The only real problem with long wires is data transfer rate. If you're not sending much information then simple twisted-pair wire could be enough. Use one wire for data and another for clock ... a bit of software to control it ... might be all you need. Higher voltages usually help because at that length you start to notice that wire has a resistance and voltages drop along it, but 5V might work if you get the line impedences right. 40m isn't really all that long.First things first though...how much data do you need to send?
I dont know how much data it is but I dont need speed.I will explain my case in more details:My "sensor" box contains: HC-SR04 and two leds.What you think?
You'll need shielded cable, ordinary audio/video cable should be good enough for this...For the engineers: Yeah, there's capacitances and stuff as well...but we're only sending a single pulse so I think we can ignore them
How would you wire these signals? Does having GND as one of the twisted wires do the noise cancelling trick ?
Your main problem will be getting enough volts to appear at the end of the wire