Homebuilt ROVs Forum

What is needed to make sure you don't have severe signal attenuation over 200ft of RS485 between two Arduino/Teensy boards? From what i understand the voltage is not strong enough to go any significant distance when using the easy transfer library. Is there a booster or something required?


Edit: I suppose the same question applies for CAT5 as well.

Buenas noches.

Échale un vistazo a esta página, que explica muy bien las comunicaciones con el RS485, espero que te sirva

https://proyectoarduino.com/comunicaciones-con-rs485/

Un saludo.


Good night.

Take a look at this page, which explains very well the communications with the RS485, I hope it will serve you

https://proyectoarduino.com/comunicaciones-con-rs485/

A greeting.

The link posted by asesorplaza1 explains it well.

For 200 feet, just use twisted pair cable (ideally shielded twisted pair). You shouldn't need termination resistors over that length.
So long as your baud rate isn't ridiculously high, you should be ok.

RS485 is not troubled by voltage drop/attenuation, the things that limit distance for RS485 are electrical noise, which is minimised by using shielded twisted pair, and deformation of the signal waveform caused by capacitance/inductance of the cable, which is mitigated by the inclusion of termination resistors.

Cat5 cable is essentially just four twisted pairs in a tube.

Asesorplaza1 and Bennachie, thank you, that is very helpful I'll have to do some reading on Termination resistors!

Zeig wrote:Asesorplaza1 and Bennachie, thank you, that is very helpful I'll have to do some reading on Termination resistors!

I'd be very surprised if you needed termination resistors with a couple of hundred feet of Cat5. If you did, the quickest and dirtiest fix is to attach a 1k potentiometers across each end and twiddle them until it works. Having an oscilloscope really helps, but I realise most folk won't have access to that. You can buy fairly cheap and basic, but functional ones online.

UTP has a max distance of 100m with Cat 5 cable. Practical with interference it is a bit lower around 80m is the max I managed in a network setup with good cable, but interference of lamp transformators.

fryslan76 wrote:UTP has a max distance of 100m with Cat 5 cable. Practical with interference it is a bit lower around 80m is the max I managed in a network setup with good cable, but interference of lamp transformators.

I'm sorry, i'm a mechanical engineer so i'm still learning a lot of the tech side of the hobby. Can you clarify on the interference of lamp transformators? Did you mean lamp transformers, and you were using them in your UTP line?

Anyways If the problem is the power why not using a transistor to amplify the signal coming out from the RS485 module?

Zeig wrote:

fryslan76 wrote:UTP has a max distance of 100m with Cat 5 cable. Practical with interference it is a bit lower around 80m is the max I managed in a network setup with good cable, but interference of lamp transformators.

I'm sorry, i'm a mechanical engineer so i'm still learning a lot of the tech side of the hobby. Can you clarify on the interference of lamp transformators? Did you mean lamp transformers, and you were using them in your UTP line?

No problems, this location where we where installing the UTP line, it had to run above the ceiling. The ceiling contained also a lot of lamps which where using transformers to adjust the voltage which causes electronic magnetic fields. And these fields are not that great for signals running through UTP cables without shielding.

fryslan76 wrote:UTP has a max distance of 100m with Cat 5 cable. Practical with interference it is a bit lower around 80m is the max I managed in a network setup with good cable, but interference of lamp transformators.

Presumably you are talking about Ethernet, which has data rates of 10Mb, 100Mb or 1Gb, depending on your network.
We are talking about data signals at 9600baud to 118.2kb (~0.01Mb to 0.1Mb). They will travel MUCH further.