RJ45 input switcher, but how?

Hi everyone,

I'm on a project where I have an arduino wich is connected to a router via an ethernet cable. But for redundancy reasons, I want to use a second (backup) cable either. So what I need is a circuit that switches between the main ethernet cable, and the bakup cable, when one of the arduino's pin is high or low. (The W5500 module is able to detect the link state, so that's how it will know when to switch to the other cable)

So I guess 8 relay would be the easiest way to do this, but they are loud and I don't want to use them if it's possible. There should be a way for this with some ic or something.

Made a little gif about it, where the perfboard is the thing i asked above.
Thanks for your answer / suggestion. Have a nice day.

Should work , but have a look at how Ethernet works - you probably don’t need to switch all cores ( but that might not give you the full redundancy). Also look at solid state switches , use of second Ethernet card .

  • wi fi for second connection ?
    -local hub ?

Wired network is a must, also second Ethernet card is unnecessary. Thought about including a network switch before the W5500 module, but it will create a network loop which is bad.

I really doesn't care if some packets are lost, also 1-2 second of downtime, but not more. So thanks for the answer but in my opinion this "pull the bad cable out, plug this backup one" type of solution is the most suitable for my purpose.

You probably don’t need to switch all cores (but that might not give you the full redundancy)

10/100 Ethernet uses only green and orange pairs (1, 2, 3, 6), you don’t need the other 2 pairs, so it it’s 10/100 you only need to switch 4 wires.
Giga-bit Ethernet uses all 4 pairs.

Having installed computer networks for years I suggest that any small gain in redundancy of the cable will be more than lost by the extra fault liability of the switching device. In any case, I’m assuming this is to the same network, not to a different network with a different internet connection; there are many other points of failure that this does not cover. In my opinion what you are doing is pointless. Just make sure you buy proper Ethernet cables, not the 20p copper coated aluminium shit available on various well known web sites. We pay upwards of about 75p per cable depending on length for copper cables in bulk from a reputable trade supplier.

Create a network loop which is bad

Yes, very bad. Don’t do that.

PerryBebbington:
Having installed computer networks for years I suggest that any small gain in redundancy of the cable will be more than lost by the extra fault liability of the switching device. In any case, I'm assuming this is to the same network, not to a different network with a different internet connection; there are many other points of failure that this does not cover. In my opinion what you are doing is pointless. Just make sure you buy proper Ethernet cables, not the 20p copper coated aluminium shit available on various well known web sites. We pay upwards of about 75p per cable depending on length for copper cables in bulk from a reputable trade supplier.
Yes, very bad. Don't do that.

So, the project is an ArtNet node. In the FOH there's the lightning console, along with a router. One cat5e cable goes to the stage. There's the ArtNet node. If the cable get damaged while the concert going, we can't control any of the stage lights.
So, if two cable goes to the FOH, and the node can automatically switch to the second cable, it's much more safe.
They use this technique with mixing consoles etc.
If you can suggest any other idea (IT wise, not arduino) in which I can use two cables to the FOH, and it's not including expensive gear for link aggregation or something, I look forward to your soution. :slight_smile: Thanks for replying.

PS.: Yes we use heavy duty cat5e cables of course, but s**t happens when you have 40+ meters of cable going to the stage.

The project is an ArtNet node. In the FOH there's the lightning console, along with a router. One cat5e cable goes to the stage. There's the ArtNet node. If the cable get damaged while the concert going, we can't control any of the stage lights.
So, if two cable goes to the FOH, and the node can automatically switch to the second cable, it's much more safe.
They use this technique with mixing consoles etc.

Ah, well, I didn't know any of that! I see the point now!

Yes we use heavy duty cat5e cables of course

OK, good!

Just a thought Peter, if you introduce any kind of relay or switch that is not designed for the frequencies that Ethernet works at then you will be upsetting the impedance matching, which might degrade the performance of the connection, or possibly stop it working altogether. I suggest that if you do this you test it will cable at least 25% longer than you will ever use and make sure it works as expected.

Thanks for the answers PerryBebbington. :slight_smile:

Obviously this function can be accomplished using an 8PDT relay, but as you said it
is loud, and also slow.

You could use four ADG511 analog switches.

(these are SPST switches so you need to connect TWO in series and invert (inverter chip) the IN# SELECT lines on the SECOND switch, resulting in switch-1 OPEN/switch-2 CLOSED operation, simulating a DPDT
switch. Two ADG511 chips per four lines means you would need a total of 4 ADG511 chps to accomplish
this function.

According to this, the voltage levels are +/-2.5V, so if you had a standard 5V, 2-conductor
Wall Wart wired backwards, (the positive wire connected to GND), you would have a simple, easy -5V P.S.
you could use for the +/- Bipolar 5V supply for the ADG511 chips.

raschemmel:
Obviously this function can be accomplished using an 8PDT relay, but as you said it
is loud, and also slow.

You could use four ADG511 analog switches.

Ethernet uses 110 ohm balanced differential pairs at high frequency, I'd worry a bit about the high capacitance of that chip, 35pF.

Incidentally where are the magnetics in that diagram PeterT?

Ethernet uses 110 ohm balanced differential pairs at high frequency, I’d worry a bit about the high capacitance of that chip, 35pF.

A valid concern considering the cutoff frequency of an RC LPF with R=110, C = 35E-6 = 41.3 Hz C = 35E-12 = 41 Mhz and for Ethernet, f = 30Mhz to 50 MHz

The 100-Mbit/sec FDDI signal runs at 31.25 MHz over UTP. A 155-Mbit/sec signal, such as that proposed for asynchronous transfer mode, can run at less than 50 MHz.

fc =1/(2* Pi * R*C)

RC LPF Cutoff Frequency

I don’t have any simulation software but I would be curious to see the waveform of a circuit with
that RC circuit with an input of 30 MHz square wave.

C = 35E-6

I think that's quiet a lot more than 35pF...

OOPs ! (Dyslexia ? ADD ?)

Try fc = 41,338,946 Hz (41 Mhz)

It might work, but if not the op will have to live with a relay , which he describes as ‘loud’ (I beg to differ. It makes a barely audible ‘click’)

I guess 8 relay would be the easiest way to do this, but they are loud

I think I would try two wireless routers in the bridge mode, and maybe carry an emergency cable just in case.

Has an Ethernet organize interface that can be utilized to control the switch port association state, just as screen switch status through an internet browser, telnet, or utilizing SNMP.

Has an Ethernet organize interface that can be utilized to control the switch port association state, just as screen switch status through an internet browser, telnet, or utilizing SNMP.

WTF? (I have no idea what you just said. it's all Greek to me !)