Ethernet testing if connection to switch is present? Data present?

[MarkusDK]

Hello.

I want to make a small contraption that i can use to check wether an ethernet cable is connected on the other end to a switch or so.
On my small 5 port switch i can see the status indicators lighting up signalling the connection speeds (100/1000base-t), so i was thinking of putting the smallest Ethernet PHY i can find in a box with a battery, and hopefully that would be it.

It just needs to output wether a switch is connected on the other end or not. Not if there is internet available or anything.

Second question.
would it be possible to go even more simple, and just put 4 LED's with resistors between pin 1-2, 3-6, 4-5 and 7-8 to flicker whatever voltage level the switch is outputting? And also show if Gigabit connection is present?
The latter would be really cool, cause i can fit that in a really small housing without the need for a powersource.

hope you guys can enlighten me

[Kjelt]

Buy another small switch connect it if there is another switch on the other side of the cable the leds of the port will light up.

[MarkusDK]

but that's not very portable and nifty, since i need an external power supply and an outlet nearby.
ideally it should have a formfactor like the Neutrik NA-housing.

[helius]

If your switch provides "Passive-PoE" it is as simple as a voltage detector between some of the wires.
Absent that, it may be possible to avoid a full PHY interface if you can detect equalization pulses on the cable (so just a sensitive comparator and a hold circuit).

[MarkusDK]

I've looked at some graphs of the ethernet data signal.
It oscillates between +2 / -2V in 1000base-t, +1 / -1V for 100Base-TX and +2.5 V / -2.5 V for 10Base-T

What i don't know is, if there is no data being sent, what is the voltage for the pins then?
but wouldn't it be doable to put a LED + resistor across the 4 pairs, and come up with a setup that can handle the voltage range +2.5V to -2.5V?

Next question.. Will this hurt the switch?

[Kire Pûdsje]

Just lookup NLP (Normal Link Pulse), or one of its successors.

[Electro Fan]

Lots of test devices are out there, you could spend even less, or more - but here is something that is portable and should tell you if a LAN or phone cable is working:

https://www.amazon.com/HDE-Network-Cable-Tester-Phone/dp/B009ZXYI1U/ref=sr_1_3?ie=UTF8&qid=1509563213&sr=8-3&keywords=rj45+tester

Or are you trying to determine if data from the remote switch is detected on the cable?  Or are you just trying to see if the cable is connected to the remote switch?

Or maybe you just need a compact battery supply to run a small 4 port switch like Kjelt suggested so you can see the lights on the ports?  Is this going to run 24x7 or just for a few seconds or minutes at a time as you walk around and check cables/data?

Or maybe your idea of putting together an LED with a resistor is the way to fly.

Here are some specs from Wikipedia:
https://en.wikipedia.org/wiki/Category_5_cable

[MarkusDK]

What i want to build, is a device to check if a, lets say 80m Cat5/6/7 cable is connected to a switch or a device in the opposite end.
A bonus would be if it could display the connected device speed (ie 10/100/1000BaseT?).
I'm well aware of those devices that check each wire one at a time for shorts and wrong connections, but that's not what i'm trying to achieve.

I've found a 3 port switch that can be powered through USB.
http://www.cyberdata.net/assets/011236/011236_3-Port_Gigabit_Ethernet_Switch.pdf
But it will end up cluncky with a USB batterypack attached and so.

It would be more fun and practical if it could be a passive device.

It is only to be used for a couple of seconds, to use for fault checking on the fly and such, where one end might be unaccessible.


Edit: If POE is present, would this kill the resistor and LED, if 48V was applied instead of up to +2.5V?

[helius]

If you don't have at least a pulse transformer terminating the cable, it's doubtful that a switch port will send anything into it. That includes 802.3af PoE and any equalizing pulses.
The reason that "passive PoE" is simpler to detect is that it is always enabled regardless if the port is connected or not. 802.3af PoE is only enabled if the negotiation between the supplier and consumer succeeds. So if your test device doesn't respond to the probe (which can be up to 10 volts), the 48V power will not be enabled.

[Kire Pûdsje]

Not a passive solution, but with just two 555 timers, you can make a circuit that can detect 10/100 Mbps, based on the NLP/FLP pulses.
On the other hand, no point in building it yourself, as indicated by others, there will be no cost nor size benefit. It will just be the satisfaction of having built it yourself.

Edit: thinking about this, by adding a (mechanichal toggle) switch to detect auto crossover (MDI-X), one could assume a gigabit network, so all three modes could be detected separately.

[MarkusDK]

Okay, so no data/potential power is between the pins if nothing is connected, like they are all 0V?
Then i guess the simple setup with 4 LED's wouldn't work.

I'm in the lighting industry for events, where i've built a DMX signal tester, that is basically just a terminator with an LED between the two data pins +/- which outputs if data is present. That is why i thought it might be possible to do the same with an ethernet cable.

Its a nice-to-have tool, not an need-to-have, but if it gets to bulky and complicated, it defeats the purpose.

[kripton2035]

I'm not sure it's so simple to make such a device.
there are commercial devices that do what you want, check speed on the lan, and check poe voltages, but they are all $500+
you can find them used for around $200, search for flukes.
it's easy to make simple ethernet connectivity testers, you get one for less than $10
but there is a gap to the next level devices you want.

[grifftech]

laptop/ Rasberrypi

[madires]

Unfortunately there's no simple solution. Please see https://en.wikipedia.org/wiki/Autonegotiation for details.

[Bratster]

Check this out:
http://www.instructables.com/id/Ethernet-link-tester/

Will only work if your switch supports 10meg however.

It's using an old AUI to ethernet converter module. Just give it power and connect an Ethernet cable to it and if it can get a link it will give you an indication.


I have made one of those based off that instructable, used it a few times it is easier than pulling out a laptop.


Sent from my Nexus 6 using Tapatalk

[MarkusDK]

WOW That is perfect for the project!
If the switch has 10/100/1000Mbps Auto-Negotiation, (which a lot has) it should work right?

[TomS_]

Any half reasonable switch or router that I have seen usually has a 1:1 transformer per pair, aka "magnetics".

So perhaps measuring continuity of one or more pairs would be sufficient?

e.g. https://www.audioasylum.com/messages/pcaudio/160168/ethernet-transformers-example-schematics-and-pictures

[Bratster]

WOW That is perfect for the project!
If the switch has 10/100/1000Mbps Auto-Negotiation, (which a lot has) it should work right?

Yep should work fine.


Sent from my Nexus 6 using Tapatalk

[MarkusDK]

So i made it work! Brilliant, thanks for the tip!
So this is the version 1.0. Now i need to put it inside an enclosure, i'm thinking some form of Hammond 1590 (smallest as possible)
I'll need to do some disassemble of the device and solder on some other LED's that i can put through the Hammond case.

My question is. How do i find a correct LED that will not fry the board when powered up?
I'm powering the device from a 9V battery.

[mrpackethead]

I'm curious to know what problem your trying to solve in the enteraiment feild?    Is this jsut so you have an easy way to know if the device is connected to a switch?

I'm curious because i could desing a simple mciroprocessor device thats pretty tiny, that woudl run off a pair of of AAA cells for quite some time, with a few LEDS to give you some status indicators...   it gets harder when you start having more complex setups with just a couple of flashign leds..  but its not entirely impossble.

[MarkusDK]

It's just a "nice to have" device project. not sure if i'm ever gonna use it.
Really just to check CAT5/6 lines are live or not, nothing more.

The smaller the better. As of now i've used either a switch or a laptop to ping back the device in the other end to check.

[kripton2035]

I just tried with one of those W5100 cheap modules
you only have to power it 5v, it tells you directly if something is connected
it even tells you for 10 or 100baseT, with the speed led, and full or half duplex with another led on the board.
they cost less than $5

[kripton2035]

also tried with a more cheaper enc28j60 module (< $2)
it works just by powering it to 3.3V, the led shows you when connected or not.
as it is 10baseT only, it only checks for 10bT connectivity.

[MarkusDK]

Is there a place to solder on two LED's, one for LINK and one for DATA?
I'll be needing to put it inside a box with an Ethercon connection, so i can't see the LED's in the socket when it's inside the box.


but that info would have been nice to have had before going with the Lancast 4320 

[kripton2035]

on the w5100 module, you have 7 smd leds for all the ethernet states. you can for sure unsolder some leds to replace them out of the box.
you also have two leds on the ethernet jack itself, to tell the connexion and the speed status.
sorry for the late info, but when I saw that about the lancast, I just said to myself "I have to check these ethernet modules I have..."
and I thought first time they needed a microcontroller to operate.
I have tested other wiznet modules, and they don't work alone.