Ethernet between two houses

[bernardgreen]

A small 12v battery would be easier trickle charged via the same wall wort.

Winston. Please give details of how you would trickle charge a battery from a DC power supply which does not have any means to set the charging current. Unregulated charging could destroy the battery.

Supplying the router from a battery that is float charged from a battery charger set up to match the battery and load is a good idea.

 

[Harry Bloomfield]

If one needed repeaters to get 50mm range, I think there might be a problem

More seriously, though, I can 'see', and have occasionally connected to ('in emergencies'!) WiFis of neighbours more than 50m away.

Kind Regards, John

I provided a relative with access, using a pair of old wifi routers, each with a home-made Yagi antenna replacing the built in antenna. It worked well over an 1/2 mile link, despite numerous house with wifi in between - though still LoS over the top.

 

[Harry Bloomfield]

The weak point is the inter winding capacitance of the transformer.

quoting from https://www.ti.com/lit/an/slvae50/slvae50.pdf

Ethernet networks are subject to many harsh conditions as a function of being in industrial applications. One particularly harsh condition is a transient surge highlighted in IEC 61000-4-5. This surge pulse is applied on the transmit and receive lines of the ethernet physical layer and can potentially damage the ethernet controller, or phy. One statement that inevitably comes up during this discussion is that the transformer in the system should isolate the sensitive phy from the pulse on the connector. However, as shown in this application report, transient pulses can couple through the transformer and potentially damage the ethernet phy. This means that adding protection between the transformer and the phy is necessary in harsh industrial environments that will be subject to transient surges.

phy = physical layer, the hardware that receives and transmits the signals on the cable

A link between two different buildings with different mains supplies will be in an environment that can be considered as harsh

Not unusual in a building which has 3Ph supply, to have various PC's on different phases and all interconnected by a wired LAN system.

 

[SUNRAY]

Not unusual in a building which has 3Ph supply, to have various PC's on different phases and all interconnected by a wired LAN system.

Also not unusual in larger buildings to be on different substations.

 

[JohnW2]

Not unusual in a building which has 3Ph supply, to have various PC's on different phases and all interconnected by a wired LAN system.

Indeed not unusual - it's even true in my house.

Kind Regards, John

 

[bernardgreen]

Not unusual in a building which has 3Ph supply, to have various PC's on different phases and all interconnected by a wired LAN system.

True and therefore the wired LAN system will ( should ) be designed using equipment which will ( should ) be tolerant of the potential differences that will occur between the various PCs and nodes of the LAN

 

[SUNRAY]

From memory of stripping dead ethernet switches the transformers were rated at something like 1.5 to 2KV

 

[bernardgreen]

From memory of stripping dead ethernet switches the transformers were rated at something like 1.5 to 2KV

True they resist being damaged by potential differences between the equipment but data quality can be affected.

When data is affected it isn't always obvious to the user as error checking / error correction / repeated packets can restore the data.

 

[Harry Bloomfield]

True they resist being damaged by potential differences between the equipment but data quality can be affected.

When data is affected it isn't always obvious to the user as error checking / error correction / repeated packets can restore the data.

All such LAN interfaces include voltage isolation between socket and the rest of the card/interface, it is part of the spec. and it doesn't impact throughput. LAN cabling uses twisted pairs, so that when interference positively affects one of the cores of the pair, it will negatively impact the opposite core and thus cancel out. LAN cables are speced to be able to transmit and receive over 100m without any issues of data loss, if properly installed.

 

[bernardgreen]

LAN cabling uses twisted pairs, so that when interference positively affects one of the cores of the pair, it will negatively impact the opposite core and thus cancel out.

If the windings of the transformer are not 100% symmetrical to the core and each other then transients in the end to end potential can create a false signal.

Bifilar and trifilar windings can be used to achieve the necessary symmetry but this construction can compromise the breakdown voltage as it relies totally on the enamel of the winding wire.

 

[JohnW2]

It seems to me that some barrels are being scraped pretty vigorously!

Kind Regards, John

 

[SUNRAY]

Unless it's changed in the last 30 years the enamel is only rated at 50v, in order to increase the rating an additional barrier or gap is added between turns.

To achieve KV's of isolation the windings will usually be on separate bobbins or sections.

I have known ethernet to be operating at high PD's between between equipment do to an incorrectly earthed generator and seeing no apparent errors.

 

[JohnW2]

Unless it's changed in the last 30 years the enamel is only rated at 50v, in order to increase the rating an additional barrier or gap is added between turns.

Indeed, but one would need some awfully massive 'surges/spikes to get anything like 50V between adjacent turns of the same winding.

To achieve KV's of isolation the windings will usually be on separate bobbins or sections.

Again indeed. Even when primary and secondary are on the same bobbin, there is usually at least some oiled paper, plastic tape or somesuch between the windings.

As I said, albeit all sorts of things are theoretically possible (aka "not impossible"), I do think that "barrels are being scraped"

Kind Regards, John

 

[SUNRAY]

Indeed, but one would need some awfully massive 'surges/spikes to get anything like 50V between adjacent turns of the same winding.
Again indeed. Even when primary and secondary are on the same bobbin, there is usually at least some oiled paper, plastic tape or somesuch between the windings.

As I said, albeit all sorts of things are theoretically possible (aka "not impossible"), I do think that "barrels are being scraped"

Kind Regards, John

I wasn't thinking of adjacent turns, rather a block of 50V worth of turns, ie a 230V winding will consist of 5 layers of turns with a barrier between them.
I'm not sure where the barrel scraping comes in, it would not occur to me to introduce any additional isolation between systems or buildings but the untimate is of course a fibre optic.

 

[bernardgreen]

there is usually at least some oiled paper, plastic tape or somesuch between the windings.

To get a good symmetry the wires for the two ( or three ) windings is twisted before being wound onto the core. Hence the isolation depemd on the enamel on the wire.