Hello,

I have searched tons of places for schematics to build my own ethernet board with the ENC28J60 IC.

All schematics suggest I use two transformers. (one with 4 pins and one with 5 pins) I searched online for a through-hole transformer that can work with Ethernet signals (through Ebay and Digikey) and I could not find one. Instead, all I find are soip or smd parts.

Is there an equivalent through-hole transformer I can use between the ENC28J60 IC and the RJ45 jack that won't cause any board to blow up?

One source said the transformer should withstand 2kV and be 350uH but I need more information so I can buy an equivalent one through-hole transformer on ebay.

any ideas?

 

Hello,

I have searched tons of places for schematics to build my own ethernet board with the ENC28J60 IC.

All schematics suggest I use two transformers. (one with 4 pins and one with 5 pins) I searched online for a through-hole transformer that can work with Ethernet signals (through Ebay and Digikey) and I could not find one. Instead, all I find are soip or smd parts.

Is there an equivalent through-hole transformer I can use between the ENC28J60 IC and the RJ45 jack that won't cause any board to blow up?

One source said the transformer should withstand 2kV and be 350uH but I need more information so I can buy an equivalent one through-hole transformer on ebay.

any ideas?

Trying to source parts on Ebay is part of your problem. What you need is not sold there.

 

https://www.te.com/global-en/produc...lq_glo_acproductflyerlink&elqCampaignId=11895
And from Mouser...
https://www.mouser.com/ProductDetail/TE-Connectivity/2301994-1?qs=/ha2pyFaduiKAKJ0E2BEhr9B6LCOoExc/NXo%2B0KIjor6NcOUmx5flg==


There are quite a few ready built boards on Ebay.
https://www.ebay.com.au/itm/ENC28J6...859731&hash=item4b1e11f031:g:aAsAAOSwgDRZcJqf
(Australian EBAY site)

 

I already own shielded RJ45 jacks themselves. Funny thing I got 30 of them free on ebay after seller failed to deliver them on time. But I need the transformer parts. I'm curious, could I somehow make a transformer from a set of shielded 350uH inductors with a 2kV rating for the wire and placing magnetic tape between the two inductors?

 

Those jacks I posted have the transformers inside already.

 

Excuse my ignorance but why would one want to transform an rj45 signal? Is this common practice to transform an rj45 signal or is this something special? My first thought when i saw this was won't that cause allot of signal noise, but i supose old phone systems had to do this didn't they. So I guess my question boils down to.

 

https://www.eenewsembedded.com/blog/5-things-you-need-know-when-selecting-ethernet-magnetics

Magnetics are Not Optional
Magnetics are part of the Ethernet specification for xBASE-T networks, and as such, they are required for all Ethernet enabled equipment. The magnetics protect against faults and transients, including rejection of common mode signals between the transceiver IC and the cable. These signals are commonly caused by electromagnetic interference (EMI), either from noise picked up by the cable or from slight impedance mismatches. The magnetics also provide galvanic isolation from Ethernet cables, and offset any DC biasing caused by connected nodes having been powered from different sources.

 

I mean I saw a couple circuits on the net (including one found here: https://electronics.stackexchange.com/questions/51648/enc28j60-no-communication-over-ethernet) which didn't use a transformer at all but instead a direct connection. I attached the schematic here:

Is there another way I can stop the EMI? Could capacitor coupling of the signals help instead of transformer coupling? I don't want to buy expensive new jacks just to get a transformer when I have piles of regular jacks, capacitors and inductors already at home.

 

If it's worth doing then it's worth doing right.
http://www.ti.com/lit/an/snla088a/snla088a.pdf?ts=1588267222742

 

I would think that circuit does have the transformer in the jack, just an odd way of drawing it.

 

Could I not use any of these transformers? https://www.digikey.ca/products/en/...162&quantity=&ColumnSort=0&page=1&pageSize=25

I mean sure they are meant for telephone and such but couldn't I maybe add inductance or something?

Since this is for a personal project, I honestly don't care if the speed is super low to todays standards (10Mbps). I just want to create an ethernet link between standard ENC28J60 part and a PC without having to buy fancy jacks. As I said in my earlier post. I have all the other parts (including basic RJ45 jack). I just need the transformer (or a way I can build a circuit that provides equivalent coupling with sufficient protection).

 

Pull one off an old Ethernet card or PC motherboard if you cannot get your hands on a new one.
As @nsaspook said, it is just not worth it to not do it correctly.

 

Could I not use any of these transformers? https://www.digikey.ca/products/en/...162&quantity=&ColumnSort=0&page=1&pageSize=25

I mean sure they are meant for telephone and such but couldn't I maybe add inductance or something?

Since this is for a personal project, I honestly don't care if the speed is super low to todays standards (10Mbps). I just want to create an ethernet link between standard ENC28J60 part and a PC without having to buy fancy jacks. As I said in my earlier post. I have all the other parts (including basic RJ45 jack). I just need the transformer (or a way I can build a circuit that provides equivalent coupling with sufficient protection).

You didn't Look at post #9

 

Ok I'll use that schematic but what resistor values do I use? I mean they're suggesting 33nF caps (I have 47nF ceramic) and theres some cap values unmarked. Could I still use 49ohm resistors and 100nF for the remaining caps?

 

https://www.eenewsembedded.com/blog/5-things-you-need-know-when-selecting-ethernet-magnetics

Cool who knew there were magnetic scrubbers in RJ45 jacks. I assume there effective because RJ45 is a standard. My intuition about phone lines does not apply then. Thanks for the link. TDIL

Sorry to Hijack the thread.