Omega 2 - Ethernet without Ether dock?
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I'm looking to package a bunch of onion omega 2 boards in some restrictive space, looking through the forums I saw mention of something similar as a "debrick" option
My plan is to run DC PoE and terminate the ethernet cables straight onto the ethernet TX and RX pins.
Before blowing my devices, I'd like to confirm how safe this is? the documents on
"Reflash Omega without Ethernet" seem to have capacitors between the ethernet connection and board, and also have some 2v and ground connectors bridged to these pins with 100ohm resistors (circuit diagram from "debrick with serial?"the Omega2 seems to only have 3.3v for one thing, and for another - I am not too sure if I should be adding voltage to my switch (I plan on having 18 of these things on the network around the house)
So... can I just connect the ethernet cables direct like this:
Or do I need the capacitors in line like this? (and will the polarity of the caps matter?)
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No, (if you plan to use an Ethernet cable to connect to the other end, say a PC.)
See the minimum part design.
https://community.onion.io/topic/1914/help-getting-ethernet-configuration-correct-resolved/10ccs_hello
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@ccs-hello - thank you so much - that looks a lot more like what I am trying to achieve.
Is there any chance you have a schematic of what you put together?
I want to connect my omega2 devices direct to my network switches - but I don't have space for the dock and expansion (and also can't justify additional $30 per setup considering I need to do this 18 times)
Any pointers would be greatly appreciated!
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Here is the exact POE schematic I am using for my Omega2.
This assumes that you are using a POE injector. I am converting the POE high voltage to 12v for some relays and then to 3.3v for the Omega2+ and other electronics.
If you are just going to pipe in pure DC to the POE pins of the cable then you won't need all that.
Note the Omega2 can't drive the RJ45 Link and POE status LEDS so I tied the POE led to the 3.3v as a power on indicator.
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That helps even more!
My initial plan was to inject DC down 1 of the unused ethernet pairs, and then use a buck converter to drop down to the 3.3v for the Omega2, so (assuming there isn't a reason that won't work) all I need is a way to safely connect the ethernet cables to the omega
I'm not concerned with notification LED's either, so I am assuming I could omit those too?
Is there a way of safely achieving this with just passive components?
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Thomas,
Jeff's schematic diagram's top-left corner is the one you need.
Please note depend on exact part number you procured on that "EasyJack" (or other commercial trade names),
the actual pinout will be different.These EasyJack type of devices are integrated Ethernet jack with Ethernet magnetics (the transformer) and some protection passive components. They are not plain Ethernet jacks.
ccs_hello
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I literally juuust clicked.... feel like a bit of an idiot for my wording... hehe
so all I effectively need is 4 resistors and 2 caps over the TX and RX pins accordingly - bridged to ground.
Do I need the cap to the TX/RC CT? I assume not? I am just not 100% clear what the 3rd cap on the following page goes to on the following:
See soldered image at the bottom of this page... (not sure about the cap at theh top of the row of resistors)Just not too sure what pin the TC/RX CT item relates to as per the pin-outs of the onion
Literally on my way to the electronics shop to buy some caps and resistors to test - hopefully I don't cook any components tonight...
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Tx C.T. and Rx C.T. tied together then go thru a cap to Ground.
There is no need to connect to Omega 2+ side.Note that EasyJack is not a common part to get in a regular electronic store.
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@ccs-hello the easyjack is just a RJ45 connector which can be soldered to - is it not? or is there more to it? for my application I am happy to terminate to screw connectors, which may simplify things for my application. I am purely concerned with what the safest way is to connect the 2 pairs of wires within a CAT5 cable to the ethernet pins of the Omega2
and I am still not clear what is meant by C.T.?
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Is this not sufficient for what I would need? with 51 ohm resisters and 100 nF ceramic capacitors?
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NO.
Example of what's inside:
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@Thomas-Mason The EasyJack is not just a connector, it has built-in transformers, see datasheet of the SI-52003-F.
Without the transformers, you'll create direct DC connections between Ethernet cable and the Omega2. You might get away with that because the other end will have a transformer, but probably impedances are wrong and if you pick up any significant DC voltage (e.g. a PoE capable switch) on the cable, it will fry the Omega2. So I'd say - definitely not recommended.
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I thought I was missing something... I was hoping to get away from the transformer chip to simplify things / lower costs...
seems the cheapest jack I can find here is the following:
Bel Stewart MagJack SI-60002-F (no LED indicators)
of if you insist on the LED's - and want an easy to prototype option, check out sparkfun - RB-Spa-1054I'll try make time to draw something up later, hopefully help a few other people out with similar needs that might be as new to this as I am
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This post is deleted!
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@Thomas-Mason
@ccs-hello said in Omega 2 - Ethernet without Ether dock?:Tx C.T. and Rx C.T. tied together then go thru a cap to Ground.
There is no need to connect to Omega 2+ side.Note that EasyJack is not a common part to get in a regular electronic store.
Not that regular but I think pretty available. For example, HR911105A. I got some from Ebay, ca USD4.5 per 5pcs:
Didn't have time yet to check them out.
I found much more difficult to find a human solderable solution for the USB protection circuit and ended up purchasing individual diodes.
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@Marcin-Debowski @Thomas-Mason
I've been using the HLJ-6115ANL from iTead (datasheet here) successfully for a few projects.
The main advantage over the Bel Stewart is that it has the pins for PPoE (passive power over ethernet, i.e. DC+ on 4/5 and DC- on 7/8). And it's even less expensive.
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Thanks Luz.
I checked the Hanrun HR911105A module in the meantime and it works without any issues. Direct connection (T to T and R to R, not a cross-over).
.After all the wiring is done, for a quick test, the network configuration file needs to be edited as per this document:
https://docs.onion.io/omega2-docs/ethernet-bridge.html#step-2-enable-the-omegas-ethernet-connection
and if all was done correctly, the ethernet port should start acting as a WAN if (and Omega as a hot-spot).
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Really interesting... here is a link for Hanrun model volume purchase, $0.60/unit:
Questions:
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What does CT stand for? Not "coil turn(s)"?
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What output pins are used for DC +/- on your HLJ model?
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Can we do PoE on the Hanrun model too? Same pins?
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Hanrun looks complete with resistors and caps, so no external components needed, I assume? But your model datasheet seems to miss the resistors and caps?
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@Athar-Mian said in Omega 2 - Ethernet without Ether dock?:
Questions:
- What does CT stand for? Not "coil turn(s)"?
Center Tap
Here is related to an Ethernet magnetics:
CT is a contact made to a point halfway along a winding of a transformer (or an inductor).
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@Marcin-Debowski Don't send PoE through that han run mag jack, the resistors inside will burn. Or, you can use a PoE injector/splitter, so you remove the DC power from the cat5 before it gets to the magjack.
