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'[EE:] 10/100TX POE Magnetics Wanted'
Adi Linden wrote:
> I am looking for a few LAN magnetics to build POE inserters. These need to
> be suitable midspan 10/100TX and support (obviously) POE. Some suitable
> parts I have been able to identify are:
> Pulse H1197 <http://www.pulseeng.com/pdf/H327.pdf>
> Falco LV1002 <www.falcomex.com/products/4/pdf/10-100Base-TX%20VOIP-PoE%20Single%20Port.pdf>
> Any idea where I can find just a few of those, 5 to 10. Or any suggestions
> for other, easy to source, alternatives?
I was under the impression that to insert POE you would just put some DC
on the line, no magnetics needed? (because both ends are already isolated)
> I was under the impression that to insert POE you would just put some DC
> on the line, no magnetics needed? (because both ends are already isolated)
One possible solution is to apply power to the two spare pairs of the
ethernet run. In that case no magnetics are required. My problem is that I
have a 802.3af compliant switch. It applies power to the signal pairs.
Looks like the Linear LTC4257 (and a few other parts) is all I need to use
the power supplied by the 802.3af switch at the far end. Digi-Key has what
I need except for magnetics. I guess my original statement was slightly
wrong in that I am not inserting power but utilizing the available power.
Not sure what the opposite end of the power inserter would be, power
also, keep in mind that true 802.3af injectors first put about 10V on
the line to test if the receiving circuit is actually an 802.3af
device and after a period of time either send the 48V or just turn the
On Fri, 4 Feb 2005 17:45:04 -0600, Adi Linden <adis.on.ca> wrote: adil
> also, keep in mind that true 802.3af injectors first put about 10V on
> the line to test if the receiving circuit is actually an 802.3af
> device and after a period of time either send the 48V or just turn the
> psu off.
Yes, that's how the whole things started. I am trying to power Cisco ip
phones from a Netgear FS108P switch. The switch has four 802.3af compiant
power source ports. After reading about 802.3af I thought that this was
going to be easy - make an adapter that swaps the spare ethernet pairs to
match 802.3af polarity with Cisco legacy polarity, and add a 25.5k
resistor across the power sourcing wires to fool the switch into believing
that a compliant 802.3af device is connected. No go. The timing and
probing of 802.3af is a bit more complex.
The Linear LTC4257 appears to be the proper device to extract power from
an 802.3af source. Unfortunatley, out of the box the FS108P switch does
not power the spare pairs of the ethernet wire. Therefore I am trying to
come up with a solution that properly splits the 802.3af powered data
pairs into data (no power) and power.
I found a few magnetics and RJ45 jacks with integrated magnetics that are
designed for POE. Unfortunately, like so many times in the past, I cannot
seem to find anyone willing to sell these at a reasonable cost in small
Alan B. Pearce
>Any idea where I can find just a few of those, 5 to 10. Or any suggestions
>for other, easy to source, alternatives?
I have had samples for free from the Pulse agents here in the UK - and that
was after I had made it clear that there was unlikely to be any commercial
sales afterwards. Very pleasant helpful lass on the other end of phone
didn't seem to mind, provided she could fill in her questionnaire.
Have you asked the factory for some samples or the
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I had approached Pulse and Coilcraft for a different project a couple of
years ago. Neither was interested in supplying samples for a small
I have since found that Mouser carries selected Pulse parts. I found
something that should work and placed an order...
True...factories often are not that interested. I
suppose those of us that are engineers and work in the
field day in...day out...have the advantage of
fostering the relationships with the rep's so when
these one-off jobs come along or even hobby projects,
samples are never an issue. Guess im spoiled!
--- Adi Linden <adis.on.ca> wrote: adil
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