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From: "Edward Rawde" <invalid@invalid.invalid>
Newsgroups: sci.electronics.design
Subject: Re: more X-rays  Silvertel PoE Supply
Date: Wed, 2 Oct 2024 23:52:38 -0400
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"john larkin" <JL@gct.com> wrote in message news:1f2sfj9tgq6016t52f9hdr22cr8kcq98tv@4ax.com...
> On Wed, 2 Oct 2024 22:54:59 -0400, "Edward Rawde"
> <invalid@invalid.invalid> wrote:
>
>>"john larkin" <JL@gct.com> wrote in message news:tvvrfj57ufu4n1c5uq4hnpmjd9hhr0rukl@4ax.com...
>>> On Wed, 2 Oct 2024 19:02:33 -0400, "Edward Rawde"
>>> <invalid@invalid.invalid> wrote:
>>>
>>>>"john larkin" <jl@glen--canyon.com> wrote in message news:kgirfj1614cfkvknad7dl2igqcb2qi5tq7@4ax.com...
>>>>> On Wed, 2 Oct 2024 17:00:52 -0400, "Edward Rawde"
>>>>> <invalid@invalid.invalid> wrote:
>>>>>
>>>>>>"john larkin" <jl@glen--canyon.com> wrote in message news:kqbrfjhrd5oto8ud8vm0395p6oo8eipige@4ax.com...
>>>>>>> On Wed, 2 Oct 2024 11:46:21 -0400, "Edward Rawde"
>>>>>>> <invalid@invalid.invalid> wrote:
>>>>>>>
>>>>>>>>"john larkin" <JL@gct.com> wrote in message news:v6mqfjd93ib6q8j7d7ontsaouidieh5b2u@4ax.com...
>>>>>>>>> On Wed, 02 Oct 2024 06:22:43 GMT, Jan Panteltje <alien@comet.invalid>
>>>>>>>>> wrote:
>>>>>>>>>
>>>>>>>>>>On a sunny day (Tue, 01 Oct 2024 14:16:09 -0700) it happened john larkin
>>>>>>>>>><jl@glen--canyon.com> wrote in <tipofjdtie76lbtd7lc2ger5uo7sglq3p5@4ax.com>:
>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>https://www.dropbox.com/scl/fo/s6wfz2xtdyd6tv32tq3fp/AET6J4oF84HG2hJMeST6F-E?rlkey=acyvuv4z0h2kg0x97azbed8uo&dl=0
>>>>>>>>>>
>>>>>>>>>>Cannot make out much from those x-rays, pictures are better...
>>>>>>>>>>you can probably see the traces just like that?
>>>>>>>>>
>>>>>>>>> The x-rays are fun, but are admittedly more useful for an opaque
>>>>>>>>> potted module or an IC or discrete semi. I can prety well trace the
>>>>>>>>> Silvertel without them.
>>>>>>>>>
>>>>>>>>> I have a gigantic scary Carribean guy who does the xrays and I wanted
>>>>>>>>> an excuse for taking him to lunch, which turned into an interesting
>>>>>>>>> hike around The Bernal Cut. He trashed the xray system software, and
>>>>>>>>> had to rebuild it, and now it can do movies, which is great.
>>>>>>>>>
>>>>>>>>> I'd like to have some products that can be powered by PoE or a wart,
>>>>>>>>> and may want to put two 24-volt PoE supplies in series to get 48, so I
>>>>>>>>> need to understand how they work. The xrays just help a bit.
>>>>>>>>
>>>>>>>>If Ag9900 just works then why would you care how?
>>>>>>>
>>>>>>> Can I overpower it with a wart? Does that need another diode?
>>>>>>
>>>>>>Maybe. See other discussion in this thread.
>>>>>>
>>>>>>>
>>>>>>> Can I run two 24v Silvertels in series to get 48?
>>>>>>
>>>>>>I don't see why not since the data sheet says isolated.
>>>>>>It shouldn't be hard to verify that.
>>>>>
>>>>> Batteries are isolated, but a series string can destroy one cell by
>>>>> back-biasing it.
>>>>>
>>>>> Some power supplies will latch up, or not start up, in series with
>>>>> others. Lots of suplies won't start (and may fail) if their input is
>>>>> pulled negative.
>>>>>
>>>>> As the number of items in a design increases, the probability of some
>>>>> stupid error approaches unity. It's usually time efficient to be super
>>>>> careful, as opposed to spinning a few PCB revs.
>>>>>
>>>>
>>>>Why do you need 48V ?
>>>
>>> To drive loads! To sell more power supplies!
>>
>>If that's the spec then good luck.
>
> The spec is anything I want it to be. We are considering
> posssibilities and will have a hard schematic in a couple of weeks.
> Some confusion is beneficial in early design stages.
>
>
>>
>>>
>>> It ocurred to me that if I use two Silvertels with outputs in series,
>>> their inputs have to be in parallel. They will probably confuse one
>>> another negotiating with the PoE switch.
>>
>>Each one would have to be connected to an independent PoE switch port.
>>
>>You're not thinking of connecting two of them to the same port are you?
>
> The box will only have one RJ45.
>
> You are very snarky.

Didn't someone else mention that word here recently?
Actually I'm just trying to figure out what you're trying to do with PoE.

Ag7100 will turn 24V into isolated 48V but I don't see why you would want to use PoE to power equipment needing 48V.

>
>>
>>I'd consider not using the Silvertel things at all but it may come down to economics rather than electronics.
>
> They are under $10, not worth the engineering to save a few dollars.
> Even with a heap of engineering, it would be hard to beat $10.
>
> Time to market is worth a lot too.
>
>>
>>>
>>> So I guess customers need to have a 48v wart if they want 42 volt
>>> outputs.
>>
>>42? Is that a typo?
>
> No.
>
>>
>>>
>>
>
> 42 is a resonable upper limit spec, given all the tolerances and
> losses and range of loads.
>
> I want to get to at least, say, 38ish to simulate aircraft DC power,
> which is in theory 32 max.
>