Re: more X-rays Silvertel PoE Supply

Oct 02, 2024 Last reply: 1 year ago 6 Replies
B


On a sunny day (Wed, 02 Oct 2024 07:45:04 -0700) it happened john larkin


> snipped-for-privacy@gct.com wrote in snipped-for-privacy@4ax.com: >
>> >>
>>> On a sunny day (Tue, 01 Oct 2024 14:16:09 -0700) it happened john larkin
>>> snipped-for-privacy@glen--canyon.com wrote in snipped-for-privacy@4ax.com:
<snip>
Found it with google maps...
> Do you make Xray movies of living things?

John Larkin won't.



Medical people do. It's called cine-angiography.



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When I got my aortic valve replacement, part of the work-up was a cine-angiogram of my coronary arteries, looking for incipient blockages.



They found a little bit of plaque, but not enough to be worth taking out when they did the aortic valve. My younger brother was less lucky - his aortic valve was fine, but he had minor coronary and his coronary arteries needed quite a bit of work, but that was fifteen years ago and they've been fine since then.


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E

It wasn't necessary for the fairly specialized product which was configured at install time with power from PoE or wart but not both. I seem to recall at least one accidental connection of both with no detrimental effect but it wasn't investigated further.

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A

I've seen a problem when the PoE module had a TL431 + optocoupler at it's output as feedback circuit. A limiting resistor was lacking, and +12.3V from a wart turned the TL431 fully on and destroyed the optocoupler. Subsequent PoE operation then had an open loop and destroyed the supplied circuit.

Arie

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E

I'd probably include an additional schottky diode to protect the TLV431, assuming the small power loss is acceptable. Also a schottky in series with the wart power. And maybe a FET to turn on a light load for the PoE when wart power is present.

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E

A seperate smaller schottky and capacitor for just the TLV431 seems to work fine in the LTC4267 simulation I just did and works around wall wart power getting connected to the TLV431.

To disconnect wart power when PoE is operating, put a low power voltage doubler on the transformer secondary and use the 24V to swich off a p-fet in series with wart power.

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A

Way too complex. A series resistor between TL431 and optocoupler was all that was needed.

Arie

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E

Only needed one BAT54 (a few cents) in my circuit.

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