Hi Bostjan,
Thanks for your feedback, but...
I am slowly and carefully reading 62368-1 for the first time.
It defines 'external circuit' in 3.3.1.1 as "electrical circuit that is
external to the equipment and is not mains".
I assumed one device = one equipment so I thought laptop is an
equipment. After your post I checked how equipment is defined in 62368-1
but in 3.3 there is no equipment definition so I don't know what is
equipment.
May be USB device (pendrive) connected without cable to laptop can be
assumed being its part, or even device powered by USB (mouse, keyboard)
can be assumed being its part, but USB can be used to connect other
equipment, I think. Do laser printer being powered separately from mains
connected to laptop is understood as being internal part of equipment?
Laptop is probably manufactured by someone else than laser printer. They
can't assume they manufacture single equipment, I think.
In past I have read about USB being used to connect active wifi antenna
located on the roof (with few hubs to extend connection length). Having
all that in mind it is hard for me to accept that for 62368-1 USB is
equipment internal circuit.
Now.
If we assume laptop with connected to it mouse, external keyboard and
printer is one equipment then going to my field: do the access control
controller with RFID readers connected to it by RS485 is also one
equipment (all powered from one 12V supply, and located in one building)
making RS485 connection being internal equipment circuit?
I don't think so.
And I repeat my main question regarding 5.4.11: Do the access controller
permanently connected to 12V supply that is permanently connected to
mains is permanently connected equipment? I think yes. Even 12V supply
has isolation in it.
If I change understanding of equipment and assume that controller + 12V
supply are one equipment than thinks get easier - such understood
equipment is permanently connected. But is it one equipment if
controller is manufactured by someone other then 12V supply.
Best regards
Piotr Galka
W dniu 2024-05-07 o 19:49, Boštjan Glavič pisze:
Hi Piotr
USB circuit is internal circuit. There are no transients expected on USB.
Clause 5.4.11 is not applicable for power supply with USB output.
Paired conductor is a telecommunication network that we had in old times
(analogue network, ISDN,...).
I hope this helps. If you need more info, you can contact me.
Best regards,
Boštjan
-----Original Message-----
From: Piotr Galka <piotr.ga...@micromade.pl>
Sent: Tuesday, May 7, 2024 5:40 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: [PSES] IEC 62368-1: To understand chapter 5.4.11
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Trying to understand 62368-1...
I have got laptop with type A power supply so it looks being not excluded from
5.4.11 by rules in 5.4.11.1.
For me USB are external circuits indicated in Table 14, ID numbers 1 and
2 (I think USB is 'Paired conductor', but even not it certainly is 'Any other
conductors').
The note in Table 14 about not taking into account transients for external
circuits installed wholly within the same building is only about transients so
I think it doesn't make USB being not indicated in table.
USB cable can be used to connect laptop to printer and in printer USB can be
earthed, I think.
Dos this means that according to first sentence of 5.4.11.2 each USB port in
this laptop should be separated from its other USB ports?
I don't believe there is such requirement.
My real problem to understand is as follows:
Typical access controller have several not separated from each other inputs
(several RFID reader inputs, door state control input, tamper inputs and
others).
I need to understand if the access controller powered from (external to
it) 12V DC buffered (= having accu in it) supply is permanently connected
equipment or not?
To disconnect it from 12V supply you need tools, to disconnect 12V supply from
mains you need tools, but 12V supply has isolation in it so access controller
is not electrically connected to mains and 3.3.3.4 says about needing tools to
disconnect from mains (if something is not connected than tools are not needed
to make it being disconnected, I think).
Being permanently connected equipment is the easiest way for controller to be
excluded from 5.4.11.
But if it is not permanently connected than its inputs are in the same
situation as laptop USB ports I described first as more common to everyone.
What I miss or wrongly understand?
Regards
Piotr Galka
P.S.
Last month free time I spend browsing about 2800 EMC-PSTC posts collected by my
mail program for few years.
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