Hi John,
I hoped you will answer my question and I got important information from
you. Thanks.
After reading your post my decision was to buy 62368-2 but I've just
checked that in PKN (Polish Standards Committee) I can buy 62368-1 what
I have done long ago but they don't have 62368-2 :( .
Even not seeing explanations the requirements should be so written that
there should be no doubts when reading them. I really don't know how to
read 3.3.1.1 to understand USB as internal, but I accept to understand
it as internal.
This laptop and USB is an example that should help me to understand the
standard and I think I got pointing in the right direction (I am using
USB (desktop RFID card readers/writers, pen-drive like devices
implementing crypto functions)).
Our access control devices accept 12 or 24V supply (I think 99%
installations use 12V because such supplies/batteries are more popular).
We use RS485 that we require the whole bus being in one building. We use
Ethernet but when connecting many controllers to it the routers/switches
also are close to them so we also specify that this connection have to
be in one building.
Since 2020 we had very hard time because ATXmega microcontrollers (and
also other ICs) we used disappeared from marked and we had to redesign
all our products to the other IC that happened to be able to buy. The
side effect is that all our CE declarations are outdated. I want to
issue new ones. And because of this I want to understand 62368-1.
Best regards
Piotr Galka
P.S.
Note out of EMC-PSTC subject but connected with standards...
Recently my heart has been hurting because while the whole world is
trying to save energy, we have been forced to issue readers that have 40
to 400 times more energy consumption for RS485 transmission than our
previous ones. And to not be eliminated from market we seriously think
about doing the same change in all our devices. Standards are not
mandatory, but if they are issued than market forces to use them. When I
imagine how many RS485 busses work all the time all over the world...
W dniu 2024-05-08 o 17:52, John Woodgate pisze:
To fully understand IEC 62368-1, you also need to read IEC 62368-2. It
includes a long explanatory text about 5.4.11. The committee realised
that it was not practicable to put all the explanations into the same
document as the requirements. The circuits feeding the USB connectors
of a device are internal circuits. But are you actually using USB or
are you mentioning it as an example? For your access controller
connected to a 12V supply that is permanently connected to mains, the
isolated low-voltage circuits in the 12 V supply equipment are
internal circuits and are not subject to transients. Anything
connected to the 12 V DC supply is ES1.
On 2024-05-08 16:21, Piotr Galka wrote:
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 <[email protected]>
Sent: Tuesday, May 7, 2024 5:40 PM
To: [email protected]
Subject: [PSES] IEC 62368-1: To understand chapter 5.4.11
CAUTION: This email originated from outside of our organisation. Do
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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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