| Author |
Message |
Guest
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 Posted:
Fri Sep 16, 2005 2:27 am Post subject:
Re: Ethernet breaker |
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Rich Noonan wrote:
| Quote: | 1) Use a managed ethernet switch at the center of the control system
and disable individual switch ports as needed. The problems are that
switch silicon
(arguably or provably) has a higher failure rate than say a
mechanical/electrical switch and to the user/safety inspector it still
looks and feels like a software switch.
|
I have seen something that reminds me of what you're asking for, except
it's completely the opposite!
Years ago I had some external (to a webserver) hardware SSL
accelerators. They were designed to go inline with a webserver's
Ethernet cable, and do the SSL work whenever traffic appeared on
TCP:443.
These boxes had 2 RJ45 Ethernet connectors on the front panel. These
jacks were connected to *both* the ethernet transceivers of the
hardware in the box *and* to each other through some DPDT relays (i
guess).
The idea was that *even* if power to your SSL box was cut, the
webserver would stay online.
So, yes, it's completely the opposite of what you're looking for, but
it makes the point that running ethernet through some relays might be
okay :-)
/chris |
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William P. N. Smith
Guest
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| Posted:
Fri Sep 16, 2005 4:17 am Post subject:
Re: Ethernet breaker |
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"Rich Noonan" <rnoonan@gmail.com> wrote:
| Quote: | William P. N. Smith wrote:
How about removing the power to a 2-port switch? Would that solve
your problem?
This would be a decent solution b/c then I wouldn't be compelled to
pour epoxy into unused switch ports :-( Have you seen 2 port ethernet
switches? Can you reference a manufacturer?
|
Hmm, Linksys BEFSR11 looks like a product that's still extant, and you
can probably put it in static routing or DMZ mode if you need to...
Under $50 at Amazon, probably cheaper elsewhere.
| Quote: | Can't unplug. HW switches would be great! Please tell me more if you
can.
|
I'm not home right now, though even if I were I'm not sure I could put
my hand on the printout. Of course, in this case, google isn't your
friend, as "cat5 switch" gets you lots of electronic 10/100 switches,
but no mechanical ones.
I do know they exist! 8*) |
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Al Dykes
Guest
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| Posted:
Fri Sep 16, 2005 4:40 am Post subject:
Re: Ethernet breaker |
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In article <08vji1hofodmd9cl6cq5io83ttsfvur2as@4ax.com>,
William P. N. Smith <> wrote:
| Quote: | "Rich Noonan" <rnoonan@gmail.com> wrote:
William P. N. Smith wrote:
How about removing the power to a 2-port switch? Would that solve
your problem?
This would be a decent solution b/c then I wouldn't be compelled to
pour epoxy into unused switch ports :-( Have you seen 2 port ethernet
switches? Can you reference a manufacturer?
Hmm, Linksys BEFSR11 looks like a product that's still extant, and you
can probably put it in static routing or DMZ mode if you need to...
Under $50 at Amazon, probably cheaper elsewhere.
Can't unplug. HW switches would be great! Please tell me more if you
can.
I'm not home right now, though even if I were I'm not sure I could put
my hand on the printout. Of course, in this case, google isn't your
friend, as "cat5 switch" gets you lots of electronic 10/100 switches,
but no mechanical ones.
I do know they exist! 8*)
|
Check blackbox.com
--
a d y k e s @ p a n i x . c o m
Don't blame me. I voted for Gore. |
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glen herrmannsfeldt
Guest
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| Posted:
Fri Sep 16, 2005 4:59 am Post subject:
Re: Ethernet breaker |
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googlegroups@marget.com wrote:
(snip)
| Quote: | So, yes, it's completely the opposite of what you're looking for, but
it makes the point that running ethernet through some relays might be
okay :-)
|
I would think a simple relay would be more reliable than a relay
switching a complex of electronics.
I think you can just short across each pair to turn it off. That
is probably more reliable than opening the circuit. (Probably one
pair is enough if you decide which one.) I am pretty
sure it won't hurt anything, but you might want to verify that
first. I think it will also have less effect on the impedance
characteristics of the line, though it might be better not to try
it at gigabit levels anyway.
-- glen |
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James Knott
Guest
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| Posted:
Fri Sep 16, 2005 7:11 am Post subject:
Re: Ethernet breaker |
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glen herrmannsfeldt wrote:
| Quote: | I would think a simple relay would be more reliable than a relay
switching a complex of electronics.
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Don't forget, you'll need a relay that can handle the signal, without
disturbing the impedance too much. |
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glen herrmannsfeldt
Guest
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| Posted:
Fri Sep 16, 2005 8:20 am Post subject:
Re: Ethernet breaker |
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James Knott wrote:
| Quote: | glen herrmannsfeldt wrote:
I would think a simple relay would be more reliable than a relay
switching a complex of electronics.
Don't forget, you'll need a relay that can handle the signal, without
disturbing the impedance too much.
|
Yes, that is why I thought it might be better to short the line.
A double pole relay with the armature of the two poles shorted,
and then the two wires of the appropriate pair to the fixed contacts.
The fixed contacts are much shorter in most relays, and so should have
less effect on the signal. Still, it might be that 100baseTX is as
far as I might want to go with it. The cable can be arranged so that
the twisted pair comes right to the contacts without a long stub,
other than the contacts themselves.
At least you don't need a very expensive coaxial relay!
-- glen |
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Tomi Holger Engdahl
Guest
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| Posted:
Fri Sep 16, 2005 8:20 am Post subject:
Re: Ethernet breaker |
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"Rich Noonan" <rnoonan@gmail.com> writes:
| Quote: | I'm looking for a device which could act as an ethernet breaker switch
based on the application or loss of power to that device. On one hand
we could accomplish what we need with a low-cost switch and two cables.
However, in our application and environment this would introduce
several new problems. What I really need is a two port fast ethernet
repeater that I could cut power to and break the link. Of course, such
a thing doesn't exist (or does it?).
Any suggestions on a part that could fill this role? We could probably
design and build a mechanical switch to break the link, but I'm trying
to find something we could buy before going down that road.
|
No ready made part recommendation.
Basicly you could build what you need by combining an Ethernet
switch and an relay connected to PC serial/parallel port
(in case you have PC nearby that runs the application).
Just connect the switch between the power source and the switch.
The computer control power to switch on/off.
If your switch uses low voltage power supply (like those small
"wall wart" powered switches), then just adding a relay to one of
the power wires is preaty easy and safe. If you know how to safely
build mains powered things (and you have necessary qualifications
to do that) then circuit for controlling mains power to device is
another option.
You can find some information on interfaceing relay to serial port at
http://www.epanorama.net/circuits/rspower.html
Another interresting RS-232 port hack:
Marko Mäkelä's electronics projects: RS-232 Solid State Relay
http://www.funet.fi/~msmakela/electronics/relay/
Parallel port interfacing made easy
http://www.epanorama.net/circuits/parallel_output.html
There are also commercial products and electronics kits
for PC interfacing.
And there are companies that make remotely manageable
power switchers that can take controllign signal
from almost everywhere (serial port, Ethernet,
telephone line, cellular phone SMS text message etc..)
besides using switch and turn it's power on/off you can use
the relay directly to cut the Ethernet signals..
A relay that cuts the connection on all the four signal carrying
wires (applied to 10Base-T and 100Base-TX) shoudl do the job.
Keep in mind in the circuit design not to cause too much
impedance mismatches and crosstalk for the signals.
Many normal signal relay contacts should carry Ethernet signals
acceptably.
Other way to cut the connection woudl be to short the signal
wire pair (one relay contact on TX pair and other on RX pair).
Short circuit should stop the Ethernet signals from getting
to other end, so should look same to cards that line is cut.
Those are just few of my ideas for this.
tomi031cv
--
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at
http://www.epanorama.net/ |
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Tomi Holger Engdahl
Guest
|
| Posted:
Fri Sep 16, 2005 8:20 am Post subject:
Re: Ethernet breaker |
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"Rich Noonan" <rnoonan@gmail.com> writes:
| Quote: | I'm looking for a device which could act as an ethernet breaker switch
based on the application or loss of power to that device. On one hand
we could accomplish what we need with a low-cost switch and two cables.
However, in our application and environment this would introduce
several new problems. What I really need is a two port fast ethernet
repeater that I could cut power to and break the link. Of course, such
a thing doesn't exist (or does it?).
Any suggestions on a part that could fill this role? We could probably
design and build a mechanical switch to break the link, but I'm trying
to find something we could buy before going down that road.
|
No ready made part recommendation.
Basicly you could build what you need by combining an Ethernet
switch and an relay connected to PC serial/parallel port
(in case you have PC nearby that runs the application).
Just connect the switch between the power source and the switch.
The computer control power to switch on/off.
If your switch uses low voltage power supply (like those small
"wall wart" powered switches), then just adding a relay to one of
the power wires is preaty easy and safe. If you know how to safely
build mains powered things (and you have necessary qualifications
to do that) then circuit for controlling mains power to device is
another option.
You can find some information on interfaceing relay to serial port at
http://www.epanorama.net/circuits/rspower.html
Another interresting RS-232 port hack:
Marko Mäkelä's electronics projects: RS-232 Solid State Relay
http://www.funet.fi/~msmakela/electronics/relay/
Parallel port interfacing made easy
http://www.epanorama.net/circuits/parallel_output.html
There are also commercial products and electronics kits
for PC interfacing.
And there are companies that make remotely manageable
power switchers that can take controllign signal
from almost everywhere (serial port, Ethernet,
telephone line, cellular phone SMS text message etc..)
besides using switch and turn it's power on/off you can use
the relay directly to cut the Ethernet signals..
A relay that cuts the connection on all the four signal carrying
wires (applied to 10Base-T and 100Base-TX) shoudl do the job.
Keep in mind in the circuit design not to cause too much
impedance mismatches and crosstalk for the signals.
Many normal signal relay contacts should carry Ethernet signals
acceptably.
Other way to cut the connection would be to short the signal
wire pair (one relay contact on TX pair and other on RX pair).
Short circuit should stop the Ethernet signals from getting
to other end, so should look same to cards that line is cut.
--
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at
http://www.epanorama.net/ |
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Rich Noonan
Guest
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| Posted:
Fri Sep 16, 2005 4:20 pm Post subject:
Re: Ethernet breaker |
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|
Thanks all for the input. For those concerned with my electrical
skills, I assure you I have almost none! I'm a software/systems eng.
at a fairly large company with access to top notch EE and ME folks.
However, like many these days our management is all about the buy and
very down on the build solutions. However, if we do go the build
direction you've given me some great bits of data to start the ball
rolling.
So, I did end up finding something fairly close to our needs. The big
question will be pricing, but it looks to be a cool device for our type
of application.
http://www2.automation.siemens.com/net/html_76/produkte/040_ind_sec_scalance_s.htm
During a discussion of this whole problem I was asked about embedded,
data inspection type security in the equipment and this Siemens device
claims to address some of that. However, most importantly to me is
that it has 2 x 10/100B-TX ports and a standard industrial type
package.
But if that doesn't work out you've got me started with some design
points to pass along for an in-house switch. Thanks again!
-Rich |
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Al Dykes
Guest
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| Posted:
Fri Sep 16, 2005 4:20 pm Post subject:
Re: Ethernet breaker |
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|
In article <pNydna4MuIxFtLfenZ2dnUVZ_s-dnZ2d@rogers.com>,
James Knott <james.knott@rogers.com> wrote:
| Quote: | glen herrmannsfeldt wrote:
I would think a simple relay would be more reliable than a relay
switching a complex of electronics.
Don't forget, you'll need a relay that can handle the signal, without
disturbing the impedance too much.
|
I'll take mil-spec electronics any day over a bunch of Radio Shack
relays and wallwart powersupplies and the odd cables and crappy
connecters and ducttape used to hold it together.
I bet if you *do* find a "breaker" it's not going to be a anything
like a mechanical relay. It will be electronic and have no moving
parts.
I asked before, You aren't doing anything safety-critical or covered
by OSHA, are you?
--
a d y k e s @ p a n i x . c o m
Don't blame me. I voted for Gore. |
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Al Dykes
Guest
|
| Posted:
Fri Sep 16, 2005 4:20 pm Post subject:
Re: Ethernet breaker |
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|
In article <lajhdclqw5j.fsf@solarflare.cs.hut.fi>,
Tomi Holger Engdahl <then@solarflare.cs.hut.fi> wrote:
| Quote: | "Rich Noonan" <rnoonan@gmail.com> writes:
I'm looking for a device which could act as an ethernet breaker switch
based on the application or loss of power to that device. On one hand
we could accomplish what we need with a low-cost switch and two cables.
However, in our application and environment this would introduce
several new problems. What I really need is a two port fast ethernet
repeater that I could cut power to and break the link. Of course, such
a thing doesn't exist (or does it?).
Any suggestions on a part that could fill this role? We could probably
design and build a mechanical switch to break the link, but I'm trying
to find something we could buy before going down that road.
No ready made part recommendation.
Basicly you could build what you need by combining an Ethernet
switch and an relay connected to PC serial/parallel port
(in case you have PC nearby that runs the application).
Just connect the switch between the power source and the switch.
The computer control power to switch on/off.
If your switch uses low voltage power supply (like those small
"wall wart" powered switches), then just adding a relay to one of
the power wires is preaty easy and safe. If you know how to safely
build mains powered things (and you have necessary qualifications
to do that) then circuit for controlling mains power to device is
another option.
|
If you want to make a windows computer turn off it's *own* ethernet
interface on and off it's easy with the "netsh" command which can be
scripted. No hardware required.
Do a netsh /? for help..
For a *inx box do a similar thing with the ifconfig command.
--
a d y k e s @ p a n i x . c o m
Don't blame me. I voted for Gore. |
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Rich Noonan
Guest
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| Posted:
Fri Sep 16, 2005 4:20 pm Post subject:
Re: Ethernet breaker |
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Al Dykes wrote:
| Quote: | I asked before, You aren't doing anything safety-critical or covered
by OSHA, are you?
|
Yes, it's safety critical and when the equipment is installed in the US
I'm sure it's covered by OSHA. But it's covered by much more stringent
industry regs which is what I'm helping respond to.
As an example, OSHA defines high-voltage as >50V. When fully
operational, areas of our equipment have >3KV running through. It can
arc almost 3 inches and you can be injured just pointing in the wrong
direction. OSHA regs, if any relevant ones exist, would not adequately
cover this.
So, that's why when a tech has defeated interlocks on the safety doors
to troubleshoot a problem in a high-voltage area it's critical that
they be solely in control of the machine. With that much danger at
play you might think they would just go through the trouble of
unplugging the ethernet as needed, but this can be challenging both
physically and procedurally. A blend of automation, direct human
interface, and careful procedure is the standard solution.
-Rich |
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James Knott
Guest
|
| Posted:
Fri Sep 16, 2005 9:45 pm Post subject:
Re: Ethernet breaker |
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|
Rich Noonan wrote:
| Quote: | Thanks all for the input. For those concerned with my electrical
skills, I assure you I have almost none! I'm a software/systems eng.
at a fairly large company with access to top notch EE and ME folks.
However, like many these days our management is all about the buy and
very down on the build solutions. However, if we do go the build
direction you've given me some great bits of data to start the ball
rolling.
|
Given the situation you described in another note, particularly the high
voltage and safety issues, you'd best convince your boss to hire a
qualified electrical engineer. This is not a job for someone with no
electrical skills. |
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Robert Redelmeier
Guest
|
| Posted:
Fri Sep 16, 2005 10:56 pm Post subject:
Re: Ethernet breaker |
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|
Rich Noonan <rnoonan@gmail.com> wrote:
| Quote: | Yes, it's safety critical and when the equipment is installed
in the US I'm sure it's covered by OSHA. But it's covered
by much more stringent industry regs which is what I'm
helping respond to.
When fully operational, areas of our equipment have >3KV
running through. It can arc almost 3 inches and you can be
injured just pointing in the wrong direction. OSHA regs,
if any relevant ones exist, would not adequately cover this.
|
Ah, much better. When looking at critical systems, it's
important to specify the preferred failure modes. Which is
worse: something not working when it's supposed to? or
something working when it's not?
Most of the posters have assumed you want a reliable network
and of course that doesn't include trash like wall-warts.
But I get the impression network reliability _isn't_ critical
(for once), but the disconnect _is_!
This is a LOTO (lock-out, tag-out) situation. A strapped down
(security Torx-head) wall-wart on a lockable breaker is OK.
But for more reliability (uptime) and less bypassibility,
I'd simply put jack and patchcord inside a lockable box.
When the tech needs isolation, he follows the written procedure
including a signoff step to open box, pull RJ45, leave air gap,
and lock box with LOTO hasp.
You will need to make sure the switch (or any live network port)
and the machines ethernet are not accessible. Otherwise, the
yahoos will run a cable when the tech is on break.
| Quote: | So, that's why when a tech has defeated interlocks on the
|
This doesn't sound good. Defeat nothing. Disarm with signoff.
Sometimes double.
-- Robert |
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Rich Noonan
Guest
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| Posted:
Sat Sep 17, 2005 1:18 am Post subject:
Re: Ethernet breaker |
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|
Robert Redelmeier wrote:
| Quote: | When looking at critical systems, it's
important to specify the preferred failure modes. Which is
worse: something not working when it's supposed to? or
something working when it's not?
|
Right. I'm often amazed how much of the former is tolerated in a
multi-million dollar machine while absolutely zero of the later can be
accepted.
| Quote: | This is a LOTO (lock-out, tag-out) situation.
|
You speak our language. Seeking a physical LOTO similiar to a
padlocked box.
| Quote: | A strapped down
(security Torx-head) wall-wart on a lockable breaker is OK.
But for more reliability (uptime) and less bypassibility,
I'd simply put jack and patchcord inside a lockable box.
|
No question, this would be the best approach and we're looking at how
it could be accomplished, but unfortunately physical constraints are
numerous. Let's just say the ethernet switch and PCs are in an
unfortunate location relative to the rest of the equipment. This is
why the design proposal (and this is very preliminary stuff at the
moment) gaining traction is a multi-position switch in a lock box, the
switch controling "breakers" on the ethernet lines.
| Quote: | So, that's why when a tech has defeated interlocks on the
This doesn't sound good. Defeat nothing. Disarm with signoff.
Sometimes double.
|
Yes, that's correct. My ill use of language b/c I don't deal directly
with that stuff. I find the tool owner and have him check state before
I touch it!
-Rich |
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