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Old December 2nd, 2017, 11:37 AM   #1
Aabeck
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OT: Prohibiting Use Of The Programmer Power Outlet

During a call to a customers they mentioned a problem with operators plugging a fan or vacuum into the unused outlet of a duplex programmer/network switch outlet, shutting the PLC/HMI comm's down when they trip the breaker.

They wanted to be able to use the port for a laptop, but turned off (not by a switch) the operators would see and try to turn on.

What I came up with was I split the duplex outlet, ran 2 wires out the back of the DIN mount outlet box and ran them to terminals 3 & 6 of an octal outlet, then took an old timer and ground off the locater pin and put it in normally.

When they want o use the outlet they just pull the timer, turn it two pins counterclockwise and plug it back in - now the outlet is powered through the NC contact from 8 to 5.
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Old December 2nd, 2017, 11:48 AM   #2
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Got to love the Operators!! I am sure you have the UL required label on the outlet that says "For Programming Computer Use Only" on it too.

I haven't had a issue with that yet but was thinking of using a small relay activated by an extra output from the PLC. Then I could force it on when I get connected to the PLC or use the HMI with a Password.
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Old December 2nd, 2017, 12:04 PM   #3
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Is there any way that you could lock it?? I have seen one somewhere that had a key lock.

Found it!! Mencom makes a locking bar for their panel interface connectors.

Last edited by mendonsy; December 2nd, 2017 at 12:12 PM. Reason: Found it
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Old December 2nd, 2017, 12:26 PM   #4
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We recently finished a project at a client site. One of the last things was installing power for a compressor. So we got the work permits arranged for, power was shut down, lock and key on the main power switch to the machines, all good to go and we merrily went ahead installing and connecting.

While we where doing our work, confident that all electrical power had been shut off, we noticed a power socket on one side of a control cabinet on one of the machines we had previously installed. Since it was on our machines, we thought we should know what they were and how they were wired. We couldn't quite figure out though. The schematics in said cabinet didn't help either. So we took out a meter to find out. 230VAC on the socket. Turns out a local electrician was hired to add some power sockets in the factory. Completely bypassed all existing power lines and main switches, so we had a factory properly shutdown for electrical power according to all regulations and a live 230VAC socket on the main cabinet of one of the machines.

Some of the lessons learned on this project: never trust a socket to be without power, check and double check. Don't trust client to stick to their own strict rules. If you do not provide for a socket for ... (insert device at will: radio, vacuum cleaner, phone charger, fridge), the client will install their own whereever they like.
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Old December 2nd, 2017, 12:32 PM   #5
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Quote:
Originally Posted by Bullzi View Post

I haven't had a issue with that yet but was thinking of using a small relay activated by an extra output from the PLC. Then I could force it on when I get connected to the PLC or use the HMI with a Password.
I've done this at a previous job with a timer on it (I believe I set it at 2 hours) in just in case someone forgot to turn it back off.
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Old December 2nd, 2017, 01:05 PM   #6
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Make sure you have usb chargers in the control room, otherwise someone is going to plug their phone into the server to charge.
the socket should have its own breaker so it doesn't shut down the PLC.
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Old December 2nd, 2017, 01:20 PM   #7
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Bullzi,
My first thought was of a controlled relay, but decided not to as it would go off if the PLC was put in program mode or faulted. The outlet is labelled properly, with another label saying "Computer Only - No Fans Or Vacuums"

Toine,
I would say over 30% of the panels I open have an externally powered outlet or device (Like a 240V VFD wired to a 480V machine, cabinet air conditioner, etc.) that are clearly marked about 50% of the time. I also found a 480 pump control panel with disconnect that had a separate 480 (unmarked) feed - the panel was over capacity and they needed to add 2 more pumps.
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Old December 2nd, 2017, 01:52 PM   #8
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Convert the receptacle to twist-lock, and you carry the short cable adapter from twist-lock to straight....

I worked at a plant where they went to all twist-lock to help prevent "missing" extension cords......after that we never "lost" one.
Twist lock sort of grows on you....only real advantage...the plug never gets "pulled" from the wall. No real cord to connector damage either, because you have to grip the plug to unplug.
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Old December 2nd, 2017, 03:03 PM   #9
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I isolate ours from everything with a 4 amp UL-489 circuit breaker and label the outlet as "computer use only".

So what if they trip the breaker by plugging something else in. They usually only do it once, and hey, I know where the circuit breaker is.

Heck, I'll just flip the circuit breaker off when I leave.
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Old December 2nd, 2017, 03:32 PM   #10
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Padees,

That was the main problem for this one - it had a 4 amp breaker, but the AC adapter for the network switch was plugged into the outlet too - one vacuum and no HMI comm's
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Old December 2nd, 2017, 03:59 PM   #11
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All our sockets on the line are UK style 3 pin plug, all sockets inside panel for laptop power are EU style 3 pin - engineer's carry an adapter.
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Old December 2nd, 2017, 06:10 PM   #12
padees
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Quote:
Originally Posted by Aabeck View Post
Padees,

That was the main problem for this one - it had a 4 amp breaker, but the AC adapter for the network switch was plugged into the outlet too - one vacuum and no HMI comm's
If this is a panel mount outlet inside the enclosure, why are they even allowed to get in there in the first place?

I know there is a lot of old stuff out there.

Another question is why the network switch has an AC adapter? Curious.

If I were using one of those, probably just hook it up to a Phoenix 2963860 single outlet with CB and another one with CB for computers or blowing the breaker with whatever they want to plug in and try.

Not much to over think here.
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Old December 2nd, 2017, 06:49 PM   #13
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The network switch was 5 volts, not the 9 to 32 volt models that can be connected to the PLC power supply 24VDC.

My question is why the switch is in the control panel with the PLC - I put them in with the HMI PC (which on this line happens to be the other end of the 15 meter line from the PLC control cabinet) and connected to the UPS power.

And, yes, the outlet is a DIN mounted outlet inside what should be a closed cabinet.
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Old December 3rd, 2017, 07:08 AM   #14
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To me, it sounds like an automation endeavor to resolve a personnel issue.
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Old December 3rd, 2017, 08:18 AM   #15
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It falls under the saying:

You have to make things idiot proof"

And then sit back and wonder at the quality of idiots working in shops today.
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