Two Questions: PLC and Control Panel

[tec.batista]

Hi there,

I have two questions. Well, is there how to monitor my output in my PLC without a sensor?
For example, if I energize my VALVE (24VDC) throughout my PLC, is there a way to know if my solenoid
was energized? (Without a magnetic sensor).

Second:

I'm currently working in a project where I have to use a transformer from 380 VAC to 220VAC. What is
the best practice in this case, i. e., Have I to put my transformer in my control panel enclosure? Have I to energize
my transformer and after that put my 3 phases in my disconnect switch and my PE direct connect in my terminal
block and after in my main circuit breaker?

Any help will be very appreciated.

 

[NetNathan]

You use a current sensor on the coil...or get a limit switch assembly for the valve...or swap to valve with limit switches..

 

[willxfmr]

1) There are a lot of ways to know the valve was commanded to move, but you would need some sort of feedback device to know if the valve actually moved.

2) Depends on how big the transformer is. 100VA would likely get put in the cabinet. 30KVA... probably not. I don't know how things are done in Brazil, but in the USA you would have over current protection on both the primary and secondary side of the transformer, and the neutral would be bonded to the earth ground on the secondary side. it's possible that the over current device could also be used as the disconnecting means, but you would have to make that decision based on the local situation.

Bubba.

 

[EJ92]

You can use valves that have End Switch, Contacts

 

[tec.batista]

Hi there,

thanks for answers. One more question: Is there a way to monitor my input. For example, if I have a
magnetic sensor atached on my cylinder and that sensor isn't work, I want to know so I can
pop up a message in HMI for maintenance porpose.

 

[LoganB]

Usually you would use a timer paired with the output that is activating the cylinder. You wouldn't know specifically if the sensor is broken, or if the cylinder didn't move for some other reason, but if you activate the output that is moving the cylinder and your magnetic sensor doesn't change state within however many seconds, you can flag a cylinder motion fault and stop production.

At that time, your maintenance people will diagnose the problem.

 

[tec.batista]

Hi there,

thanks for answser. But in this case I'm primarily concerned with my input. I want to know if
there is a broken sensor or any other input isn't working properly. In my PLC programming, things
only work if all necessary inputs are working, but if one sensor is broken I wanna know what specific
sensor isn't working and pop up a message for the maintenance guy. I will use a s7 1200.
Sorry if you already answered me properly and I didn't get it yet. Thanks.

 

[cardosocea]

Hi there,

thanks for answers. One more question: Is there a way to monitor my input. For example, if I have a
magnetic sensor atached on my cylinder and that sensor isn't work, I want to know so I can
pop up a message in HMI for maintenance porpose.

You can probably wire the same sensor on two inputs...
In most automated systems, functions only work if the inputs are correct, you are not unique in this case.
One way to overcome this is to trigger a message to the operator telling him which signal is missing to achieve a certain command... or display a screen telling him the state and sensors needed for a function to be enabled.
Another way of doing this may be by connecting your digital sensor in an analog input and monitor the value. I did this in the past and it worked ok to monitor the line on a digital sensor.

 

[rdrast]

Use sensors with a live zero; like all 4-20mA or 1-5V sensors/switches.

 

[godcixelsyd]

I don't know a lot about it, but remember seeing IO-Link at a trade show. From my understanding it's supposed to be able to get more information from the sensor, including a "health check".

 

[tec.batista]

Thanks for answers. But I want to monitor my input using only software resources. I thought , for example, if my plc program got stuck in a network(s7-1200) I could in some way scaning my program and see where my program is stuck and by deduction I could find out my bad sensor or at least point out one direction for find out my bad sensor(s).

For make myself a bit more clear: I want to do this automacally without me looking in any PLC programming enviroment screen for find out where my program is stuck and what sensor is a bad sensor. I want to pop up a message in a HMI for maintenance porpose. Is there a way to do this using only software resources?

Is there a way to do this using only software resources?

 

[EJ92]

Can the situation be timed? (for the input) if so... time it out. if no response from the input...((ALARM))

 

[tec.batista]

The problem is: I have 42 digital sensors and the client wants to know precisely if any of these sensors are working properly. if not, the system has to pop up a message in HMI...Personally I think that's not possible only by software resources. Let me see if I understood what you said. Are you saying if is it possible to timing the whole process or if is it possible to timing while the program is awaiting for response of one generic sensor? Sorry, my english is not that good. Maybe I was bit confused....

 

[EJ92]

I'm not sure what the purpose is for your sensors.. It all depends on that. If its a emergency stop sensor. they have to be tested manually. but if its a sensor that has too respond too an Output. Then maybe you can time out the situation,(with reasonable timing) if the time has expired, with no response from the sensor. then you can fire an Alarm for that sensor. it might not work for all situations.