Help with few signals in PLC

[gogycro]

Hello everyone,

I'm new in PLC, so I need little help. Today I got EPLAN electric scheme of one pump station with digrams of DI, DO, AI and other, so I start to write a program for it, but I have 2 problem that I don't know how to solve.


1. I got one digital input, that is used for "Check the phase sequence voltage", there is no output for that, what shell I do with that ?

I was thinkig something like this:

.............I3.6..............M3.6
|-----------||------------------()-----|

I3.6 is bit for phase sequence voltage maybe they will use it for something else, so I can put a memory bit for it.




2. I have 2 digital input one for REMOTE CONTROL ON and one for REMOTE CONTROL OFF, I really don't know what to do with them?? People want to control pump station remotely, but I'don know how to do that, do I need to put digital input in every line of code or only in one ??

I just finnished faculty and they threw me to lions.
I'm using Simatic Step 7 and writing in ladder, so please can someone help me, with some tips and also give me a good tutorials or books to start with


Best regards,
Goran

[peterc101]

1. input for phase sequence is safety , pump should not run if sequence is not ok


2. local and remote control is used a lot in distand pump stations , but i am sure you have more inputs that 2 for control , post your full i/o list

[gogycro]

1. input for phase sequence is safety , pump should not run if sequence is not ok

I understand that, but there is no output for that, so I don't know what to do with it, save that bit in memery or draw it directly in Network for starting a pump ?

2. local and remote control is used a lot in distand pump stations , but i am sure you have more inputs that 2 for control , post your full i/o list

I know that is used a lot, but I'm new in this, so I don't know how to realize that in PLC. I can't just put 2 DI, logicly I need to connect it with something or connect it with all networks.

[sanruku]

Hi

-- DISCLAIMER --
No one will do your homework for you.
Try to solve your own problems.
Ask, read, ask more, then read more.
We are all contributing free time.
Finding good information is a skill on its own.
-- END DISCLAIMER --

We all have to start somewhere, so don't worry!

1. UNDERSTAND THE PROBLEM!
2. Try a solution.
3. If the solution doesn't work, then it's not a faulty solution, but rather your understanding of the problem! Go back to (1)

Don't EVER NEVER assume ANYTHING. Your assumptions may result in damaged equipment, or even lost human lives.
The more experienced you become, the more questions you will ask.
Ask the people that gave you the problem, most likely they understand the problem better than you do.
(i.e. "Are the two DI in (2) switches or push-buttons?" )
After that, discuss with them your proposal, maybe they find something wrong with it. Keep the good ideas and throw away the rest.
Try and document everything in PAPER!

Since you are working in LADDER (good for you!), it is a simple electrical circuit, with little or no advanced logic.
Try to formulate simple sentences like: "If REMOTE_CONTROL_ON is ON and REMOTE_CONTROL_OFF is ON, then FLAG_REMOTE_CONTROL is OFF".
Then you will find that your problem becomes easy to solve.
PLC's have plenty of memory for LADDER logic, so use it.

For manuals/info, go to Siemens Support. They dedicate HUGE resources for that. Exploit it!

glhf