When PLC programming

So what does the one that comes off the bottom and goes back the other way activate/do sorry if I am having a hard time understanding that one. Oh wait just read it again why would them need to be in parallel what would that do in that line.

being in parallel just allows either of those instructions to help turn on the output, if the instruction to the right of that branch is also on.

So, either (or both) of the instructions on the branch must be on, and that third instruction must be on to turn on the output.
 
Greg, please do yourself a favor and stop trying to program and buy or borrow some cheap push buttons and an ice cube style relay. Preferably low voltage DC so you won’t kill yourself. Seriously!

Wire these up to work like your drawing. I believe this would greatly increase your understanding of how relay logic works.

Too many beginners put the cart before the horse when it comes to programming.
 
Simple statement here. Hope it gives you an, "ah-ha" moment one day.

Ladder logic executes from left to right, then top to bottom, completing each branch in this manner.
 
Simple statement here. Hope it gives you an, "ah-ha" moment one day.

Ladder logic executes from left to right, then top to bottom, completing each branch in this manner.


Careful, this is true for AB and others but not true for all.

Modicon and SCADAPack for example scan top to bottom, left to right one network at a time. (saw tooth manner)
 
Greg, please do yourself a favor and stop trying to program and buy or borrow some cheap push buttons and an ice cube style relay. Preferably low voltage DC so you won’t kill yourself. Seriously!

Wire these up to work like your drawing. I believe this would greatly increase your understanding of how relay logic works.

Too many beginners put the cart before the horse when it comes to programming.

I disagree 100%, the best way to learn is getting thrown into the fire. I also learned PLC programming before even knowing that relays existed. Keep studying hard Mr. Greg!
 
I disagree 100%, the best way to learn is getting thrown into the fire. I also learned PLC programming before even knowing that relays existed. Keep studying hard Mr. Greg!

I don’t totally disagree with you about getting thrown into the fire. My point is that understanding true hardwired relay logic/wiring should be done before doing programming.

Understanding that a NC push button is not the same as a NC PLC contact and why how a standard 3-wire control circuit with seal in contacts relates to PLC logic, etc.

All of this will lead to safer (failsafe) programming.
 
We have all the stuff PLC's switches sensors push buttons and more I have been reading about programming. But when I get confused on some of the stuff I read and cee in the papers I like to ask about them to understand a bit better on what I am reading about programming I can't ask I book to better explain an example. So I come to people who can so I will understand it better.
 
Wire these up to work like your drawing. I believe this would greatly increase your understanding of how relay logic works.
++

I remember when I first encountered PLC coming from PC programming and DCS world how difficult it is to "think" like ladder logic. For some electricians though, it all seems easy because they have the intuitive understanding for relay logic.

One of the interview I went to they left a bunch of relay, light, and switch on a table and asked me to wire up a flip-flop or latching circuit to test if I get it.
 
We have all the stuff PLC's switches sensors push buttons and more I have been reading about programming. But when I get confused on some of the stuff I read and cee in the papers I like to ask about them to understand a bit better on what I am reading about programming I can't ask I book to better explain an example. So I come to people who can so I will understand it better.

Greg, I applaud you asking questions & wanting to learn. My point can be summed up in one word: Fundamentals.

You need to learn the fundamentals of how these devices work. Keep up the hard work.
 
I teach 3 day classes at our local community college. In the basic PLC class, I can usually tell who has taken the motor controls/relay logic classes. They catch on to ladder programming much quicker and do better with the PLC hardware circuits.
 
Greg,
Just a suggestion, get a minimum of two PB’s each with one set of N.O. & N.C. contacts and one 3-position maintained selector switch with contacts on each side.

Have fun.
 

Similar Topics

Hello colleagues, Some time ago I started my adventure with programming. With your help and the courses, things are starting to come together...
Replies
13
Views
593
Dear All, I need a sample PLC program to count the output pulse of a mass flow meter so that a specific amount of mass (for example 100gm)can be...
Replies
2
Views
82
Hi Please I have zeilo smart relay #SR2A201BD but I don't have it's programming cable. Can I use any general usb/rs232 converter? Or need...
Replies
2
Views
80
Hi, Does anyone have thoughts or know of, can point in the right direction any published materials with a plumbing centric point of you explaining...
Replies
1
Views
125
@ All: what is your best guess on a potential range in increase in efficiency in % (i.e. saved programming hours, greater output, etc.) when...
Replies
5
Views
291
Back
Top Bottom