Ladder Logic

Since i am new to plcs i decided to do courses i now understand plc principles. My problem is to write aladder out of the exercise below.
---¬----][----¬---------------------()--
I:1/0 O:2/0
----][----
I:1/1
-----]/[--]/[-----------------------()--
I:1/0 I:1/1 O:2/0
The first rung the switches are parallel and the second there are in series. I donot know how to do it right but from your support i will learn

Controlling One Light from two Locations
Create, enter and test a program which will perform the common electrical function of controlling a light from two different locations. Clear your program and utilize toggle switch (I:1/00) and switch (I:1/01) to control Lamp (O:2/00)... (Hint: If both switches are On or if both switches are Off, then the Lamp should be On! This of course is just one approach to solving this problem)

Can anyone explain to me as simple as possible where i am getting it all wrong Thanks in advance

I:1.0/0 I:1.0/1              O:2.0/0

----| |-------| |--------------()

                     | 

I:1.0/0 I:1.0/1      |

----|/|-------|/|----|

How does that look?

pp

Hi Densam

A very common mistake in the early days of getting to grips with ladder logic is the idea of using the same output coil in two different locations. This appears to be what you have done here.

As the PLC scans the logic of your first network it will decide whether the coil should be on or off. It then immediately scans the second network and decides whether the coil (same coil, I assume) should be on or off. Effectively, it doesn't matter what the earlier decision was, it will always be overwritten by the later decision. At the end of the scan when the PLC then updates the physical output status, it takes the last calculated value which of course came from network two. This doesn't matter whether the two references to the coil are right next to each other (easy to spot and fix) or whether they are separated by 20K of other instructions (not so obvious). Duplicating an output can make sense once you appreciate all the consequences and implications, but for this example I don't think it's the right answer.

You can either try to combine the logic of the two networks in to one network, giving only one reference to the coil; or you can continue to resolve two different logic conditions, but use different outputs for each and then add a third line combining these two output states in to the final desired result that you want. For a simple application like this I would suggest the former is more appropriate.

As I type I see Paraffin Power has beaten me, but all he did was give the answer. That's not what you wanted, was it?

Ken

Ken - I bet it was.

PP - Oh no it wasn't ...

Here is how a typical light swtich would be wired in your home using three way switches. In a PLC with toggle switches on the inputs we want to emulate the same function. paraffin power shows the solution, hopefully this sketch will help you understand the function so that the next one will be a piece of cake for you.

Hie Guys

Ken M thats great i had done it first as Prafin had done but i was not sure about the question. Like both on or off light is on, what happens if there are opposite then the light should be off. Probably i am thinking too much and getting confused.I will in future use Alaric analogue, electrical i okay it only the relation

Hie guys

Since Paraffin, Ken M. and Alaric loosened my thinking i have been able to do some of my exercises, but i am stuck with the last one with the explanation bellow. I have clicked attach files then uploaded but i do not seem to see the ladder i have tried. I will try to paste see what happens. Ihave failed to paste. Who can tell me what to do its in paint.
How do i url an image?

In this exercise we want you to modify your program so that it adheres to this additional criteria:

• If the door is currently opening, pressing the Close Switch will immediately halt movement. Door movement will remain halted when the switch is released.
• If the door is currently closing, pressing the Open Switch will immediately halt movement. Door movement will remain halted when the switch is released.
• Once movement is halted by the either of the foregoing actions, the operating you can the open or close.
• The utilization of Binary or Integer Table bits to Flag specific conditions within your program would be appropriate. Also, the retentive OTL and OTU instructions may be utilized freely at your discretion.

Thanks everyone

May be igot it this time

Thanks

I was short sighted only focused on using binary bits and -(L)-, -(U)- never thought of one shot. I think this is because i am following exercises and do not put everthing into practice. I am using logixpro my other problem is to put my tried ladder on the forum for everybody to see how far i have gone, but i can't. I save my ladder on paint when i click replay post on additional options then attatch file it uploads but i do not see it on my typing window i do not know where it goes, why? Is there something i am doing wrong?. I like assistance when i have put in mine first so i can quickly see were i am going wrong.

Thanks
Densam