Simple problem-ladder diagram

Hello to all,

I have one problem and hope you'll be able to help.

I want to write simple ladder diagram program. I want to programm the following logic:

There is one push button PB1 as input and two outputs. When user presses PB1 outout 1 will be active. Next time when PB1 is pressed, output 1 will be turned off and output2 will be active. Again, new press of PB1 will turn off output 2 and turn on output 1.

What would be the easiest way to do this?

Can you give me any advice?

Thanks

Advice, use the search feature on this site and look for thread topics on Flip-Flop, Toggle, etc. You will find plenty of help!

Attempting the task first, is a good idea.
SEARCHING is even better. Especially when the answer is on the first page here.

Thanks for help.

I'll first use search in the future.

Hello,
I have one more question.
Why there is need for 1sec timer in Terry's example. I tried without timer and it's working OK...

I'm trying to solve this on my own.
This is what I'm trying to realize in ladder:
Let's say that output 1 is named TARGET_BIT.
Previous value of TARGET_BIT is named T_B_prev.
Equation is the following:
TARGET_BIT = PB*NOT(T_B_prev)+NOT(PB)*T_B_PREV, where * means AND function and + means OR function.
In form of table:
PB|T_B_prev|TARGET_BIT
0 0 0
0 1 1
1 0 1
1 1 0
Problem is as you know how to set up T_B_prev. At the end, TARGET_BIT becomes T_B_prev, but I don't know
how to assign that.
So one network will be as follows:

         PB    T_B_prev      TARGET_BIT

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

 |                        |

 |                        |

 |     T_B_prev     PB    |

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

      

Now, how to perform transfer of TARGET_BIT to T_B_prev?
If I just add second network something like this:
TARGET_BIT T_B_prev
|----| |---------( )
since program is executed in cycles, this will not solve the problem.

Basically, in the begining I was trying to solve this problem with above's equation, but now, I'm not really sure this is the right way.
How to think in terms of cyclic execution, are there any tips and tricks?
Thanks

Your circuit is performing exactly like your truth table. As you said, it is simply occuring every scan instead of only at the instant the the pushbutton is pressed.

Basically you want some method that will cause the first two lines of your truth table to execute on the first button press and the second two lines to execute on the next button press. Another way of saying this is you only want to have the PB condition in your circuit true for a single program scan after the button is pressed. The condition will then be false for all other scans until the physical button is released and pressed again.

I'm being purposely vague. Let me know if you need more hints.

Keith

Yes Keith, that is what I need. I have found solution by searching the forum. However I'm trying to make ladder that will contain my network to implement the equation.
This is what I manage to do, it seems to work, but I'm interested if there is more elegant solution:

PB aux(positive edge) enable_PB

 

|-------| |-----(P)-----------------(Set)

 

 

 

enable_PB Qp Qn

 

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

 

| |

 

| enable_PB Qp | 

 

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

 

 

 

PB enable_PB

 

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

 

 

 

Qn Qp

 

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

 

Thanks

Eureka!

Which is a little town NE of Peoria where Ronald Reagan went to college.

Did you read the whole thread that rdrast pointed to or just the first post.


I entered a solution at post 37.

To be honest no, I didn't read the whole thread.
I've read only first 3-4 postos, ut I 'm glad I manged to do it myself.
Thank you all for help.