Powering an output on and off

aaron4132

Member
A
Join Date
Nov 2014
Location
Nebraska
Posts
3
How would you program 1 output to be powered on and off like a cell phone using only one input (a NO pushbutton)
Does anybody have the relay logic for this?
 
aaron4132 said:
How would you program 1 output to be powered on and off like a cell phone using only one input (a NO pushbutton)
Does anybody have the relay logic for this?
Click to expand...

Actually, most cell-phones require you to press and hold the "power" button for several seconds to turn the phone off, and a short press to turn it on.

This isn't necessarily your standard "flip-flop" arrangement.

Is that what you want aaron4132 ?
 
No. I do not want to to work like a standard cell phone.
After one push on the push button I want the output to turn on and after a second push on the push button I want the push button to turn off.
If this is a standard flip flop I guess I am a little confused by it. I am new to Plc programming. If this is a flip flop circuit which do you think is the simplest to understand
 
aaron4132 said:
That makes no sense to me
Click to expand...

Aaron,
This sounds like a homework assignment so people here will not just give you the answer. We will only help you to discover the answer on your own.

Firstly you know your input and output list. Now try and write some pseudocode to explain what exactly each output should do when the input is in changed. To help you I have given an example below for a switch (not a push button):

Code: 
If input on then turn on output
Else turn off output.

Once you have tried the pseudocode then we will help you to correct it, then once it is correct then you can start to "translate" it into PLC code.

Regards
Ian
 
What it means is if you push the button and the light is on then turn it off conversely if it is off turn it on.
Google, "flip flop circut diagram" see if it helps.
 
Does anybody have the relay logic for this?
Click to expand...
Yes, but do you really want actual relay logic, or do you want Programmable Logic Controller ladder logic? (Ladder logic simulates relay logic, but there are many differences).
 
Output := OneShot(Input) XOR Output

To convert this into RLL you need:

  1. A rung that creates a bit that is true for one scan only when the input button in pushed, this is called a one shot.
  2. A rung that does an XOR (exclusive or) of the one shot bit and the output.





The truth table for an exclusive OR is

   +-----+-----+-------+

   |  A  |  B  |A XOR B|

   +-----+-----+-------+

   |  0  |  0  |  0    |

   |  1  |  0  |  1    |

   |  0  |  1  |  1    | 

   |  1  |  1  |  0    |

   +-----+-----+-------+

 
Last edited:

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