Ladder Diagram Help

Hello, all! I'm just getting started with PLCs and am attempting to design a ladder diagram with the following stipulations:

Input: 1 Push-button
Outputs: 2 Bulbs

When the push-button is pressed, the first bulb turns on. If the push-button is pressed again within 3 seconds of the first press, the first bulb turns off and the second bulb turns on. The second bulb will turn off after the next press of the push-button (regardless of time), and both bulbs will be off. If the push-button is pressed 3 seconds after the first press, the first bulb turns off, and both bulbs will be off.

I have attempted using both counting and timing functions but have been unsuccessful in finding the correct design. I am designing in a program called "Connected Components Workbench." Any help would be greatly appreciated! Thank you!

Folks won’t write your homework for you but all will help you through it. Post screenshots of what you have so far.

I understand. However, although this is for a collegiate class, it is not homework. Rather, it is a challenge put forth by my professor for those who have completed all previous labs. I am unable to provide screenshots as I do not have the school's program downloaded to my computer. I am simply looking for logic help as I contemplate the solution to the challenge. My thought process thus far is as follows:

The push-button must actuate either a timer or counter that will toggle the energization of bulbs. If the push-button is pressed within a designated time it will perform a different operation than if it is pressed after such designated time.

I apologize if my first question seemed like I was looking for an easy solution to my homework. Instead, I am seeking a solution to this problem to further my understanding of PLC logic. I appreciate any help offered! Thank you!

The way you describe it is correct, and you're on the right track. I don't think you'll need a counter (what are you counting?) but you'll certainly need the timer.

Think of it this way. When you receive a button press, there are three different scenarios that could be in play:
1. Both lights off
2. First light on
3. Second light on

Then, within the second scenario, you have two possible sub-scenario's:
a. First light came on less than 3 seconds ago
b. First light came on more than (or exactly) three seconds ago

For each of those scenario's and sub-scenario's, you have to take a separate action.

Sketch something out (even just with pen and paper) and upload your efforts, people will gladly keep helping you along if you're clearly making the effort!

ecarlstrom said:

I understand. However, although this is for a collegiate class, it is not homework. Rather, it is a challenge put forth by my professor for those who have completed all previous labs. I am unable to provide screenshots as I do not have the school's program downloaded to my computer. I am simply looking for logic help as I contemplate the solution to the challenge. My thought process thus far is as follows:

The push-button must actuate either a timer or counter that will toggle the energization of bulbs. If the push-button is pressed within a designated time it will perform a different operation than if it is pressed after such designated time.

I apologize if my first question seemed like I was looking for an easy solution to my homework. Instead, I am seeking a solution to this problem to further my understanding of PLC logic. I appreciate any help offered! Thank you!

Click to expand...

To assist you in acquiring "CCW", to have it on your computer, follow and click on this video that I found with Google.
Link:
https://www.youtube.com/watch?v=DYh-xDCaSjw

There may be easier and better ways to do this, but, here's another hint, you "CAN" use a counter to determine the number of pushes on the switch. Then, on a new rung, use a count of "1" to determine the logic needed when in the "1" push condition. On another new rung, use the count of "2" to reset the counter and all the logic. Use the reply by ASF and this info.
This may be a bit confusing and may be wrong altogether so use this info if it helps.

since you have written down the requirements, may I suggest that you do a flowchart.

if that doesn't work, do this.
break down your assignment into segments and analyze each part.
then try to combine the parts.

regards,
james

Earlstrom: I would like to suggest that you download the engigeering environment for the Codesys soft PLC development system, which supports a number of architectures, including Windows. It is relatively easy to create ladder diagrams in Codesys and run them in the Windows environment, which in demo mode will run for about an hour. You can restart the PLC when the demo mode expires and run the application again, unlimitedly. If you find this useful and need the licensed version version you can get their USB dongle from their store, or you can buy a Raspberry PI and buy the license for the Raspberry Pi which is around US$ 100.

The Windows version is more expensive (close to US$ 800, I think).

This system also supports Ethernet master protocols such as EtherNet/IP, EtherCAT and Profinet, so if you need to get actual IO or actuate stuff, you can buy used remote IO from Ebay and make cool stuff with relatively low investment.


Good luck.