I input 2 outputs

Hi all. I am new to programming. I've done some so far without issues. Now, I have to write one for a design using 1 pushbutton to stop and start a vfd. We have 1 input and 2 outputs. The input is the button, and the outputs are stop AMD start to the vfd. I am using an Allen Bradley 525. I know the stop input on the vfd needs to have +24vdc on it before it will start using the start input on vfd. Could anyone help me with this? I am pretty stuck. Thank you.

Welcome to the forum.


Sounds like you are looking for a flip flop.


Search the forum for that.


Good luck!

Thanks. When I click the search bar, it goes away. I tried several times. *

Be aware, also, the 525 can be wired and programmed to run and stop, forward, using only one of the outputs. If this is for a class, though, they may require you to use both outputs.

Esnow said:

Thanks. When I click the search bar, it goes away. I tried several times. *

Click to expand...

Try here

http://www.plctalk.net/qanda/search.php?searchid=10071956

Sounds like homework.
If that's the case, most people on this site will want you to show what you've done so far. in other words, we won't do the work for you but help you learn/figure it out for yourself.
What have you tried so far?

https://accautomation.ca/creating-a-flip-flop-circuit-in-the-plc/

The above link may help you out.
Regards,

If started, button rising edge trigger sets stop bit, resets start bit. If stopped, button rising edge trigger sets start bit, resets stop bit.
On first run I set stop bit and reset start bit. Start bit and stop bit are connected to my stop and start outputs.

Then I changed it...I used the button input to set a "button pressed " bit, if that bit is true, I unlatched vfd start input. Unlatched the stop input, and unlatched my button pressed bit. Then next rung, I did button pressed is true, then latch start input, latch stop input and unlatch button pressed bit. Now, i can get the 525 to start, for a second. Reaches 10 HZ ( my vfd parameter A410, reset frequency. Is 40 Hz.) Vfd stops AMD shows 0 hz on display but motor is creeping til I either stop with the button on drive, or it faults out due to overvurrent. Also, after I power down and back up the vfd or after stopping using button on drive, it doesnt start again until after I redownload my project to the controller. Could that be due to rungs being out of order?

I'm not looking for anyone to do my work for me. Trust me, I've come here for help as an absolute last resort.

Question, do you want the vfd to run while the button is pressed? Or do you want first button press to start, second button press to stop?

Also, check the settings on the VFD. It can be configured a variety of ways.

Dhitzfelder said:

Question, do you want the vfd to run while the button is pressed? Or do you want first button press to start, second button press to stop?

Click to expand...

1st press starts, 2nd stops. 1 input does both. Separate output for start to vfd AMD stop to vfd. The weird thing where it was faulting has been resolved. The mechanical guru has the chain too tight. I disconnected the motor and it goes to full Hz. My issue now is I cant get it to stop. Picture link below. Thanks to all.

https://ibb.co/JnQpdbr

First off, thank you for showing the work.
So, the first thing you need to do is get a copy of the manual and review the I/O wiring examples and how the unit needs to be configured. The drive needs to be configured to use the I/O as inputs for controlling it. Once you understand how the I/O inputs work and how you would wire them if you were just using switches, then you can apply the PLC outputs to the equation.
A hint, if all you need to do is start/stop the drive without direction change, you can do it with only one input to the drive. You can still make two work (sticking to the “1 input, 2 output” requirement), but it will be redundant.
Another hint, once you figure out how to wire it, I’d be looking at a “flip/flop” routine in your ladder logic.
Good luck and let me know what you come up with (and any further questions).

Here is the user manual

https://literature.rockwellautomation.com/idc/groups/literature/documents/um/520-um001_-en-e.pdf

What is the brand and model of PLC you are using?

In your ladder logic, the third rung will never activate since the "button pressed" bit is unlatched in the second rung. You will want to add an additional NC contact, such that rung 2 only activates if "button pressed" is on, AND VFD start is on.

There is an additional problem. If you get the above to work, even a rapid momentary press of the button will be seen in multiple sequential scans of the program, and it will cycle between "on" and "off" states until the button is released. Many PLC programs have the option of using an edge trigger (or ONS-oneshot bit in Allen Bradley) such that it will only scan on the rising edge of the input button input.