Timer

Hi, would you check the attachment, its a output control by two TON timers. when start the program I want light be On then after 7sec light be of for 7sec and on again...Do you think it is good ladder logic? Also how Start instruction XIO can be sealed, If Start is a Momentary push button?
Thank you very much.

Your program in this topic:
http://www.plctalk.net/qanda/showthread.php?t=54827
Was close to working how you wanted it. Infact, I'm pretty sure all you have to do is change the TOF to TON and it will flash on/off once started.

Your program posted here, will work, but the start input must remain on at all times you want it to flash. Take the info about the .EN and .DN bits from your other topic and work the program to hold in the timer until the stop button is pressed.

You had a working seal on the start timer in your other program, but it was only sealed once the timer was Done (DN). You can work a seal on the timer in the same way using the Enabled (EN) bit.

Per Tharon's suggestions:

Why use 2 timers?

One timer, Timer.PRE = 14

Output controlled by LEQ, Timer.ACC, 7

I would ordinarily use :-

CMP Timer.ACC <= (Timer.PRE/2)

That way I only have to change one data-table value to control the on/off overall cycle time, but still maintain equal mark/space.

However, CMP is not available in SLC/MicroLogix.

No, but the LES, LEQ, GRT, GEQ, and LIM instructions are. They will work just fine doing it that way as well.

2 timers makes adjustment simpler if you only want to adjust one of them.

OkiePC said:

2 timers makes adjustment simpler if you only want to adjust one of them.

Click to expand...

agreed, and conversely, 2 timers makes adjustment more complex if you don't want to adjust just one of them, and will introduce 1 more scan time error if reset using the .DN bit on the timer Enable-In. I mostly use XIC Timer.DN RES Timer

But it's horses for courses, I'm easy whichever way.

Thank you for info.

I had to do this the other day and was cursing Logix 5K for not having a square wave generator like some of the others'....

Here's my quick and dirty method of doing it.