about off delay timer

[rickysaikat]

how can I use an off delay timer by the replacing on delay timer in the control circuit of star delta starter ? it will be helpful to me if I wil get the circuit diagram

 

[Gil47]

What PLC are you using

If Allen Bradley I would suggest you stick with a TON as they are easily understood where a TOF is often mis understood
I think I could count on my fingers the number of times I have used a TOF.

If you insist on using a TOF then read the help files on the TOF until you fully understand its operation

 

[MichaelG]

I think the OP was talking about a hardwired Star Delta Starter
Existing uses an ON delay Timer relay

Want's how to wire it with an OFF delay timer that he can get his hands on

 

[Ron Beaufort]

apology: I'm pretty sure that what follows is going to take us further away from the question that the original poster had in mind ... still – a stone has been turned that I think needs a little more clarification for safety reasons ...

Greetings Gil47 ...

let me start out by saying that I wholeheartedly agree with you on the TOF vs. TON points that you made ... but for the benefit of any "beginners" (and even some "beyond beginner" readers) who might pass this way in the future, I think we need to go just one step further with the TOF vs. TON discussion ...

the only point that I'd like to add is that it's entirely possible use EITHER of these two "timer" instructions in a program and have the system function PERFECTLY in normal day-to-day operation, BUT then later to experience something "bad" when the system goes through some type of unforeseen startup situation – simply because the "wrong" timer was applied ...

one specific situation that I've run across in the past is covered in the discussion for Figure A in my Email Quiz #121 - "Surprises at Go-To-Run" ... if anyone's interested, it's available free from a link near the bottom of the Sample Lessons page of my website ... (the answers to the quizzes are also available as separate free downloads) ...

the point I'd like to make is summed up this way in the quiz:

The basic idea is that PLC programs often work PERFECTLY in normal day-to-day operations – but then may give surprising (and embarrassing – or even DANGEROUS) results when the system is restarted after a shutdown; or experiences a “flicker” in the plant’s power supply; or is switched between the Program Mode and Run Mode; and so on.

so in closing, once again, I fully agree with the advice posted by Gil47:

read the help files on the TOF until you fully understand its operation

I just wanted to add that beyond just reading and understanding the help files, you should ALWAYS check the operation of any programs that you write (and/or work with) not only

(a) in their normal day-to-day operations – but also

(b) for how the systems will function in various situations when they first enter the Run mode ...

the differences between TOF and TON timers is a commonly overlooked area where one size definitely does NOT "fit all" ...

 

[widelto]

I agree with Gil47, I have written a lot of programs but never have used TOF. It seems confused to me.

 

[Tharon]

That "Go To Run" flicker Ron is describing happened to me last month. I wasn't really thinking, and had to start an event after someone let go of a pushbutton.

Then one day later I was downloading an updated program and put the processor into Program Mode and back into Run Mode. And suddenly the machine cycled as if someone pressed the button. Almost closed a press on a set of tools sitting inside of it. Luckily there were safeties in place like a Light Curtain which allowed me to quickly stop the machine from anywhere.

I had to change my Timer configuration to avoid it starting to time when the processor was put into run mode or started.