I urgently need help for difu and difd!!!

Hey all, I'm still new to PLC and I considered myself a quick learner so I wanna shoot straight; can someone help me to explain "in a very simple" manner regarding both DIFU and DIFD.

All I know is that it complete one-complete cycle. What does that mean actually?

Is is when you press a push button (PB) in longer time, but the DIFU function only recognize it like "push-release" manner?

Please I do hope someone could explain it to me.

THANKS IN ADVANCE

50248210030SAM said:

Is is when you press a push button (PB) in longer time, but the DIFU function only recognize it like "push-release" manner?

Click to expand...

Yes, much like that, but likely much quicker than you could do by hand...

Often called a 'one-shot'. The bit will turn ON immediately, and remain ON until the program reaches this same rung again (1 scan later). At that point it will turn OFF, and remain OFF. It will not turn ON again until the rung with your DIFU/DIFD becomes FALSE, then TRUE again.

DIFU turns on for 1 scan when the preceding logic goes from false-to-true
DIFD turns on for 1 scan when the preceding logic goes from true-to-false



-Eric

Thanks for helping, say that I want to activate one gate that release....a piece of pizza base, so all I have to do is to create a button that activates a DIFU function with its own bit, then the DIFU bit will open the gate then close immediately like "open-and-close" manner?

I tried this but it doesn't work? Where did I do wrong?

What plc are you using? Can you upload your program?

I'm using CX-Programmer
links http://www.plctalk.net/qanda/attachment.php?attachmentid=21342&stc=1&d=1330772463

Can you print it on MSword? I cannot open your program, I do not have cx-programmer on this pc. Thanks

theripley said:

Can you print it on MSword? I cannot open your program, I do not have cx-programmer on this pc. Thanks

Click to expand...

print means....? Sorry I quite didn't get you

Your output in the program only turns on for one PLC scan, which you never see it, unless self hold or set [latch].

BTW, to use one shot in CS1G PLC, you can right click on the contact, 0.00 in your example and select "Differentiate Up" which will show an upward pointing arrow in the ladder. [downward pointing arrow for a differentiate down selection].

Differentiate up or down are used for[in you case] to finish up one cycle of your sequence and stop there, even your push button is continued to press. But you need to write the rest of the sequence.

Or, if you are interfacing the output 100.00 to another device that device may not be catching the one scan of your PLC output time, so you have to stretch it, or hold it until that device give an acknowledgement.

Regards
_______

Thanks to everyone and chavak for helping. Yeah I had finally solved the case, by adding timers to give the output quick open-and-release motion.

p.s. who would've wondered there would be another one great helper from my own country, chavak.