Clock pulse for Allenbradley

[techie_imtiaz]

i want to know the instruction for Clock pulse(On/Off for few seconds automatically) used in Allen Bradley, just as BLINK in Codesys and SM0.5 & SM0.4 in Siemens.

 

[OkiePC]

What particular Allen Bradley PLC are you using?

 

[sthompson]

i want to know the instruction for Clock pulse(On/Off for few seconds automatically) used in Allen Bradley, just as BLINK in Codesys and SM0.5 & SM0.4 in Siemens.

As OkiePC pointed out, it depends on which AB PLC you are talking about. They usually have a free running clock that you can use bits from. Have a look at the S or Status File information.

Stu.....

 

[TConnolly]

In the SLC500 and Micrologix line there is the free running clock mentioned previously located in word S:4. Each bit in word S:4 toggles at 2^n time base intervals where n is the bit number.

For a PLC/5 you can set up a free running timer with either a 1 second time base or a .01 second timebase. If that timer were T4:0 for example, bit T4:0.ACC/0 toggles at the time base, T4:0.ACC/1 toggles at 2 times the time base, T4:0.ACC/2 toggles at 4 times the time base, T4:0.ACC/3 toggles at 8 times the time base, etc. Make the preset of the free running timer 32767 and unconditionally unlatch bit 14 with an OTU T4:0.ACC/14, that way the timer will never time out and it will never need to be reset.


For ControlLogix there are several options. You can set up a free running timer. But a better way for periodic functions is to create a dedicated program in a periodic task to perform the function without a timer.

 

[Honga]

There's a thread from about a week ago which discusses this on the Logix and uLogix platform. You could probably search my recent posts.