Time base issue after upgrade?

Hi Folks,

I'm having some issues with a program I converted from a ML1000 to a ML1200.
Originally I had a ML1000 running the program, but I needed to expand the outputs and upgraded the PLC to a ML1200. I downloaded the program with updated processor information and it works fine, but there is a status light that is supposed to flash. The program is using the S2:4/5 for a time base to flash the light. As far as I can tell it's flashing so fast it looks like it's on all the time.

Has anyone dealt with something like this? I snooped around in the S2 table but didn't see a parameter to change.

Thanks in advance for any help.

Well I figured it out. I've never played with any of the S2:4 free running clock stuff before, but it cycles based on a range, i.e. S2:4/0 is the fastest cycle, and S2:4/15 is the slowest.

S2:4 there is just what it says. A free running clock. Every processor 'Tick', 1 is added to S2:4. When it is eventually all 1's, it rolls back over to zero. That means, .00 is the fastest tick, .01 is half that speed, .02 is half of .01 and so on.

To answer your opening question...

duesxmechanicus; said:

...I'm having some issues with a program I converted from a ML1000 to a ML1200.
Originally I had a ML1000 running the program, but I needed to expand the outputs and upgraded the PLC to a ML1200. I downloaded the program with updated processor information and it works fine, but there is a status light that is supposed to flash. The program is using the S2:4/5 for a time base to flash the light. As far as I can tell it's flashing so fast it looks like it's on all the time...

Click to expand...

Q: Upon change in processor, why was there an apparent change in the duty cycle rate of the S:4/5 clock bit being used for a flashing indicator light?...

A: The resolution of the Free Running Clock in the SLC and MicroLogix 1000 is 10ms (millisecond) or 0.01s (second).

Whereas...

The resolution of the Free Running Clock in the MicroLogix 1100/1200/1400/1500 is 100us (microsecond) or 0.0001s (second).

17481 - S:4 Free Running Clock Comparison
Access Level: TechConnect

Because the MicroLogix 1200 Free Running Clock resolution is much finer than the MicroLogix 1000, the duty cycle rate for the same S4 clock bit will increase considerably.

To use the example in the technote, but with your duty cycle clock bit - S4:5...

(Edits/additions in Bold)

If bit S:4/5 is monitored in an SLC (or MicroLogix 1000) then that bit will be on for 0.32 seconds (320 milliseconds) and then off for 0.32 seconds (320 milliseconds) for a total cycle time of 0.64 seconds (640 milliseconds). If bit S:4/5 is monitored in a MicroLogix 1100/MicroLogix 1200/MicroLogix 1400/MicroLogix 1500 then that bit will be on for 0.0032 seconds (32 microseconds) and then off for 0.0032 seconds (32 microseconds) for a total cycle time of 0.0064 seconds (64 microseconds).

A new duty cycle rate of 64us, I'm sure, would not be suitable for a "flashing" indicator light. At this rate, yes, the light would appear to be ON steady. The output on a MicroLogix 1200 would not be rated for this duty cycle rate. Typical On/Off response times are 10ms.

The nearest direct equivalent S4 duty cycle clock bit in the MicroLogix 1200, to the S:4/5 640ms duty cycle (On/Off @ 320ms) clock bit in the MicroLogix 1000, would be the either the slightly faster S:4/11 @ 410ms duty cycle (On/Off @ 205ms), or slightly slower S:4/12 820ms duty cycle (On/Off @ 410ms).

Regards,
George

Geospark said:

Q: Upon change in processor, why was there an apparent change in the duty cycle rate of the S:4/5 clock bit being used for a flashing indicator light?...

A: The resolution of the Free Running Clock in the SLC and MicroLogix 1000 is 10ms (millisecond) or 0.01s (second).

Whereas...

The resolution of the Free Running Clock in the MicroLogix 1100/1200/1400/1500 is 100us (microsecond) or 0.0001s (second).

17481 - S:4 Free Running Clock Comparison
Access Level: TechConnect

Because the MicroLogix 1200 Free Running Clock resolution is much finer than the MicroLogix 1000, the duty cycle rate for the same S4 clock bit will increase considerably.

To use the example in the technote, but with your duty cycle clock bit - S4:5...

(Edits/additions in Bold)

If bit S:4/5 is monitored in an SLC (or MicroLogix 1000) then that bit will be on for 0.32 seconds (320 milliseconds) and then off for 0.32 seconds (320 milliseconds) for a total cycle time of 0.64 seconds (640 milliseconds). If bit S:4/5 is monitored in a MicroLogix 1100/MicroLogix 1200/MicroLogix 1400/MicroLogix 1500 then that bit will be on for 0.0032 seconds (32 microseconds) and then off for 0.0032 seconds (32 microseconds) for a total cycle time of 0.0064 seconds (64 microseconds).

A new duty cycle rate of 64us, I'm sure, would not be suitable for a "flashing" indicator light. At this rate, yes, the light would appear to be ON steady. The output on a MicroLogix 1200 would not be rated for this duty cycle rate. Typical On/Off response times are 10ms.

The nearest direct equivalent S4 duty cycle clock bit in the MicroLogix 1200, to the S:4/5 640ms duty cycle (On/Off @ 320ms) clock bit in the MicroLogix 1000, would be the either the slightly faster S:4/11 @ 410ms duty cycle (On/Off @ 205ms), or slightly slower S:4/12 820ms duty cycle (On/Off @ 410ms).

Regards,
George

Click to expand...

I've got it at S4:11, but will probably lower it down to S4:12 or s4:13 on the next revision to lower the duty cycle.

...Thanks in advance for any help.

Click to expand...

You are retrospectively welcome oh verbally economical one.

Geospark said:

You are retrospectively welcome oh verbally economical one.

Click to expand...