RS 500 time base

I want to setup a timer for .5 sec in RS 500. I know using time base 1.0 it wont let me do .5. How would I set the timer up? What time base should I use etc? Processor is a 5/05

Can't you use 0.01 sec as the time base and 50 as the PRESET?

I am not sure. never had to set a timer that low.

Just click on the 1.0 in the timer box, a drop down menu shows where you can select 0.01, it also shows 0.001 even if the CPU being programmed doesn't support it, until you try to verify the file or line.

So I set it up with 0.01 sec as the time base and 50 as the PRESET???

That is correct. 50 in the preset multiplied by the .01 timebase = .5 seconds.

Yes that's correct.

thanks alot

FYI

As you are using an SLC 5/05...

The SLC family of controllers, and also the MicroLogix 1000, do not support the 0.001 timer resolution...

21425 - Valid Time Base settings for MicroLogix and SLC processors
Access Level: Everyone

Regards
George

Right; the 1 millisecond timebase was first introduced in the MicroLogix 1500, and then the 1100/1200/1400 got it. That technote is old enough to pre-date the MicroLogix 1100.

In ControlLogix and CompactLogix, the only timebase available is 1 millisecond.

This is the reason all TIMER instructions are flagged with conversion "errors" when you convert a PLC/SLC program, so you'll check to see if the program is using the .ACC or .PRE values and can change them to match.

PLC/SLC Translation Tool - Timers

Ken Roach said:

...In ControlLogix and CompactLogix, the only timebase available is 1 millisecond.

This is the reason all TIMER instructions are flagged with conversion "errors" when you convert a PLC/SLC program, so you'll check to see if the program is using the .ACC or .PRE values and can change them to match.

Click to expand...

Ken,

Sorry, I have my magnifying glass out...

You're probably working from memory, but it's not exactly the TIMER instructions that are flagged with a Program Conversion Error (PCE), but more any direct references to the PRE and ACC DINTs themselves. Eg. A MOV to a TIMER PRE.

The conversion of the SLC Timers' timebase is usually handled ok.

Eg. T4:1 TON - Timebase 1.0s PRE 123s

After conversion...

T4[1] TON - Timebase 0.001s PRE 123000

So the Timer instructions should function as before and should not need a PCE.

If a Constant value was being MOVed to a Timer PRE in an SLC and the Timer's timebase was 1.0s, then the Constant value would have been set for a 1.0s timebase.

Eg. MOV 200 T4:1.PRE

This is setting the PRE to 200s, but because it is a Constant value, the Translation Tool retains the value during conversion. It's not clever enough to know that it is now MOVing that Constant to a DINT that is now using a value 1000 times greater than before, and so multiplying 200 x 1000 and setting the converted MOV instruction's Constant value to 200,000. This is beyond the capabilities of the Tool.

So the conversion flags the rung with the MOV instruction, that references the PRE, with a PCE instruction, invalidating that rung, and forcing you to have to review it. You would then edit the MOV...

MOV 200,000 T4[1].PRE

...remove the PCE, and revalidate the rung.

Now you could just remove the PCE without editing and the MOV will then validate ok. However, you are now MOVing 200 to the TIMER PRE, and not 200,000. This will give you a 200 milliseconds PREset, instead of the required 200 seconds.

So all direct references to Timer PRE and ACC are PCE flagged for review.

The same goes for Counters.

G.

Well I am confused. I just want to setup a half second timer. How do I need to set it up?

jtashaffer ,
Sorry for the confusion , use the 0.01 timebase and 50 as the preset - as Aabeck said in post #4 .
A lot of folk read these threads so Ken mentioned a problem with converting timer instructions from SLC to a different family of Allen Bradley PLC's ( programmed with RSLogix 5000 not RSLogix 500 ) .
Paul

Ok thanks.

Yes, apologies for the tangent!

It had looked like you were sorted, so we(I) are doing what we(I) usually do best once a thread is wrapped, waffle on!

Do you want some more confusion?

ControlLogix and CompactLogix are programmed using RSLogix 5000, as opposed to 500, which you are currently using.

As Ken mentioned, the 5000 based controllers are fixed at 0.001s, whch is a 1 millisecond timebase. So you always have to enter your Preset value as a representation of a millisecond timebase...

RSLogix 5000:
E.g. You want a 1 second Timer Preset

1sec = 1000ms

Set PRE = 1000

1000 x 0.001 (1ms) = 1 sec

The PREset is just a value, a multiplier if you will. It is not a time or timebase. It determines how many 1ms pulses will elapse before the Timer ACCumulater will equal the PREset and set the Done bit.

For 3 minutes you would have to enter a PRE of 180,000!

How's your confusion now?

I'm waffling off home now...

G.