Not sure why this is? (Step 7)

I was just messing around with the following code:


Why isn't M 40.0 being 'set' ??

I know that as soon as T 9 comes on, it then turns itself off on its Start Input but I would have thought that the scan would evaluate the rest of the Timer before evaluating the Start Input. Clearly it doesn't but I wondered if there is a reason for this as the scan is operating counter to what I would have expected.

Many thanks for any info on this

;-)

I have not used STL but in ladder I would usually check that M40.0 is on before t9 is turned off
even use AN M40.0 instead of t9

See how I went - I have not been taught or read a lot yet

Ian,

You're completely right.

I do know how to make the code work but I was more interested in the intracasies of the scan.

I would have assumed that M 40.0 would have Set as the power would have gone through the Timer for one scan (until the next scan then turned the timer off).

This isn't the case. So the timer must be evaluated at the end of the scan to decide it is 'true' (i.e. timed out). Then on the next scan this opens the T 9 contact and prevents the RLO going through the timer to Set the marker.??!? (I'm presuming / guessing...)

???

we will both have to wait on Kalle or one of the other guys to correct it then
.

Old type timers are executed async to scan.

As stated by Turpo.....

Don't use the timer itself but assign it to a flag instead.

L D[AR2 said:

As stated by Turpo.....

Don't use the timer itself but assign it to a flag instead.

Click to expand...

Thanks LD.

TurpoUrpo said:

Old type timers are executed async to scan.

Click to expand...

Thanks Turpo, that was the answer I was looking for. That explains it. ;-)

The old S5 timers are prime examples of good employees.
You tell em once what to do and they do it. No need to check back on them. Once it's done they'll inform you right away.
The new IEC timers are kinda like younger employees. You have to tell them what to do each and every time. The moment you stop telling them what to do, they stop working.

[/off topic]

When working with s5 timers, always remember: They don't need to be scanned to be working, which also means they don't update their status at the point where you scan them.

Jeebs said:

[/off topic]

When working with s5 timers, always remember: They don't need to be scanned to be working, which also means they don't update their status at the point where you scan them.

Click to expand...

Thanks Jeebs ;-)