SFC andST problem

[Nolly]

Hi all, Happy new Year.
I'm a ladder man forced to use SFC's and ST using Eurotherm's T2750/Eycon PAC s/w (Lin Tools).
I'm constructing a sequence and have fallen at the first hurdle! I have a simple vertical conveyor driven by a motor that needs Forward/reverse operation. The motor starts but if I trigger the sensor the motor continues.My S/text is :
(*Step2 ConvDown*)
If
ConAtBtm.OP = 1 Then (*bottom sensor*)
ConvRev.OP := 0 ; (*Motor*)
Else
ConvRev.OP :=1 ;
End_if;
_________________________________
Step 2 settings : Action: ConvDown. Type: Text. Qualifier: N normal ( I've tried using P initial.)

The transition to the next step: ConAtBtm.In = 1.
I have 16 steps in the sequence and the other steps are working ok. I've spent hours tring to sort it. Hope someone can help.

 

[Ken Moore]

So...what if the step is the motor running. Transition is the sensor, next step stops motor.

 

[Nolly]

Thanks Ken - That solved my problem. So simple. I removed the ST from the first step and just left the variable :=1 and in the second step Variable:= 0
Why didn't I think of that. Every day's a school Day! Works a treat. Have a good year.
Nolly

 

[cardosocea]

bear in mind though that this is effectively using a latch/unlatch ladder logic in ST form.

The equivalent to what you'd do would in Ladder is:



ConvRev.OP := NOT ConAtBtm.OP ; (*Motor*)