Hi all, great site here and looks like quite a brain trust for PLC's.
I have a question and have looked through ALL FAQ's and did not see any reference to this particular item although I did learn a lot of other things. I am actually a DCS programmer but my fellow PLC programmer is in IRAQ (Nat. Guard) and I am trying to modify his code.
r--------------------< L1 >----r
a | a
i | i
l -< U2 >-----l
First let me explain L1 and U2 designations above;
L1 is actually B16:4/3 <L> (designated as stop pushbutton)
U2 is actually B16:4/4 <U> (designated as start pushbutton)
I just could not get these numbers easily printed in Email.
Like I said I am a novice at PLC code. I guessed
that the above code would keep L1 latched at all times except when the "stop" pushbutton was pressed on the attached Panelview and U2 unlatched at all times except when the "start" pushbutton was pressed.
There are no < U1 > or < L2 > used in the ladder subroutines.
The "stop" functions ( <L1> XIC and XIO ) and
the "start" functions ( <U2> XIC and XIO )
work fine throughout the program as written. I
attempted to add a latching contact to latch a "stop" signal.
r r
a----------|/|------------< SL >---a
i i
l l
-|/|- is actually an XIO of <L1>
<SL> is actually B10:3/2 <L>
Although all XIC and XIO of <L1> throughout the
program work, my added attempt at a latch <SL>
never latches. I added the attempted latch one rung below the rung which goes to the pushbuttons in parallel (<L1> and <U2>)
It's almost like the pushbutton is instantaneous
instead of writing to the table and holding for a full cycle.
Anyone see what I am doing wrong?
I hope this all lines up and makes sense as I am writing it offline and uploading it.
PS: SLC 500/05
I forgot to say that I made other non-related changes and everything verified and worked except the attempted latch.
Thanks in advance for any and all help!
I have a question and have looked through ALL FAQ's and did not see any reference to this particular item although I did learn a lot of other things. I am actually a DCS programmer but my fellow PLC programmer is in IRAQ (Nat. Guard) and I am trying to modify his code.
r--------------------< L1 >----r
a | a
i | i
l -< U2 >-----l
First let me explain L1 and U2 designations above;
L1 is actually B16:4/3 <L> (designated as stop pushbutton)
U2 is actually B16:4/4 <U> (designated as start pushbutton)
I just could not get these numbers easily printed in Email.
Like I said I am a novice at PLC code. I guessed
that the above code would keep L1 latched at all times except when the "stop" pushbutton was pressed on the attached Panelview and U2 unlatched at all times except when the "start" pushbutton was pressed.
There are no < U1 > or < L2 > used in the ladder subroutines.
The "stop" functions ( <L1> XIC and XIO ) and
the "start" functions ( <U2> XIC and XIO )
work fine throughout the program as written. I
attempted to add a latching contact to latch a "stop" signal.
r r
a----------|/|------------< SL >---a
i i
l l
-|/|- is actually an XIO of <L1>
<SL> is actually B10:3/2 <L>
Although all XIC and XIO of <L1> throughout the
program work, my added attempt at a latch <SL>
never latches. I added the attempted latch one rung below the rung which goes to the pushbuttons in parallel (<L1> and <U2>)
It's almost like the pushbutton is instantaneous
instead of writing to the table and holding for a full cycle.
Anyone see what I am doing wrong?
I hope this all lines up and makes sense as I am writing it offline and uploading it.
PS: SLC 500/05
I forgot to say that I made other non-related changes and everything verified and worked except the attempted latch.
Thanks in advance for any and all help!
Last edited: