coding w/o one_shot_falling

HI, being a novice and currently having brain "****" My problem is: I need to trigger a long ( 3 min.) timer when I start a shut down sequence. The limitations are: the PLC I'm using is only capable of 0.01 time base and 32,xxx. So I'm using a delay on break timer with a counter to reach the required real time, but without the one shot falling command, I'm not seeing away to trigger the timer. I thought of either NAND &/or NOR logic but having a problem implementing it.

3 minutes would be 180 seconds or a preset of 18,000 to a .01 time base timer. I take it from you description that it's capable of up to 32 thousand somehting. Why then would you need the counter? Can you be more specific on you PLC type and model number?

If your PLC function set doesn't include one shots, here's how to roll your own.

 

Trigger  Inhibit1     One_shot_Rising

--] [-------]/[--------------( )----

 

Trigger                    Inhibit1

--] [------------------------( )----

 

 

Trigger  Inhibit2      One_shot_Falling

--]/[-------]/[--------------( )----

 

Trigger                    Inhibit2

--]/[------------------------( )----

 

The coil "One_Shot_Rising" will turn on for one scan when "Trigger" goes from OFF to ON.
The coil "One_Shot_Falling" will turn on for one scan when "Trigger" goes from ON to OFF.