PLC timed sequence

J

Thread Starter

JustinDee

Hi,

I have previously wrote a programme for an automated machine I have built using a Zelio logic relay.

It’s a simple timed sequence using cycle timers. When the door is shut and start button is pressed the 5 timers start there off/on delays.

I now want to switch to twido PLC to better communicate with our HMI and to be able to alter timer presets.

I have used a series of TON + TOFF timers to get the same off and on delays which seems to work.

But if I put a (E-Stop) or (reset) switch in. I’m unable to cancel the timed sequence I need some way to be able to stop all TON+TOFF timers

I noticed the TMi.V is read only.

Is there any way to stop+reset timers to 0

I’m sorry if this is not enough information please let me know and I can maybe take screenshot of program to better explain.
 
P

PLC Programmer

You can use the emergency stop signal as a DI. Use it to move values (Zero in your case) to the presets of these timers.

It should work quite simply.

Please let me know your result.
 
>... start button is pressed the 5 timers start there off/on delays.

> But if I put a (E-Stop) or (reset) switch in. I’m unable to cancel the timed sequence

Not familiar with that particular brand, but with ladder logic there are several ways to accomplish what you want to.

If the 5 timers are cascading (when the first timer is done, the second timer starts, 2nd done, 3rd starts, etc.), the most effective way is to place "If not E-Stop" as condition in first timer rung. Because timers are cascaded,when rung for first timer is no longer true, it resets first TON. Rung with 2nd TON that had if 1st TON done as condition, will no longer be true, which resets 2nd TON, etc. etc.

Another way is to use an MCR or JMP instruction to lock out rungs with timers is estop. Another way is to output to 5 RES instructions on estop to reset all 5. Another way is to include If not estop condition on each of the 5 rungs with timers. Etc. Etc.
 
P

PLC Programmer

Bin95,

Such a scenario can occur when PLC has redundancy.

Have faced similar scenario with the Siemens PLC before but not a Schneider.
 
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