Safe power up delay module

I would like to know how to write a power up sequence in ladder that is safe.

I have to fix a problem with a plc controller that is interfaced to a CNC turning center. It is used to control an index chuck. I have never seen an example of this and would appreciate any help you could offer. The PLC is an omron CPM1

First, define "safe".
Then implement it.

Realistically, there is no such thing as "safe". You try to make the system fool-proof.
The Universe tries to make bigger fools.
Given time, the Universe will win.

If you are looking for how to do "first scan" logic, here's a way:

Most PLCs (you'd have to check the manual to see if Omron is one) reset all coils prior to executing logic. Therefore, if your first two rungs are:

  ALWAYS_ON    FIRST_SCAN

-----|/|----------( )



               ALWAYS_ON

------------------( )

You have a bit that indicates a powerup condition.
Use it as needed.

good post allen

only to add

While coils normally do reset to zero on power up (unless they are retentive or latching coils), words do not, nor do bits of those same words.

I usually use the power up/ first scan bit to move zero's into words that I want to be zero, and move the appropriate values into words that I want to be constants. Definetely depends on the program/process as allen mentioned.

the Omron Always on contact is 253.13
the always Off is 253.14
first scan is 253.15

the best power up routine would be a timer.
with the function 02 and 03.
I/L and I/CL interlock and interlock clear function.

There should be some form of feedback from the CNC centre as well.