Manual Operations from a Sequencer

Hi there,

I have a sequencer that has 75 steps. The customer now wants to perform some of the steps external to the sequencer. For example a wash. This would involve opening a valve and running a pump for a time. This is already in the sequence.

How would you do this? I have seen it done before where they load that step number into the step register and then when done jump back out but it looks a little messy. Any opinions appreciated.

If the step number is 54, then simply move "54" into the positioning register. XIC (manual address)MOV 54 REGISTER). Does the customer also want it to only run that single step? Or pause after the step has been completed?

First: we have no idea what brand of plc.
Second: we have no idea how is the sequencer done
Third: we have no idea is that part of needed to happen "semi auto"
Fourth: we have no idea if on what language is ur program done in
Fifth: we have no idea if they want to deviate from ur "standard" routine

Do i need to continue, or do you provide all info that is needed?

How many manual operations are they likely to use? If only a few I would make it so they have to put the system in manual, then select Manual Wash button. This would set a flag in the PLC and move for example step 54 into your sequencer. Then having this flag set would allow you to exit the sequencer at step 58 for example and go back to idle.

Obviously, a lot depends on how the sequencer is structured. My sequencers usually have a "suspend/freeze" function. When the sequencer is suspended, you can put individual devices into "manual mode" and do whatever you like, then put everything back into "auto mode" and "resume" the sequence. But if these washes will be a semi-regular event, I'd probably do something better. One of the slickest sequencers I ever saw had the capability to build every step from a list of operations. Every possible operation was in a list. Every operation could use up to two parameters (for example, a pump speed and a time). Once you built a sequence you could store it as a recipe. I'm going to try it myself one day. I almost started to try to duplicate it on a project last year, but punted because of time and budget considerations.

I always send the sequencer output data to internal registers and map them to the real I/O in other logic. The sequencer bit outputs will be in series with the AUTO mode.
A separate branch examining a manual mode bit will exist where needed to drive outputs. It will be placed in series with manual control requests from HMI and/or wired controls.
There is no reason you can't have yet another sequencer acting on those outputs in another parallel branch.