Hand/Off/Auto logic RSLogix?

[cntrlfrk]

rsdoran seems to be referring to a HOA switch which controls the entire machine operation. Alaric, and others, seem to be referring to a seperate HOA switch for EACH OUTPUT.

I agree. I think this is where the confusion/ disagreement lies. I have worked most of my career in processing plants (conveyors, pumps, blowers etc...) so in my experience with HOA's here in the MidWest, most have been on buckets in MCC's or by the equipment themselves, so they were associated with one motor/device. So 'Hand' was simply a manual 'run' command ,override of PLC logic. As one post mentioned, local/off/remote is used as well, sometimes in combination with a local start/stop button or on a VFD panel.

 

[optimus2861]

Operation is in Auto. Hidden manual switch is in OFF. Operator does not know this because the switch is not visible. The operator needs to switch it to Hand (Manual ON) without interrupting the process.

Except you can't exactly do that with a typical three-position hard-wired switch anyway - you always have to pass through "OFF" to get to "HAND". If you've got something like a VFD or soft-start involved, you're likely looking at a restart delay to boot.

My opinion is this: if the operator has to take something out of Auto and put it into Manual in order to run production (as opposed to cleaning out a mess or some other short-lived function), the programmer's got something wrong with the Auto logic that needs to be fixed. On top of that, most systems I program are interlocked in such a way that, if you take a motor out of Auto, stuff that depends on it is going to refuse to run (unless the operator puts that in Manual too, then stuff that depends on that won't run, etc). That's a very effective way to thoroughly discourage the use of Manual mode.

 

[Tharon]

We have many machines that were adapted from an Operator operation to a Robotic operation.

On these machines, we added what we called "Setup" and "Robot" modes. As long as the robot is off, the machine can always go into "Setup" mode, regardless of where in it's sequence it happens to be. But the machine can only go into Robotic mode during the Load or Unload portions of the cycle.

This Setup (manual) mode is for times when something goes wrong with the robot or machine, and it needs to be manually finished or moved.

I've always felt that switching into automatic modes needed to be monitored more carefully, and manual modes don't really care, cause your going to be moving the machine around manually anyway.

We also don't require the machine to be Off when switching between the Robotic or Setup mode. You can run the machine manually up to the point where you need to remove the parts, switch it over to robotic mode, leave the cage, turn on the robot, and the robot will take off right where you left the machine.

 

[DRThorne]

take a look at this thread

http://www.plctalk.net/qanda/showthread.php?t=2028