Sequencer logic vs. Run parameter

[Crabpot172 1]

Hi there. I work in the food safety field and I am working with alot of older code that is always based on the use of sequencers (SQO and SQC in 500) and even in the 5000 versions, for recipe storage. I have always used the run parameter array (in 5000)as a simple way of saving multiple recipes and I see no reason why it would be more effective as sequential logic and shifting registers. This is being used in CIP systems and makes any adjustments impossible for the operators or anybody other than the programmer(me) to make changes to recipes. Does anyone know why this seems to be an industry standard? I am sure there is a very good reason, but I"m just missing it. Any help and insight would be greatly appreciated.

[OkiePC 14]

It's probably some dude's favorite instruction. I seriously doubt it is an industry standard. I work in food too, and have found a much lower level of skills involved in the programs I have looked at from OEMs in this field. Some of the programs are okay, but most of them are pretty amateur, some of them downright terrible. I have one system full of sequencers...I wondered what they were doing with all those SQO instructions...turns out they are using them to compare the real time clock with a list of operator settings for defrost times...I would have just used indirect addressing on the input side of the logic, but as they say, "there is no wrong way to program."

[Gerry 13]

In the dim, dark past it was common to use a drum sequencer to control the CIP sequence. The program was on a punched card that was stepped through the device. Same concept as a player piano. The SQO emulates the drum sequencer and makes conversion from relay systems that used them relatively painless.

[BobLfoot 302]

As a fellow food industry programmer 2 thoughts come to mind. 1 - A lot of these systems were c onverted from Drum Relays. As a matter of fact we took out our last Drum Relay back in 2010 believe it or not. 2 - Most Sanitation Managers I've worked with don't want operators tweaking the CIP recipes, so the SQO etc which forces a programmer to make changes is loved by them. Operators can hack passwords, but not PLC usually. Just my humble 2 cents.

[OkiePC 14]

I upgraded 19 tire machines (times two sides per machine) from Tenor Stepper (mechanical drum steppers) to SLC 5/04 on tire assembly machines, I was very happy to see the last one land in the metal bin. I had to do the job in four hours per machine, so I spent about 4 months "sitting on my bucket" getting good at panel rewiring for half the work day at least 3 days per week. The first one of course took almost six hours, all the I/O wiring had to be pulled back and rerouted, much of it replaced then the logic debugged. There were six slots of I/O something on the order of 40 outputs and 40 inputs. After that, I could do them in three hours, once I knew which wires to toss aside and came up with a quicker ways to replace them in pairs and threes. I was known to have a big cardboard box full of wire and relays when I rolled my computer cart away from the job. I bet I personally filled three medium sized dumpsters with old hardware in those 4 years.