RSLogix 500 Program Review & Advice Needed

Hey Guys, I have a program for some sprayers on my auto line. Its written except I need to add an adjustment and I have tried several ways but am stuck. I will do the work if I can get some direction.

The program is pretty easy -
- There are 3 sprayers, all are the same
- Upon power up the close valve is actuated.
- Then whne limit switch is actuated and held closed
- The timer starts and is used as a delay
- Then a sprayer timer starts while a valve opens
- Then another timer ends and a close valve timer starts.

What I need is for there to be two options the first sequence as I described it above and a second sequence.

In the second sequence if the limit switch is is released early I need the sprayers to bypass the the above sequence and go straight to the sprayer timer (opening the valve and spraying the parts) and then continue from there until the end of the above sequence is complete.

I have included the program for review.

Thoughts?

iadapt said:

In the second sequence if the limit switch is is released early I need the sprayers to bypass the the above sequence

Click to expand...

Define 'early'.

As soon as the limit switch is released, is early.

In the second sequence if the limit switch is is released early I need the sprayers to bypass the the above sequence. . .

Click to expand...

I could not be sure what address is "the limit switch". For Tank 31, would that be Input I:0/0 "Tank 31 Rack Position"?

Hello Lancie1, yes sorry about that. The rack position is the limit switch.

Is your program working now, or is there a problem with it?

My first impression is there sure are a lot of timers (7 for each tank)! You have a timer for time to open the valve and another for time closing. Is this because there are no limit switches or sensors on the valve? Using field sensors is usually the preferred method because then the PLC knows what is happening and doesn't have to rely on the less-sure timer method.

Lancie1 said:

Is your program working now, or is there a problem with it?

My first impression is there sure are a lot of timers (7 for each tank)! You have a timer for time to open the valve and another for time closing. Is this because there are no limit switches or sensors on the valve? Using field sensors is usually the preferred method because then the PLC knows what is happening and doesn't have to rely on the less-sure timer method.

Click to expand...

Full Disclosure: I haven't looked at this program, nor do I have software available on this home computer to do so.

I generally agree that measurement is always preferable to inference, but I have written programs that rely upon timers as a backup to limit switches to infer that a hydraulic cylinder stroke has been completed. I did this because the application demanded that the process not be aborted due to a mere limit switch failure. In the event of a LS failure, the operator receives an alarm, but must then verify via visual inspection whether an actual failure of the hydraulic ram has occurred prior to shutting down the process. If the LS has failed, but the cylinder is stroking normally, then the timers allow the sequencing of the rams to continue operation without the LS input functioning.

The timers open a motorized valve. The program does work, I didn't write it a programmer I know did. Its just that the cranes it works with sometimes adjusts priority and may come to pick up the part from our tank (which is what actuates the LS) earlier or later than the timer is set for.

I haven't tied the two systems together yet. I just need the sequence to permit the sprayers to come on if the rack position/limit switch is lifted early or late (at anytime). for a timed period then close and reset for the next cycle.

Does that help?

Yes, that helps. I will try to study it and first figure out how the logic works now, in order to modify it to turn the sprayers on if the limit switch makes early.

Thanks lancie1 don't be afraid to have me do the work to learn. I do need it figured out by Monday. So thank you for your help.

Monday! Being retired, I forget that the world has deadlines. I will start now. I think it is not difficult to do what you want. The hardest thing will be to keep from messing up the parts already there.

..... the cranes it works with sometimes adjusts priority and may come to pick up the part from our tank (which is what actuates the LS) earlier or later than the timer is set for.

Click to expand...

On way would simply be to use the limit switch and a OSR one-shot to set the timer Accumulated Value to be equal to the Preset Value. That would allow everything else to stay the same, but would make the logic react immediately, but without risking changing any logic in the circuit (except the timer).

I'm not sure I have it all . The OSR will set a timer?

I may need an example

I think this is what Lancie is saying...

Double click an empty rung and paste in the code:

XIC LIMIT_SWITCH ONS B3:0/0 MOV T4:0.PRE T4:0.ACC

Make the ONS (in my case B3:0/0) a unique address not used anywhere else in the program

Yes, that was what I meant. Thanks, MSP.

I loaded the MicroLogix Tank 31 program rungs into the LogixPro simulator to see how it works.

Basically when all 3 of the Inputs (I:0/0, I:0/1, and I:0/2 are open, the Tank 31 sequence starts off with the 20-second Valve Close step, then alternates to the 10-second Valve Open step, then repeats as long as the I:0/2 Tank High Level switch alternates between first closed then open as the tank fills and empties (or the T4:4 Tank Fill Timer is done).

If the I:0/0 Tank 31 Rack Position LS closes, then the Soaking, then Spraying steps are started and cycle until I:0/0 opens.

When the Tank Low Level Switch I:0/1 goes open at low level, the Tank 31 Fill Timer T4:4 is started and runs for 30 seconds.

In the second sequence if the limit switch is is released early , I need the sprayers to bypass the the above sequence and go straight to the sprayer timer (opening the valve and spraying the parts) and then continue from there until the end of the above sequence is complete.

Click to expand...

Do you mean immediately energize Output O:0/1 Valve Open, then enable the Spray Timer T4:3 (but not the Soak Timer T4:2)? In other words, what part of the sequence needs to be bypassed?

With the current logic, it will be difficult to bypass the following: T4:1 Valve Open Timer that is in parallel with the O:0/1 Valve Open, T4:16 Flight Bar Limit Switch Timer, and the T4:2 Tank 31 Soaking Timer.

On the other hand, if you mean merely to cut short the T4:0 Valve Close Timer, then simply when the I:0/0 Tank 31 Rack Position Limit Switch closes, then do as MSP said. The OSR Ons-Shot Rising is so that the bypass only happens one time each time I:0/0 closes.