Car wash blues

[howardc69]

car wash blues

OK, well ran into the too many instructions dialogue box, so am going to type the whole thing over again, thank you once again for the assistance.
Howard

 

[Lancie1]

You must have a bunch of unused symbols in your program. In my version, I deleted everything that is not being used. Try this Version 5. Anyway, typing the same program in again will not reduce the number of instructions. If the attached version does not run, then we can look at ways to reduce the number of instructions.

 

[howardc69]

car wash blues

OK, I was almost half way done lol, you beat me again.

 

[howardc69]

car wash blues

OK i had created a lot of extra instructions to show lights for the 5 cycles at each stage, i deleted them all and added the extra instructions.

 

[Lancie1]

I think that you could add some more lights, within reason. Having 1 for each motor during each mode would add about 20 outputs, maybe too many instructions. But adding a light for each motor, and for each mode only adds about 9 more outputs. If you first delete all the stuff that is not doing anything important for you, then 9 more outputs can be added.

In the attached version 6, I deleted all the Latch instructions (latch not needed because the Vehicle Sensor stays on throughout the cycle). I also then was able to delete the unlatch and the Timer Resets (becaue the TON timer resets automatically when its trigger bit goes off). After doing that, I added 9 Outputs for Slot O:4 lights, as shown. The total was only 1 Kbyte more than Version 5. I tried to match the O:4 Outputs up so that the same number was related to the same Output device in O:2.

 

[howardc69]

car wash blues

This is what I did, I just wanted the water pmp, soap pmp, brushes, wax pmp, and blower outputs on line 002 so that i don't have to scroll through each one to see them activated. Getting rid of the latches is good that gives me the room to add some more instructions to get the garage door open closed lights to come on with out having to activate the switches other then the vehicle sensed one.

 

[Lancie1]

This is what I did, I just wanted the water pmp, soap pmp, brushes, wax pmp, and blower outputs on line 002 so that i don't have to scroll through each one to see them activated.

That will not work very well, because you will also need to activate those outputs for Modes 2,3, and 4. It is called the "double-coil syndrome".

 

[howardc69]

car wash blues

No, they are extras so that i can see the out puts activated, the outputs are where they are supposed to be, what i put on line 2 is just for a visual. It works great to watch the timing nothing else.

 

[Lancie1]

What I am trying to explain is that if you use more than 1 OTE Output Energize instruction for the same Output address in the same program, then that Output will not function correctly. The PLC scans all rungs and tries to do what those rung requested. When it scans O:2/1 Water Pump on Rung 002, that Output might be TRUE and call for it being ON. So far, so good. But when it scans the SAME O:2/1 later on Rung 032, that Output may be OFF. The output cannot be both ON and OFF at the same time, so the last version always wins. If you look at the Output on Rung 002, then it will show as OFF, even though the Rung 002 logic may be calling for it to be ON.

That is why it is called the double-coil syndrome. If you want to see the state of your outputs, I suggest using the LogixPro I/O Simulator window, and simply look at the nice lights that they give you for each Output. No need to have two versions of each output (that will cause errors in your program).

Also, in the real software RSLogix 500, you cannot put outputs in series as you did on Rung 002. When you try this in RSLogix 500 (the software that LogixPro simulates), when you Verify the rung, you get the errors shown in the attached picture. The reason behind this dates back to the circuits that RSLogix simulates - relay ladder logic. With real physical relays, if you wire two or more in series, you reduce the voltage through the relay coil (to 1/2 for two coils, 1/3 for 3, and so on). Relay coils running at 1/2 or less voltage will not operate correctly, so no electrician would ever do such a thing.

Now, as we get farther and farther away from the original thinking, the computer nerds writing the current software have no knowledge of where it came from, so they do what they want, and later versions of RSLogix (Logix 5000) do allow relay coils in series (for better or worse).

 

[T Gibbs]

If you want to see them activated, just put contacts addressed to those outputs in line 2 instead of duplicate coils.

 

[howardc69]

car wash blues

ok, i see your point, ill fix it and keep trucking