Would it be cheating to use a timer on Logixpro Silo exercise 1?

[JScot]

I've got this thing to move the box into position and fill it, but when the box starts moving again, it moves past the level sensor, and the level and prox sensors are in the same state as it is when an empty box is in position, so, of course, it dumps material all over the floor.

Using a timer to get it past the Prox sensor seems like the simplest solution, but he hasn't gone over timers yet at this point. Would it be cheating?

I've tried to use a bit to set the state of the machine, but it's just not working out.

 

[JScot]

I guess since 13 people have read this and nobody replied, I'll take that as a yes.

 

[JScot]

Took me a half a fifth of apricot brandy and a Blue Moon. But I finally figured it out.

Now If I can just find an employer that will let me get my buzz on at work...

 

[JScot]

Apparently, I have a tiny miniscule leak. The example fails at 1119 boxes due to the escape of product into the plant.

I have no idea what's going on.

 

[dcooper33]

Well the lessons learned on your own, the hard way, are the ones that stick
Now perhaps you should use the liquid muse for your late night coding and morning coffee for your documentation!

 

[JScot]

Sage advice.

I think maybe I have a delay of 1 step between box full and close solenoid valve?

 

[dcooper33]

Apparently, I have a tiny miniscule leak. The example fails at 1119 boxes due to the escape of product into the plant.

I have no idea what's going on.

Try this:

XIC B3:0/0 XIC I:1/3 XIO O:2/4 OTE O:2/1

I haven't used LogixPro in years, but I think this is going to be more positive a check on your solenoid valve than what you have.
You could also try adding a debounce on your box in position prox. Stop the motor immediately, obviously, but wait for your timer to expire after a box arrives before opening the solenoid.

EDIT:

I think maybe I have a delay of 1 step between box full and close solenoid valve?

Quite possible. Move your full lamp logic above the solenoid logic.

 

[jaywillnot]

The thing you have to realize about programming is the same program can be written many different ways...and usually are because almost everyone has their own techniques.

That being said, I used a counter to operate the solenoid valve. I also placed a GEQ condition to ensure the solenoid valve cuts off prior to the material overflowing.

Also, you can change your scan time to accommodate the time and or count pulses vs the action of the solenoid valve.

 

[JScot]

If this thing is overflowing if it runs one millisecond too long, then the level sensor needs to be recalibrated. Somebody call a technician!

 

[JScot]

The thing you have to realize about programming is the same program can be written many different ways...and usually are because almost everyone has their own techniques.

That being said, I used a counter to operate the solenoid valve. I also placed a GEQ condition to ensure the solenoid valve cuts off prior to the material overflowing.

Also, you can change your scan time to accommodate the time and or count pulses vs the action of the solenoid valve.

This is true, but if the level sensor is only ON or OFF, and you were using a counter, did you even use the level sensor?

 

[Lancie1]

I think maybe I have a delay of 1 step between box full and close solenoid valve?

Quite possible. Move your full lamp logic above the solenoid logic.

This is the secret magic trick that makes this program work without spilling material. If the solenoid output is above the Box Full logic, then the PLC must scan 1 extra time before the solenoid closes. The way Bill Simpson wrote this student training exercise, that one extra scan spills enough material that eventually the floor fills up and the system shuts off.

PS: A timer would not help you any for this 1-scan error problem.

 

[JScot]

Moved the lamp logic above the solenoid logic. It didn't help.

 

[JScot]

Added XIO I:1/4 to the solenoid logic.

Fixed it.

Also, i should mention, again, that I'm avoiding using any techniques he hasn't mentioned yet, and he hasn't talked about timers and counters at this point. Timers are in the next lesson after Silo.

Am I correct in assuming this was his intention?

 

[dcooper33]

Moved the lamp logic above the solenoid logic. It didn't help.

Added XIO I:1/4 to the solenoid logic.

Fixed it.

The XIO of O:2/4, which was latched by I:1/4 in your original program, that I suggested before suggesting moving the lamp logic above solenoid logic, also would have fixed it. I suggested the lamp as permissive rather than sensor because it is held high until the box is out of position.

Am I correct in assuming this was his intention?

Very well may have been. But you shouldn't let that stop you! Lancie is right, you don't need a timer for this, but I'm a firm believer in using whatever tools are at my disposal to get a job done. If your instructor has explicitly stated not to use certain instructions, then that is one thing. If not, then he should praise students who "think outside of the box" (or bottle). Something to keep in mind.

 

[JScot]

The XIO of O:2/4, which was latched by I:1/4 in your original program, that I suggested before suggesting moving the lamp logic above solenoid logic, also would have fixed it. I suggested the lamp as permissive rather than sensor because it is held high until the box is out of position.



Very well may have been. But you shouldn't let that stop you! Lancie is right, you don't need a timer for this, but I'm a firm believer in using whatever tools are at my disposal to get a job done. If your instructor has explicitly stated not to use certain instructions, then that is one thing. If not, then he should praise students who "think outside of the box" (or bottle). Something to keep in mind.

I tried your code, and it worked. Thanks.

So when I finish all the examples on this trainer, do you think I'll be ready to program PLCs in a real life job?