Conveyor logic

I am trying to write a simple program for two conveyors.

The first (infeed cnveyor) discharges onto a bi-directional (cross conveyor)

The cross conveyor will change directions every time i get a signal (discharge complete)

The problem i am having is getting the cross conveyor to go one direction first.

I am using a micrologix 1200PLC and would be happy to send the program file to anyone that might be able to help.

Thank you in advance
Reeltime

I have attached a copy of the program i am working on.

Reeltime

Can you print your RSS program to a PDF file, then post the PDF? I might be able to help you then.

Trying to get it printed now. Used a ONS for the auto SS. I believe this will work, but I still have some questions.

The program i had in the previous file was pretty messed up. I have changed it, and i think i am close. This is the .RSS file.

I am having to re-download acrobat so that i can print it in .pdf

Reeltime

The cross conveyor will change directions every time i get a signal (discharge complete).

Click to expand...

Usually for this alternator-type of change, you need some logic to alternate the Output that gets used every other time. One easy way is to set up a parallel output LATCH bit for the Output for the 1st direction, called something like "Direction 1 Has Run". Then for the Output for the 2nd Direction, put in a parallel UNLATCH bit for "Direction 1 Has Run". Now for the Cross-Conveyor Start PB for each direction, put in a parallel XIO for Direction 1 (to run it first) and a XIC for Direction 2 (to run it second). Now the direction will alternate every other time that you trigger the Cross-Conveyor start.

The attached picture shows a typical example for alternating a bi-directional cross-conveyor. Depending on what is your "Discharge Complete" signal, you may need to run it through a One-Shot function first.

Here is a pdf copy of the logic i have. See if you think it will work.

Reeltime

bRAIN fRIED. Going to bed. Look forward to seeing responses in the morning.

Thank you in advance to all who can assist.

Reeltime

It is sort of disorganized, but I will check it best I can.

1. The key to alternating from LEFT to RIGHT direction are RUngs 24 and 27. Looking at each of those, you have logic to select each direction, but it seems to me that there is nothing that will first select Left or Right, then alternate to the other direction on the next run. Your opertion seems to depend mostly on the Hopper High Level Sensors.

2. For example, on rung 24, there is B3:2/4 OneShot Conveyor Auto Mode that could pick the Right direction first, but it depends on the level in the Right Hopper. On rung 27, the Left Cross-Conveyor can never be used until the Right Hopper is full and the Left Hopper not Full. Are those the correct conditions to determine whether the Cross-Conveyor shifts from Right to Left and Left to Right?

3. Earlier you said the altrnation should depend on "Discharge Finished". Is that signaled by your Hopper High Level Sensors? If not, then your logic is not correct. It seems to me that bit B3:1/15 OAS Mixer Discharge Complete" should be the signal to switch from Right to Left and vice-versa.

4. I think that the Timer bits T4:15/DN and T4:16/DN as located could cause your contactor Outputs O:0/1 and O:0/2 to rapidly flip back-and-forth between Right and Left. Each timer bit probably should be in series, T3:15/DN in series with the 3rd parallel branch of Rung 24, and T4:16/DN in series with the 3rd parallel branch of Rung 27.

5. None of these bits are true "alternator" bits that depend strictly on which direction the Cross Conveyor run in the PPEVIOUS run, but instead depend on external input conditions of level sensors, timers, and so on. You may find it would be simpler and more accurate to set up a Latched bit for "Cross Conveyor Has Run Right" and let that be the deciding factor on WHICH direction to switch. The other bits then need only to determine WHEN to make the switch. Without that, your Cross Conveyor may make 2 or more runs in the same direction.

6. You really should interlock your Cross Conveyor Outputs, so that only 1 can ever be ON at the same time. It appears that the last "MOV 2" to N7:1 (the Left Contactor) will be ON most of the time.

I didn't have much time to look at the logic being used but I figured I would post this PDF I picked up off one of the forums a while ago. Thought you could maybe use the discharge complete to one shot one of the alternator logic rungs, and making that bit an XIO for one side of the conveyor and an XIC for the other.

Adam C.

Adcla02,
After you uploaded the file, I have added 3 more alternator methods to the collection. Method 11 on Rung 17 is the best one for Reeltime's job. It is a case where 2 motors alternate based ONLY on which one ran previously. This is actually the same method that I used back in Post #6. The timers are only needed to demonstrate the method. For most applications of Method 11, remove the timers.

Here is an easier-to-read PDF copy.

Lancie1,

I didn't realize that was yours , just figured I would throw it on the thread quick before work. Thanks for that, as well as all the other substantial contributions you've made.

Adam C.

No problem! :site: I put it on here for anyone that needs some alternator logic.

Thank You!!

I want to Personally thank Lancie1 and adcla02 for their awesome help with the dilemma i was in. You guys were an awesome help. Sorry it has taken so long to post a thank you, I just got back in the country.

I was able to take bits and pieces of what you posted and apply them to what I was doing. IT WORKS!! May not be the way anyone else would have done it, but it has been tested and has no issues.

Again, a huge THANK YOU to the forum members who helped.

Reeltime

Reeltime,
Feel free to post your solution. I am always glad to learn new methods and programming techniques.