Need Help with Programming

[Big_Robo]

Hello i need one of you fine gentlemen to help me with some ladder logic. I'm brand new to PLC's and admire you guys, i'm a long time stalker first time poster.

I have attached a very crude pic and basically want each conveyor (black and red) to feed onto conveyor blue simultaneously without crashing parts together. So e.g. black runs for 30 sec then red for 30 secs but if black hasn't any parts it continues to run red and vice versa.

I have tried and my attempts have failed could anyone help me out.

 

[PapaSmiff]

Welcome to the forum.

A couple of questions first, please:
1. Is this homework?
2. What kind of processor is this?

A point to ponder: you mentioned that you wanted Red and Black to feed "simultaneously" on to Blue without crashing packages. As I see it, the only times you will want both Red and Black to run will be when neither S1 nor S2 is made - at which time, no packages will be transferring onto Blue.

 

[Big_Robo]

Hello
It was a task given to me by the control engineer who will be going off sick for a while. It is going to be for a training rig for future apprentices.
It will be running from S7

The pondering point is correct i apologise should have been more clear.

Sorry for being a total noobie.

 

[dogleg43]

To me this appears to be more than just programming.

Are the sensors already installed and where are they?
Are there any gate or stops in place to keep the parts from jamming?
What type of conveyors are they, belt, rollers, etc?

These are all I can think of right now.

 

[Big_Robo]

I appreciate all the replies and even people looking at it. Hoping to learn fast this PLC lark is some hard hitting stuff.

Yes sensors are already installed S1 and S2 are part present sensors
S3 is belt M3 full/stop sensor
No stop or gates in place as of yet
All conveyors are belts.

Inserted another pic with S3 sensor.
Thankyou all for the help it really is appreciated i just don't know where to start or the correct way of going about it. I dont know how to switch belts to feed equal amount of parts and to stop them feeding conveyor M3 at the same time.

 

[JaxGTO]

Simple method is M1 and M2 run continuous until:
S1 blocked. Continue to run both unless S2 is blocked. If S2 blocked then stop M2. Wait 30 seconds then stop M1. Wait the time it takes for a part to clear the merge point and then stop M1 then run M2 for 30 seconds or until S2 clear for x seconds. Then run both again.

Complicated method, put M1 and M2 on servos or VFD's.
Use S1 and S2 to measure the length of the parts/gaps, then speed up/down M1 M2 to merge the parts onto M3.

I did that once on a merge belt with 4 belts moving at 520 FPM to merge boxes together that went under a barcode reader.

 

[Big_Robo]

Simple method is M1 and M2 run continuous until:
S1 blocked. Continue to run both unless S2 is blocked. If S2 blocked then stop M2. Wait 30 seconds then stop M1. Wait the time it takes for a part to clear the merge point and then stop M1 then run M2 for 30 seconds or until S2 clear for x seconds. Then run both again.

Complicated method, put M1 and M2 on servos or VFD's.
Use S1 and S2 to measure the length of the parts/gaps, then speed up/down M1 M2 to merge the parts onto M3.

I did that once on a merge belt with 4 belts moving at 520 FPM to merge boxes together that went under a barcode reader.

Thankyou so much, i have an idea of what to do now but i know this is beyond cheeky could you do a basic ladder code showing where is best to use the timers. I am sorry i'm a complete noob and just need to use it as a reference.

 

[Alen bradley]

Thankyou so much, i have an idea of what to do now but i know this is beyond cheeky could you do a basic ladder code showing where is best to use the timers. I am sorry i'm a complete noob and just need to use it as a reference.

That is the basic ladder logic. You are suppose to learn it and write it yourself instead of others to write for you. Have a go at it and if you have problems, come back here.

 

[Ronnie Sullivan]

My advice; learn some basic programming first before you tackle conveyors.
Although seemingly easy on the face of it, conveyors can be extremely complicated to get right.
I do a lot of conveyor systems that when completed look great while everything is flowing perfectly. Nobody see's the hundreds of 'what if's' going on in the program though.
Queuing, merging and priority are a few of the things that have to be right.

good luck

 

[jrwb4gbm]

Some of the what ifs include separation of parts. Suppose two parts are pushed together, how would you know if it is two parts or just one long part? Which belt has priority, if necessary? Are all parts same, or are some different? How do the parts enter the belts, randomly, or continuous? What provisions are being made to stop parts from entering the stopped red or black belt? How are you planning to clear the conveyor at the end of the run, or shift? As you can see, there is much more to conveyor design than your simple definition and cannot be programmed without considering many variables, as others have said. I have only mentioned a few things.

 

[L D[AR2P#0.0]]

Which S7 software are you using - Classic S7 or TIA portal?

 

[Big_Robo]

Which S7 software are you using - Classic S7 or TIA portal?

classic S7 version 5.5

I am just really having trouble on how to outline the basic programme. if it was one long conveyor feeding another no problem but i dont know how to get it to switch between the 2 feed conveyors.

 

[Ronnie Sullivan]

If it was just one conveyor, even easier..........

There is meaning in that sentence.

 

[boneless]

I agree with Ronnie.

Start program as if it was one conveyor, get that running smoothly and then add the second.

If you have concrete questions about some code, many here will be happy to assist.

A big part of learning PLC programming, is experimentation and research. Since this is for a training rig, you are safe to try and fail without people dying.

 

[dcooper33]

I agree with Ronnie.

Start program as if it was one conveyor, get that running smoothly and then add the second.

If you have concrete questions about some code, many here will be happy to assist.

A big part of learning PLC programming, is experimentation and research. Since this is for a training rig, you are safe to try and fail without people dying.

+1
You have to approach complex problems as a group of simple problems that are tied together. Start solving all of the simple problems first. This will get your brain thinking in the proper terms.