Conveyor start&stop

I am looking for a very simply example program.We have 3 conveyor bants let's say B1,B2,B3.When we give group start then firstly B3 after B2 more after B1 will be started(with time interval).If we give group stop then firstly B1 after B2 more after B3 will be stopped (with time interval).I use S7-300.Any help will be appreciated.Thanks in advance...

Now all you have to do is decide whether to use
relay with time delay relays,
Vfd control with or without timers,
or PLC with or without VFD.

Once you have made those decisions let us know which one you make.

Dan Bentler

All of them in S7-300 plc software

It sounds like you know how you want the system to work. Whic bit are you stuck on?

Basic example


---| |--------------------(B3 run)----
start P/B

--| |---------------------(T1)----------
B3 running

--| |---------------------(B2 run)------
T1 done timing

--| |---------------------(T2)----------
B2 running

--| |---------------------(B1 run)-----
T2 done timing

Hi everyone!
I have the same problem to solve and I have written the exact same program as "Peoplehouse" has but my instructor wants us to use toggle type switch as a stop switch and he wants a start and stop for each belt.Ploblem being is that when I turn toggle back on the timer starts again and he does'nt want that he wants to be able to start each belt indevidually aafter turn of and then on the toggle stop switch.Thanks for any help and we are using old equip. at school.

I think your instructor has you learning a good design criteria ie the E stop and how to properly implement.

The E stop (toggle switch) shuts down all conveyers.
Each conveyer must be independently restarted by the START switch.
Each conveyer can be independently stopped with STOP

The solution to your problem right now is:
how in the ladder logic do you have the estop in series with All start stop switches.


Read up on master control relay.
Read up on safety circuits.

The E stop via master control relay:
1. Leaves power to the PLC
2. Kills power to inputs
3. Kills power to outputs UNLESS they must run to make machine "safe" Dont worry about this now
4. Kills all control power
5. In a "maximal" design kills main power to motors etc.


Dan Bentler

Decster said:

Hi everyone!
I have the same problem to solve and I have written the exact same program as "Peoplehouse" has but my instructor wants us to use toggle type switch as a stop switch and he wants a start and stop for each belt.Ploblem being is that when I turn toggle back on the timer starts again and he does'nt want that he wants to be able to start each belt indevidually aafter turn of and then on the toggle stop switch.Thanks for any help and we are using old equip. at school.

Click to expand...

In a typical conveyor group start system I have seen (crushing / screening plant) conveyor 3 feeds back to conveyor 1, If one conveyor stops all must stop. If one doesn't start you end up with a big mess.
If the conveyors are just in series you don't usually have a group start, you just start the far end first 3, 2, 1 of course if 3 stops 2 & 1 must stop immediately.

Decster said:

Hi everyone!
I have the same problem to solve and I have written the exact same program as "Peoplehouse" has

Click to expand...

Ok, and welcome to the forum!!!

Decster said:

but my instructor wants us to use toggle type switch as a stop switch

Click to expand...

A little more precision is needed in your description here. To programmers the word "toggle" has a special meaning that is totally different than the word "toggle" in an electrical only context.

Decster said:

and he wants a start and stop for each belt.Ploblem being is that when I turn toggle back on the timer starts again and he does'nt want that he wants to be able to start each belt indevidually aafter turn of and then on the toggle stop switch

Click to expand...

This last part of your description is also a little vague and needs clarification. This is one reason that the two previous answers were so different.

BTW. A good process description will lead to good results.

In the real world, you would always pull back some type of run status from the device and use a form of seal in circuit.

Russell

I've always kept the power to the Inputs in an E-Stop condition should an operator or technical person try to reposition machinery where position detection sensors are in play. I would hope they wouldn't do that but production demands sometimes make people do stange things. This way the controller "sees" these new positions.

Yeah I didnt notice that. I cant think of an instance where I would remove power from my inputs. Also I would group my outputs such that those affecting safety would be disabled via hardwire, but others not (ie, status lamps and such).

Modes,Interlocks,Statusses

In all conveyer systems that we have done there is a basic control structure. This goes down to device Level.

Firstly you would have different modes.Say Auto and Manual. In Manual mode the conveyer will start regardless of interlock states (Other belts running downstream ect.) and auto mode, all interlocks active.

You can go further to deviding the interlock as Startup and operational interlocks.

I always use S7-Graph for Sequences as it is easy to troubleshoot and already makes available Step no's ect needed to display where in the Startup sequence you are active.

Before a device can start i verify that all interlocks are healthy and that the device (Conveyer motor) is healthy.

I then issue a start command...After running feedback is confirmed you check the interlocks and statusses of the next drive and issue that one a start command if the conditions permit....and so on and so forth.

Dont forget the siren!!!

R

My impression is that Tulip and Decster need a program that works like the attached.

Features:
System Start PB
System Stop PB
Each Conveyor has individual Start and Stop Pushbuttons
System Auto-Start Timer that can start each motor after a different time delay.
System Auto-Stop Timer that can stop each motor after a different time delay.

Hi and thanks for all the feedback. Sorry I have'nt responded sooner but I had a hernia operation and have been down for about a week.The type toggle swith is really a selecter switch with just On/Off and now that I'm feeling a little better I'm going to try some of your suggestions and see if I can get it to work and learn more about how this works.You guys are GREAT and I hope you can help me with some of my later exersizes.

Thanks again,
Decster