Control circuit for sequence operation

Thread Starter

shashixs

Joined Jul 7, 2020
4
I have a conveyor motor (say C1) which feeds material to 2 parallel screens. These screens can be operated either both simultaneously or one at a time. The conveyor receives feed from a diff conveyor (say C2). Now if both screens are running and if any of the screens were to shut down,the C2 motor should trip but C1 should keep running. Similarly,if only one screen is being operated and it shuts down,C2 should trip and C1 will keep eunning. Can anyone help with:
1. control circuit diagram
2. Relays required and wiring diagram
Thanks in advance
 

GetDeviceInfo

Joined Jun 7, 2009
1,729
How do you select that one or two screens must be running for normal operation?
In single screen mode, is it a specific screen, or any screen, and how is that implemented?
 
Last edited:

AnalogKid

Joined Aug 1, 2013
8,488
Sketch of the physical layout, and a table of the various conditions - ?

Also, what is a screen (in the context of your system)?

ak
 

Irving

Joined Jan 30, 2016
798
My guess, from the original description is that it's some form of grating that the conveyer C1 deposits material onto and it shakes so small stuff falls through and the bigger stuff remains on the screen, and gets shaken onto an output conveyer.

But the OP seems reluctant to provide enough info to be sure we understand the problem fully. Half-baked Info = half baked answers...

We need to know that a screen is supposed to be running, by positive & specific monitoring of the position of a switch for example, that provides power to the screen. Maybe a secondary contact. It's not sufficient to just use presence or not of the power since that might have failed even if the switch was on. Call this shouldRun1 & shouldRun2.

Now we need indication the screen is running, again a positive indication. Maybe a vibration sensor if that can be isolated enough that it only registers movement of its screen and nothing else. Call that sensor isRunning1 and isRunning2.

So:

shouldRun1 AND NOT isRunning1 OR
shouldRun2 AND NOT isRunning2

Is the error condition. There may be additional timing logic because there will almost certainly be a delay between turning a screen on and it's actually being up to speed and operational. That wasn't specified by the OP but is a vital piece of information. And of course isRunningX is an absolute, you might want to know for instance that's it's running but not shaking enough, but that wasn't specified (yet).

Now the OP stated the if either or both screens failed C1 should keep running but C2 should stop. So call the signal to allow a conveyer to run as enableC1 and enableC2.

So we have

enableC1 = TRUE
enableC2 = NOT
(shouldRun1 AND NOT isRunning1 OR
shouldRun2 AND NOT isRunning2)

As stated by the OP. The relay logic to implement that is trivial, so not only will I not deal with that here, I will decline to provide a solution.

Why? Because IMHO there's a big problem with this sort of ad hoc consultancy. We have no idea if this is some homework question or a real life scenario on which someone's safety depends.

The logic shown is what was asked for but as a process control solution it is, if you'll forgive the pun, full of holes!

As a case in point, C2 is enabled to run when both screens are not selected to run. Is that right, I wonder? And there are no error conditions for C1? The OP only stated a subset of error conditions and not operating states so we have no clear answer to that. There are many more elements to this, timing as I said already being one. What about the situation where a screen is deselected but doesn't stop due to some fault condition? What happens if the sensor to detect shaking gets stuck on, arguably we need multiple sensors and a voting system. Etc., etc. There needs to be a much more rigorous analysis of the situation and a much more detailed problem statement, especially where heavy machinery and personal safety is concerned.
 

andrewmm

Joined Feb 25, 2011
395
Your almost there.

First define your inputs. I think you mentioned your monitoring S1, S2, and C1
then define your outputs, what you are controlling.
 

GetDeviceInfo

Joined Jun 7, 2009
1,729
For consideration. Doesn't completely fulfill your logic, but...

circuit.png
One may consider delaying your conveyors based on shaker or downstream conveyor currents. In this rendition, all devices would start together so your source needs to be considered. Delays could ease that.

I put together a batch concrete plant for a fellow building modular walls. Sourced a used SLC 500 with all the I/O required for under $100. Weigh hoppers, conveyors, mixer, and auxiliary.
 
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Thread Starter

shashixs

Joined Jul 7, 2020
4
My guess, from the original description is that it's some form of grating that the conveyer C1 deposits material onto and it shakes so small stuff falls through and the bigger stuff remains on the screen, and gets shaken onto an output conveyer.

But the OP seems reluctant to provide enough info to be sure we understand the problem fully. Half-baked Info = half baked answers...

We need to know that a screen is supposed to be running, by positive & specific monitoring of the position of a switch for example, that provides power to the screen. Maybe a secondary contact. It's not sufficient to just use presence or not of the power since that might have failed even if the switch was on. Call this shouldRun1 & shouldRun2.

Now we need indication the screen is running, again a positive indication. Maybe a vibration sensor if that can be isolated enough that it only registers movement of its screen and nothing else. Call that sensor isRunning1 and isRunning2.

So:

shouldRun1 AND NOT isRunning1 OR
shouldRun2 AND NOT isRunning2

Is the error condition. There may be additional timing logic because there will almost certainly be a delay between turning a screen on and it's actually being up to speed and operational. That wasn't specified by the OP but is a vital piece of information. And of course isRunningX is an absolute, you might want to know for instance that's it's running but not shaking enough, but that wasn't specified (yet).

Now the OP stated the if either or both screens failed C1 should keep running but C2 should stop. So call the signal to allow a conveyer to run as enableC1 and enableC2.

So we have

enableC1 = TRUE
enableC2 = NOT
(shouldRun1 AND NOT isRunning1 OR
shouldRun2 AND NOT isRunning2)

As stated by the OP. The relay logic to implement that is trivial, so not only will I not deal with that here, I will decline to provide a solution.

Why? Because IMHO there's a big problem with this sort of ad hoc consultancy. We have no idea if this is some homework question or a real life scenario on which someone's safety depends.

The logic shown is what was asked for but as a process control solution it is, if you'll forgive the pun, full of holes!

As a case in point, C2 is enabled to run when both screens are not selected to run. Is that right, I wonder? And there are no error conditions for C1? The OP only stated a subset of error conditions and not operating states so we have no clear answer to that. There are many more elements to this, timing as I said already being one. What about the situation where a screen is deselected but doesn't stop due to some fault condition? What happens if the sensor to detect shaking gets stuck on, arguably we need multiple sensors and a voting system. Etc., etc. There needs to be a much more rigorous analysis of the situation and a much more detailed problem statement, especially where heavy machinery and personal safety is concerned.
Can you draw the physical layout and show the error conditions
For consideration. Doesn't completely fulfill your logic, but...

View attachment 211638
One may consider delaying your conveyors based on shaker or downstream conveyor currents. In this rendition, all devices would start together so your source needs to be considered. Delays could ease that.

I put together a batch concrete plant for a fellow building modular walls. Sourced a used SLC 500 with all the I/O required for under $100. Weigh hoppers, conveyors, mixer, and auxiliary.
Thanks a lot!
 
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