storage bin control circuit

[Rocboni]

Recently completed a job wiring a grain bruiser with several cross and elevator conveyors ect, we built a panel for it and I am I interested in how a particular part of it was done.

I understand how the conveyors were interlocked so that the intake could not be started before the elevator ect however the system had a storage bin above the bruiser. It had a high and a low lever probe, these probes switched the intake conveyor on and off. Probes just had N/O and N/C contacts.

The high level stopped the intake conveyor and the low level started it, but it didn't start as soon as the high level was uncovered it waited until the low level probe was uncovered. How was this done? The panel was only done with relays and I think a timer was used to allow the grain to fill after the start button was pushed until the low level probe was covered then allowing the automatic filling to take over, no PLc was used.

It would be easy enough for one probe to switch the motor on and off, but it would be constantly switching hence the head of grain in the bin. Obviously elevator could fill the bin quicker than the bruiser could empty it.

Just after a diagram of this particular part if anyone can help Me understand it?

 

[Bobster]

Hi Rocboni,

Whoever your working for will have the wiring diagrams, it's part of CE marking the panel and system the company is selling. Otherwise they would be breaking statute law.

If you post up a picture of the drawing I will happily go through it with you. There are a couple of ways I can think of to achieve that outcome.

 

[Rocboni]

Hi, I don't have access to the drawing, nor did I think to take a picture of the diagrams when I was on site,I won't be returning either.

 

[Bobster]

Can you not ask anyone for a copy? Surely if it's to further your education nobody would mind?

Did your company build the panel? Or am I miss understanding your post?

 

[Rocboni]

Yes we built the panel, I have seen the diagrams but I couldn't understand that particular part, I have asked the manager a few times to get them but no luck, he designes all the panels, he is not forthcoming with info either, and we never get the time to talk.


Just wondering if there's a standard method of doing it, not looking to build a panel just want to understand how this is done

 

[Bobster]

Yes we built the panel, I have seen the diagrams but I couldn't understand that particular part, I have asked the manager a few times to get them but no luck, he designes all the panels, he is not forthcoming with info either, and we never get the time to talk.


Just wondering if there's a standard method of doing it, not looking to build a panel just want to understand how this is done

There are standards to be met, most commonly in panel building EN 60214.

As for control philosophy, as long as the safety requirements are met within that standard, and any others regarding the particular use of the panel, there isn't really from what I've seen a standard.

I'll sketch something up, you say all the panel contains is relays correct?

 

[Rocboni]

I know there are standards for wire colours ect.

Yes all it contained was a row of 4 pole relays the contacators and overloads aswell as a timer I think.

 

[Bobster]

The conveyor can only start if the low level AND the high level aren't covered.
The motor can't run when the high level is covered.

View attachment 35114

View attachment 35115

View attachment 35116

 

[Bobster]

Not sure why so many attached there, and obviously there will be a start stop button that will put power to this little section of the circuit.

Could have possibly been using the timer to de-bounce the signals from the level probes. So that a bit of falling material wouldn't immediately start or stop the conveyor. E.g the probe needs to be covered or uncovered for say a second before any action is taken.

 

[Rocboni]

Why the n/o start button? How does it work wit normally closed contacts, surly as soon and grain hits the lower level probe the coil would drop out?

The timer was there as there was another probe right at the bottom to stop the bruiser if no grain was in the bin at all which shut down the whole system. So the timer bypassed this for a few seconds to allow grain into the bin?

 

[Bobster]

Sorry Rocboni this was just a 20 second sketch.

The N/O is a contact from the conveyor start relay. Once the coil on the end is energized it is latched until the high level becomes active.

This drawing is showing the logic behind the system, not how it would be wired.

High levels should be wired fail safe, so in fact the HL relay should be N/O to. I just thought the principal may have been easier to get your head around to start off with.

 

[Bobster]

This may make it a little clearer

View attachment 35118

The probes will change state when covered

 

[Rocboni]

Thanks Rob, I tend to be able to read a wiring diagram easier than ladder logic, however I understand this now and is exactly what I was looking for, I knew there would be a simple way to do it I just couldn't see it.

 

[Bobster]

No problem, obviously there will be a lot more to the system as a whole to meet regulations.

 

[Darkwood]

There are several ways to achieve what you are questioning, each may be suitable for different set-ups. ...

>PLC - control can do all the logic and output to the feed when conditions are satisfied within its program.
>Changeover relay - this is a simple basic way of doing it where each probe will change the relay state when conditions are met.
>Sensor probes - you can get probes that do alot of the work themselves, ie altering sensitivity and delay timer functions.

Like Rob has noted, whatever the method it will be subject to regulation and probably fall under the BS60204, I have fitted a similar set up in the past utilising a plc logic program I did that using edge triggering and delay functions to avoid false detection as material drops past the probes.

Without anymore info, its a difficult call to say exactly how you system works as simple things like the probes themselves can change the control system required dependent on which ones you use.