Conveyor Start/Stop

One way would be a photocell. If nothing is on the conveyor to interrupt a light path, this can signal the conveyor to stop.

The basic interlocking system in conveyors for safety and production reason is to trip the conveyor if succeeding conveyor or the equipment to which conveyor feed is stopped or tripped. But you are asking otherwise. It can always be done. Just check the no load current and current at minimum load. Fix an interlock for any value in between to trip the conveyor. But it lead to frequent stops for batch process.

It is not advisable to auto start conveyor due to safety reasons. However, you may not need it because it must be in operation if preceding equipments feeding to it are to be started.

You said:..It is not advisable to auto start conveyor due to safety reasons.

Unless someone has changed the principals of conveyors... ALL the systems I've worked on over the last 30plus years have been autostart.. How else to you start and stop a conveyors?

Basic interlocking for stopping the drives, automatic restarting as has been said should be avoided. As for detecting product you need some form of beam interruption device linked to a timer at the feed point. Without the timer the drive will stop for just the slightest interruption in the flow.

There are many types of both manual and automatic conveyor cut offs, or a combination of both. I worked in a plant that had a fast moving conveyor system involving several different processes. If any part of the line got jammed or went down, the entire line would shut down and have to be manually reset. It worked well.

Once you determine the parameters of when you want shut down to occur, there are many systems that would work. They are quite common.

Photo cell and timing relay. Set photocell on out feed section of conveyor so that as it's picks up the present of a product it starts the next section of the conveyor up. Set timer so that product runs the length of that conveyor to next section. Timer needs to be one that resets time each time photocell picks up an product.

I have done this with a VFD that has kW monitoring and a micro PLC (some VFDs have the ability to do all of this internally though). You can't totally stop the conveyor, but you can put it into creep mode and save energy. Here's how that works. Run the conveyor fully loaded and record the kW and determine the percent of full load (kW) rating of the motor. Run it unloaded and record the kW and similar percent. Set up the analog output of the VFD to be sent to the PLC. In a conveyor, kW should track directly with speed, meaning at any percentage of full speed, the kW should be the same percent of normal kW, which you have just determined. Then program the PLC so that if the kW output of the motor is ever below 50% of what the kW should be for that speed, this means the conveyor is unloaded, or under loaded, so the PLC then commands the VFD to run at a preset minimum creep speed. The reason that you need the creep speed is to know when the conveyor gets reloaded again, otherwise you must monitor it with some external sensor that may or may not be accurate. So what you do is keep watching the motor kW and if a load drops on the conveyor at creep speed, the kW will spike above the minimum setting, then you remove the preset creep speed command and allow the drive to go tonthe speed it needs to.

Two more notes on this: 1) it doesn't matter if you don't need variable speed, this can be done at a fixed full speed on the VFD. But you need the VFD for the creep speed issue because that is how you can use the motor itself to determine that a load has just dropped on the conveyor. A motor that is stopped cannot tell you anything about the load. 2) kW monitoring is important here because current monitoring alone can be fooled by voltage drop. kW is always going to be representative of actual shaft loading.

Sandeep,

Gurus have given many inputs to consider...

Some additional points to consider , which are not clear from the posted information,

1.Which conveyor would be stopped,one at the start of a line or one in between a series of conveyors. ..Control system for conveyor would be determining this design

2. Depending on weight of product , would you consider belt-weight sensing systems to stop conveyor.

3. What are possible overflow margins / time for which other conveyor components of the system will hold material and not fall over by spillage

Dear Gurus,

I think we are close to solve the problem.

We have three conveyors-

1)Infeed conveyor having Drum motor of 0.12Kw.

2)Weighing Conveyor having the same Drum Motor.

3)Rejection Conveyor having geared motor 0.37Kw which we are going to change in drum motor with dc drive 0.4Kw.

Is it possible to take start signal from Photo sensor.

And stop signal from 0 load signal from load cell.

Please explain.

Regards,

Sandeep

On thing you can do is set a photoeye at the beginning of the conveyor and one at the end. When the product enters the conveyor, use a counter to count up. When it leave, count down. As long as the count remains 0, the conveyor should be off. This is good if you have multiple products on the conveyor at one time.

· Normally the upstream conveyors are given interlock from the downstream conveyors running status so that the material conveyed do not get clogged at the discharge chute .

· In your case , you need the interlock from the upstream conveyor material flow.

· The best would be to provide a ultrasonic material sensor which works in radar principle and it can detect the availability of material over a wide area . The unit to be calibrated .

· If 'no material' is sensed ,then an interlock can make the downstream conveyor to run at a creep speed , otherwise it will continue to run at the set normal speed .

CAUTION:

· It is not advisable to start and stop the conveyors frequently , the motor is likely to get damaged , especially if it is a high KW rated.

· Also it is not advisable to run a motor at a very LOW speed for long duration , the cooling fan of the motor would be just turning without giving any proper cooling effect to the motor windings.

You are in India. Turn the conveyor off manually using a human. This is the most cost effective solution for your geographic region.

Please give technical answer.

I dont have time to read this in india.

where I will go to hire one person to Switch on /off.

Thanks for suggestion.

if you don't have time to read ANY answer in India, then why ask and what would be the point in anyone replying to you.

It would seem to me that you don't like what you have read in the replies you have been given, so you've now come up with your own answer...and I quote..

where I will go to hire one person to Switch on /off.

GA from me!

you are probably being a little harsh

English is not Sandeep's 1st language

the idea that the solution is to hire someone to babysit a conveyor is absurd

Sanddep expressed that & requested technical, not procedural solutions...

"the idea that the solution is to hire someone to babysit a conveyor is absurd"

Actually, I disagree. I work(ed) as an automation engineer for an alternative energy company in Silicon Valley (California). We designed all of the processes and machinery to manufacture our core component here in the US. We set up and operated the pilot plant, proved out the concept and manufacturing economics etc. etc. etc. for 3 years. 6 months ago the CEO (of Indian descent) announced they are going into full production and building a brand new plant...in India. 99% of us who did the work to get them there are now unemployed, I was kept on for a few more months during which I was transferring our knowledge to EEs in India. They knew ABSOLUTELY NOTHING about automation and in fact, when a process seemed too complex or expensive to them, they simply abandoned it and hired a human to stand there and do some inane repetitious task. Why? Because they could I guess. So it irks me that corporate greed is moving production jobs to places like India, yet many of the low wage engineers there have no idea how to do simple tasks like the one in this thread (are you KIDDING ME? You can't figure out something THIS simple? REALLY?). So what's their answer? Post his problem here and then get snotty about DEMANDING that someone do his freaking job for him? FOR FREE?

No. Absolutely not. I could have done that job in my sleep, but now I am collecting an unemployment check from my fellow taxpayers because I cannot find any engineering jobs here that are not being filled by unskilled low wage alien H-1B workers with dubious engineering credentials. I lurk in here because I like to keep abreast of what others are doing, but I think I'll have to leave. So many of the posts here are from idiotic "engineers" who are not capable of doing the job that they undoubtedly took away from someone more qualified but are willing to work for less.

This is BS!

And to those who have by now convinced themselves that I am a xenophobe, I am not. I have worked with many very good and very qualified engineers from many different countries and I have no qualms about where someone is from. But believe me they are getting laid off as well, because if they know what they are doing, they tend to believe they should be justly rewarded. The problem I am ranting about is IDIOTS like this OP who are doing the work that used to be done by qualified people, from wherever they were, but are willing to work cheap and burden others with their inadequacies.

FOOWEE (Frustrated Out Of Work Electrical Engineer)

you put into words what I couldn't be bothered to do in reply to Garthh. You are so right..... GA from me!

Become a member, we need new blood with a different take on life, I'm getting rather lonely being the only one.

One less person out of work.

Dear Brich,

Please try to understand I dont like to read someone like Wal (commentetor).

I am just using your suggestions to understand something electronic controls.

I am not Electronics Engineer. I am Mechanical Engineer.

Please dont misunderstand me.

Dear Brich,

Now I feel comfortable.

If anybody dispointing me. It's ok.

But somebody taking it by geographic way.

I think, it's not good.

Please close this matter here only.

let's share some technical Ideas.

Thank you very much .

Regards.

Actually looking at your motor sizes

"

1)Infeed conveyor having Drum motor of 0.12Kw.

2)Weighing Conveyor having the same Drum Motor.

3)Rejection Conveyor having geared motor 0.37Kw which we are going to change in drum motor with dc drive 0.4Kw.

"

all conveyors must be in the same room?

At least one end of each conveyor must be in the same room; or else there will be a discontinuity, and product will fall off. Please just think about it a little.

You have contributed nothing.

Some replies are indicating conveyor could be 1km long but look at the size of the motors. The replies have to be put in prospective in the fact that all the conveyors (not just start and finish (st*pid) could actually be in one room and there is not a proble with start stopping individual drive.

Just what, exactly, was wrong in my post? (Which you evidently did not understand.)

speaking of perspective try looking at the date...

sandeep got the information he needed or he would be posting to this thread

I predict you will have a short & rocky tenure on this forum

Deep, please take time to read this.

You seem really fixated on a 'technical ' answer.

I have given you a possible solution. The apparent provocation was deliberate on my part.

Where to hire? Hmmm, let's see.....probably don't have to. If things have stopped then surely somebody will be idle.

If you really want to remove human intervention from this then there has already been enough information tabled for you to design a "technical" solution. I don't think there is any need to repeat the suggestions or micro design it on a sight unseen basis.

Now, once you have the ultimate answer you will need to cost it, estimate the human resource allocation for implementation and commissioning, have a guess on the MTBF and upkeep commitments and so on.

With the information in hand you will table it at the next capex and opex budget meeting hoping that you will have the required resource allocation approved.

What will you be asked?

How will this increase the bottom line? When will this break even? Can't somebody just turn off the conveyor?

Darn those bean counters!!!

Now, when you are an engineer AND it's your money all good, but.......

Why?

What will you gain?

The cost of starting up multiple conveyors might outweigh the savings, if power savings are the issue.

Depending on how long each conveyor is will depend on how long it take to run up to speed, and working backwards from the machine thro several conveyors (irrespective of speed) to material source, if I understand you, you want everything to start when material is ON the first conveyors.

It CANNOT work that way...well it can..but the word is "function" NOT "work".. and the result is as you have stated.. burnt motors etc...

I would leave them running, and get your system checked and all the conveyors interlocked.

I agree with brich on power concumption. But if the conveyor is to be down for a lenghty time you may want to fully stop it. I have done this in the past for long and short conveyors. Mostly for robotic aplications with a few more bells and whistles but this was the basics of my system. Which included three belt driven conveyors.

I had one photoeye on the output of the feeding conveyor interlocked to start the next conveyor if it was stoped. On the second conveyor I had a photoeye that triggered a counter in the PLC that would time how long it took for one part to reach the end of the conveyor. The timming was tricky since it was possible for the conveyor accepting the parts to be stopped and not up to speed. To help with a the not up to speed motor I added another photo eye at mid point of the conveyor. This photoeye would track if the part arrived within the timming range I had determined. If it did not arrive a beacon would flash indicating there was a problem. If all was good the conveyor would keep moving. At the end of the conveyor was another photoeye that would trigger the next conveyor and trigger the conveyor to stop if there was no more parts incoming. If there was no parts the conveyor would shut off after 15 minutes.

Dear T

Thank you very much

this is what I want

Please brief me

which and how many and where I suppose to locate Photo Sensor

Which PLC I can Use

We are using Indicator which is counting Products

Is it possible to take signal from it or PLC is must

step one make up a truth table, which will help you determine all of the possibile states of all the conveyors & sensors

you can probably do the whole thing with relays & plug in timers

It depends on the material. Different stull needs different solutions.

Perhaps you are not focusing on the correct problem. It seems to me that the overall problem is the stoppage of production. I feel that most of your energies should be spent getting production restarted, and preventing the stoppages in the first place.

If your conveyors are overheating due to being unloaded, how do they handle being fully loaded?

Yes, you could save energy having them shut down when not doing something usefull. You have to ballance the cost of the implementation of the shutdown against the savings in energy.

I think you might be better served by putting your resources into preventing the situation by fixing the source of the stoppages in the earlier lines.

Gentlemen.. can we get back on topic? Who cares how its spelt or who uses what grammar!!

Very true - so long as people take the time to work out what is meant. So, having missed the OP's post #13 was sarcasm in response to #11, and reacted with umbrage to #13; thereby evoking a flurry of geopolitical and ethnic stereotype "On Topic" ranting [complete with GA's for zip to do with 'sensing materials']: You are hardly in the position to object to (posted OT) banter on grammar, spelling, and dare I say, the impact on comprehension; instigated similarly, courtesy of AP 2 'nit picking' at Kris's attempt to normalize the testicle free AP games.

Not an objection, a request.

Not a criticism, an observation