Direct Logic Plc's (automation direct)

[Johnny Rotten]

Ronnie, I will do that. Yes, if what has been said about Stage is true, I will learn it. From what I have read, it has potential to work 'similar to' how we think. And how we 'think' is how any machine ends up 'running'.

One thing I hate about RLL is trying to guess what 'new rung 54' is doing while everything previous has been 'happy'.

It turns out that 'new rung 54' has changed timing on more things than one could ever imagine. I'm sure you have been there Ron.

So, yes, I hate RLL. RLL is realy an adaptation of something that has nothing to do with 'scan times'. It is old school schematics adapted to a computer, in simple terms. I do realize that!

I do not have the benefit of tweaking older programmes in 'my' data bank. I making it all up.

Thanks Ron so much for the link, I will get there, not for a bit, but I'm here for a byte.


John

 

[elevmike]

Thanks ElevMike. That's great information, and I'm with ya all the way. After the motor stops from high pressure, do you put a time delay in before restarting and returning the 'ram'?

TWO pressure switches.. The first pressure switch activates the ram return. This might be adjustable to some extent. The idea is to detect how compacted the refuse is compacted...before bursting the container etc..since each compacting will stop at a differnent position the only way to tell this is via a pressure switch. The second pressure switch is an equipment protection device, to prevent damage to the system as a whole. The second pressure switch must be reset manually.

I'm in a quandry about the hopper. I am going to put a photo eye in the hopper and time delay the response to lessen nuisance 'cycle starts'

Any thoughts? yea.. the photo eye is a BAD idea... Who's going to clean the photo eye on EVERY cycle?? I think the operator decided when to start the compact cycle.

I dont remember what we did about this but the project was simmiler.. There was a 100+ HP shreader (construction materials usually). The shreadder fed a conveyer which used magnets to remove metals, then dumped directly into the compactor. Actually the compactor was ramming into a 40 ft walking floor, or pushout box trailer. The whole thing was very effective, since they charge and dump by the cubic yard. I think they got like a 7 to 1 ratio at the end of it all.

 

[kamenges]

Most of the paper bailers I've seen in the past used emitter/receiver ultrasonics. These seemed to work pretty reliably. Granted, you have some ambient noise. But you will be time filtering anyway so the occasional spurious trigger shouldn't hurt you.

Keith

 

[Johnny Rotten]

Thanks so much ElevMike. I will adjust the gain on the light source and burn any deviant dust particles.

If I told you who the client was, you would not believe it. Anyhow, I will take this to my 'team', and work on it.

I do not see any other options other that a photo eye, but you may, and probably do, know better.

The hopper is steel, so perhaps a shielded proxy?

The hopper is 4' wide.

Maybe we could 'shove' sticks in that silly hopper, and 'yell' to the operator to start that 'guy' as needed.

Of course, he would have to yell back to stand clear.

Thanks again,
John

 

[elevmike]

Most of the paper bailers I've seen in the past used emitter/receiver ultrasonics. These seemed to work pretty reliably. Granted, you have some ambient noise. But you will be time filtering anyway so the occasional spurious trigger shouldn't hurt you.

Johnny,

This seems to be your best bet. My fist thought would be some load weighging device, but you also should look into the ultrasonic sensors also.

Free advice worth evey penny: Never tie youself into a system configuration that you know will be diffucult to work with. It's a recipie for disaster and pi$$ed off customer etc...

For reasons unknown by me we have a bailer in the warehouse collecting dust for the last 30+ years. Maybe over the weekned I'll go out and take a look at it. I'll let you know what I find out.

Mike.

 

[testsubject]

Another possibility is to use a Linear Resistive Transducer located physically inside the cylinder. It is like a steel shaft sliding in and out of a hollow steel shaft. the voltage change is directly proportional to the stroke length. i.e. A 10" stroke cylinder would change from 0vdc to 10vdc at full stroke. I recently used one and it works quite well. A little pricy but if you only have a couple of components instead of several...

 

[Johnny Rotten]

Thanks everyone for your help. We ended up going with the original design and will make changes if needed.

John

 

[lynn davis]

Johnny
I just looked at your problem with the photo eye. Just a thought, could you use a encoder or other device for a pulse trigger on the conveyor head roll shaft and caculate the material going in then stop the feeding. useing the ram upper limit to reset the counter?
Lynn

 

[Johnny Rotten]

Unfortunately, no. The material on the conveyor will not be consistent. My software is basically complete, just have to sim it before the control board is installed in the field. Then, the real fun shall begin.

So, I've gone with 1 (one) photo eye in the hopper. I've been told by 'higher ups' not to worry about dust. I may have to add a second photo eye, but will try time filtering for now.

We have gone with 1 (one) pressure switch as the hydraulics have a pressure relief valve that is adjustable. I am also time filtering the forward/reverse cycles. If the ram gets 'jammed' it will time out.

Thats basically it. The existing Shredder has 'stop/start/reset...etc' pushbuttons, and I am not too happy about having the plc start/stop this machine automatically. Again, 'higher ups' have told me not to worry about this. Of course, no safety devices have been bypassed.

Of course safety will be my number 1 issue.

Thanks once again everyone. What an amazing source for excellent information. Hope as time goes on, I can become one of those sources.

John

 

[elevmike]

Ok so I was at an aprartmet complex today where the elevator machine room was adjacent to a trash compactor. Basicly tennents dump their trash in a shute that lands it in a hopper, then the contents of the hopper is compacted into the rolloff box. Low and behold the hopper has a reflective photo eye mounted on the side about halfway up. The photoeye is mounted on the outside, peeking through a 2" hole. The reflector is also mounted on the outside in the same manner making it easy for anyone to wipe the lenses now and then. So Watching it for a few minutes, it seems the photoeye must be blocked for like 10 seconds in order for the compactor to activate.

Maybe Mr. Rotten's on the right track after all...

 

[Johnny Rotten]

Hopefully Mike. I've had to work on those 'guys' as well. I finished the wiring today, but 4 centimeters of ice prevented us from running it. Once I have it working, I would like to post my logic, and pictures. How do I do that here?

I found out last week that we were going to stay with one solonoid valve. As soon as you start the motor, this baby is in forward. The solonoid only puts it in reverse. I will have to do a little re-working on the timing.

John

 

[Ron Beaufort]

I would like to post my logic, and pictures. How do I do that here?

how to post a (zipped) logic file

how to post graphics

 

[Johnny Rotten]

As you can see, it's all good to go. Yes that is my control cabinet.

My next project will be making a PLC out of wood. 2x4's(ouch, 50x100mm) pinecones and various spring loaded saplings will be the brains.

Not sure if I will use tcp/ipx, to 'talk' to my other installations. I do beleive fire will be involved.

Merry Christmas everyone.

John Paul Miron



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[Johnny Rotten]

Thanks TESTSUBJECT, ELEVMIKE, Tom Jenkins, Steve Bailey, Ron Beaufort, and of course Mr. Phil.

I would have gone this way anyhow, its a simple machine. It is not structured as nicely as wished. 'Are you done yet?'

Mechanical guys did a nightmare of a job. We had the hydraulic unit running last Monday. Not allot of time to debug.

May be interest to others; - had to have two seperate machines automated together.

Used 120V relays to interface with other machine. Mechanical guys had to cut .70M (about 2', no toes) of conveyor to allow the bin to fit. Not too sure why. I booted up my comp., noticed that, and left.

E-Stops work great. Two separate E-Stop circuits/two machines/two voltage sources. Interlocked each E-Stop circuit through corresponding ESR's. Called them ESR1 and ESR2. 'Reset' pushbutton did not work at first (for ESR1), as ESR2 was de-energized, vica-versa. Dooh! Fixed. Wired Reset P.B.'s to be in parallel with interlocking contacts, just so the machine would start. Felt stupid.

The E-stop in my logic is 'abit' overdone. It is only used as a secondary failsafe, so don't get that wrong if you read it. I just took an input from ESR2 into the PLC. Other than that, it is hard wired.

Initially thought (did) wiring the PLC Input (for E-Stop) after the E-Stop P.B.'s would work nicely. That circuit still had to get to the ESR (held closed), and what if a wire from another of the D0-06AR inputs backfed that relay. One little strand from another input wire could have kept that ESR in. Of course I changed that.

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Johnny