Direct Logic Plc's (automation direct)

Johnny Rotten

Member
Join Date
Dec 2004
Location
Ontario, Canada
Posts
194
New member here, as of today, Dec. 9, 2004. I stumbled upon this site and found it to be amazing. I've been taking courses on A/B Plc's, Siemens, and Direct Logic. The bigger plants in sounther Ontario are still 'stuck' on A/B, but we all know that will change. I am just in the process of real world software programming, but have wired/commisioned large systems for many years. What are peoples thoughts on Direct Logic? Would anyhone have any Recycle/Baler/Compactor programmes they would like to share? I am not asking for a freeby. But it sure would be nice to know my programming structure is 'normal'. Plc's are funny, and is there a pre-defined structure that everyone goes by? I'm just making it all up from the top of my head, but it works well. I focus on layout, simplicity, and 'easibility' for others to understand how it works. I am currently programming two Direct Logic D0-06AR/and AA Plc's. Anyhow, looking forward to talking with 'you' pro's. Thanks in advance, John Paul Miron.
 
The AD PLCs can certainly be programmed in plain vanilla ladder logic but you may wish to give the RLL Plus stage programming a try. It does take a different mindset though.

Instead of analysing - what turns on this output - you divide up the sequence into defineable steps and keep subdividing until each section has a definable action (this is what action is taking place) and a condition (this is what occurs - timer timeout, count achieved, input making or unmaking - to change that action).

Once thoroughly anlysed the logic almost writes itself - each action with a stage. Within each stage are the outputs which are on in that stage and the conditions to JUMP to the next stage. The writing, testing and troubleshooting get much easier.

Check out their examples in the PLC CPU manual.
 
I stand with Bernie on this one. Block/Stage programming is where AD really shines and the software is so much more intuitive than RSLogix (IMO).

Now, I think in Block/Stages when programming. It has become second nature with me. There are some on this board that do not care for it but I swear by it. Give it a whirl. You may be really surprised how easy it is.
 
I did a compactor for a friend of mine a few years ago. Actually it was pretty simple, and done with a DL-105.

The hydraulic system had a pressure releif/bypass valve, and a couple of pressure switches. On the "compacting" stroke the ram was driven until a pressure switch tripped, then the unit would return until it hit a limit. The second pressure switch was to shutdown the motor in case of overpressurization of the system.

It went somewhat like this:
1) start motor, wait two seconds
2) energize valve to compact materials.
3) pressure switch 1 trips, compact valve coil is dropped.
4) return valve coil is energized and ram returns to home position.
5) when ram hits home limit, return valve is dropped, motor is shut down.

Additionally there are a couple of protection timers, and as mentioned before a pressue limit switch, and a pressure releif valve.
 
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'?

This is also an interesting project as we must interface a converyor and compactor (horizontal) with an existing paper shredder. The paper shredder is worth about $100 Large ones as Tony Soprano would say, so its a challenging project.

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'. I originally was gonig to put one at the bottom of the hopper, delay it for 10 seconds or so (field adjust) and start the compact cycle; the second photo eye would go at the top of the hopper with a small time delay (in the logic of course), to stop the conveyor and shredder to basically avoid a great big mess. I am currently thinking on just using one photo eye, centre high, and use timming functions in the logic to decide when to start the cycle and when to stop material comming in the the hopper. Any thoughts?

Thanks Bernie, and TestSubject too. Talk with you all soon.
John
 
Unless the garbage in Canada is a lot nicer than ours, I would think fouling of a photo eye could be a problem. I guess I would look at a load cell on one leg of the hopper to indicate when the load is high enough to run the compactor, and on low load start a timer that times out and stops the compactor.
 
Interesting, its just paper. Clean and dry.

I do not believe the mass at 50 Kilograms would give similar results to 110 Pounds of garbage.

But I think the garbage may weigh more, but not sure. Could be some potential field tweaks.

John (im joking of course)

thanks Tom
 
Shredded paper is likely to be pretty dusty. To a photocell, a coating of dust may be indistinguishable from a full hopper. One solution is to periodically blow a puff of compressed air over the photocell. That works pretty well as long as your air supply isn't prone to be loaded with water or oil. Another possibility might be to check to make sure that the eye gets cleared every time the ram extends. If it doesn't, you signal a fault condition and sound an alarm or shut the compacter down.
 
Thanks Steve, the shredder is dropping the paper (shredded of course) onto a converyor.

The converyor takes this and drops it directly into the compactor hopper.

That is a great idea!

It will be an extra to the contract. Just joking.

Could an airline be brought out and placed beside the photo eye? Put a 120V valve on it, and fire it accordingly?

John
 
That's what I've done. I had a Fife edge guiding system that would get a little squirrelly when dust accumulated on the analog photosensor that made up the position feedback for the actuator drive. I included a regulator so we could control the pressure. As I recall, we fired the solenoid valve for a half second pulse every hour. If your hopper turns out to be very dusty, you may want to fire the solenoid more frequently.

Just be sure that the air supply is dry. The dust will accumulate faster on a wet surface, and be more difficult clean off once it dries. Quite often balers like this are located near an outside door and subject to wider temperature variations than other places in the building. If you're going to get water accumulating anywhere in your air lines, that's the sort of environment where it's most likely.
 
I have a few (dozens and dozens) of photo-eyes that are installed in a very dusty environment. I have airlines installed on the more remote eyes as well as the more critical eyes. The rest of the eyes are less critical and are easier to access for a quick wipe across the lens.

Some of the lines are activated only periodically (by timer or event), others are on constantly.

In a couple of places, where I'm looking for material fill, I've had to replace the original eye with a Bindicator. The environment was too dusty, with varying humidity and temperature (producing a fog you could cut with a knife!). The eyes occasionally read the dust in the air, or the fog, and produced false positives. (Sonar units did not work because those conditions varied so much.)

The Bindicator has no such problem. The material level has to be up to the Bindicator to produce a "Full" signal. In some cases two or three Bindicators are required to indicate the "true" level status. In some cases, material fills higher on one side than the other.

The Bindicator has a simple set of Normally Open and Normally Closed contacts. The detector is a small paddlewheel. It is driven by a fractional HP (1/60? ..really small) motor. There is a slip-clutch arrangement that allows the motor to keep turning while the paddlewheel is stalled by the material. At the clutch there is a set of contacts. If the motor is turning but the paddlewheel is not, then the torque applied by the motor causes the contacts to change state.

It's a really simple arrangement.
 
Paper is one of the harder materials to deal with. Paper can plug up a compactor very easily. When the bail is almost made it takes very little to complete the bail. A full hopper would be disaterous.

With a preloading conveyor a set of load cells would be perfect. It wouldn't take long to figure out how much would be needed to finish a bail.

My experience is with an old HRB-II bailer, rebuilt many times.
 
Very nice LogBoss. Im stuck with photo eyes, and am going to 'go with it' so to speak.

My basic idea is this, and everyone will find fault in it im sure.

Put a photo eye at the bottom of the hopper. This is not in direct line of the falling product, so starting the 'ram forward' cycle after this 'guy' has been 'closed' for 10 seconds or so, seems to make sense. That will only ensure the chambre is full, or 'bail' if that is what it is called.

As stated before, I'm using RLL, so on that particular rung, the photo eye contact (in logic) will start a timer. If that timer reaches 5 or 10 seconds (field adjusted) the ram will go forward. It will stop if it hits the ram forward limit, or high pressure switch.

If the upper photo eye does similar, it will indicate the hopper is full, and stop product.

When all photo eyes are happy, product will commence.

Keep in mind, im keeping this one very basic.

There is much more to this project, and the motor timing functions are a great idea.

This old 'guy' and I mean machine, not me, only has one pressure switch.

We are going to send the 'bale' into a very large container, and just keep sending and sending. So it is not really a compressed 'bale' of paper going into the large container.

The pressure switch will activate only when this 'huge', and I mean HUGE container, is full. So we are 'bastardizing' a horizontal baler, to do things different.

Having two pressure switches only makes sense, as I would hard wire the 2nd pressure switch into the E-Stop circuit accordingly, as well as an input on the PLC.

Should have it working before Christmas.

A load cell is out. Totally. It does not 'tell' the converyor to 'stop', its just a guess. Not appropriate here. (the load cell said 'she' was only at 50 Kilos, but the plant manager said the mess on the floor... damn dry stuff, or was that the heavier stuff, who hit the button for dry?)

Anyhow, thanks again.

I am rather shocked to find this site. Like I said, Im a newbie to real world software programming, but Im not stupid. I was always the top of my class, which means little.

Thank you so much for your help, because it is real, and it trully makes sense. It is practical, and again, amazing.

It allows one to choose from a vast array or great ideas. Ideas that work, I hope.

Anyhow,

John
 
you know, Johnnie, you're certainly welcome to stay with that regular-old ladder logic programming ... but ... I'd sure like to see you at least take a look at stage programming too ... the basic idea is that if you're still using ladder logic on that Automation Direct system, then it's pretty much like driving a car with an automatic transmission - but still manually shifting from gear to gear ... sure, you can do that ... but why would you want to? ...

anyway, if you want to at least take a quick peak at stage programming, here's a painless way to see how it works ...

previous post about stage programming

let us know what you think ... and welcome to the forum ...
 

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