Would this be a difficult PLC application? 3

[enzo2015]

Hi ,


I would like to build a machine that does what I’ll describe below. I’m not sure if some of the smaller ladder logic PLC’s I’ve seen can do all of this, but what I read in their descriptions, it seems so.
Maybe someone here could tell me if this is possible, and where I go to find a programmer for this system. Thanks for reading this



I’ll try to explain as best I can.
As you see in the drawing:

http://photobucket.com/albums/d58/ERmd/ENG forum/?action=view&current=PLCdiagram.jpg

There is a LCD screen with various display views. “A” shows the machine is operational view. “B” shows set temperature for each tank(Tank1&Tank2). “C” shows 3 adjustable operation parameters,Soak, Ramp, Tail, Total time, and Vent.
The way this works is through a series of timed solenoid valves, and sensors. There will be some sort of button to activate the start.
At that time Sol. 2 will open for soak time, then at the finish of that time Sol. 2 stays open and sol. 4 opens for ramp time, and at the end time of ramp, Sol. 2&4 stay open, and Sol. 5 opens until tail time is reached , then Sol.4&5 close.
Sol. 2 stays open until total time is reached, then closes. After a 3 second delay(maybe this time is changeable as well) Sol. 3 opens for a set “Vent” time, then closes.
After all have closed, display”A” reads ready again.

I should also point out that display “A” shows the words”Soak, Ramp, Tail, Total, Vent” as it goes through those times. These words will be shown where “Ready” is in display “A”

There are 3 sensors that are for water levels.
Sensor 3 tells Sol. 1 to open if water falls below sensor location in tank 1.

Sensor 1 is a safety that if air is in the system at this location, Sol. 2,4,5 close, and Sol. “Vent” opens until sensor 2 reads water again, then Sol. 3 can close, and system can read ready.


The PLC also needs to control 2 PID zones(Tank 1 and 2) individually

I would like an internal clock to be settable to turn the machine on and off.

This seems to be most of it, I might add a few minor details, but what do you think? Is this a very difficult project for a PLC and programmer? Also any leads where I can find a pragrammer would be great.


Again Thanks very much for reading all this=)

 

[Skogsgurra]

No, doesn't sound very complicated at all.

One of the mini-PLCs will do it. And the programming is so easy nowadays that you should be able to do it yourself. You have already done the toughest part; to decide what the "machine" shall do and how it shall do it.

I would use a logic diagram to program the function and I think that you should be able to have the program ready and tested (simulators available in many of those micro-PLCs) in a couple of days. Most of that time will be needed to educate yourself. A PLC programmer with some routine will do it in a couple of hours.

What you may need to add outside the PLC is the PID functions - they are usually not included in small PLCs. On the other hand, they are more or less commodities these days.

Gunnar Englund

http://www.gke.org

 

[AGomaa]

Just to add some of the Automationdirect micro PLC includes P&ID functions. However using separate PID controller will make your design much simpler. By the way most of PID uses analog output, I can not see one in your application. if it is for temperature control you may include an output from the PLC to stop heating/cooling during some stages of the process.
Programming is not big difficult fro such application as Gunnar mentioned. If you interested I can help.

 

[enzo2015]

Hi,
thanks to both of you for your help. I want to think a little more on this project, but if "AGomaa" wants to help me with programming, please contact me when you have time at:
jepy@mac.com

Thanks again....

 

[ADMIRALKEN]

This is a very straight forward and somewhat simple application. The plc programming will not take long. There are several small PLC's that could handle all your logic, including the PID functions. I don't know what kind of budget you have, but the "LCD Screen" is going to be the most expensive piece. You didn't mention it, but is there going to be an independant E-stop on this?

 

[enzo2015]

As far as the E stop, yes, I'm trying to iron out all details. One E stop would probably be the sensor #1, where if air was present at this location, the machine will take action with all solenoids to correct it. Would that be correct? Also, is the E stop controlled by the PLC, or something else?

I would like someone to help with programming, if it's not too expensive. Please contact me if interested, thanks....

 

[ScottI2R]

Enzo,
I would not leave E-STOP up to the PLC. Possibly program a self monitoring SAFE STOP function into the system,(this would effectively diable the system on its own), but there definatly needs to be an E-STOP control that can be operated by the human factor. In a nutshell, I am saying that I do not trust ANY machine to stop itself in the case of failure. E-stop should be hardwire into the electrical design. Also allow for contol of the process should E-STOP be required. eg) You would not want an overhead crane to release it's load because of an E-stop.

BTW, I am not sure, but I believe the AB Micrologix 1500 series includes PID control.

Hope this helps

Scott

In a hundred years, it isn't going to matter anyway.

 

[ewbdale]

Enzo,

What part of the country are you in?

Ernie

http://rasp-controls.com/

 

[sqdguy]

I would run the power of all your outputs thru a contactor. Hard wire an Estop to the coil of the contactor. Add a contact to the Estop and run that into the input of the plc to show status.

 

[Ozee]

Enzo2015

I was involved with a similar application. The guys who implemented the software can be contacted at

http://www.spsoftwareautomation.com.au.

They offer solution based on Allen Bradley or Siemens as well on other PLCs. They should be having a very similar software like the one you have described.

Cheers

 

[snox135]

We actually have an application vey close to this, except on a larger scale. One thing you might want to look into is instaed of 3 sensors switch to one analog sensor. Then you can use it's value to turn things on and off as you wish. Then you could also display the actual level on your screen.

For the E-stop I agree with sqdguy. This is how we have your E-stop's set up.

 

[milmat1]

If budget will allow, Use a GE-FANUC Quik-panel control with a small 90-30 Rack (5-slot). You will have PC control with the TouchScreen HMI all in one.About 3000.00
And you program the logic, script functions, Screens all in the same software.(Proficy Machine Edition).
The operation you described will be an easy one,
Gunar hit it on the spot "You have already done the toughest part; to decide what the "machine" shall do and how it shall do it." Thats the biggest challenge we have in programming, Be cause the sales people generaly don't know what they sold !!


It's easier to get forgiveness than permission !!!!!!

 

[Lsmith]

I have used Moeller Mini PLC,s for various small applications. Have a look on the moeller web site and you will be amazed at what these mini plc,s can do. The easy has text blocks that can display messages on the screen which could save you money as you dont need to fit a separate HMI. The software and cables are cheap compaired to some other makes on the market. There is a built in simulator which you use to test your program before using it. Its very easy to learn and is not complicated at all. Try it and you will be amazed. As far as e-stops are concerened i agree with all the others it needs to be hardwired outside the plc.