Greetings

Hello All

Just joined forum and am looking forward to learning new things. My background is in HVAC and I am trying to get my company into the current century as far as controls are concerned.

I have been trying for days to make a simple Alternating motor
control, these are floor mounted medium temp hot water dist. pumps

Here is what I want to do. one single discrete input (NO) that will alternate motors upon each change of the "ON" state.

1st sequence - when the input is on then motor #1 comes on, when input is off then motor #1 turns off.

2nd sequence - when the same input is on then motor #2 turns on, when input is off then motor #2 turns off

I want it interlocked so both can't come on when the input is true.

I also want a true proof input applied. this is a discrete NO input that is a pressure switch that will confirm that the pump is actually pumping water via a pressure change, I would like this input to be able to switch motors in the event that the proof input is not in the "ON" state. this is protecting against a sheared coupler from motor to pump, our older methods with Siemens only use a current sensor on the motor which tells me the motor is running but in the case of a sheared coupler no water is being circulated and the building suffers freeze ups. I would also like a 15 min OFF DELAY as well, this will keep the boilers from tripping out on high limit if the pump immediately shuts off when input is off, this is not a good thing.

Please forgive my rambling and lack of terminology, I am newer to plc implementations and want to learn more on the HVAC side of things. I am not neccessarily asking for the program all nice and pre packaged and written for me, I would like to see some existing examples for other controllers ( so I can figure it out ) and any tips as well. I want to learn it, not have someone do it for me.

I am wanting to use a basic click PLC with 120 v output to pull in control relays to activate the control voltage of the appropriate motor starter.

Any help is greatly appreciated.

Jordan

Hello Jordan, and welcome to the forum.

I have not worked with the Click PLC yet, but I would expect that what you're looking for is commonly called a flip-flop. This subject has been beat to death here so you should be able to find tons of information by using the forum search feature and put flip flop as the search terms.

Each time the input goes true, you want to select the other pump.

While it is true you want the selected pump to run.

If the pump is commanded to run, but the aux contact input does not turn on within say one second, then you will consider that pump "faulted" and switch to the other one. (You'll need a delay, because the contactor will take a few milliseconds to close)

One detail you didn't cover: If the switch is turned off, the pump will continue running for another 15 minutes, but if the switch is turned back on during that time, what do you want to happen?

Paul

Jordan,

Welcome to the forum.
It seems that you have a head on your shoulders, and you are familliar with your application, (Which is a good thing)
Often enough, your criteria will change as you get into things......

What you need to do is write some pseudo code, a written listing of the application that you would like to follow.
This will help you transfer that information into WHATEVER code-type that your controller accepts. (ie Ladder/STL/VB/C++)
Do you have any software or hardware that you can test on?
The application is very simple, and I am sure that you can tackle it once you attempt it first.

OkiePC said:

Hello Jordan, and welcome to the forum.

I have not worked with the Click PLC yet, but I would expect that what you're looking for is commonly called a flip-flop. This subject has been beat to death here so you should be able to find tons of information by using the forum search feature and put flip flop as the search terms.

Each time the input goes true, you want to select the other pump.

While it is true you want the selected pump to run.

If the pump is commanded to run, but the aux contact input does not turn on within say one second, then you will consider that pump "faulted" and switch to the other one. (You'll need a delay, because the contactor will take a few milliseconds to close)

One detail you didn't cover: If the switch is turned off, the pump will continue running for another 15 minutes, but if the switch is turned back on during that time, what do you want to happen?

Paul

Click to expand...

Paul

Thank you for the flip flop tip, I will search it in a minute.

To answer your question, during the 15 min off delay, if the input would turn on, then I wouild like the other pump to cycle on.

The switch I am refering to will be a simple temp controller sensing outside air temp and either make or break upon whatever I have set at, So I was assumnig that I would not get a ton of input changes here in colorado being as cold as it is. I would set if for 65 degrees, if it is under 65 then the switch would be on for days in some instances, I should have clarified that a little more.

BTW I am from Tulsa........Nice to talk with you

Jordan

SNK said:

Jordan,

Welcome to the forum.
It seems that you have a head on your shoulders, and you are familliar with your application, (Which is a good thing)
Often enough, your criteria will change as you get into things......

What you need to do is write some pseudo code, a written listing of the application that you would like to follow.
This will help you transfer that information into WHATEVER code-type that your controller accepts. (ie Ladder/STL/VB/C++)
Do you have any software or hardware that you can test on?
The application is very simple, and I am sure that you can tackle it once you attempt it first.

Click to expand...

SNK

Thank you For your suggestions. although I am not sure if my head is on straight or not.

I have downloaded the click software and am getting ready to order a click PLC for a cooling application on an air handler. So I will have a unit or two in a few weeks, I have been trying all sorts of things in the software but cant really test until I have a unit set up on the bench. I have used the syntax check and come up good but I don't believe that will simulate what I am trying to do, it will just tell me if i left anything out.

Thanks
Jordan

JordanR said:

... I have used the syntax check and come up good but I don't believe that will simulate what I am trying to do, it will just tell me if i left anything out.

Thanks
Jordan

Click to expand...

The syntax won't tell you if you left anything out or not. It just tells you that the elements you have connected are connected in a way that does not violate the rules of the software.

Hi Jordan,

Here is a clasic on the flip-flop and may help

http://www.plctalk.net/qanda/showthread.php?t=22175

Jordan,

A debounce may be needed for the pressure sw. No promises that it works. But I will refund your money if it does not.


Edit: I can tell already it does not work. I put the branch up in rung 4 (flip flop) in the wrong spot. Oh well this gives you something to do!

milldrone said:

Jordan,

A debounce may be needed for the pressure sw. No promises that it works. But I will refund your money if it does not.


Edit: I can tell already it does not work. I put the branch up in rung 4 (flip flop) in the wrong spot. Oh well this gives you something to do!

Click to expand...

Milldrone

WOW........I am in over my head, I worked on my version last night at work, similiar to yours but not quite the same. I printed yours out and I am going to study it tonight at work.

I only got as far as trying to get them to switch automatically if the X002 input goes away, I have not even tried doing anything with the OFF delay for the pumps.

Anyway......Thanks for taking the time to do that. send me your address in email and I will send you a six pack of beer ( I'M Serious )

Jordan

JordanR said:

To answer your question, during the 15 min off delay, if the input would turn on, then I wouild like the other pump to cycle on.

The switch I am refering to will be a simple temp controller sensing outside air temp...

BTW I am from Tulsa........Nice to talk with you

Jordan

Click to expand...

Hi Jordan! I am in OKC and live out west of Minco.

I bet your temp sensor will have a hysteresis setting so that it does not go off and on rapidly unless there is a significant temperature bounce.

I downloaded the Click software but it doesn't want to run on my PC

I get the splash screen when I try to start it, and Task Mgr shows the click.exe process running, but the app never opens up...I think I'll try it on my laptop when I get off work...

Anyone else have this trouble?

Paul

OkiePC

Yes it does, this one input (O/A) will keep one of these pumps on for days on end, then we will get a 68 degree day and then the pump will switch unless there is a malfunction and it would switch sooner, atleast that is what I am hoping for. Milldrone did some great set up and I ordered the parts yesterday. So I will be able to do extensive bench testing just using contactors and two toggle switches as inputs.

CLICK is running for me on my home PC and my personal laptop, nver had any issues except forgetting to download the USB driver for the cable LOL

Thanks for helping on this, I plan on giving full credit to all those that have helped on the last screen in the C-more micro that I am going to add to this. Figured that is the least I can do.

Jordan

JordanR said:

I am going to study it tonight at work.

Click to expand...

Jordan,

Don't study too hard. There are some errors. I believe this new version will work. The minimum time run timer (s) on this version should make more sense to someone new.

JordanR said:

Anyway......Thanks for taking the time to do that. send me your address in email and I will send you a six pack of beer ( I'M Serious )

Jordan

Click to expand...

You can always private message me (feature of this website).

OkiePC said:

I downloaded the Click software but it doesn't want to run on my PC


Anyone else have this trouble?

Paul

Click to expand...

Paul,

I checked the AD forum, and could not find a thread with anyone that could not run the software.

ypf_108,
You need to download the software http://support.automationdirect.com/products/clickplcs.html

Paul,
Maybe try re-installing it...