Help with plc motor sequence

Eugenious

Member
Join Date
May 2009
Location
california
Posts
8
Hello,Can anyone help me with this program I'm trying to develop?

I'm using a AutomationDirect CLICK plc.

Sequence will start and stop using a remote start/stop station.

I have 4 conveyor and crusher motors and here is how I want the sequence to go:

Starting sequence:
motor 1 starts
motor 2 starts after motor 1 run confirm and 30 sec. Delay
motor 3 starts after motor 2 run confirm and 30 sec. Delay
motor 4 starts after motor 3 run confirm and 30 sec. Delay

* I need to monitor motors in such way that if any of them doesn't start within programed time then they allshould stop or not start.
Also got an e-stop that needs to imediatly shut down whole sequence in case it gets pressed.

Stopping sequence:
motor 4 stops
motor 3 stops after motor 4 stop confirm and 30 sec. Delay
motor 2 stops after motor 3 stop confirm and 30 sec. Delay
motor 1 stops after motor 2 stop confirm and 30 sec. Delay

Thanks for your help.
Eugene.
 
Hello,Can anyone help me with this program I'm trying to develop?

I'm using a AutomationDirect CLICK plc.

Sequence will start and stop using a remote start/stop station.

I have 4 conveyor and crusher motors and here is how I want the sequence to go:

Starting sequence:
motor 1 starts
motor 2 starts after motor 1 run confirm and 30 sec. Delay
motor 3 starts after motor 2 run confirm and 30 sec. Delay
motor 4 starts after motor 3 run confirm and 30 sec. Delay

* I need to monitor motors in such way that if any of them doesn't start within programed time then they allshould stop or not start.
Also got an e-stop that needs to imediatly shut down whole sequence in case it gets pressed.

Stopping sequence:
motor 4 stops
motor 3 stops after motor 4 stop confirm and 30 sec. Delay
motor 2 stops after motor 3 stop confirm and 30 sec. Delay
motor 1 stops after motor 2 stop confirm and 30 sec. Delay

Thanks for your help.
Eugene.

Trying to develop ?

This is PLC's 101 and fairly straight forward using cascading timers and set\reset bits, what are you stuck on ?
 
the e stop has to pull all power and cannot be wired into the PLC unless its safety related. So wire it to the Main power contacter.
Use contactors with feedback to the PLC if one trips it'll send the lack of closure to the PLC rest is in the programming and fairly basic Is there a particular step your having trouble with?
 
Monitor each motor run command and if run status is not achieved (within a few seconds) when the command is energized, set a fail to run alarm bit.

Setup a run permissive for each motor; a bit that has to be set in order for the respective motor to run. Condition the permissive bit with anything that should shut that motor down; ESD, fail to run alarm, etc.

You'll probably want your alarms to seal in and require a reset once the alarm condition has cleared.


the e stop has to pull all power and cannot be wired into the PLC unless its safety related. So wire it to the Main power contacter.
Use contactors with feedback to the PLC if one trips it'll send the lack of closure to the PLC rest is in the programming and fairly basic Is there a particular step your having trouble with?

I disagree with this comment about the ESD wiring. I am not aware of any standards stating this requirement of an ESD. ESD systems are typically based on end user or company standards, requirements, and / or preference. I have seen plenty of systems with hardwired ESD's. I have also programmed plenty of systems where the ESD is handled in the PLC. Bringing the ESD buttons back to the PLC as individual inputs allows you to determine, much quicker, which ESD station was tripped.
 
Code does NOT allow estops to be handled in the PLC (unless it's a safety-rated PLC). Yes, you can bring back an aux-signal to the plc to monitor which estop has been activated, but the PLC cannot be used to provide the EStop function.

Also, you cannot re-energize the power simply by pulling the estop button. It has to be intentionally, manually reset.


Though I'm not entirely sure why this discussion is going on in this thread... Eugenious, exactly what are you having problems with???
 
I agree with blamb on the ESD. The ESD indication need to take the fastest path to PLC in order to reset the program to a safe state. Some contactor take a second too long to drop out so what happens when someone push/pull the E stop rapidly would result in multiple pump/motor to drop out and start all together because the PLC hasn't seen the E-Stop yet. The result can be very bad.
 
Great link mordred. My only issue is that it doesn't mention the practice of running an aux contact off your e-stop into the plc for the plc to know that the e-stop has been hit.
 
Eugenious - Sorry that this thread has gotten so off track. Please let me know if my first post helped you at all or if you are still having trouble with your logic.
 
Bobbias: The reason it doesn't mention running an aux to the PLC is because the PLC is just monitoring -- that's purely within the code. That article is only concerned with LIFE SAFETY -- which is the purpose of the ESD. The monitoring aux isn't life safety...
 
Now that we're talking about e-stop safety...

Now that we're talking about e-stop safety,do you guys know if I use a 4PDT ice cube relay as my safety relay(even though it's not a real safety relay), would I be committing a big mistake?

And regarding the plc programming help,thanks so much for the great tips,i'm one of those types of electricians that used to work only with relay logic, until not too long ago until I convinced my company to make it much easier.
And before I begin a new project I just like to ask around to make sure I do my best.
Appriciate all the help.
 
if I use a 4PDT ice cube relay as my safety relay(even though it's not a real safety relay), would I be committing a big mistake?
I've seen a lot of contractor-installed equipment and I've never run across a real 'safety' relay, just standard control relays. Both A-B bulletin 700 types and ice cube relays are in use. The important thing, as I understand it, is that an electronic device (relays being electromechanical) not control a safety circuit, unless it's rated for such duty.
 
if I use a 4PDT ice cube relay as my safety relay(even though it's not a real safety relay), would I be committing a big mistake?

Yes
 
The thing to keep in mind when choosing a relay for your ESD is to make sure that the contacts of the relay are rated for the current that you will be switching. As Doug-p mentioned, there are plenty of systems out there that use standard relays for this purpose, as well as AB 700 type relays. It all depends of the size and purpose of your ESD.
 

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