Allen Bradley L32E 1769 PLC (MOV) Instruction

Hey
I was having some problems with a MOV instruction.
I have a pressure that once it reaches a certain pressure I want it to close two valves.

What I have is a GEQ instruction in front of two MOV instructions in parallel.
when the pressure (A>= B) move a 0 to close both valves.
I thought this should work but I cant even get it to write to one of the valves.

any idea what im doing wrong?

I appreciate the help

What about if you set a latch when value A is greater than B, then latch is going to close both valves.
You did not mention when the valves are going back to be open.

Yeah, you probably have destructive bits going on. What is opening/closing the valve now? Probably an OTE/coil that you need to break instead of writing a 0 on top of.

Instead of writing a O, try doing a momentary UNL to the valve output.

Thanks guys for the feedback
Currently for both valves there being opened and closed by an operator
Via SCADA software from a control room.

For safety reasons if the operator gets busy and the pressure
Increases to the Setpoint on the GEQ instruction then
both valves need to close and if the pressure goes below the
Setpoint in the GEQ instruction then the operator can reopen
The valves again.

Currently I’m just writing a value to the output in the plc
The raw value is 0-10000 and in the SCADA software I scale this
To 0-100. The operator inputs a 0-100 to move the valve.

Is there a better way to accomplish this than using the MOV instruction?
I’m just needing a instruction to write a value to the valves output.

Thanks

So this is a variable valve that gets controlled by an analog output I'm guessing?

I think the issue is that somewhere in the code something is already writing a value to the analog output tag. It's not good enough to simply write a 0 to this tag, you have to STOP writing the original value to the tag at the same time, or the last instruction wins- in your case it sounds like the original instruction comes shortly after your new "MOV 0" instruction.

I agree its like another command is overriding the MOV statement but its pretty simple and straight forward.

All i have is a GEQ instruction that says once it sees a pressure setpoint then it moves to both MOV instructions that are in parallel and writes the value to close both valves.

is there a better way to do this?

thanks

does this output have to be setup for PID (Data Format) before i can use the MOV instruction to write to the valve to close it?

thanks,

I think you're going to have to upload your code or give us more information about your situation. Way too many unknowns to give you any useful advice.

OK I can do that, let me know were to send it to

thanks,

I guess to keep things simple.

I have a raw output that opens/closes a valve. this valve is manipulated by entering a value to move it.

The valve raw output has a range from 0 -10000. If i want to move the valve half way, I input 5000 or 12mA.

What is the best instruction to use in a Rslogix 5000 program that can write a value of 10000 to the output of the valve.

Currently I'm using a MOV instruction, but its not writing the source value to the output. Not sure why


thanks,

As rupej stated in an earlier post, you need to provide more detail. A MOV instruction should work, but what address are you writing to with Source B in the MOV instruction? You need to make sure that the same Tag is not being written over by another instruction in the program.

Thanks guys
Here is more info about my issue.
I need to just make sure what i'm doing a correct method or maybe you can direct me to a better way to make this work?

I have two Analog outputs connected to a 1769-OF4CI card. I have both of these cards "Data Format" configured as Percent Range and I also have the
limits for both of these cards configured at Low=0 and High = 10000
Local:3:O.Ch0Data = Valve_1
Local:3:O.Ch1Data = Valve_2

An Operator will move Valve_1 to say 50% open and Valve_2 to 75% Open by writing a value to the Output addresses Local:3:O.Ch0Data and Local:3:O.Ch1Data, this works fine.

What I need to accomplish is at a defined pressure point that I have set (I'm using the GEQ instruction to say if A>= B), I need to close both of these valves at the same time.

How would I overwrite the operators setpoint that they have set to make the valves close no matter what the valve the operator has set?

thanks,

How is the dat from the operator being written to the PLC id it written once when the operator inputs it or it being continually being written to thr PLC.
If it is being written continually then you need to disable this when you want to write zero to it.

Alan

Thanks Guys I got it working.
It was my fault, I had some scaling errors that was conflicting with the MOV instruction.

I appreciate your direction to lead me to correcting this issue!


Thanks