rslogix 500 and scp instruction

stu

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Join Date
Aug 2005
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hi guys, i need help i have a automation direct hmi and vfd and i have a ab ML1200 i have wrote a program to run the vfd and to use a the hmi to control the speed of the drive, but i have a problem with the speed ie if i have the speed set on 999 on the hmi it is 27.8hz on the vfd if i set the hmi on 1000 the vfd goes up to 56.9hz there is no control. i have used a scp instruction but i dont know much about setting them up can someone help.
thanks all the best
stu
 
HOW is the speed on the VFD being controlled? Is it by an analog output from the PLC? Is it by a value being sent over communication from the PLC to the drive. Is it by a value being sent from the display to the drive? Please define this. Then we'll go on to the next question.

You mentioned an HMI, Micrologix 1200 and a VSD in previous threads. Is this the same setup? In that thread you mentioned the diplay speed was in BCD. Did you do any conversion of that?
 
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hi
the vfd is being controlled by a value from the hmi-ml1200 to a analog output module direct to the vfd,using a scp instruction.

INVERTER SCP.jpg
 
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/Sigh.

Just to get you started, try filling in some blanks.



Actual PLC Brand: _______________________________



Analog Output Card Model Number: ________________



Analog Output Card Configuration: _______________



Actual VFD Brand: _______________________________



VFD Configured Speed Input Type: ________________

 (0-10V, -10/+10V, 1-5mA, 4-20mA, Frequency, other)



Ladder Logic with your SCP:  (Post).

 
Along with answering RDAST's questions there is this point. In your previous threads you mentioned that the control on the HMI was in BCD and that you couldn't change that. If so you cannot directly use the setting from the HMI. You will have to use the FRD command to convert the number from the display to a standard integer. Otherwise you get the jumps you mentioned.
 
bernie_carlton said:
Along with answering RDAST's questions there is this point. In your previous threads you mentioned that the control on the HMI was in BCD and that you couldn't change that. If so you cannot directly use the setting from the HMI. You will have to use the FRD command to convert the number from the display to a standard integer. Otherwise you get the jumps you mentioned.
Click to expand...

so does that mean if i put a frd command i put source n7:2(the hmi value and dest- O:1.2 (OUTPUT CARD)??

THANKS FOR YOUR HELP
STU
 
No - in the FRD command the source will be N7:2, the destination will be some unused 'N' location. Then THAT location will be the Input (top variable) in your SCP command.
 
bernie_carlton said:
No - in the FRD command the source will be N7:2, the destination will be some unused 'N' location. Then THAT location will be the Input (top variable) in your SCP command.
Click to expand...
what figure does the input max & scale max have to be?
does the scale max have to be 16383?
 
rdrast said:
/Sigh.

Just to get you started, try filling in some blanks.



Actual PLC Brand: _______________________________

 

Analog Output Card Model Number: ________________

 

Analog Output Card Configuration: _______________

 

Actual VFD Brand: _______________________________

 

VFD Configured Speed Input Type: ________________

(0-10V, -10/+10V, 1-5mA, 4-20mA, Frequency, other)

 

Ladder Logic with your SCP: (Post).

Click to expand...

Do you think we could get Phil to make this a canned response?
Would save a lot of time as opposed to asking 20 questions

Dan Bentler
 
Actual PLC Brand: AB ML1200_____________________________


Analog Output Card Model Number: _1762-OF4_______________



Analog Output Card Configuration: _______________



Actual VFD Brand: AUTO/DIRECT_______________________________



VFD Configured Speed Input Type: _____4-20ma___________
(0-10V, -10/+10V, 1-5mA, 4-20mA, Frequency, other)



i hope that will help
 
what figure does the input max & scale max have to be?
does the scale max have to be 16383?
Click to expand...

Input max = the highest number you will have the operator enter on the display.

Start the 'scale max' at half the full range. Try the system. Check the RPM when the max RPM is entered from the screen. If the measured RPM is low then raise the 'scale max' and retry and vice versa. It will probably get you to the right answer (assuming over and under speed won't hurt your machine) faster than trying to calculate it.
 
See PDF below for data table values for your card. They differ depending on how you have the card configured. ( not answered above)

dataformatOF4.jpg
 

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