FB/DB Issue

Hi guys, I am seeking your advice once again.

I have created a function block (FB1) to count 3 motor's running hours that I can re-use. The FB1 has one input variable to say the motor is running and 4 outputs for secs, mins, hours and days which I then store in a data block (DB4). DB4 is used to store all the motor's running times. I have used the same FB1 and created 3 different instance data blocks (DB1, DB2 and DB3).

The FB1's are called by a function call (FC1). FC1 is called in my main OB1. 

My problem is this:

In my FC1, the three FB1 calls are on separate networks in my ladder code. When I go online and monitor the running times in DB4, only the function block that appears at the top of the ladder code seems to store a value. I am very confused as to why this is happening. Is it a scanning issue or would duplicated addresses cause this? Maybe I should create a separate data block for each motor?

Please ask and I can post pictures of all my blocks if needed. It is hard to explain without the images, I know.

Thanks David

Hi, 

Can anyone help me with this problem?

Thanks David

DS_7

Hi, 

Can anyone help me with this problem?

Thanks David

David, by your own admission it is more helpful to have some pictures. More - we do not know which software or hardware you are using. It will be most helpful to understand how you measure that there is a problem.

Normally each call of the DB should have its own instance DB - is this what you have? Multi instances of an FB is a {rude word} to monitor. It will depend on what environment you have to instruct you how to do that properly.. if that is your question.

BR

Thanks for the reply DP. 

I am using step7 v5.5 and PLCSIM with a dummy project just to test if it will work before I download the code on a real CPU.

I will explain better and post pictures of my program when I get home. 

David

Ok, 

I am using step7 V5.5 and the PLC simulator to test a piece of code for counting running times of 3 electric motors.

I have created a function block (FB1) which is used to generate the running time. At the output of these function blocks I MOVE the FB time output's to a separate address in data block (DB4). I use the same FB1 for 3 different motors, which I have separate instance data blocks DB1, DB2 and DB3.

The function call FC1 is used to determine if a motor is running and to call the FB1 for each motor. FC1 is called in OB1.

Now when I simulate all 3 motors running by setting their running flags high and go online and monitor data block 4 I expect to see all the times start to increase. BUT this does not happen, only the FB1 that appears at the TOP of the ladder logic starts to count. This is exactly what I want to happen but I just don't know why all 3 motors running times can't all be incremented at the same time with the same FB1. 

I will attach images of the most important part of each block in new posts. Please don't hesitate to ask any questions. 

Thanks David 

This is the block where I am trying to monitor all 3 motor's running times but only one motor's time actually starts incrementing.

It is also the FB that appears at the top of the ladder logic for some reason?

Hello.

Could you please make screen captures of all the networks in FC1 while it is simulating? A PDF print-out would be most welcome of the whole program.

I recommend you use a tool such as ShareX to make screen captures.

Regards.

Hi DP,

Yeah, I never thought of attaching all the blocks in a single PDF document. I will get that sorted and re-post the program.

Thanks for your help

David.