Add Delay to to the Analogue out

[T J SHARON]

Hi all, 

 

I have an FB (ST) which will calculate the UINT values that need to send to DA outputs. Currently i was requested to add a delay between the calculated output & DA units.

I am not sure how to do it? can I just use a TON? Any sample ST code?

 

[chelton]

How big a delay are you wanting to achieve?

You will need to push the current value onto a stack at a defined rate. Then move the last value of the stack to the output.

If you were to create a delay of 10 seconds updating every 100ms you would need 100 registers.

 

 

[T J SHARON]

hi Chelton,

Mostly 1-5 seconds delay.  

Do you have any sample prgm?

 

[chelton]

Try something like this. Time delay is adjustable from 0 - 10 Seconds

IF EN AND Run AND NOT Ring_Buffer_Initialize THEN 
	Ring_Buffer_Write_Index:= 0;
	Ring_Buffer_Read_Index:= 0;
	Ring_Buffer_Size:= LIMIT(0,Time_Delay,10);
	Ring_Buffer_Size:= Ring_Buffer_Size*10;
	Ring_Buffer_Initialize:= TRUE;
END_IF;
IF NOT Run THEN 
	Ring_Buffer_Initialize:= FALSE;
	RB_Loaded:= FALSE;
END_IF;
IF P_0_1s AND Run AND NOT ONS_Trig THEN
	Ring_Buffer[Ring_Buffer_Write_Index]:= Analogue_In;
	Ring_Buffer_Write_Index:= (Ring_Buffer_Write_Index+1)MOD Ring_Buffer_Size;
	IF Ring_Buffer_Write_Index = Ring_Buffer_Read_Index THEN
		RB_Loaded:= TRUE;
		Analogue_Out:=Ring_Buffer[Ring_Buffer_Read_Index];
		Ring_Buffer_Read_Index:= (Ring_Buffer_Read_Index+1)MOD Ring_Buffer_Size;
	ELSE
		RB_Loaded:= False;
	END_IF;
	ONS_Trig:= TRUE;
END_IF;
IF NOT P_0_1s THEN
	ONS_Trig:= FALSE;
END_IF;


	

 

[T J SHARON]

thanks 

It seems like a code for FB.

 

Could you please specify the input,output and internal variables and data type? I managed to identify some.

• EN (bool) ------>INPUT
• Run (Bool)------>INPUT
• Ring_Buffer_Initialize (bool)
• Ring_Buffer_Write_Index
• Ring_Buffer_Read_Index
• Ring_Buffer_Size
• Ring_Buffer_Read_Index
• RB-Loaded (bool)------>OUTPUT
• ONS_Trig (bool)------>OUTPUT
• Ring_Buffer[ ] ------>INTERNAL
• Analogue_In (UINT)------>INPUT 
• Analogue_Out(UINT) ------>OUTPUT

Appreciate all your help

Regards,

T J sharon

Edited January 28, 2020 by T J SHARON

[chelton]

Yes code for a FB

• EN (bool) ------>INPUT
• Run (Bool)------>INPUT
• Ring_Buffer_Initialize (bool) internal
• Ring_Buffer_Write_Index UINT internal
• Ring_Buffer_Read_Index UINT internal
• Ring_Buffer_Size UINT internal
• Ring_Buffer_Read_Index UINT internal
• RB-Loaded (bool)------>OUTPUT
• ONS_Trig (bool)------>internal
• Ring_Buffer[ ] UINT array [100] internal
• Analogue_In------>INPUT
• Analogue_Out ------>OUTPUT
• Time_Delay  UINT INPUT

 

I put a bool output (RB-Loaded) that indicates the buffer is full and the time delay is active.

There is no value moved to the analogue output on start-up until the delay is reached. 

Edited January 28, 2020 by chelton
missing variable

[T J SHARON]

hi Chelton.

Thanks a lot.

Let me go thru and work it out.

[T J SHARON]

HI, 

Its tested and working well.

I have 8 Analogue inputs and will be using 8FBs, which need 800 words for Buffer_Ring array.

But i don't have much free words in H-memory for Buffer_Ring array. 

Is there any way that i can assign  Dmemory for the array? ( Assign "AT" in the Fb variable session not possible as this FB is using simultaneously for different Analogue inputs)

 

 

[chelton]

Can you increase the FB memory allocation area?

(PLC menu → Memory Allocation → Function Block/SFC Memory → Function Block/SFC Memory Allocation)

Another option would be to change the array variable from internal to an in/out variable the just pass a DM array in as a parameter on each instance 

[T J SHARON]

Hi , 

 

I already extended FB areas of H-memory. Is there any issue if I change my over all FB memory allocation to d10000 ?

Mean while I will try the feasibility of using IN-OUT  method.

 

 

[chelton]

I can not see any issue with changing the auto allocation memory area from H*** to D*** but I haven't had to do it on any projects.

You would just need to ensure the memory area will remain free.

D20000-D29599 and D30000-D31599 are for special I/O memory.

 

[T J SHARON]

Hi Chelton, 

thanks a lot.