PSEUDO-Random generator in STL/SCL

duckie112 · Apr 11, 2012

Hi, for an assignment on school I need to make a PSEUDO-random generator coded in STL/SCL wich needs to make random numbers from 50-999 and from 5-30 minutes. I have searched the forums and came across some but couldn't figure out how they worked and if they were for Siemens S7. Also the random numbers need to be stored in 2 MW markers and the function needs to be called between 1-5 minutes.

KalleOlsen · Apr 11, 2012

Check www.oscat.de, there's a random generator included.

Kalle

duckie112 · Apr 11, 2012

KalleOlsen said:
Check www.oscat.de, there's a random generator included.

Kalle

Is that site also in english? My German is very terrible.

L D[AR2P#0.0] · Apr 11, 2012

Here's an S7-300 implementation:

http://www.plctalk.net/qanda/showpost.php?p=240792&postcount=10

duckie112 · Apr 11, 2012

L D[AR2 said:
Here's an S7-300 implementation:

http://www.plctalk.net/qanda/showpost.php?p=240792&postcount=10

I tried that when I was searching the forums a bit more only found that 1 to be actual useful a bit. Heres the problem I have with it: Whenever I write that code in my FC2 block it says it cant copy the block to the PLC anymore. And whenever I delete that code the block can be copied again. And whats exactly inside DB1?
I understand the first part a bit but the 2nd part I'm having problems with. First if I change L 100 to
L 1000 and MOD that will it be range 1-999 then? Second can I store the random number in like say MW20 since the last part from SLD 4 I don't quite understand. (I'm practically new to SCL/STL and learning it for the last 3 weeks.)
EDIT: Never mind

got it working but it seems it makes random numbers higher then 100. The values its generating is good enough for my random minutes but not good enough for the random 1-999. Also is it possible to generate the numbers every minute? Since its generating it very fast now and they need to stay like a minute the same.

duckie112 · Apr 11, 2012

The 0-999 part with random parts is solved with /D 1000 from the result so it stick with a Rounded value between 0-999 (sometimes above 1k but thats almost never) also I was able to call the block every 15 minutes now (forgot I had a looped mechanism wich goes on for 14 then off for 2 seconds and go on for 14 again etc.

L D[AR2P#0.0] · Apr 11, 2012

The second part counts the occurances of the numbers between 0-99 and stores the counts in DB1. I imported the DB into xcel to draw the charts.

duckie112 · Apr 11, 2012

L D[AR2 said:
The second part counts the occurances of the numbers between 0-99 and stores the counts in DB1. I imported the DB into xcel to draw the charts.

Ah ok that's how that part works

Oh well with some work arounds with math functions I got the results I wanted so thanks for the help.

Peter Nachtwey · Dec 5, 2012

See this
http://www.codeproject.com/KB/recipes/SimpleRNG.aspx

If I had to do this over again I would probably make it a function block with m_w and m_z declared as VARs. I would still need some way of randomizing the initial value of m_w and m_z.

Code:

(*
	RNG calculates random numbers from 0 to 1.
	RNG requires two in_out variables to maintain state.
*)

FUNCTION RNG : REAL
	VAR_IN_OUT
		m_z : DWORD;
		m_w : DWORD;
	END_VAR
	VAR
		u: DINT;
	 END_VAR
	m_z:=DINT_TO_DWORD(36969*DWORD_TO_DINT(m_z AND 16#FFFF)+DWORD_TO_DINT(SHR(m_z,16)));
	m_w:=DINT_TO_DWORD(18000*DWORD_TO_DINT(m_w AND 16#FFFF)+DWORD_TO_DINT(SHR(m_w,16)));
	u :=  DWORD_TO_DINT( SHL(m_z,16))+DWORD_TO_DINT(m_w);
	RNG :=DINT_TO_REAL(u+1)*2.328306435454494E-10+0.5;
END_FUNCTION

shooter · Dec 7, 2012

peter he graduated last year.

bara_hence · May 28, 2013

Peter Nachtwey said:
See this
http://www.codeproject.com/KB/recipes/SimpleRNG.aspx

If I had to do this over again I would probably make it a function block with m_w and m_z declared as VARs. I would still need some way of randomizing the initial value of m_w and m_z.

Code:

(* RNG calculates random numbers from 0 to 1. RNG requires two in_out variables to maintain state. *) FUNCTION RNG : REAL VAR_IN_OUT m_z : DWORD; m_w : DWORD; END_VAR VAR u: DINT; END_VAR m_z:=DINT_TO_DWORD(36969*DWORD_TO_DINT(m_z AND 16#FFFF)+DWORD_TO_DINT(SHR(m_z,16))); m_w:=DINT_TO_DWORD(18000*DWORD_TO_DINT(m_w AND 16#FFFF)+DWORD_TO_DINT(SHR(m_w,16))); u := DWORD_TO_DINT( SHL(m_z,16))+DWORD_TO_DINT(m_w); RNG :=DINT_TO_REAL(u+1)*2.328306435454494E-10+0.5; END_FUNCTION

One question the last line

Code:

RNG :=DINT_TO_REAL(u+1)*2.328306435454494E-10+0.5;

is different from the original at http://www.codeproject.com/KB/recipes/SimpleRNG.aspx is this because the PLCs inferior resoulution??

If written as the original:

Code:

RNG :=DINT_TO_REAL(u+1)*2.328306435454494E-10;

Peter Nachtwey · May 28, 2013

bara_hence said:
One question the last line

Code:

RNG :=DINT_TO_REAL(u+1)*2.328306435454494E-10+0.5;

is different from the original at http://www.codeproject.com/KB/recipes/SimpleRNG.aspx is this because the PLCs inferior resoulution??

If written as the original:

Code:

RNG :=DINT_TO_REAL(u+1)*2.328306435454494E-10;

With out the 0.5 the routine returns -.4999999 to 0.49999999. The 0.5 adjust the random number to be between 0.0 and 1, that's all.

PSEUDO-Random generator in STL/SCL

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L D[AR2P#0.0]

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