CHILLER OPERATING HOURS

[naifmbo]

HI EVERY BODY,
HOW CAN I PROGRAM MY S7-300 IN FBD TO GET MY CHILLER OPERATING HOURS,BECAUSE THE TIMERS AVAILABLE ARE LIMITED BY 2H46M30S(HOURS,MINUTES,SECONDS)?

THANKS.

 

[HenryLamboo]

Hello naifmbo,

I don't know how to do this with a Siemens PLC, but what you can do is counting the minutes. Use one timer which is set for a minute. If the timer is ready add one to a counter and restart the time.

Best regards,
Henry

 

[Rheinhardt]

Hi naifmbo,

Use your timer and set it for 1 hour Time, if an hour is over increment a counter in a normal memory area and trigger the reset on the timer, you can use a DINT that should cover the time span. Your hours get stored in the DINT and the timer can reference your minutes and seconds.

Hope it helps

Regards
'
Rheinhardt

--Off all the things i've lost , i miss my mind the most--

 

[naifmbo]

WHAT KIND OF TIMER I HAVE TO USE?

 

[Keldog]

I'm not sure if Siemens has retentive timers or not but if they do use them so if you have to shut down your chiller you don't lose the timer, cause if you use a normal timer when the chiller shuts down you will lose what ever time is timed on the timer.

 

[Rheinhardt]

Hi Naifmbo,

I would use your 1second bit in your clock byte and increment a normal INT value for seconds, when INT value == 60 Increment your minute INT and so on, I though about the timers and it would be alot easier using INT value with your clock byte.

You only INC on a positive edge of the clock byte bit.

Maybe somebody else can assist in the matter

Hope it helps.



--Off all the things i've lost , i miss my mind the most--

 

[Rheinhardt]

Here is a small program i wrote.

A "Unit_Running"
= L 20.0
A L 20.0
A "1 Second pulse"
AN "Mask Run"
JNB _001
L 1
L "Run _Time"
+I
T "Run _Time"
AN OV
SAVE
CLR
_001: A BR
S "Mask Run"
A L 20.0
AN "1 Second pulse"
R "Mask Run"


Here it just counts in second pulses if running and not and i retain the value.

You can now compare the run time to 60 seconds for 1 minute and so on.

Regards

--Off all the things i've lost , i miss my mind the most--

 

[naifmbo]

Reheinhardt can you explane it in FBD?

Thanks.

 

[Rheinhardt]

Copy the code to a block in Step 7, Use covert to LAD FBD, both should work, i posted it in STL due to Non LAD function in this forum, if you notice there is a L20.0 is a and bit that the LAD part of Step 7 uses.

In your hardware configuration use the Clockbyte, make BYte 0,

Now the 5th bit would be the 1second bit, it is on for 1 sec, then off and then on and so on.

So on a positive edge i trigger a increment, i use the mask bit so that the PLC does not increment on each scan, i reset the mask bit when i see low value at pulse bit.

When you convert this code to STL you will see it is really very simple, you need to read the help file on the clockbyt, you cvan change this adress to 0 on the hardware configuration properties of your CPU.

Hope it helps.

Rheinhardt

--Off all the things i've lost , i miss my mind the most--