[CANbus message storing]

Hello!

I need to communicate with an external device using CANbus, Layer 2standard.

I have a question regarding the stored values.

The external device sends Unitronics PLC 8 bytes of data. Let's assume the data frame first two bytes are byte 0, (most significant bit) : AA BB  and byte1 CC DD. 

I will store the values in Mi's, starting with Mi0.  How is the data saved? Does the MSB stay as MSB, so that the  MI0 value would be AA BB (43707 in DEC) and MI1 would be CCDD( 52455 in DEC).

Or the outcome would be Mi0= CCDD, Mi1=AABB? 

 

Thanks in advance!

 

[Measuring time between 2 events]

Thanks for Your fast reply. The example helped me!

Hi Tempo,

There are several ways to measure the interval between two events. One of them is actually what you suggested, hence storing the timer current time into a variable.

The attached application demonstrates how you can do that (with several other features).

 

This application was taken from the U90Ladder sample projects folder. There are several other timed based applications, so you can check what method is better for you.

If something still isn't clear, please let me know.

[Measuring time between 2 events]

Which is the most precise method, how do measure time between two events? I have a device with analog output. I need to measure the time between, when the analong input to m91 is greater than 0 and when it reaches to maximum AI value. It is a force sensor. 

Is there a way to store timer elapsed time value in a mi? It seems I can display it on HMI, but it is not somewhere in the memory?

The example under help uses 1 sec pulse, but it is way to long time.

 

Best regards

[watering system with 2 pumping centres]

Those i/o modules are all connectable with each other? I just choose the the appropriate one with needed i/o's and hook it up? 

I think i will build my system with V130, EXRC1, XL module D16A3-RO16 and AI4-AO2. 

[watering system with 2 pumping centres]

But would CAN bus mean that i have to use 2 controllers? Because it seems to me i can use only a special cable  (EX-A2X) to connect a controller to a expansion module, which i would place in the second watering station. 

[watering system with 2 pumping centres]

Hello

I have been given an assignment  to automate a conveyor line watering system. The system consists of 2 pumping centers. The distance between them is about 20-30 meters. I need to check that, but its about that in lenght. 

1 pumping center consists of 2 electrical motors. One motor is controlled with VFD, the other is just on/off. There are 6 electrical waterpipe valves for spraying the conveyor. They were switched with an power optocoupler.  Also there are 5 water level sensors. In addition, there is 1 flow meter, which analog output is currently connected to VFD, which controls  water pump engine. Other motor is just for mixing the liquid. The pumping centre was connected to siemens PLC system via fieldbus i/o module.

Now the siemens PLC system is gone and I decided to put up a system with Unitronics PLCs, as we studied them in the university. I planned to  use a Vision 230 in one center and in the the other some external i/o module. Flow rate comes to plc, which then controls the VFD via analog output and sends info about  pumping rate to the other centre, so that the pumping rates would be the same. 

The pumping rate will depend on conveyor speed and can also be set by buttons. I chose 230 as it offers buttons, which are beneficial in a factory.

 

My question is about connecting the two center stations. What is the best solution for it, as its a factory with a lot if electromag interferences? 

 

Also, in the old systems motor contactors were switched directly from PLC output module. Is that ok thing to do? Motor contactors in use are Siemens 3RT1015. Why arent flywheel diodes used in parallel with the contactor coil? Or i dont need do use them if I use relay output of the PLC?

 

Im sure I will have a lot of questions coming up, as this is my first project in real life. 

 

Thanks in advance