Jump to content

watering system with 2 pumping centres

Recommended Posts


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







Link to comment
Share on other sites

I would use CANbus with Unitronics UniCAN protocol.  This is very simple to use and works great.  Use a good quality cable, run the cable away from VFD and power cables and EMI shouldn't be a problem.  Flywheel diodes are not mandatory but are recommended.  It depends on the coil and how often it is switched on and off.  In your case, I would use them on the Siemens 3RT1015.  I don't bother on small relays with infrequent switching.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...