We have a watering system for several households where we pump water from a nearby lake.
There are two pumps where the speed is controlled by two frequency controllers of 0-50 Hz and 400VAC.
There is a pressure sensor (0-10 bar) that today feeds a PLC. If the pressure is 0-5 bar both pumps spin at 50Hz (max speed), above 5 bar up to 7 bar first one pump scales down towards 0Hz and then the other pump. At 7 bars pressure both pumps are at standstill at 0Hz.
The frequency controllers is controlled by a VDC between 0-5VDC, e.g. 3VDC input means 30Hz to the motor.
The PLC is old and has been overheating a lot this summer so it needs replacing. I've already built a simple temperature and pressure control in the RPi using a Arduino One board so I figured I could continue on that project and add the frequency control as well...
Would this be something that I could build?
Is there already something similar?
What do I need to adjust the 0-5VDC output to the frequency controllers?