Allows injection and measurment of 4-20 mA current loops into a CANopen network.

How it began

For a long time, the sprinkler irrigation system of the family yard has suffered from a recurring problem. The irrigation pump that supplies water to the sprinkler circuits is driven by a simple pressure switch, which, with the help of an accumulator, starts and stops the pump motor at an approximate fixed pressure. This approach causes that the range of the sprinklers increase as soon as the pump starts, until the circuit reaches the maximum pressure, time when range starts to decrease as the pressure drops while the pump is stopped.

After some research on how to solve this issue and make sprinkler operate smoothly the constant pressure system path seemed the way to go. A system based on a closed loop in which on the one hand a pressure transducer measures in real time the pressure of the circuit while a control system (PID initially) manages the speed of the pump motor through a frequency converter can solve the problem. It seems obvious that there is nothing special about this control system as all components can be purchased from any automation manufacturers, but if I do that, where is the fun?

That’s how the idea of building the entire system component by component comes up, starting with this module in that will read the 4-20 mA signal from the pressure sensor of the circuit and passing it to a CANopen network.

What it offers

This module allows capturing up to four 4-20 mA current loop signals and expose them to a CANopen network. Both the four analog signal inputs and the CAN interface are fully opto-coupled.