As a proof of concept, I stacked a few Arduino shields to test if I can stop a gate with overcurrent detection. My setup is composed of:

- (mandatory these days) Arduino Uno

- seeedstudio grove shield, (very handy) to add 3 push buttons: Open, close and stop test functions

- protoscrewshield with screw terminals to connect power supplies, motors, ...

- relay shield: 4x 3Amps 24V relays

- a revamped board of mine (hot-glued on top) with (very basic non-inverting) amplifiers and 0.100ohms shunt resistors.

On my installation a motor sinks about 0.5A in normal conditions. I measured a 5A stall condition, so I setted a 2.5A limit to stop a motor. An inhibition time of 1 second is used to ignore the first second when a motor starts and its currents consumption increases before stabilize after about one second.

I used a dummy load from arachnid labs to test if the microcontroller triggers when current reaches its limit.

As the current shunt voltage analogRead() function only get a sample from the AtMega controller, I will add some sort of filtering to dampen the spike that might occur and the voltage shunt measurement. (Probably a moving average filter).