This is the circuit for my planter test stand used to test seed meters for uniform seed placement. The blue board on the left is an Arduino Uno Rev.3. On the right is an Arduino Proto Shield that mounts on top of the Uno with "headers". I've added the wiring illustrated. Where I have drawn the row sensor wires, I actually have a piece of cable cut off an old row sensor that has a male weather-pack connector where the row sensor connects. The Arduino is supplying +5v power to the row sensor through the red and black wires. For interfacing to a PC via USB cable, take off the Bluetooth module and wiring but keep the 10K resistor that holds the seed sensor signal wire high (to +5V). The Arduino needs to be powered from its round power connector or through the USB cable to a PC.
The Arduino code: