Provides a simple but flexible isolated or common ground opto-isolator board. Use 4N35 or similar opto-isolators. Size resistor for input voltage... for example, if input voltage is ~12V, use a 1.2 to 1.5K resistor. Resistors can be either 0805 SMD or thru-hole type (pads exist for SMD under the space for the thru-hole resistors). J1 will tie the two input grounds together. J2 will tie the input ground to the output ground (usually used with J1). You may use pin headers for the jumpers or just us a wire. This board is intended to used for example with an Arduino board using pull-up inputs and low-active logic, that is, a high input on the opto-isolator will close the transistor and pull the Arduino input to ground, making a low on that Arduino input equal a high on the opto-isolator input.
