Here are some common optoelectronic components.
The light emitting diode, usually known as LED, is a special diode constructed so as to emit light when a current flows through it.
Connected in series with a resistor to prevent damage to the LED. Typically the forward bias for the LeD is 2V. The LED normally operates with a forward current of about 5mA to 40mA. There is normally a significant change in brightness between 5mA and 15mA after which the change is less noticeable. An LED has a very low resistance when conducting and a resistor is normally needed to limit the current to no more than 40mA. This is not required for the Arduino as the output of each of the pins on the Arduino is less than maximum current for the LED.
In series with resistor R1 voltage across R1 is normally input voltage - the forward voltage of the LED (2v). Using R = V/I we can determine the appropriate resistor required based on the supply voltage. Typically a resistor of 220Ω or 330Ω is used for a 5V power supply giving a current of about 10 to 15mA.
The optoisolator / optocoupler is used to provide electrical selection between devices. This can be used to pass a signal to a part of the circuit operating on a different voltage, or to isolate parts of the circuit where it is neccessary to provide physical separation.
The switched output is created as a bipolar junction similar to a transistor, but uses the optical trigger instead of a current applied to the base. There are other isolators that use a triac connection inplace of the bipolar transistor (see below).
The optotriac isolator is similar to the optoisolator, but switches through a triac instead of a bipolar transistor.
Please view the copyright information regarding use of the circuits.
