Photodiodes are common light receptors.
An opto-isolator is an electronic device that uses light to send signals between parts of a circuit. This allows circuit elements to communicate without an electrical connection. The advantage of this isolation is to prevent voltage spikes from affecting multiple circuits. It also helps reduce noise and interference in audio and video equipment by preventing electrical current from flowing where it is not intended. Most opto-isolators are very cheap, costing less than $1.
Operating an opto-isolator is a fairly basic process. When an electronic signal reaches the opto-isolator, that signal is converted to light. The light is then transmitted to a receiver. Once the signal is received, it is converted back to an electronic signal.
There are two basic types of opto-isolators that have their own uses. A digital opto-isolator changes the state of its output to match that of the input. It should be used when a bit or pulse output is required. An analog isolator reproduces the input using an analog signal. This type of opto-isolator should be used when the amount of signal is the crucial factor.
The medium opto-isolator is made up of three basic parts. A solid casing protects against external light leakage to the insulator. A light-emitting diode (LED) or other small light source sends the signal, and a photosensitive part receives the signal. The most common light receptors are photodiodes and phototransistors. From the outside, an opto-isolator looks like a transistor that has additional leads attached to it.
In many cases, the term “optocoupler” is used interchangeably with “opto-isolator”, but there is a difference between the two devices. Both transmit information between elements of a circuit while allowing the elements to remain isolated. The difference comes from the potential voltage of the circuits. An opto-isolator is designed for use with systems where the potential voltage is between 5,000 and 50,000 volts, and optocouplers are only designed for use on systems where the potential voltage is less than 5,000 volts. Using the wrong device may cause the system to crash.
Moisture can also cause major problems for opto-isolators. If there is too much moisture in the air, electricity can arc, destroying electronic insulation. Barometric pressure can cause similar problems and air pollution can cause similar problems. The best way to avoid this problem is to keep electronic devices that use opto-isolators in a climate-controlled area.