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(30) 4N35 Optocouplers; Cheap! Useful! Also known as optoisolators. Experimenters and hobbyists, stock up! Replace those reed relays with "solid-state" relays using optocouplers! * Unused, surplus components - you save! * Various manufacturers but similar specs * May have a few bent pins due to bulk packaging * Use to isolate one circuit from another * Use to couple together circuits that have different impedances * Use to replace relays which are expensive, bulky, and inherently prone to failure * Add a couple of transistors and switch high current loads, just like a relay! * Lots of documentation and application information available - see links! 9 are shown here - you get 30! An optocoupler is an LED (in this case, an infrared-emitting LED) and a phototransistor in one package. These 4N35 optocouplers come in a standard 6-pin DIP package. A phototransistor will conduct a current between its emitter and collector when light is applied to its base. The LED in the optocoupler provides the light. When the LED turns on, the light from the LED makes the base of the phototransistor bias forward. This turns on the transistor, allowing current to flow in the second circuit. Using an optocoupler, you can make one circuit control a second, separate circuit via an optical, not electrical, connection. Since the two circuits are not connected electrically, you can connect together two very different kinds of circuits, with very different impedance levels. An optocoupler can be used to provide input pulses to another circuit or it can be used as a solid-state "relay." If you add some transistors to the output of the optocoupler, it can be used to switch much higher currents, just like a relay. The optocoupler, however, is a solid-state device that is cheaper, smaller, and less prone to failure than a relay! Below I provide links to some great documentation on optocouplers from the Vishay company. This documentation includes a datasheet for the 4N35 optocoupler and useful application notes, including how to switch high currents using an optocoupler and a couple of inexpensive transistors (see "app04")! Enjoy experimenting! Link: Optocoupler application notes at Vishay Link: 4N35 datasheet at Vishay |