 Welcome to Optical Encoders. An optical encoder is an electromechanical device that provides feedback information in a closed-loop motion control system. This information is for both rotary and linear mechanisms. Optical encoders provide information for direction, position, and velocity. Let's adjust the velocity of this motor. You can see how adjusting the velocity of the motor affects the velocity of the conveyor belt. An optical encoder typically has four major elements, light source, light sensor, optical disc, and signal conditioning circuitry. The light source is typically a light emitting diode, or LED. Instead of producing a light that is visible to humans, an infrared light is usually transmitted. The light sensor is a phototransistor. Because the sensor is sensitive to infrared energy emitted by the light source, ambient light has a minimal effect on the sensor. Optical disc. A disc is placed between the light source and the sensor. It is connected to the shaft being measured so that the disc and shaft can rotate together. As the disc is rotated, light alternately passes through the translucent slots and is blocked by the opaque areas between the slots. The phototransistor is connected to the signal conditioning circuitry. The signal conditioning circuitry consists of a load resistor and the Schmidt trigger. Let's see how the circuitry works as the light is alternately blocked and passed to the transistor. When light is present, when light passes through a slot on the disc, the following conditions occur. The transistor turns on. Since there is minimal resistance, the voltage drop across the transistor is near 0 volts. The 0 volt potential at the transistor's collector is fed to the input of the Schmidt trigger, which results in a 0 volt potential at its output. The near positive 5 volts from the power source drops across the load resistor. When the light is blocked by the opaque area between the slots, the following conditions occur. The transistor turns fully off. Since it acts like an open and there is a large resistance, the voltage drop across the transistor is near positive 5 volts. The positive volt potential at the transistor's collector is fed to the input of the Schmidt trigger, which results in a positive 5 volt potential at its output. Near 0 volts drops across the load resistor. The Schmidt trigger converts pulses from the phototransistor into the square waves required by the computing device that received the feedback signal for the closed loop system. Let's do a quick review. The type of light typically emitted by the light source of an optical encoder is A visible or B infrared. The answer is B infrared. When light strikes the phototransistor of the optical encoder, A its resistance is low, B a near 0 volt potential is at its collector, C the output of the Schmidt trigger is near 0 volts, or D all of the above. The answer is D all of the above. When light from the light source of the optical encoder is blocked, what drops across the load resistor? A near 0 volts or B positive 5 volts. The answer is A near 0 volts. And finally, the function of the optical encoder's Schmidt trigger is to convert A pulses into square waves or B square waves into pulses. The answer is A pulses into square waves. You have completed optical encoders. If you like this video, please follow our channel.