An optocoupler or optoisolator, contains a light-emitting diode (LED) and a photodetector. It is designed to transfer signals from one circuit to another yet keep them galvanically isolated. It prevent high voltages from affecting the system receiving the signal.
Photoresistor-based opto-isolators are the slowest type of optocouplers, but also the most linear isolators and are used in the audio and music industry. Most opto-isolators available use bipolar silicon phototransistor sensors and reach medium data transfer speed, which is enough for applications like electroencephalography. High speed opto-isolators are used in computing and communications applications. Other industrial applications include photocopiers, industrial automation, professional light measurement instruments and auto-exposure meters.
Common applications for opto-couplers include microprocessor input/output switching, DC and AC power control, PC communications, signal isolation and power supply regulation which suffer from current ground loops, etc. The electrical signal being transmitted can be either analogue (linear) or digital (pulses).
Generally these optocouplers comes in a single package which contains both LED and a phototransistor. Some other versions comes in pairs of LED and phototransistor.
An optical coupler, also called opto-isolator, optocoupler, opto coupler, photocoupler or optical isolator, is a passive optical component that can combine or split transmission data (optical power) from optical fibers. It is an electronic device which is designed to transfer electrical signals by using light waves in order to provide coupling with electrical isolation between its input and output. The main purpose of an optocoupler is to prevent rapidly changing voltages or high voltages on one side of a circuit from distorting transmissions or damaging components on the other side of the circuit. An optocoupler contains a light source often near an LED which converts electrical input signal into light, a closed optical channel and a photosensor, which detects incoming light and either modulates electric current flowing from an external power supply or generates electric energy directly. The sensor can either be a photoresistor, a silicon-controlled rectifier, a photodiode, a phototransistor or a triac.
Optocouplers and Opto-isolators are great electronic devices that allow devices such as power transistors and triacs to be controlled from a PC’s output port, digital switch or from a low voltage data signal such as that from a logic gate. The main advantage of opto-couplers is their high electrical isolation between the input and output terminals allowing relatively small digital signals to control much large AC voltages, currents and power.
An optocoupler can be used with both DC and AC signals with optocouplers utilizing a SCR (thyristor) or triac as the photo-detecting device are primarily designed for AC power-control applications. The main advantage of photo-SCRs and photo-triacs is the complete isolation from any noise or voltage spikes present on the AC power supply line as well as zero-crossing detection of the sinusoidal waveform which reduces switching and inrush currents protecting any power semiconductors used from thermal stress and shock.
The light is proportional to the signal, so the signal is thus transferred to the photo-transistor. Opt couplers may also comes in few module such as the SCR, photodiodes, TRIAC of other semiconductor switch as an output, and incandescent lamps, neon bulbs or other light source.
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| Optocoupler |
An optical coupler, also called opto-isolator, optocoupler, opto coupler, photocoupler or optical isolator, is a passive optical component that can combine or split transmission data (optical power) from optical fibers. It is an electronic device which is designed to transfer electrical signals by using light waves in order to provide coupling with electrical isolation between its input and output. The main purpose of an optocoupler is to prevent rapidly changing voltages or high voltages on one side of a circuit from distorting transmissions or damaging components on the other side of the circuit. An optocoupler contains a light source often near an LED which converts electrical input signal into light, a closed optical channel and a photosensor, which detects incoming light and either modulates electric current flowing from an external power supply or generates electric energy directly. The sensor can either be a photoresistor, a silicon-controlled rectifier, a photodiode, a phototransistor or a triac.
Optocouplers and Opto-isolators are great electronic devices that allow devices such as power transistors and triacs to be controlled from a PC’s output port, digital switch or from a low voltage data signal such as that from a logic gate. The main advantage of opto-couplers is their high electrical isolation between the input and output terminals allowing relatively small digital signals to control much large AC voltages, currents and power.
An optocoupler can be used with both DC and AC signals with optocouplers utilizing a SCR (thyristor) or triac as the photo-detecting device are primarily designed for AC power-control applications. The main advantage of photo-SCRs and photo-triacs is the complete isolation from any noise or voltage spikes present on the AC power supply line as well as zero-crossing detection of the sinusoidal waveform which reduces switching and inrush currents protecting any power semiconductors used from thermal stress and shock.
The light is proportional to the signal, so the signal is thus transferred to the photo-transistor. Opt couplers may also comes in few module such as the SCR, photodiodes, TRIAC of other semiconductor switch as an output, and incandescent lamps, neon bulbs or other light source.
Applications of optocouplers
Photoresistor-based opto-isolators are the slowest type of optocouplers, but also the most linear isolators and are used in the audio and music industry. Most opto-isolators available use bipolar silicon phototransistor sensors and reach medium data transfer speed, which is enough for applications like electroencephalography. High speed opto-isolators are used in computing and communications applications. Other industrial applications include photocopiers, industrial automation, professional light measurement instruments and auto-exposure meters.
Common applications for opto-couplers include microprocessor input/output switching, DC and AC power control, PC communications, signal isolation and power supply regulation which suffer from current ground loops, etc. The electrical signal being transmitted can be either analogue (linear) or digital (pulses).
Working of Optocouplers
Most commonly used is an opto-coupler MOC3021 an LED diac type combination. This IC is interfaced with a microcontroller and an LED is connected in series to the IC, which glows to indicate a logic High pulse from the microcontroller so that we can know that current is flowing in internal LED of the opto-IC. When logic high is given current flows through LED from pin1 to 2. So in this process LED light falls on DIAC causing 6 & 4 to close. During each half cycle current flows through gate, series resistor and through opto-diac for the main thyristor / triac to trigger for the load to operate.
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