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What-is-An-Optocoupler.pptxjhfvehdsbxjnicjh9uqwhsa cxzjsniwuqsacbhx zkcsojhubcx jkohubcqjxa kmosibuqjcs axkosbfj scaxibfjc
- 1. WHAT IS AN OPTOCOUPLER: How It Works
- 2. Optocouplers go by many names.You may refer to it as an optoisolator, photocoupler, optical coupler, optical isolator. Nevertheless, optocouplers are integrated electronic components. Generally, the most basic types consist of a rectangular body with four to six pins. Each pin is a subcomponent. The first pin is the anode, the second is the cathode, the third is the collector, and the fourth is the emitter.
- 3. The optocoupler is essentially a solid- state relay that interconnects two separate electronic circuits. The first circuit will connect across the first two pins (pin 1 and 2), while the second circuit will connect to the last two pins (pin 3 and 4).This allows the first circuit to control the second circuit.
- 4. HOW DOES AN OPTOCOUPLER WORK? We can use the optocoupler to transfer electronic signals between two isolated circuits. Sometimes voltage spikes and noise may occur in one circuit. Without the optocoupler isolating the circuits, these disruptions may spread to the second circuit and cause destruction. The optocoupler prevents this damage from occurring in both circuits. Additionally, the optocoupler will only allow electrons to flow in one direction because of its semiconductor materials. Consequently, this allows the two interconnected circuits to use different voltages and currents.
- 5. THE STRUCTURE OF AN OPTOCOUPLER
- 6. The above diagram illustrates a phototransistor connecting two circuits. If you look carefully at the phototransistor portion of the diagram, you’ll notice that there is an LED symbol on the left. Contrastingly, there is a transistor symbol right. We can easily spot the above figures that a phototransistor is a modified version of a normal transistor. Moreover, you can understand why we call the (third and fourth) terminals on the transistor side collectors and emitters. Furthermore, you can also see why we call the first and second terminals anode and cathodes.
- 7. Transistors generally have three terminals. However, there is a small difference here. The base pin in a normal transistor circuit is missing from the phototransistor circuit. This is because the transistor in an optocoupler works slightly differently. Instead of using electronic signals from the base pin, the transistor in an optocoupler uses light from the LED. The light shines from the LED and hits the transistor, switching it on and allowing current to flow in the main electrical circuit.They react to optical input as opposed to just electrical input current.
- 8. OPTOCOUPLER TYPES Resistive Optocoupler These were the earliest optocouplers. They use incandescent light bulbs, neon lamps, and infrared LEDs as light sources. Additionally, they use cadmium sulfide for transistor material. People also refer to these types of optocouplers as vactrols. A vactrol is a combination of a light depending resistor and light source both put into a small 100% light-proof case. In earlier designs incandescent lamps were used as light sources.Today LEDs are used because of their faster response, duration of life and current consumption.
- 9. Diode Optocoupler Diode optocouplers use gallium arsenide infrared LEDs for light sources and silicon photodiodes as receptors. This makes them the fastest type of optocouplers – especially when they utilize PIN diodes. Transistor Optocoupler Just like diode optocouplers, they also use GaAs infrared LEDs as light sources. However, they either use bipolar silicon phototransistors as sensors. This makes their transfer rates and response times faster than resistive optocouplers but slower than diode optocouplers.
- 10. Opto-isolated couplers Opto-isolated couplers use infrared LEDs along with silicon-controlled rectifiers. Their transfer speeds may vary. However, they’re not as fast as diode-based optocouplers in any configuration. Nevertheless, they still have a decent response time and transfer rate. Opto-isolated Triac These types of optocouplers use a triode for alternating current as a sensor type. This is in addition to their GaAs infrared LED as a light source. While they don’t have fast transfer rates, they have very high current transfer ratios.
- 11. Solid-state relay This simple optocoupler uses a simple light-dependent resistor (LDR) and a white LED. The LDR varies its load resistance based on the light exposure. Thus, in darkness, it has a very high resistance. Inversely, when we expose it to bright light, it has a lower resistance. In this context, it will function as a photodiode. They can have very high transfer speeds and unlimited current transfer ratios.
- 12. INTERNAL STRUCTURE OF OPTOCOUPLER
- 13. This the internal structure of the opto-coupler. On the left side pin 1 and pin 2 are exposed, it is a LED (Light Emitting Diode), the LED emit infrared light to the photosensitive transistor on the right side.The photo-transistor switches the output circuitry by its collector and emitter, same as typical transistors.
- 14. Intensity of the LED directly controls the photo- transistor. Since the LED can be controlled by a different circuitry and the photo transistor can control different circuitry so two independent circuits can be controlled by Optocoupler. Also, between the photo-transistor and the Infrared LED, the space is transparent and non- conductive material; it is electrically isolating two different circuits. The hollowed space between LED and photo-transistor can be made using Glass, air, or a transparent plastic, the electrical isolation is much higher, typically 10 kV or higher.
- 15. MAIN FUNCTION OF OPTOCOUPLER As discussed before few Optocoupler used in DC circuit and few Optocoupler used in AC related operations. As the Optocoupler does not allow direct electrical connection between two sides, the main application of the Optocoupler is to isolate two circuits. From switching other application, same as like where transistor can be used to switch application the Optocoupler can be used. It can be used in various microcontroller related operations where digital pulses or analog information needed from a high voltage circuits, Optocoupler can be used for excellent isolation between two circuitry.
- 16. RECTIFIER CIRCUITS Many electronic circuits use DC voltage for operation.We can easily convert AC voltage or current into DC voltage or current by using a device known as a p-n junction diode. A p-n junction diode allows electric current to flow in forward bias condition and blocks the current in reverse bias condition. Simply, a diode allows electric current to flow in one direction only. This unique property of diode allows it to act as a rectifier.
- 17. WHAT IS RECTIFIER? A rectifier is an electronic device that converts an alternating current into a direct current by using one or more P-N junction diodes. A diode behaves as a one-way valve that allows current to flow in a single direction. This process is known as rectification.
- 18. A rectifier can take the shape of several physical forms such as solid-state diodes, vacuum tube diodes, mercury-arc valves, silicon-controlled rectifiers, and various other silicon-based semiconductors switches.
- 19. DIFFERENT TYPES OF RECTIFIER Uncontrolled Rectifiers The type of rectifier whose voltage cannot be controlled is known as an uncontrolled rectifier. Uncontrolled rectifiers are further divided as follows: Half Wave Rectifier Full Wave Rectifier
- 20. Half-wave rectifier The type of rectifier that converts only the half cycle of the alternating current into the direct current. Furthermore, the AC power source only supplies power to the load one half every full cycle, meaning that half of its capacity is unused.
- 21. Full-wave rectifier The type of rectifier that converts both positive and negative half cycles of the AC. One kind of full-wave rectifier, called the center-tap design, uses a transformer with a center-tapped secondary winding and two diodes.
- 22. Controlled Rectifiers A type of rectifier whose voltage can be varied. These rectifiers are preferred over their uncontrolled counterparts. There are two types of controlled rectifiers, and they are Half Wave Controlled Rectifier and Full Wave Controlled Rectifier. Half-wave controlled rectifier has the same design as the half-wave uncontrolled rectifier except we replace the diode with an SCR.
- 23. WHAT IS RECTIFICATION? Rectification is the conversion of alternating current (AC) to direct current (DC). This involves a device that only allows one-way flow of electric charge. This process involves diodes or other devices to allow current to flow in only in one direction, effectively eliminating the negative portion of the AC waveform.