Exploring the PC817 Optocoupler: Working Principle, Package, Manufacturer and More
21 December 2023
Ⅱ. How PC817 optocoupler works?
Ⅲ. Where can we use PC817 optocoupler?
Ⅴ. How to measure the quality of PC817?
Ⅵ. Manufacturer of PC817 optocoupler
Ⅶ. The relationship between PC817 collector-emitter voltage and diode forward current
An optocoupler, also known as an opto-isolator, is a combination of an infrared LED and a phototransistor. It is designed to optically couple electrical signals through a device without the need for electrical connections. In this article, we will introduce the PC817 optocoupler in detail. It is composed of high-performance GaAs light-emitting diodes and high-sensitivity NPN silicon transistors, which can effectively isolate and amplify input signals. PC817 photoelectric couplers are widely used in signal transmission between circuits of measuring instruments, computer terminals, thyristor system equipment, photocopiers, and household appliances (such as fans, heaters) and other equipment. By completely isolating the front end from the load, the intent is to increase safety, reduce circuit interference, and simplify circuit design.
The PC817 serves as an optical isolator, incorporating both an infrared diode and a phototransistor to facilitate electrical isolation of signals between two circuits via an optical bridge. With a power consumption of 70 milliwatts, this optocoupler boasts a cut-off frequency of 80kHz. Notably, it features a maximum emitter to collector voltage ratio of 80V and a maximum collector current ratio of 50mA. The PC817 is highly versatile, exhibiting compatibility with TTL, CMOS, and various other digital logic families. To accommodate different needs, it is available in SOP-4, DIP-4, and SSOP-4 packages, making it an adaptable and efficient choice for applications requiring signal isolation in electronic circuits.
Replacements and equivalents:
• 6N136
• HCNR201
• MOC3041
• PC817A
• PC817C
• PC817D
PC817 is a device that converts electrical signals to optical signals and optical signals to electrical signals through photoelectric conversion. The working principle of PC817 is to utilize the photoelectric effect and the working principle of PN junction to realize the isolation and transmission of signals. When the current flows through the light emitting diode, a light beam is generated and this light beam will be irradiated into the photosensitive triode. When the photosensitive element in the photosensitive transistor is excited by the light beam, the photoelectric effect is formed, resulting in a change in the current in the photosensitive transistor. This current change can be amplified and output, while being isolated from the input current of the light-emitting diode. Therefore, PC817 completes the conversion and isolation of electrical and optical signals.
1. Application example
The PC817 optocoupler has an optical control based transistor. Therefore, the IC basically has an IR LED and a phototransistor. When the IRLED is energized, the light it emits falls on the transistor and conducts. The pin configuration of the IR LED and the phototransistor are shown below.
This IC is used to provide galvanic isolation between two circuits. One part of the circuit is connected to the IRLED and the other part is connected to the phototransistor. The digital signal provided to the IRLED will be reflected back to the transistor, but there will be no hard electrical connection between the two. This is very convenient when we are trying to isolate noise signals from digital electronics.
2. Application fileds
(1) Communication equipment: It is often used in communication equipment for optical isolation and photoelectric conversion to effectively isolate high-frequency signals and provide clear signal output.
(2) Power management and switching power supply control: PC817 optocoupler can be used to realize non-isolated and isolated power management, such as switching power supply control, over-voltage protection, under-voltage lockout and so on. It can accurately transmit power management signals to protect the stable operation of circuits and equipment.
(3) Instrumentation and measurement equipment: PC817 optocoupler plays a key role in instrumentation and measurement equipment. It can be used to realize the isolation and conditioning of measurement signals and maintain the accuracy and stability of signals.
(4) Automation control system: PC817 optocoupler is widely used in automation control system for electrical isolation and signal transmission. It can be used in conjunction with microprocessors, PLCs and other control devices to realize the isolation of input signals and the driving of output signals.
To measure the quality of the PC817 optocoupler, we can take the following steps. First, we prepare a multimeter or oscilloscope to measure parameters such as resistance, current, and voltage. During this process, we make sure that the test equipment is working properly and is wired correctly.
Before making measurements, we must disconnect the power supply connected to the PC817 optocoupler to avoid electric shock or damage to the test equipment. Next, we connect the two probes of the multimeter to the input terminals of the PC817 optocoupler (pins 1 and 2), and select the resistance range of the multimeter. We start by measuring the resistance at the input, which is usually between a few hundred and a few thousand ohms. Next, we connect one probe of the multimeter to the output of the PC817 optocoupler (pin 4), and the other probe to ground. We select the DC voltage range of the multimeter and measure the voltage value at the output end. To check the working status of the photodiode, we use a light source (such as a flashlight or LED light) and shine light onto the LED (pin 3) of the PC817 optocoupler. At the same time, we measure the voltage value at the output terminal (pin 4) with an oscilloscope or multimeter. When light strikes a light-emitting diode, there is a noticeable change in the expected output voltage. If there is no change or the change is not noticeable, it may indicate a problem with the photodiode. Next, we check how the input is working. We connect the input end of the PC817 optocoupler to the circuit and give it an appropriate input signal. We measure the voltage or current at the output (pin 4) with an oscilloscope or multimeter. If the output terminal can respond correctly to the input signal and produce corresponding changes, then the input terminal is working properly, otherwise there may be a problem. Through the inspection of the above steps, we can initially judge the quality of the PC817 optocoupler.
PC817 is an optocoupler produced by Sharp Corporation of Japan. Sharp Corporation is a company with a long history, founded in 1912. Initially, their main business was the production of electronic components. With the continuous development of technology, Sharp gradually became involved in the electrical appliance industry and became one of the world's largest LCD TV manufacturers in the early 21st century. Nowadays, Sharp has operations in 25 countries and 62 regions around the world, and is a large comprehensive electronic information company. Sharp mainly produces semiconductor devices, including memory ICs, optoelectronic devices, imaging products, LCDs required for IR data communications, radio frequency components, microprocessors or microcontrollers, and a variety of other ICs.
In the forward operating state, the relationship curve between the diode forward current If and the collector voltage Vce of PC817 optocoupler is nonlinear. When If is small, the change of Vce with If is small; while when If is large, the change of Vce with If is large. This nonlinear relationship enables the PC817 optocoupler to achieve linear amplification and transmission of signals in the circuit.
Frequently Asked Questions
1. What is the function of PC817?
The features of the PC817 IC Optocoupler include the following. This IC includes internal protection for both input & output from electrical isolation and it protects up to 5KV. This IC is used with an additional resistor through high voltage devices to function through fewer voltage devices.
2. How much current does a PC817 draw?
The absolute maximum current through this LED is 50ma, but in practice the current should be limited to no more than 20mA for safe use with a uC. A resistor value of 470 ohms which gives a current of 10ma will work for most applications as a staring point.
3. How do you use a PC817 optocoupler?
PC817 IC includes an LED & a phototransistor which are connected jointly optically. The signal can be transmitted optically in between an i/p and an o/p side without any physical connection. To any microcontroller or any DC device with less voltage, it can be connected directly.
4. What is the difference between PC817 and 4N35?
The PC817 is a photo-transistor type of optocoupler while the 4N35 is a photo-triac optocoupler. The photo-transistor devices are primarily used in DC circuits, whereas the photo-triac devices allow control of AC-powered circuits.
