How to judge the quality of optocouplers collected online .

Method 1 Use the PN junction of the digital multimeter to measure the end, the red pen "battery + pole" is connected to the "1" end of the optocoupler, and the black pen "battery-pole" is connected to the "2" end of the optocoupler (even if the light-emitting diode of the optocoupler is positively conducted), use another meter to measure the resistance of the "3" and "4" terminals, disconnect or turn on the input terminal (light-emitting diode end), and the resistance of the output end should change significantly, indicating that it is good to change the optocoupler. In addition, the multimeter at the LED end can be replaced by a battery string current-limiting resistor. Method 2 The judgment method of optocoupler PC817 is to detect the light-emitting end of the optocoupler with the diode file of the multimeter, and then add a voltage of about five volts to the light-emitting end to judge the quality of the triode end Method 3 Place the multimeter in the R*100O block, and connect the black meter pen to the 1 end and the red pen to the 2 ends, the resistance is generally 5K -8K, and this value is the forward resistance of the light-emitting diode.

The smaller the better, the reverse resistance should be as large as possible, generally more than 10m, and then the black pen is connected to 3 ends, the red pen is connected to 4 ends, the resistance value should be above 100K, after the table pen is adjusted, the resistance value on the opposite side should be, otherwise the optocoupler is damaged.

In switching power supply circuits, damage to the optocoupler and ancillary circuits is a common cause of excessive output voltage.

This does not prove to be good, and there is still one step to be done. It can be proved that it is good to use 2 multimeters to measure at the same time, let the light-emitting tube emit light, and turn on the photocell. The 1-2 end can be used with a No. 7 or No. 5 battery, and the test time should not be too long.

Copy with a 5V battery

and a four-legged multimeter;

Measure the resistance on both sides separately;

One side is infinite, one side is connected to the primary pole of the power supply, and the other side is measured with a resistance value of 6-8k, which means that the optocoupler is good.

1. Optocoupler:

Also known as optoisolator or optocoupler, referred to as optocoupler;

It is a device that uses light as the medium to transmit electrical signals, usually encapsulating the luminaire and the light receiver in the same tube shell;

When the input terminal is energized with a signal, the luminaire emits light, and the light receiver receives the light and generates photocurrent, which flows out from the output terminal, thus achieving this"Electrical-optical-electric"Conversion;

The optocoupler that couples the signal at the input end to the output with light as the medium has the advantages of small size, long life, no contact, strong anti-interference ability, isolation between output and input, and one-way transmission of signals, and has been widely used in digital circuits.

2. Structural features:

The insulation resistance between the input and output terminals is generally greater than 10000m, and the withstand voltage can generally exceed 1kv, and some can even reach more than 10kv;

Because the optical receiver can only accept the information of the light source, and not vice versa, there will be no feedback phenomenon when the signal is transmitted from the light source to the optical receiver in one direction, and its output signal will not affect the input terminal;

Since the light-emitting device is an impedance current driving device, and noise is a microcurrent voltage signal with high internal resistance;

Easy to work with logic circuits;

Fast response;

No contact, long life, small size, impact resistance.

The measurement of the photoelectric coupling device is very simple, the foot is single-conducted, the foot is not passable, it doesn't matter what watch is made, which watch pen is connected to that foot, this when you repair things for a period of time, you will not consider it.

It can be judged with a multimeter, and it can be seen whether the diode or triode of the optocoupler breaks down.

I use two pointer tables to judge the good and the bad...

Optocoupler. The main advantages of the combiner are: one-way signal transmission, the input and output terminals are completely electrically isolated and isolated, the output signal has no impact on the input end, the anti-interference ability is strong, the work is stable, there is no contact, the service life is long, and the transmission efficiency is high.

Optocoupler is a new type of device developed in the 70s, and has been widely used in electrical insulation, level shifting, interstage coupling, drive circuits, switching circuits, choppers, multivibrators, signal isolation, interstage isolation, pulse amplification circuits, digital instruments, long-distance signal transmission, pulse amplification, and solid-state relays.

SSR), instrumentation, communication equipment and microcomputer interfaces. In a monolithic switching power supply, a linear optocoupler can be used to form an optocoupler feedback circuit, which can change the duty cycle by adjusting the current at the control end.

Achieve the purpose of precision voltage regulation.

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1. Use the multimeter ohm file to detect the light-emitting diode, anyway, measure the diode of the light-emitting diode, if the measurement value is small, and the other measurement resistance is very large, it means that it is a light-emitting diode and its pn junction is good, such as the two-pole of the light-emitting diode anyway, its resistance value is = 0, or the resistance value is very large, indicating that the diode of the light-emitting diode has broken down or has been broken (the piece has been broken). For example, the two poles of the light-emitting diode are small, and they may be two anti-parallel diodes. Then use the meter to detect the two poles of the phototriode, if the measured resistance value = 0 or very small, it means that the piece is broken.

2. Power-on inspection: when it is not determined that it has been damaged through the above inspection, two resistors (such as 1K) can be connected according to the above figure, and the voltage of R2 should be measured when the switch is not closed should be = 0, and when the switch K is closed, the voltage indication = 12V, it means that it is good here. If it still indicates = 0, then use a voltmeter to measure the voltage at both ends of the diode, such as the voltage at the two ends of the diode = 10v, the two poles of the diode can be reversed, and the voltage of the diode is also = 10v, indicating that this piece is broken.

If the voltage value is about or so, it means that the diode has been turned on and the transistor is reversed. The two poles of the transistor can be reversed, and then the R2 voltage is measured, if the indication = 10V, it means that the tube is good. If =0v is still indicated, the tube is bad.

BAI detects the quality of optocouplers:

DU 1. In the case of live board, the input DAO drive waveform and the output internal drive waveform can be measured: capacitance.

2. If there is only input and no output, then there must be a problem with the optocoupler;

3. If there are both input and output waveforms, it means that the optocoupler is fine.

4. At this time, you can check whether the power supply and driving signal are normal, etc.

Common detection methods:

1.Replacement method.

2.The voltage test method is to see if the voltage is the same as the normal value.

3.Resistance test method, check the resistance value of each pin to the ground.

4.Intuitive method, with the eye to observe whether the appearance of the optocoupler is damaged.

1. The input end of the optocoupler can be regarded as a light-emitting diode for calculation. Current limit is 20mA. The input voltage minus the diode drop divided by 20mA is the resistance of R1.

2. R2 is a pure pull-up resistor, as long as it is matched with the equipment at the output end, it will not make the optocoupler output transistor current too large, generally 1K-100K can be, the specific number of choices, it depends on how much current the equipment in the other section needs.

Novices don't know how to measure the quality of the optocoupler, the master teaches you a trick, and you can learn it in a few minutes.

With a battery and a multimeter with four feet and six feet are generally four-legged, measure the resistance value on both sides, one side is infinity on both sides, this side is connected to the primary pole of the power supply, the other side is measured with 6-8k resistance, the reverse measurement infinity, this side is connected to the secondary pole.

It is good to use an oscilloscope to measure the signal before and after the optocoupler and compare it, without distortion and distortion. All other tests were ineffective.

It depends on what kind of optocoupler is, and on one side of the voltage, on the other side, with a multimeter to turn on and off, isn't it?

Generally speaking, the output stage of the optocoupler is a phototriode, and its base depends on the light-emitting diode at the input end to induce the base current (as shown in the figure below). When the appropriate current is applied to the LED at the input, a good optocoupler output stage triode is turned on. Using this feature, you can preliminarily judge the quality of the optocoupler, of course, to see whether the parameters of the optocoupler meet the index, and a number of measurements are required.