To quickly check the performance of optocouplers, radio amateurs make various tester circuits that immediately show whether this optocoupler is working or not, today I will propose to solder the simplest tester for testing optocouplers. This probe can test optocouplers in both a four-pin package and six, and using it is as easy as shelling pears, insert an optocoupler and immediately see the result!
Necessary parts for optocoupler tester:
- Capacitor 220uF x 10V;
- Socket for the microcircuit;
- Resistor from 3 kOhm to 5.6 kOhm;
- Resistor from 1 kOhm;
- Light-emitting diode;
- 5V power supply.
How to make a device for testing optocouplers, instructions:
The optocoupler tester operates from 5 volts, if less, then not all types of optocouplers can work correctly, any charge can serve as a power supply for mobile phone. When correctly inserted into the tester panel of the working optocoupler, the LED will flash, which means that everything is in order with it, the frequency of flashes depends on the capacitance of the electrolytic capacitor. If the optocoupler is burnt out or inserted on the wrong side, the LED will not light up, or if there is a breakdown of the transistor inside the optocoupler, the LED will simply glow but not blink.
The socket for checking optocouplers is made from a socket for a microcircuit and 4 pins are left at one end, for checking an optocoupler in a 4-pin package, and 5 pins for a 6-pin package are left at the second end of the socket. I soldered the remaining parts of the device for checking optocouplers by surface mounting on the contacts of the socket, but if desired, you can etch the board.
It remains to choose a suitable case and a simple optocoupler tester is ready!
Description, characteristics, datasheet and methods for testing optocouplers using the example of PC817.
In continuation of the topic “Popular radio components for repairs of switching power supplies”, we will analyze one more detail - optocoupler (optocoupler) PC817. It consists of an LED and a phototransistor. They are not electrically connected to each other, due to which, on the basis of PC817 it is possible to implement galvanic isolation of two parts of the circuit - for example, with high voltage and low. The opening of the phototransistor depends on the illumination of the LED. I will analyze how this happens in more detail in the next article, where in experiments, by applying signals from the generator and analyzing it with an oscilloscope, you can understand a more accurate picture of the operation of the optocoupler.
In other articles, I will talk about the non-standard use of an optocoupler, the first in the role, and in the second. And using these circuit solutions I will assemble a very simple optocoupler tester. Which does not need any expensive and rare devices, but only a few cheap radio components.
The item is not rare and not expensive. But a lot depends on it. It is used in almost every running (I don't mean some kind of exclusive) impulse UNIT POWER AND FUNCTION feedback and most often in conjunction with the very popular radio component TL431
For those readers who find it easier to perceive information by ear, we advise you to watch the video at the very bottom of the page.
Optocoupler (Optocoupler) PC817
Brief characteristics:
Housing compact:
- pin pitch - 2.54 mm;
- between rows - 7.62 mm.
The manufacturer of PC817 is Sharp, there are other manufacturers of electronic components that produce analogues, for example:
- Siemens-SFH618
- Toshiba-TLP521-1
- NEC-PC2501-1
- LITEON-LTV817
- Cosmo-KP1010
In addition to the single optocoupler PC817, other options are available:
- PC827 - dual;
- PC837 - built;
- PC847 - quad.
Optocoupler test
For quick check optocouplers, I conducted several test experiments. First on the breadboard.
Breadboard option
As a result, we were able to get very a simple circuit to test PC817 and other similar optocouplers.
The first version of the scheme
I rejected the first option for the reason that it inverted the transistor marking from n-p-n to p-n-p
Therefore, in order to avoid confusion, I changed the scheme to the following;
The second version of the scheme
The second option worked correctly, but it was inconvenient to unsolder the standard socket
under the microcircuit
Socket SCS-8
The third version of the scheme
The most successful
Uf is the voltage on the LED at which the phototransistor starts to open.
in my version Uf = 1.12 volts. 
The result is a very simple design.
So I'm already gearing up for the next one. And it was prompted by this reading on the forum of questions from members of the forum who intended to independently repair any electronic device. The essence of the questions is the same and it can be formulated in the following way - “What electronic component in the device is defective? At first glance, it is quite a modest desire, however, it is not. For knowing in advance the cause of a malfunction is like “knowing the purchase”, which, as you know, is the main condition for living in Sochi. And since we haven’t noticed anyone from the glorious seaside city, novice repairmen have to do a total check of all the electronic components of the failed device to detect a malfunction. This is the most prudent and correct action. The condition for its implementation is that the electronics lover has the entire list of test devices.
Schematic diagram of the optocoupler tester
To check the health of optocouplers (for example, the popular PC817), there are test methods and test schemes. I chose the circuit I liked, added a measurement of the voltage drop with a multimeter to the light indication of serviceability. I wanted information in numbers. Whether this is necessary or not will become clear over time, during the operation of the console.
I started with the selection of installation elements and their placement. A pair of medium-sized LEDs of different glow colors, a DIP-14 chip socket, the switch chose a non-latching, push-pull action in three positions (middle neutral, right and left - connection of the tested optocouplers). I drew and printed the arrangement of elements on the case, cut it out and pasted it onto the intended case. Drilled holes in it. Since it will be checked, there will be only six and four-legged optocouplers removed unnecessary contacts from the socket. I put everything in place.
Mounting of components from the inside is naturally carried out by a hinged method on the contacts of the installation elements. There are not so many details, but in order not to make mistakes when soldering, it is better to mark each completed section of the circuit with a felt-tip pen on its printed image. Upon closer inspection, everything is simple and clear (what goes where). Next, the middle part of the case is installed in place, through the hole in which the power supply wires with a soldered tulip-type connector are passed. The lower part of the housing is equipped with pins for connecting to multimeter sockets. This time (for a test) they were M4 screws (well, a very convenient option, provided that they are related to measuring device as a "workhorse" and not an object of worship). In conclusion, the wires are soldered to the connection pins and the case is assembled into a single whole.
Now check the performance of the assembled set-top box. After installing it in the sockets of the multimeter, selecting the measurement limit of "20V" constant voltage and turning it on, 12 volts are supplied to the prefix from the laboratory PSU. The display shows a slightly lower voltage, the red LED is lit, indicating the presence of the required supply voltage of the tester. The microcircuit under test is installed in the panel. The switch lever is moved to the right position (the direction of the installation site of the tested optocoupler) - the red LED goes out and the green one lights up, a voltage drop is observed on the display - both of which indicate that the component is working.
The prefix to the multimeter - the tester of optocouplers turned out to be efficient and serviceable. In conclusion, the top panel of the case is issued with a memo - a sticker. I checked two PC817 optocouplers that were at hand, both are working, but at the same time they showed different voltage drops when connected. On one it dropped to 3.2 volts, and on the other to 2.5 volts. Information for reflection on the face, in the absence of communication with the m / meter it would not exist.
Tester operation video
And the video clearly shows that it will be much faster to check an electronic component than to ask a question about whether it could fail or not, and besides, with a high degree of probability, simply not get an answer to it. Project author Babay from Barnaula.
Discuss the article ADDITION TO A MULTIMETER - OPTOPAR TESTER
Instruction
If the optocoupler, the serviceability of which is set to, is soldered to the board, it is necessary to turn it off, discharge electrolytic capacitors on it, and then unsolder the optocoupler, remembering how it was soldered.
Optocouplers have different emitters (incandescent lamps, neon lamps, LEDs, light-emitting capacitors) and different radiation receivers (photoresistors, photodiodes, phototransistors, photothyristors, photosimistors). Also they are pinned. Therefore, it is necessary to find data on the type and pinout of the optocoupler either in the reference book or datasheet, or in the circuit of the device where it was installed. Often, the pinout of the optocoupler is applied directly to the board of this device. If the device is modern, you can almost certainly be sure that the emitter in it is an LED.
If the radiation receiver is a photodiode, connect the optocoupler element to it, observe the polarity, in a chain consisting of a constant voltage source of several volts, a resistor designed so that the current through the radiation receiver does not exceed the allowable one, and a multimeter operating in the measurement mode current at the corresponding limit.
Now enter the emitter of the optocoupler into operating mode. To turn on the LED, pass through it in direct polarity. D.C., equal to the nominal. Apply rated voltage to the incandescent lamp. Carefully connect a neon lamp or a light-emitting capacitor to the network through a resistor with a resistance of 500 kΩ to 1 MΩ and a power of at least 0.5 W.
The photodetector must respond to the inclusion of the emitter by a sharp change in mode. Now try switching the emitter off and on several times. The photothyristor and photoresistor will remain open even after the control action is removed until their power is turned off. The remaining types of photodetectors will respond to each change in the control signal. If the optocoupler has an open optical channel, make sure that the reaction of the radiation receiver changes when this channel is blocked.
Having made a conclusion about the state of the optocoupler, de-energize the experimental setup and disassemble it. After that, solder the optocoupler back to the board or replace it with another one. Continue repairing the device that includes the optocoupler.
An optocoupler or optocoupler consists of an emitter and a photodetector separated from each other by a layer of air or a transparent insulating substance. They are not electrically interconnected, which makes it possible to use the device for galvanic isolation of circuits.
Instruction
Connect the measuring circuit to the photodetector of the optocoupler in accordance with its type. If the receiver is a photoresistor, use an ordinary ohmmeter, and the polarity is unimportant. When using a photodiode as a receiver, connect a microammeter without a power source (positive to the anode). If the signal is received by an n-p-n phototransistor, connect a circuit of a 2 kilo-ohm resistor, a 3-volt battery and a milliammeter, and connect the battery with a plus to the collector of the transistor. If the phototransistor has p-n-p structure, reverse the polarity of the battery connection. To check the photodinistor, make a circuit from a 3 V battery and a 6 V, 20 mA light bulb, connecting it with a plus to the anode of the dinistor.
In most optocouplers, the emitter is an LED or an incandescent bulb. Apply the rated voltage to an incandescent bulb in either polarity. You can also apply an alternating voltage, the effective value of which is equal to the operating voltage of the lamp. If the emitter is an LED, apply a voltage of 3 V to it through a 1 kΩ resistor (positive to the anode).
Using the proposed probe, you can check the NE555 (1006VI1) microcircuits and various optodevices: optotransistors, optothyristors, optotriacs, optoresistors. And it is with these radio elements simple methods do not pass, since simply ringing such a detail will not work. But in the simplest case, you can test an optocoupler using this technology:
With a digital multimeter:
Here 570 is the millivolts that fall on the open transition to e optotransistor. In diode continuity mode, the drop voltage is measured. In the "diode" mode, the multimeter outputs a voltage of 2 volts pulsed, rectangular to the probes, through an additional resistor, and when connecting P-N transition, the ADC of the multimeter measures the voltage falling on it.
Tester of optocouplers and microcircuits 555
We advise you to spend a little time and make this tester, as optocouplers are increasingly used in various amateur radio designs. And I’m generally silent about the famous KR1006VI1 - they put it almost everywhere. Actually, on the tested microcircuit 555, a pulse generator is assembled, the operability of which is evidenced by the blinking of the LEDs HL1, HL2. Next comes the optocoupler probe.
It works like this. The signal from the 3rd leg 555 through resistor R9 enters one input of the VDS1 diode bridge, if a working optocoupler radiating element is connected to contacts A (anode) and K (cathode), then current will flow through the bridge, causing the HL3 LED to blink. If the receiving element of the optocoupler is also working, then it will conduct current to the VT1 base by opening it at the moment of ignition of HL3, which will conduct current and HL4 will also blink.
P.S. Some 555s do not start with a capacitor in the fifth leg, but this does not mean they are malfunctioning, so if HL1, HL2 did not blink, short-circuit c2, but if after that the indicated LEDs did not blink, then the NE555 chip is definitely faulty. Good luck. Sincerely, Andrey Zhdanov (Master665).
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