So I’m already ready for the next one. What prompted me to do this was reading questions on the forum from forum users who were determined to repair any electronic device themselves. The essence of the questions is the same and can be formulated as follows: “Which electronic component in the device is faulty?” At first glance, this is a completely modest desire, however, this is not so. Because 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 no one from the glorious seaside city has been spotted, novice repairmen are left with a total check of all 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 enthusiast has the entire list of testing instruments.
Schematic diagram of an optocoupler tester
To check the serviceability of optocouplers (for example, the popular PC817), there are testing methods and testing circuits. I chose the circuit I liked and added a voltage drop measurement 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 microcircuit socket, the switch was chosen without locking, with a push action in three positions (middle neutral, right and left - connection of the optocouplers being tested). I drew and printed out the arrangement of the elements on the body, cut it out and pasted it onto the intended body. I drilled holes in it. Since they will be checked, there will only be six and four-legged optocouplers from the socket, removing unnecessary contacts. I put everything in place.
The installation of components from the inside is naturally carried out using a hinged method on the contacts of the installation elements. There are not many parts, 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 examination, 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 case is equipped with pins for connecting to the multimeter sockets. This time (for testing), they were M4 screws (well, a very convenient option, provided that you treat the measuring device as a “workhorse” and not an object of worship). Finally, the wires are soldered to the connection pins and the housing is assembled into a single whole.
Now check the functionality of the assembled set-top box. After installing it in the multimeter sockets, selecting the “20V” DC voltage measurement limit and turning it on, 12 volts are supplied to the set-top box from the laboratory power supply. The display shows a slightly lower voltage, the red LED lights up, indicating the presence of the required supply voltage to the tester. The chip being tested is installed in the panel. The switch lever is moved to the right position (direction of the installation location of the optocoupler being tested) - the red LED goes out and the green LED lights up, a voltage drop is observed on the display - both indicate the serviceability of the component.
The attachment to the multimeter - optocoupler tester turned out to be functional and usable. Finally, the top panel of the case is decorated with a reminder - a sticker. I checked two PC817 optocouplers that were at hand, both were working, but they showed different voltage drops when connected. On one it dropped to 3.2 volts, and on the other to 2.5 volts. Food for thought; if there was no connection with the m/meter, it would not exist.
Video of the tester working
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 have failed or not, and besides, with a high degree of probability, you simply will not get an answer to it. Author of the project Babay iz Barnaula.
Discuss the article ATTACHMENT TO THE MULTIMETER - OPTOCOUPLE TESTER
Description, characteristics, Datasheet and methods for testing optocouplers using the example of PC817.
Continuing the topic “Popular radio components for repairs of switching power supplies,” we will analyze one more part - optocoupler (optocoupler) PC817. It consists of an LED and a phototransistor. They are not electrically connected to each other, due to which, based on PC817 it is possible to implement galvanic isolation of two parts of the circuit - for example, with high voltage and with low voltage. The opening of the phototransistor depends on the illumination of the LED. I will discuss how this happens in more detail in the next article, where in experiments, by feeding 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 optocouplers, first in the role, and in the second. And using these circuit solutions I will build a very simple optocoupler tester. Which does not need any expensive or 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 popular (I don’t mean any exclusive) switching POWER SUPPLY and plays the role of 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 recommend watching the video at the very bottom of the page.
Optocoupler (Optocoupler) PC817
Brief characteristics:
Compact body:
- pin pitch – 2.54 mm;
- between rows – 7.62 mm.
The PC817 is manufactured by 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 PC817 optocoupler, other options are available:
- PC827 - dual;
- PC837 – built;
- PC847 – quadruple.
Checking the optocoupler
To quickly test the optocoupler, I conducted several test experiments. First on the breadboard.
Option on breadboard
As a result, we were able to obtain a very simple circuit for testing the PC817 and other similar optocouplers.
First version of the scheme
I rejected the first option for the reason that it inverted the transistor markings from n-p-n to p-n-p
Therefore, to avoid confusion, I changed the diagram to the following;
Second version of the scheme
The second option worked correctly, but it was inconvenient to solder the standard socket
for a microcircuit
Panel SCS-8
Third version of the scheme
The most successful
Uf is the voltage on the LED at which the phototransistor begins to open.
in my version Uf = 1.12 Volts. 
The result is a very simple design.
Tester for checking optocouplers
Failure of an optocoupler is a rare situation, but it does happen. Therefore, when soldering a TV for parts, it would not be superfluous to check the PC817 for serviceability, so as not to later look for the reason why the freshly soldered power supply does not work. You can also check the optocouplers that came from Aliexpress, not only for defects, but also for compliance with the parameters. In addition to dummies, there may be specimens with inverted markings, and faster optocouplers may actually turn out to be slow.
The device described here will help determine both the serviceability of the common optocouplers PC817, 4N3x, 6N135-6N137, and their speed. It is made on the ATMEGA48 microcontroller, which can be replaced with ATMEGA88. The parts being tested can be connected and disconnected directly into the included tester. The test result is displayed by LEDs. The ERROR LED lights up when there are no connected optocouplers or their malfunction. If the optocoupler, when installed in its socket, turns out to be working, then the corresponding OK LED will light up. At the same time, one or more TIME LEDs corresponding to the speed will light up. So, for the slowest one, PC817, only one LED will light up - TIME PC817, corresponding to its speed. For fast 6N137, all 4 speed LEDs will be lit. If this is not the case, then the optocoupler does not correspond to this parameter. The speed scale values of PC817 - 4N3x - 6N135 - 6N137 have a ratio of 1:10:100:900.
The tester circuit for checking optocouplers is very simple:
click to enlarge
We connected the printed circuit board for power via a micro-USB connector. For the parts being tested, you can install collet or regular DIP panels. In the absence of such, we simply installed collets.
Microcontroller fuses for firmware: EXT =$FF, HIGH=$CD, LOW =$E2.
Printed circuit board (Eagle) + firmware (hex).
Using the proposed probe, you can check NE555 (1006VI1) microcircuits and various optodevices: optotransistors, optothyristors, optosimistors, optoresistors. And it is with these radioelements that simple methods do not work, since simply ringing such a part will not work. But in the simplest case, you can test the optocoupler using the following technology:
Using a digital multimeter:
Here 570 is the millivolts that drop at the open junction of the optotransistor. In the diode continuity mode, the drop voltage is measured. In the “diode” mode, the multimeter outputs a pulse voltage of 2 volts, rectangular in shape, to the probes through an additional resistor, and when the P-N junction is connected, the ADC of the multimeter measures the voltage dropping across it.
Optocoupler and IC tester 555
We advise you to spend a little time and make this tester, since optocouplers are increasingly used in various amateur radio designs. And I’m generally silent about the famous KR1006VI1 - they install it almost everywhere. Actually, the 555 chip under test contains a pulse generator, the functionality of which is indicated by the blinking of LEDs HL1, HL2. Next comes the optocoupler probe.
It works like this. The signal from the 3rd leg 555 through resistor R9 reaches one input of the diode bridge VDS1, if a working emitting element of the optocoupler 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 base of VT1, 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 faulty, so if HL1, HL2 do not blink, short-circuit c2, but if even after that the indicated LEDs do not blink, then the NE555 chip is definitely faulty. Good luck. Sincerely, Andrey Zhdanov (Master665).
To quickly check the functionality of optocouplers, radio amateurs make various tester circuits that immediately show whether a given optocoupler is working or not, today I will propose to solder the simplest tester device for testing optocouplers. This probe can test optocouplers in both four-lead and six-lead packages, and using it is as easy as shelling pears, insert the optocoupler and immediately see the result!
Required parts for optocoupler tester:
- Capacitor 220 uF x 10V;
- Socket for 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, not all types of optocouplers can work correctly; any charger for a mobile phone can serve as a power supply. When the working optocoupler is correctly inserted into the tester panel, the LED will flash, which means that everything is in order with it; the frequency of flashes depends on the capacity 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 testing optocouplers is made of a socket for a microcircuit and 4 pins are left at one end, for testing optocouplers in a 4-pin package, and at the other end of the socket there are 5 pins for a 6-pin package. I soldered the remaining parts of the device for testing optocouplers by hinged mounting on the contacts of the socket, but if desired, you can etch the board.
All that remains is to choose a suitable housing and a simple optocoupler tester is ready!