Hello everyone, welcome to the ZimZimDIY channel. As usual today, I will introduce electronic devices. Easy to learn in the style of the ZimZim channel. And the one that is our target today is the opto coupler or in our home called the opto. Let's think of it as an electronic device that emits light on one side and the other side receives light back in. Let's understand its basic working characteristics first. Let's go to its shape first. It has 4 legs. On its body, there is a circular groove or notch. The leg closest to it will be counted as leg 1. We will count down to the end. When it's the end, we will count from the bottom right to the top right. We will call it according to the theory. Leg 1 is the anode leg and leg 2 is the cathode leg. The letters above, of course, are the number of the opto. You can use the opto number to search the datasheet for details on Google. Normally, we often choose to use an opto to separate 2 circuits from each other. Let's say I have a board. My board has Circuit A and Circuit B. My Circuit A will connect pin 1 to pin 2, while Circuit B will connect pin 3 to pin 4. Although the opto can work with many other circuits, but the two circuits, as I said, will work completely separately. When the two circuits are not connected to each other, but work together, how is it good? The advantages are: 1. If one circuit malfunctions, malfunctions, is damaged, or short-circuits, it will not affect the other circuit at all. 2. This type of connection allows one circuit to automatically control another circuit. So it is applied in various applications, such as in switching, using opto as feedback to the IC to know the operation of the other side. Or using hot ground and cold ground separation. And since the opto is made of semiconductor, it will only allow current to flow in one direction. Therefore, we need to connect it. Must enter the + and - poles correctly. If the power is entered incorrectly, the opto will not work. The opto can be connected to use the same power supply, work together, or separate the power supply by independently arranging voltage and current. If we increase its capabilities by adding 1 transistor to the output, it will be able to carry more current. The opto is not the same. It has many forms, both for use with DC and AC power, both Phototransistor for General Purpose Switching DC, Phototriac for Controlling AC loads, Photo-scr for Controlling AC loads. But in this video explanation, we will use the basic version to explain. Let's look at the symbol of the opto. If you notice, we will see leg 1 and leg 2 are the symbols of light-emitting diodes. Light-emitting diodes are LED bulbs, right? But inside, it will not be a normal LED bulb. But it will be an infrared LED as we understand it. But the value of infrared light is beyond the perception of the human eye. So we can't see this light. But we can test it by pressing and holding the remote control button. And then we look at it through the mobile camera. We will see lightning coming out. That is infrared light. In addition to our mobile phone cameras, the other side can also sense light here. On the opposite side, it is called a phototransistor. Its symbol looks like a transistor, but it does not have a Base leg. Therefore, its bias is to receive light. If we simulate its operation, when the power supply is fed to leg 1 and leg 2, infrared light will be emitted. When the phototransistor senses that light is shining on it, it will allow the current flowing through leg 3 to flow to leg 4. This is the principle of operation. But in reality, it will have an insulator covering it, so we cannot see the light while it is working. And having an insulator covering it helps prevent external light that may shine and disturb, causing the circuit to malfunction. We can try to make a simple circuit by arranging the current of the infrared LED tube. The current operation is the same as an opto. But I may have to use some electrical tape to wrap it to prevent the light from the TV remote that shines in. I will try to change it to an opto. Note that they can be used interchangeably and efficiently. It works better than OPTO. In fact, it does not have only 4 legs. Some have 6 legs, some have 8 legs. The more legs, the more detailed it is. It can check the operation at many points. And in almost every switching circuit, it will be used to check the DC electric current to see if it is working properly. I will talk about the details later. For the initial measurement, let's think of one side as a diode, one side as a transistor, one side is a diode. If you have a needle-type multimeter, set Rx1 or Rx10 to measure legs 1 and 2 alternately. It must go up 1, not 1. If it goes up both times, it is a short circuit, it is considered a short. If it does not go up both times, it means the tube is broken. For the transistor side, set Rx1k or Rx10k. The measurement is the same, which is to measure legs 3 and 4 a