 Okay, so what are socket testers? Okay, so I just got this definition from Wikipedia. So socket tester or receptacle tester is a small device, okay? 3-PROCK, 3-PROCK power plug. Okay, so it's plug your power socket and then it has 3 indicator lights. Okay, so the lights will indicate if there's any fog in the wiring of your power socket. Okay, so the power socket here that I'm using is this model Harvotest HD107E. Okay, so the 3 indicator lights are actually on the top. Okay, so this socket tester is a bit more advanced. Most socket testers actually don't have so many features. They only have 3 lights, but this one also have an LCD screen there. Okay, so this is a bit more advanced. Okay, so you can see from the status here, right? Depending on which lights come on, it will indicate what is the fog in the power socket if there's any. So currently, so you can see when I plug to a proper working power socket, right? The first 2 lights come on. So you can see these 2 lights on. So it means, correct? If it's anything other than this state, that means there's something wrong with the wiring already. Okay, so this LCD display also shows extra details. Okay, so the RCD current to test. Okay, so this first value, 37mA, is the amount of current that it will pass to the earth line so that to actually simulate earth war. So you can see this big one over here. So it press this, right? It will send 37mA from the life to the earth. And then you will trigger RCCB trip at home. But so it don't anyhow press. Okay, so okay, then the next one is the life to neutral voltage. So 237, okay? Pretty normal. Another one is the neutral to earth voltage. So this one should be 0, or at least close to 0, to be normal. Okay, so let's go into the functions of this socket tester. Okay, so I just plug it here and consider it guys. Okay, now it's green. So it's okay. Yep, I can see. Okay, I'll just leave it here. Okay, so these are all the functions. When everything is good, right? It just shows the first 2 lights. Okay, so I actually simulated this. So I just take the very wires and connect to the pins behind the socket tester to simulate the different ports to try to engage all the different modes. So let's say there's open neutral. So open neutral means that the nothing connected on the neutral light. Then you will show only one light, the middle one. It can show life and ground reverse. So I simulated here, life and ground reverse. Then you show you the second and third light. Then there's also life and neutral reverse. So only the left and the right light. Okay, okay. There's also other modes like open ground so your earth wire is not connected. Okay, but life and neutral is still there. Okay, so it shows you this light. There's also missing life. Okay, if missing life means totally there's no power already. So nothing will come on. Okay, there's also an 8th mode which is the earth and neutral reverse. But this one is the same as... This is the same as... Oh, sorry. This one is thought... I think I put a typo here. This will be off. Okay, so this one is an undetectable error. Because earth and neutral they are actually about the same voltage level. They're connected together actually at the circuit breaker side. So this one can't really detect it. So there's an error here. This supposed to be off. Okay, okay. So all curiosity. So let's open this thing. So this is the circuit board inside. Okay, so open it. You can see the wiring. So actually from the 3 pin socket there they connect using thermal wires which are soldered onto the PCB. Okay, and then the LCD has red and green backlight. So basically if it's something wrong, then the red backlight will come on. Otherwise it will just show a green backlight. So let's look at some chips inside. So one of these chips is a power regulator. So this one is a non-isolator when it just converts from the AC power to 5 volts. So this is probably to power the microcontroller inside. The microcontroller is the one that is driving the LCD display. Okay, so this one is not isolated. So if for some reason you're going to play with it, you try not to connect to the boss okay while you're playing with it. Because the DC portion is also live. Okay, so this one is for low cost. Because this iVis socket tester is less than $20. So yeah, as long as you're not supposed to open it while using it. So it's okay. Okay, then there's another one DC-DC 3 volt regulator. Okay, sorry. So the DC-DC 3 volt regulator actually powers the microcontroller. It takes the source from this 5 volt regulator. Okay, this one here. Okay, so of course, I will wonder how the three lights, how are they controlled right? Based on the different connections of your spouse. Okay, whether they are 40 or not. So using some tracing using the continuity mode of the multimeter. So this is what was traced out. Okay, so a bit of painstaking work. Okay, so from the three different AC power lines. So this is a schematic that is drawn on chi-cat. Okay, so roughly what is here. So they have some diodes here some resistors here. Okay, some LEDs. And then this one over here is an opto isolator. Okay, so this opto isolator signal is connected to the microcontroller. So that it knows so it can receive the whether this particular line is energised or not. Okay, so how does this result in the different operational states of the three different LEDs? So let's say everything is correct. That means all life neutral and earth lines are connected correctly on your boss again. So this is the path of where the current will take. Okay, so the life of the mouse so that okay Okay, so you can see from the life right, so the power flow from the life through this diode here. Okay, so one loop so it already turn on. The other one okay the current can flow in this way. Okay, so on the negative side when the life goes to the negative cycle right. So now the potential of life goes below the earth the current actually flows from the earth in this way. Okay, so what about the open neutral it means the neutral is not connected. So only this light the center light will turn on. Okay, so this center light will turn on because the earth and life is connected together. Okay, so when the light goes to the negative cycle right the power of flow from the earth to the life. So only the center part will turn on. Okay, life and ground reverse. Okay, so life and ground reverse here we have the second and the third LED turn on. So I guess put it here so we connect earth and life this way. So it can just follow the path. So now this bottom line is life. Okay, so you flow this one flow this way. Okay, and then the other two lines are earth and neutral. So the life can flow to earth and neutral on the opposite cycle. Okay, so you flow through the second and the third LED. Okay, so what about life and neutral reverse? This way. So life and neutral reverse only the first and the third LED will turn on. Okay, so in this case it will be this way. For the first LED you flow whenever the life goes to the negative cycle. Okay, so the current will flow from neutral to life. Okay, then for the third LED the current will also flow from earth to life on the negative cycle. Okay, so what about life or ground reverse? It missing ground. Okay, so it's like this. So like this part is not connected. Okay, life is taking the place of the earth. So the current will flow through actually all of them. Okay, so there is an indication for this first and second LED. You notice that the first and second LED is actually dimer than the third one, at least from the neutral. You can see. It's slightly dimer. So it's because the current is actually flowing across these two circuits. So there are two sets of resistors that can explain the slightly or lower current. Okay, so open ground. So open ground is like this. So open ground is only the first LED. Okay, don't worry. Okay, missing life. Okay, missing life means there's no power and also nothing like that. So that's really obvious. Okay, earth and neutral reverse. Okay, so earth and neutral reverse is actually the same as the correct aim because earth and neutral is to the socket tester is indistinguishable. So this is something that is actually is a common thing across all socket testers. If you connect earth and neutral wrongly, most socket testers cannot distinguish them. Yeah, okay. So that comes to the end. So like that. Oh, I'm going to pass it around. I'm going to take a look. Okay, I can just point. Yeah. Okay, so mysterious law. So the point I went here is that actually this socket tester is not that complicated design. I mean, you saw the circuit is very simple actually. But I find it actually very elegant. It's truly just a bunch of resistors and LEDs connected in a way right, able to solve most of this problem or trying to detect whether your power socket is connected correctly or not. So actually it's very, very good. This design. Okay. So I think that is yeah, that's all. You guys have any questions? I think I still have a bit of time. The earth and neutral are very connected in your house? Yes, at the circuit breaker side. That's the breaker. I've also heard this before or after the breaker. If, yeah, but it's around that. Yes. It's to tie the neutral line to, of yeah, it's to to stabilize neutral. And so it's like a linkage right? It probably I'm not sure. I don't, lucky I don't, I'm not L.E.W. So I don't know what it is. I don't know. I'm not sure what it is. You can go after. Yeah. Because of that connection I think there's no way. There's no way. Yeah. Need more specialised schools. Okay. That's all. Thank you.