I went on eBay and I looked for the worst set of Christmas lights I Could find the cheapest Janest ones and this video got off to a terrible start because when it arrived I was feeling this unusually light controller and thinking it feels very weak and flimsy and I squeezed it and all the plastic B Oh there we go, it's really burst. now it's just really junk. Okay, right, that's going to make testing this a little bit harder. Anyway, this listing described these and this is a good start as Economic Star String Light Outdoor Fairy Garland Lamp Wedding Party Christmas and not sure how many lights are on this string I Don't think it's the full quantity of 100 that they usually have.

so let's um, plug this in now. and uh, we can see the power. So if I bring up my little Chinese testure it seems so appropriate for this. plug it in, make sure it's off and I plug this in here.

Oh, there's another cap falling off and I turn it on. Uh right. Okay, not me. a great connection and I set it to it's drawing about 2.6 wats.

but I set it to the static mode I think it's a couple away from here and it draws about 4.7 Watts which means roughly 2.5 wats is been disip across each section, most of it across the resistors. in this, the power factor uh and the current cuz I measured in the hopp uh the power factor is near Unity mean because it is resistors in here and the Uh current was about 10 milliamps per section. So what I'm thinking you're doing here? Look at the size of that circuit board that is Tiny What I'm thinking of doing here is the resistors have a really bad color code on them. It suggests a very high value, but the resistor is a three band color codee Orange, green, red.

Now which way you supposed to read that because it could read in two directions: Red green orange would be 25k, 25k, 253 and green Orange red would be uh, 3.5k I'm not sure which way you're supposed to read it. these pull out quite easily. So what I'm thinking of doing I'm going to peel off the plastic off one of these. Well, I'll try that right now.

I shall get a sharp knife and just slit this uh, sleeving off and we shall see what value that resistor actually is and do some computations of how much power it's dissipating. So I'll see if I can get this off. I'm not sure how long it's going to take. Sometimes this is quite hard to get off.

if it takes too long. I'll pause. it already is taking too long, right? Yeah. I Think at this point in time I'm inclined to this coming off this coming off.

No, it's not coming off right. Tell you what? Yeah. I'm going to pause momentarily while I do this he said. just continue anyway.

Um, oh tell you what. I think we've revealed it. No, no, Tell you what. I'm going to pause and I'm going to work out, find the value of the resistor and I'll work out the power dissipation one moment please.

The sleeving has been removed, revealing that the color code is indeed orange, green, red which comes in at 3.5k And it means that the 10 milliamp that's passing through each string when they're static is, uh, equating to about 35 volts dropped across the resistor and that when multiplied by the 10 milliamps gives 35 watt for what looks like an E WT resistor. Now that would be fine if it was in its flashing mode, but not in the static mode because in the static mode, that's a lot of power to disappear tap. So what I'm going to do now: I'm going to plug it in and I'm going to just let it roast for a while quite literally at in the static mode and I'll get the temperature off that with the thermal imaging camera and then I'll uh tell you what it was. So I'm going to do that right now.

one moment please. Oh yeah, I can smell the hot plastic already if we Zoom down in the display here. I don't know if you're going to see this but the temperature down here. Oh, actually, I'm going to have to shift that up a bit he said, nudging the precarious death trap up.

H the temperature is about 100 C on the that resistor there. so they are getting very, very hot. Okay, let's explore how many resistors they've used. I Mean it says that was about 35 volts across that? We'll tell you what.

I think they're roughly about 10ish Led that's about 30 volts. So I've got 210 volts to drop divided by uh, 35 volts equals there's going to be about six resistors per section I wonder if what we'll T up with that? I'm going to unravel this set and count them one moment. I was close. There were seven in each section.

Now, what about this little safety plate that's supposed to know? It comes off easily as well, revealing Hot Melt Glue. Excellent. Let's get the circuit board out of here. So a little drizzle of isopropanol onto the Hot Melt glue should cause it to release fairly quickly and have just ripped a track off the PCB.

That's all right. It's also to be expected. The PCB is absolutely tiny, right? Okay, you know what happens now. I Shall reverse engineer this and we'll take a closer look at it one moment, please.

Okay, let's explore I shall Zoom down this just a little bit. It's a very small minimalist circuit board so the main Supply comes on and these two terminals here and it goes straight to the bridge right far. It does also go to this: 2 megohm resistor 20 and 520 and 5 Z 2 million ohms and that is used as a reference to the chip for the zeroc crossing point for things like phase angle control for dimming. This is a fairly sophisticated chip just mass produced to the point of Ridiculousness.

The chip gets its power from the positive, the positive track goes out to the LEDs, but it also goes to this resistor 154 15 and 4 150,000 ohms. And then there's a little capacitor here, which I measured the value at 2.2 Mard but I did measure in circuit and that provides power to the chip. The rectified but unsmoothed AC H goes out to the LEDs. the positive goes to the LEDs and the negatives are switched via this.

These little uh, tiny thyris just thers are used because it's a very cheap and easy way of doing this and uh, that then uh gets controlled by the chip. There is a button here connected between the Chip's input and the Zer volt Rail and that's used to select the patterns. It's the same type of generic button you'd find in carot controls. There's also a couple of pads here.

They're either for an external button maybe or maybe for a little backup capacitor just in case it was a H button bounce issue, right? Let's take a look at the schematic. very similar to the others. Ultimately, because it uses a very similar chip I shallom just a tiny bit more. At the risk of just doing too much, here's the AC K on there's the brid r fire.

The output provides the unsmoothed um DC Direct the LED strings which have resistors and LEDs in them. There is that tap taken off for the 2 Mega resistor to detect the zeroc crossing point for timing purposes. There's a power supply of the 150k resistor, the little 2.2 megard capacity measured in circuit, and there's the little button that goes to the zero Vol rail I should Mark that as the Zer volt rail Zer volt rail which uh, lets it tell when you're selecting the modes. These are the two 406 thyers.

thyers are designed to switch um DC but their ideal for this for we've rectified unsmooth DC because they won't turn off unless it passes through the Zer Crossing points. they rely it going down to the Zer Crossing Point Um 100 or 120 times a second. The LEDs and resistors are two arrays of 10 LEDs and 7 3.5k resistors per section. The reason that the resistors get so hot is ultimately because they've used a very small number of LEDs.

The strings of much bigger numbers of LEDs uh, have less voltage to drop across the resistors so they stay cooler. Um, and that is it. There's really not much to it. very simple, very cheap, and nasty.

But there we have it. Uh, the cheapest LED string I could find off eBay I Don't know if I mentioned this, but the listings said 4 31 that I wouldn't pay that for them. It was something. It was like 2 or 3 quid for them.

Um, which is what they used to sell the 100 LED strings for, but prices have gone up. so what will I use these for? Well, probably I'll pull the little caps off them because they come off quite easily. They're just a a smear of hot milk glue and I'll put them in other lights, but to be honest as they are, they're not great. they're just running a we bit too hot for Comfort Ironically, if you had the 110 volt 120 volt set would be more suited to that because there's less power to disate Across the resistors.

but they could also have lowered the current from 10 milliamps per string to about 5 milliamps. and that would also have significantly reduced the power dissipation. and they could have just they've used seven resistors. they could have used 10.

They could have used one pair LED just to spread the dissipation ac across the whole set, But there we have it. quite neat for the tiny little circuit board, the horrifically flimsy case, and the minimalist string of LEDs Well worth exploring.