Having made lots of videos about the really crap and dangerous Mains voltage LED Lights on eBay I thought let's take a look at a set of the low voltage ones and these ones in the listing show the low voltage power supply and uh, this one came from Auto Motor Biker 2019. Uh, good positive feedback actually and they arve fairly quickly. This is looking promising so far and quite affordable. Let's see if the power supply lives up to our expect ation though.

So I open it up and here is the low Voltage Power supply. This is the important bit. It has the controller built in. uh oh.

It's also worth mentioning on the box. Aside from saying the manufacturer's uh name which is Meo Mingen Bang to U Zan gong C, it also has Apex C Specialist Limited that's a improval thing the C and it gives a UK address. That is interesting. So this is promising: a plug.

plug them in. and the good news is that they do remember their last setting. You got a little button here to change the settings, but it does seem to well. I've never tried if it uh, defaults, let's try it.

so let's unplug it for a while. now that I've put it that to the Hideous flashing setting and we'll plug it back in and see if it remembers it. Yes, it does. Okay, so the UK versions these things tend to operate at Uh Android American vers.

These things tend to operate at 31 volts. The reason for that? I'll just zoom down onto that a little bit. The reason for that is because uh, they're sort of keeping within the safe low voltage levels. but also by going for 30 volts, that means that this 300 light set can have Uh 30 LEDs in parallel and then another 30 and then another 30 all connected in a series parallel arrangement to make up to 30 volts.

Now in the past, the other ones have been very hard to open. It's typically this back here has uh, been super tightly glued on and it takes ages to get off. and I think that's going to happen again, but coming off it will. Um I think I'm going to end up doing what I've done in the past.

Uh, basically get the plers and physically just gouge it off because if it's anything up to the standards of the complin sets of Lights, this will be sitting into a sort of GrooVe and it'll be absolutely glued to death or ultrasonic welded to death to the point that you know it, It's really destructive getting it apart, so given that that takes a fair amount of time due to chewy plastic, I'm going to pause while I do that one moment, please. Messi But we are in now. Let's see if we can get more out now. It's worth mentioning that usually these just slide in and go onto pins at the back, which whichever uh type of plug you have locally.

it just has little uh, spring contacts like this, but it's also got them at this end. including the button here is H just going over a little tactile switch and it's got the springy bits. So let's get the long those PES here. Grab the circuit board and see if it pulls out.

It does and you know what? I'm seeing here the interesting bit and I'll Zoom down a bit in this. see that the pins. It's got great separation here and it's got the proper class y It's got the pins protruding out from the Transformer See, this set of lights did not cost much more than the dangerous Mains voltage ones and yet it's got all these safety features and a bit of filtering bill. Look of it right.

Tell you what, you know what happens now. going to take a picture of this and then we shall explore the circuitry. and so I'll just do that right now. One moment.

please, Reverse engineering is complete. Let's explore. And I cannot lie, that was a very long one moment please. For the reason that there was an unidentifiable chip in the power supply, right? let's zoom up and I shall show you bits on this circuit board.

Here is the 10 ohm input fuse: fusible resistor. Notice of a gap here surrounding that, giving it plenty of room to blow. Clear? That is amazingly good. We've got some filtering.

We got two smoothing capacitors with an inductor between them. We've got a Transformer with that extra spacing out for separation with the Uh triple insulated wire. And because this system uses just two windings uh, it's not like the secondary sandwich between a scense winding or half primary and second primary and then the sents. It's literally just the primary in the middle and then it looks like the secondary W over the top.

This is good. good for separation. There is a proper clasp W pter for interference suppression. Um, And then we get to the other side.

We just get the output terminals to the LEDs. We've got a smoothing capacitor in the secondary and we got a button um and again, the input is just spring-loaded Terminals And if you look down the inside of this uh plug, you can see those little pins that it just slots over. Very nice. It's actually a pretty good power supply.

I Have to say, on the other side, we find that pesky chip. oh that is so annoying. Uh, the number of that chip is 216, 3s or 120 dge I Drew a blank in that and it's quite odd in the way it works as you'll see in the schematic. so there's a fuse, there's a brid direct far.

there's the capac's other side, there's the chip. It's got a little snub. Network Here it's got a sense resistor, it's got the a feedback circuit, and uh, it's also possibly got either bootstrap or maybe that's its main source of power. Don't know cuz I Don't know what that chip is.

There's a good chance it's a clone of another chip, but without knowing what it is, it's hard to say I Couldn't find anything that matched the pin out. Very frustrating I've had to work it all out myself on the other side after this massive isolation. Gap We have a standard diode. It's not a short key, but there is the provision for a uh snubber Network that You' normally find across shortkey diodes because the shortkey diodes, although they've got a fast response and a low forward voltage um versus a standard silicon diode which I think shots is silicon as well, but a standard format diod H they do not like the reverse voltage being exceeded and even a light Spike will actually damage those diodes.

We have the smoothing capacitor with a little uh, stability discharge resistor across it. um and then we've got the main chip that's more or less it really other than the memory chip and a couple of capacitors because this seems to generate a supply that I believe is 3.3 Vols And then there's this strange link here I Don't know if that was for extra filtering, but it's between these two capacitors you shall see on the schematic and there's a little switch going to an input. that is it. uh oh things worth they of note the two outputs uh, each of a capacitor going to the negative uh position but they've not occupied it.

I wonder if that's just for noise filtering the output as it changes state. but I don't think uh, it would be needed because the wiring itself would probably have capacitance right? Let's take a look at the schematic. Let's start with the hard bit that took me the most time to reverse engineer because uh, it would have been so handy with a manufacturer's data sheet. Here's the incoming: AC Supply It goes via the fusible resistor, then there's a B direct fire and then it goes to the Uh first electrolytic capacitor 4.7 Mard 400 volt through a very high value 2.2 uh millihenry inductor.

Uh, the inductors. They're normally measured microhenry. this is red red red 2,200 microhenry by the look of it. Um, so that's 2.2 mli Henry and then another 4.7 microfi for anol capacitor.

So good filtering. Ah, now we come to the the spicy bit. the there's a single primary winding that looks as though it's used for sensing uh as well. And uh, there is a positive connection going here.

Two connections I presume that's the drain of a moset I Reckon that although it's going up to the positive real I think it's an end channel moset in this, but I Can't say cuz I don't know what's inside. Not seen a block diagram, but there's two uh 2 megaohm resistors in series that I reckon is what's commonly referred to just the HV Supply IT Supplies the power to the chip that it might uh cap internally and then uses it to charge what I think is the power supply capacitor here and when it's running I reckon that this is the Uh source of the mosfet inside and also the sort of General negative reference inside the chip. Hard to say, but certainly that capacitor goes there and it kind of makes sense. Um, and when it turns this coil on, it measures the current across this resistor to determine when it's reach the saturation point of the Uh.

the primary and Uh detects that voltage cross there by this current sense input. There's also a resistive divider here, which is most like the feedback to detect a rough emulation of the voltage on the other side. then there is a snubber network. The only extra notable feature here that H it's got the Diode.

It's got the Uh 330 Ohm resistor which is odd and then it's got the usual capacitor with a discharge resistor. Arrangement The point of that is that when the Uh transistor in here turns off before the other side can turn on of the coil as's a magnetic field collapses, you can get a sharp Spike and what happens there is it gets diverted through this diode and charges up this capacitor just to take the tiniest little nip off the edge. Um, and then this Uh resistor here just keeps that discharge ready for catching the next Spike and the 330 resistor might be to raise the voltage. A We bit over that H cuz it might be using that to generate a supply Ra.

If it's not just purely doing it through these very high value resistors, that is what I think I may be right I may be wrong. The Zer volt rail also has that 2.2 Narat class Y1 safety capacitor. the uh, these capacitors. This bridg is from the negative one side, the high voltage side to the negative of the low voltage side.

and the point of it is it's to provide a path back for current leakage through capacitance through the windings that would otherwise be radiated from the the string of lights. So it's just purely for RF suppression. And but it has to be rated in this case for human contact. So this capacitor is a big chunky one for its value because it will fail safe.

if it cracks, it's not just going to short out like cheaper capacitors might. Let's take a look at the other side. the secondary. you can let me know if you can identify that chip.

Uh, just from how I've described it in the pinout. Hopefully I've got the pin out right? Here's the other side. it's so much easier. Oh yes, this is massively easier.

Here's a secondary and after the inductor been uh had a magnetic field put into it by the other side and then it turns off. It couples it across the flyback Style by that collapsing field, then generates a voltage in this that goes via this diode and charges up this capacitor with a little shunt resistor across it. There is the option of that capacitor and resistor not used in this circuit because they've used a US 1G which is a standard diode but the super ultra fast one which uh, just. it's a nice rugged Diod.

It's fine for this application. It's quite a low current application that gives us our 31 volt. Rail and it goes to this mystery Xhr 1410b uh LED Control Chip just dedicated to Christmas Light Control I Only found one reference to this in the internet. It was a Russian uh Forum where the guy was saying what's this chip I've That happens quite a lot with these specialist chips.

You always find that some Russian person has done exactly what I've done and tried to find out what that chip is and uh, failed. It's a manufacturer specifically. it's it's for the Christmas Light manufacturers. It's for the people making these power supplies.

It's not for anybody else really. H There's a little button that goes to the Zer volt rail that you click to select a patterns. There is an output in this that seems to be an internal regulator that takes the 31 volts and gives a 3.3 volt rail. couple of passs.

and then that uh that zero ohm link that uh I'm not really sure what the reason that was, but they've got a couple of capacitors. nice stable. Supply I Guess that may be using that internally. Uh, that probably will be for the circuit in there as well, so it will be generating that not just for itself, but also for the 24 CO2 memory chip, which is a Serial memory chip.

It's got a data line, it's got a clock line plus it's got three address lines which are almost invariably tied to zero. Z Volt rail. Um, it's got the negative and the right protect line, which is also tied to the Zer volt rail. Um, because it's not really in use and that is it.

I Have to say I Was expecting this to be trash and it's not. It looks pretty darn good. Um, it looks as though it's totally compliant with the UK regulations. It's layer.

the circuit board is uncluttered. It's just a nice generic design. Uh, that's nice. That's a good thing.

Um, and so, and you look at the price of that that one versus the price of these crappy Dangerous Ones And there's very little in the way of price difference if at all. but you're getting one that's more versatile and safer. Ah, strange, strange times. eBay Selling Safe products? What has the world come to? H But there we go.

That is it. Uh, the inside of a cheap generic set of of eBay Christmas lights, gray import. but uh, seemingly they've come via Sensible Channel, so maybe not so much of a gray import. And they've got a a compliant and safe power supply.

Amazing stuff!.