A laverno light fitting commonly sold by shops like aldi or little in the uk, and this one is designed for outdoor use and is based on just standard five millimeter leds in here i mean it's quite a smart effect. It projects, i would say, a fairly dotty sort of pattern of light around the outside, but let's take it apart and see what sort of construction it is. So i shall unplug it and one of the first things i noticed about this is well obviously you're not going to be able to change the leds once you've. If you've installed this light fitting and it fails, then that's it you're going to have to get a new light fitting unless you could repair it yourself, which is only something that people like us could do.

There is a ventilation hole in the bottom of it. This is good. This is to avoid water building up inside this and reduce the risk of condensation. That's the best way to do that.

I've already had a go at kind of opening this, and i used brute force, and it came apart like this. This is just held together by a white, silicone shmoo and it divides into two circuit boards, and it looks as though the main supply comes straight in onto the bottom circuit board here. So, let's remove these screws and we'll take a look under here at the main circuit board, and can i get this out i may have to. I may have to get this uh bottom bit from the case as well.

So the circuit board initial thoughts here are that this looks as though it's based in the capacitive dropper. It's got a bridge, rectifier um. It's got what looks like a ptc thermistor, which is unusual, that's basically an over current device. I'm not sure why they'd have it like that it does the circle of leds and i'm guessing that this circuit board here is just another circle of leds that are basically connected in series of those ones, so that all the leds are in series.

That's why, when one led fails you're going to lose the lot, that's a thing that happens with these. Is this going to liberate anything? No, it's not going to liberate anything i may have to. I may have to get destructive here. I shall explore this further.

Oh there's actually a layer of clear plastic in there right. I will have to explore it further right. Tell you what uh i shall pop the cover off here and we'll try and get that circuit board out, and then i can reverse engineer it and we'll look at the circuit diagram. We can see what the function that ptc thermistor is.

I'm guessing. It's basically an over current device ignore the fact that this has got earth here, but i've only connected two wires i'll make sure this doubly is unplugged uh, it's just the flex that i had available. It is effectively well insulated inside. As far as i can see, everything's in sort of plastic trays, but there's always that risk that uh, because it's metal that it should really be grounded.

I should put that cable out of the way. Now. How is this gon na come apart? Can i get this circuit board out? This circuit board is lifting up, but it's knocked me out all the way. What if i push this wire in here, i shall push the wire in as far as it goes and see if that liberates anymore.

No, it's not really liberty anymore. I may have to just reach in with a pair of snips and cut this. That seems a good idea. This saves time.

I have cut it it saved time. This is a bit we need for the reverse engineering. I see one surface mount resistor in the back. Why have they done that? That's odd um.

Can i get this apart anymore? Not really. It is glued completely together, as is this one. This is where i cut myself in the on the metal uh. I may just i'll pause momentarily i'll, reverse engineer the circuit board and we'll take a look at the circuitry, we'll see what the function of a oh, i can see what that is.

That's odd, that is, a self-resetting fuse they've put in series of the whole circuit. That's very strange: it is rated for a mains voltage. I believe i wonder why they've used a self-resetting fuse unless it was that, like that thing that, if you use an ordinary fuse with capacitive droppers, if you've got a lot of electrical arcing in the vicinity and something else failing, it can actually cause a lot of Current through this circuit and that could pop the fuse but you'd think that would strain the leds as well. It looks as though they put a bit of thought into this design.

It's very strange right. Tell you what i shall posmo entirely to reverse engineer this right. Well that took a bit of reverse engineering, very weird circuitry, indeed, lots of things to try and protect leds from just blowing up. So we've got two circuit boards, the main circuit board and the satellite circuit board, which is over at this side, and it starts off with the ptc uh fuse, which i believe is rated for 250 volts around about 200 micro milliamps.

And then it goes to the 330 nano farad capacitor. With a 510 k discharge, resistor actually mounted underneath the capacitor itself to save space. It then goes through a bridge rectifier for bridge rectifier and has a 100 volt, 10 microfarad, smoothing capacitor a transient suppression component bidirectional. One and then a 51k resistor to provide a slight load, presumably to help make sure this discharge is to make sure the leds go out in a controlled manner, and you don't get that thing of leakage glowing.

I wonder why they've used the ptc thermistor here i get the feeling that, in certain circumstances, when you get arcing and electrical noise, capacitive droppers like this can actually pass a fair amount of current and with that the little bypass capacitor of the leds and down here. It's possible that you could get a sort of burst of high current and that self-resetting fuse is presumably for that reason it's quite a high value, though i wonder if it would ever really fail um. So the first section of leds, this rim of 12 leds around the outside, is here, and it has that little capacitor across it, so that if there's any excessive spikes and noise, it will be shunted across those and likewise there's another capacitor here, which i i drew Afterwards, that's why it's gon na be sort of d2 around the 51 cubic, but it's uh on the satellite circuit board and it bypasses all the circuitry so that any noise will just go through this capacitor. This capacitor will just basically protect the leds and circuitry from that.

The circuitry on the satellite pcb has a current regulator, but it's actually based on a 7805 voltage regulator. It's not an uncommon way of doing this. They've got a 300 ohm resistor here, going from the output of the regulator to the ground connection, so that whatever current is flowing through. That regulator is effectively flowing through all the leds as well and by setting a known, resistor value.

It works out as let me bring a little calculator i equals v, which is the 5 volt, the regulator's regulating to divided by the 300 ohms, which is across the output, and that gives about 16 milliamps, so 16 or 17 milliamps will be flowing through these leds And because that sinceres the whole circuit, it will be flowing through the whole lot of leds on both circuit boards. There is another 51k resistor here for some reason and another 300 ohm resistor here, um, presumably just means of protecting against in rush current to uh the regulator. I'm not really sure why they've done that, but i'm guessing maybe they've. Maybe they just wanted to put another 300 ohm resistance, resistor in series with the main led circuit, but they just decide to put it off on the satellite circuit board instead, but it's very strange circuitry.

The construction is also strange. It is a whole bolted together. It's like this section that was coupling the the body onto this of housing is just a square section, with a little spacer, a little cylindrical spacer and then the usual threaded rod that you find inside these things with the plastic inserts at each end, to actually protect Against trapping of the cable, it's been treated as a double insulated fixture, but the fixture does have a ground uh that connects onto the actual main body work itself. It's an interesting construction.

Likewise, all the even the bottom led bit has its own cable grip uh before it goes into the main circuit board at the bottom and uh. It has it's a chromium, surround that sandwich around the leds for visual effect and for light reflection and then the little cover that goes on top to hold this in position. And then it goes up to the next one, which also sort of plastic inserts for insulation. But there we go odd circuitry, but that is what's inside.

That's of. Is it laverno? Let me just grab the box levarno. Indeed, liverno locks. That's! What's inside one of these lights, it was extremely hard getting this to bits because it is glued.

It's plastic to basically glued so solidly that the only way to get it out is to actually break things. So this is a disposable light and the first one of these little five millimeter leds it fails means that ultimately, if it starts flickering or it burns out completely, then it's a case of disconnecting the whole light fitting and replacing it which i'm not keen in that. I prefer things that you can change lamps in individually, but this is how it's gone these days. It means that your average do-it-yourselfer is now being forced to do more and more electrical work and, in particular, in the case of this one, it feels they're going to be doing it outside with metal objects in a wet outdoor environment.

It's not necessarily a good direction to go, but an interesting light nonetheless, and certainly well worth taking to bits.