You probably didn't realize that Mercedes-Benz also manufacture light fittings Unfortunately Mercedes don't realize that either. The slogan for this particular one is Style of Create New Styling due to show the Vogue House to Reside the life and the instructions are very clear: cut off power supply rectifier, pull down to bad tubes Are you ready to change the LED Dome light source module Oh yeah. light group of absorption on the chassis plate with the lampshade. The new lamp modification is complete.

All that sounds very straightforward. Let's take a look at the Mercedes-Benz series LED module luxury and here's why it's called the Mercedes-Benz series. It looks a bit like their logo I Think we should test this. So the first thing I'm noticing here.

it is one of these ones that sticks on with magnets. That'll be the absorption bit and it's got what looks like a little Buck regulator or even an isolated regulator inside it. Let's bring up the hoppy. the wires haphazardly into the hockey as one does.

Oh, they're stiff and unpleasant. wires. very thin wire, also very short wear. She'll try poking underneath here like that.

uh I'm sure stuff these and it probably doesn't really matter where they go which order because it is AC and I shall plug the hop in and hopefully this won't just blow up. I Mean hopefully it does blow up to be honest. Oh, it's cold white, Vicious cold white. You won't be able to see the hobby.

Uh, the hobby is seeing 18 Watts which is quite ferocious. Uh, 0.56 per Factor That's typical 129 milliamps at our local power supply which is currently 248 volts. How generous. Almost a quarter of a thousand volts we have.

That's lovely. Very useful. So how's this going to open? usually? Well, there's that little plastic cap that covers the ballast I Wonder if it's all fully charged up in high voltage and stuff like that? Uh oh, it looks like it's using a bright power type chip. Let's discharge that capacitor.

Let's just do it with my fingers. There's discharge. Yes. And also, oh, this isn't screwed on.

It's actually just little clips that hold it on. That's interesting. Let's maybe pop that off as well. So take a look at this well.

I'll actually find out what chip it is for this. I'll try and even stay in short, maybe even Zoom down so you can even see what I'm looking at. That would be quite good. How unprofessional.

Uh, okay, so the chip is A I Could just cut to the chase here. Well, I can't read the chip Anyway, it's got very big text right one moment, please. Okay, exploration has been done. It is time to explore this and then hack it.

Obviously we're gonna hack it. There's the hackable bit here. so the supplies coming on here with live in neutral and the live is going via this tin little track here which is the fuse. It's going to a bridge right far and then it's going straight out to that smoothing capacitor.

It's a buck regulator so this is just an inductor. It's got the dedicated chip dp9501b with the current Cent resistor and another resistor down here. and let me zoom in. There's just a little tiny bit and another resistor down here that sets the over voltage.

Protect. Um, there is the standard Buck regulator arrangement of a Freewheel Diode capacitor, but they've added one thing. it's not in the manufacturer schematic. They've added a 200k discharge resistor.

It's just hidden behind here and I'll show you that right now. Show you there is that resistor just tucked right up against the capacitor. You might know. did you see it? It's very tiny.

It's a little surface mount resistor. Interestingly what they've done here is they have used uh, surface mount resistor for program the current plus also this blue, red gold uh, through-hole resistor in parallel with it to fine-tune that current. uh, blue red gold. The gold is actually a divider in cinema multiplier so that is basically six two and a divider.

so it's 0.1 at 6.2 ohms but goodness knows what's underneath. I could always cut that off and find out. We will cut it off and find out. and then we'll swap it and see if we can get the current down to a certain acceptable level.

So the actual schematic, it's very close. The only thing that's really different here uh, from the manufacturer schematic is the addition of a resistor over here in parallel the output. That may just be to ensure that when things are turned off, the voltage goes down to a sensible level. and that is 200k.

So that is basically going to act as a discharge resistor. I Wonder if that's also potentially going to be a sort of anti glue resistor? But anyway, we have until I've need to come in here. Ignore the Earth symbol here. What that means is it's the zero volt reference.

It's the circuit ground reference they've kind of. That's misleading when they use that Earth sort of thing because it makes it look like an earth connection. There's a smoothing capacitor. Here's a chip.

Uh, there's the current sense resistor. There's the over voltage protect resistor. Now, the over voltage protect resistor measures the voltage. Uh, that is being applied across these.

Uh, LEDs how does it do that? How does it monitor that? Oh, it will probably be monitoring from here. Uh, let me turn this down a little bit. It's quite Savage That's better. Um, but you set, choose the resistor.

It's got a given current and if you look at the manufacturer's data sheet, it says the over Voltage protect has a current of 40 microamps and it's got a voltage threshold of 150 millivolts, which will probably set by choosing that resistor for that level. Um, it will set the voltage across that. Not quite sure how that works. The current sense input, on the other hand, is very straightforward.

It's 0.6 volts, 600 millivolts. This data sheet has an anomaly. It mentions the mosfets voltage rating, but then also gives it presumably the on-state resistance. but it's high.

In the case of this one dp9501 it says 8.5 ohms that's way too high I Would have thought that would be millions, could be wrong, but that I'd Expect that to be a milliohms. Here's the operation: when the circuit is running. This has a mosfet inside that switches down to the current sense. So the current flows through the current sense pin to the zero volt reel.

and when it does that, the current flows in the positive through the LEDs through the inductor and that end is positive and that end is being peeled. negative and it flows to zero volts. Measuring the current in the process once it reaches the inductor, will initially push back against that current. But once it reaches the threshold of 0.6 volts across that resistor and this is how you program the current through the LEDs, it turns off when it turns off.

This end stops being positive because the magnetic field collapse isn't This angles positive and this end goes negative. As the fuel collapses, it goes through this freewheeling diode and back through the LEDs. So in both Cycles the charge and discharge of the inductor, it puts current through the LEDs and that capacitor. Smooths That Uh, so this is a bit we're kind of interested in here for hacking this.

Let's take a look at the resistor underneath that. So if I go back to this picture here and we break the image up a bit again, let me bring the socket board in. I Measured about two ohms across. That, let's cut that resistor off and see what's blue.

I Would expect a much lower value resistor than even the uh, the volume of the three-hole one and the value is 1.8 Ohms. That is very low 1.8 Ohms. Can you see that? Uh, so let's remove that resistor and double it to about actually increase it even higher too. Uh, 4.7 Ohms is a nice value I've got because that was roughly two ish before.

this one was basically 1.8 ohms being tuned marginally to possibly 1.5 I'm going to make it 4.7 and it was 18 Watts before we'll see what it is afterwards one moment, please. when I make that modification, the hack is done. I actually put a 3.9 Ohm resistor in which it's roughly double what was there before, so it should theoretically have the power. Dragon We'll find out now the LEDs in this: it's parallel pairs all the way around.

Presumably that's to um, well, partly to fit in the power and within a given voltage. But it will also mean that if one LED fails uh, the other will pass the current. It's not a great situation. they're not well matched.

When I was probing them with a meter, one would always be bright, one would be dimmer so it's not perfectly matched. LEDs That's not great. Other things worth mentioning: The over voltage protect chip is also interesting in that if you put it to the ground rail, it turns output off and they actually suggest that you could use that as an enable and disable uh. controller.

Don't know how Flash control if it could be positive modulated. But anyway, I have made my modification. Yeah, well, let's turn the LED down the way. Let's point it down the way.

that's better so it doesn't just swamp late in everybody's eyes and that way we'll be able to see what the emitter actually says. So I'm stuffing the wires into the hopper here into its completely non-compliance electrical connections. This may just it's always mass and dicing with death with these things. Let's plug it in and see what happens.

Nothing. Oh, that's not good. That's probably because I've got a bad connection here though. Air that just doesn't like that resistor I've put in I Shall try fumbling the connections here and also make sure that things are plugged in properly.

Oh, maybe I blew that up. Exciting. No, it's not liking at all. Is it is that too is? Have I gone too high with that resistor value? Uh, hold on if it's not running.

I should get a fairly high voltage across the capacitor the death beaming capacitor. Let's prove that although it has its own power supply inside, well so that will be affecting that, look at anything across there Am I getting a good connection to the thing at all here. The hockey is notable for it's not exactly what you call an ideal electrical connection system. Let me bring in my more dangerous one.

Oh, here we go. Why don't I think you're using this thing? That's better. Let's give this another go. and then I'll maybe experiment with swapping that resistor about.

Are these connections still made on here? Let's screw this video up, Shall I Let's just leave it in because it's more convincing when. uh, when you see what does actually happen in real life. So I shall pop that wire down there and that one down there. and uh, plug this in giving this circuit board away from here.

Turn it on. Nothing at all, right? I Have to explore this further one moment, please. Ah, problem solved and it's a weird one. An interesting one.

It is now working at a reduced power of 12.5 watts, which is a good step down from the 18. Watts originally I'd rather it was lower, but it turns out that it was capping the voltage to 50 volts. and if you work out, if I get the Kink calculator in, there are 24 circuits of LEDs with roughly about three volts per LED. It means that it needs a 72 volts and the reason it was capping the voltage at 50 volts is because the current through the current sensor resistor seems to affect the over voltage protect reading as well.

That's strange, that is unexpected. Now there is another option there. If you were in that situation, you could either increase the value of this resistor or remove it completely because without the resistor, it removes the over voltage protect and that means well. let's do that for the sake of experimentation.

So let's unplug this and I shall remove this extra parallel resistor I put in to get the resistance down low enough to get the correct sort of current that I was kind of needing for the for the thick. Well get it closer to what it was before. This is just experimental experimentation going on right here. And there's that surface mount component which I shall.

uh, this is all unplugged. I shall just dab some children out of sight and wipe it off. or I might just chop off I might just chop off, it's easier. Hold on.

Let's abuse my side Cutters and cut that resistor off if I can. This is not what you should do. these said: Cutters This is why I usually have to order lots of them because I usually destroy them like this. So I've cut that over a voltage sense resistor I Reckon Well, it's either going to blow up now or it's going to operate at a power level of probably about six months.

Shall we find out? I should pop here the screwdriver which I've just dropped. Yeah, just dropped that screw. not to where I'll just use this one again I'll prop that up so you can see it lit I shall plug it in and hopefully it won't just go kabin. So this is without over Voltage protect and now it is lighting at the expected 6.2 Watts So that's interesting.

Uh, very useful to know. I guess that when they're designing these, they must have to basically, uh, experiment with the values, put a potentiometer, maybe on the over voltage protect, turn it up to the point that the LEDs go out, measure the value and just use a slightly higher value than that. But there we go. Educational.

Didn't expect that. I'm pretty sure I'm getting Deja Vu Now that I thought I'd react to like the past by doing the same thing. and in reality it was probably the over voltage protect from that very same chip. So the answer there is you can hack them, but it's a bit more complicated than than the other lights.

and if you do hack them, um, you can lower the power of this light and you can make say for instance, you can make it last like 10 times as long by running a fraction of power because quite often they grow these things. But there we go. Interesting stuff. and I've learned something about the Dp9501b that resistor there.

the value of it is dependent on the current sense resistor. Very interesting stuff, but that is your Mercedes-Benz later I I drove Mercedes-Benz vans in the past they're not just saying for big people, the biggest, longest, most awkward van I've ever driven was a Mercedes-Benz It was just the long wheelbase one. Very scary I'm pretty sure I took a sign and a traffic hell and once with it. but these things happened I didn't go back and look I just drove off.

But there we go. the uh, their Mercedes-Benz unofficial LED light and how to hack it.