As I sit in my apartment, surrounded by the comforting glow of LED downlights, I am reminded of the four years I've spent living here. It's a cozy space, and I've grown accustomed to its quirks and charm. But one aspect that never fails to impress is the electrical wiring – it follows the latest standards with ease, and my landlord has added a bonus feature by including a surge relay in the corridor.

The surge relay is an intelligent component that turns on or off its internal relay output whenever it detects mains voltage on its input side. In my case, it's connected to all the LED downlights in the corridor, which are controlled by a series of push buttons. These lights were a pleasant surprise when I first moved in – they dim themselves automatically in four steps whenever powered up rapidly.

However, as with all things that promise much, one light has let me down. After only 1.5 years of use, it stopped working, and I had to order a replacement. With the price tag of around 20 euros, I thought it was time to investigate what went wrong. But little did I know, this would lead us on a journey to uncover some fascinating insights about LED technology.

My curiosity got the better of me as I began to dig deeper into the world of constant current drivers and pulse-width modulation (PWM). It turns out that my old light used PWM, which caused it to flicker. But what caught my attention was the concept of constant current driving – it's a method that ensures stable power delivery to LEDs, eliminating the pesky flickering.

As I delved deeper into the world of LED technology, I discovered that one of the ICs was not labelled, leaving me with no information about its functions. So, I hooked up all my test equipment to get a better understanding of how the circuit works. The first thing that struck me was that even when the LEDs were turned on for an extended period, the current flowing through them barely changed. In fact, the voltage across them decreased, revealing that we are dealing with a constant current driver.

To dim the brightness of the LEDs, another IC comes into play – it basically controls the constant current flow with a certain duty cycle, which decreases as the LEDs go through their four dimming steps. This is why you see the flickering on camera; the LEDs turn on and off rapidly with a frequency of around 280 Hz.

But that's not all – we also have an RC timer circuit to let the system know when it's time to move to the next dimming step or restart with maximum brightness. It's not a bad concept, but as I continued my investigation, I realized that it can be executed much better than this. That's why I'm excited about the new downlight of the exact same type.

The main PCB is now secured in place with screws instead of glue, which is an awesome improvement. They've also eliminated the wired connection to the LED PCB and replaced it with a more reliable header construction. The amount of components on the PCB has decreased dramatically, reducing the risk of faults.

But what really caught my attention was the new design of the LED PCB itself. Instead of using fewer LEDs like before, each one now requires higher voltage than the old ones. This means that the combined voltage drop is significantly higher, which wastes less power – even when we decrease the voltage down to the darkest dimming level.

As I calculated the efficiency of all the dimming steps, my point was proven: this new design produces less heat and has a higher efficiency. It's incredible how a simple hardware revision can change so much about the product. Needless to say, I'll be happy to use this new version in place of my old downlights when they decide to quit working.

As I conclude this journey into the world of LED technology, I hope you've enjoyed it as well. Perhaps even learned something new along the way. If that's the case, don't forget to like, share, subscribe, and hit the notification bell. Stay creative, and I'll see you next time.

WEBVTTKind: captionsLanguage: enHi there, as you probably don't know, I havebeen living in this apartment for almost 4years now.And I have to say that I am quite happy withthe electrical wiring.Not only does it follow pretty much the neweststandards but my landlord also threw in abonus by using a surge relay for my corridor.In case you do not know a surge relay is basicallyan electrical component that turns on or offits internal relay output whenever it getsconnected to mains voltage on its input side.In my case the internal relay is connectedto all the LED downlights in my corridor whilethe input side is connected to a bunch ofpush buttons which I basically only have topush for a brief moment in order to turn onor off my lights.Another awesome feature of those LED downlightsis that they dim themselves in 4 steps wheneverthey get powered up in rapid succession.But as you might already have noticed, oneof those lights died on me after only 1.5years of usage.Now of course I could order a replacementwhich I actually already did but for a priceof roughly 20€ I thought it was time toget to the bottom of this problem and havea closer look at the light in order to findout why it actually does not work any more.And be prepared for a surprise because alongthe way we will also investigate the samedownlight type but with a newer hardware revisionand oh boy there are a lot of changes.Let's get startedThis video is sponsored by JLCPCB which isa PCB manufacturer that I have been usingfor years.And currently they are improving their deliverytimes.They want to achieve 2-3 days for the USAand 3-5 days for Europe.So why not test out their fast service byuploading your Gerber files today and thusordering high quality PCBs from them.First off I obviously pulled the faulty downlightout of the ceiling, opened up its cablingenclosure and freed it from its mains wiringconnection.Of course I turned off all the fuses whiledoing that and now is also the time that Ihave to warn you that we are dealing withmains voltage here which can cause major injuriesif not handled correctly.You have been warned.But anyway as soon as I got the light on myworkbench I firstly had a closer look at itsouter appearance and I have to say that itsquality did not seem half bad.So after removing the protective sleeve whichcovered the mains voltage wires, I hookedthem up to a mains power connector with WAGOclamp terminals in order to confirm that thedownlight truly does not function.But to my own surprise the light lit up withoutany problems and was also able to dim itselfafter continuously powering it on and off.Now at this point I was very confused, becauseI actually removed this downlight from theceiling and reinstalled it there three timesalready and it never worked so far.The first culprit that came to my mind thoughwas that it was easily possible to bend themains voltage wires 90 degrees at the pointwhere they enter the lights body.In the worst case this could lead to a cablebreak with the inner copper wire being partlyor completely broken.And guess what after I finished my more indepth electrical investigation on the lightwhich I will tell you about in a second, Iactually checked for a cable break and asit turns out that was the main culprit.And the manufacturer apparently knew aboutthis problem as well because after I unpackedmy ordered replacement downlight, it turnsout that they added a mechanical constructionin order to prevent such cable breaks, brilliant.While having a look at this improved versionof my LED downlight I also started to wonderwhat else they changed and thus I quicklyhooked up the new light to mains voltage inorder to find out that they even changed thedimming feature.It still dims itself in 4 steps but did younotice that this time there is no flickering.If we compare it to the old light we can clearlysee the difference.And that was the moment to dig deeper andthus I started with the old downlight by unscrewingit from its metal body.Next I pulled the main body out of the plastichousing and continued by removing the lightdiffuser with the help of a screw driver whichI then also used to lift out the PCB withthe LEDs and later also the PCB with the mainelectronics on it.And after I was done removing all of the thermalcompound it was finally time to look at thePCB and its electrical circuit in order tofind out how it works.The first thing I noticed though was thatthe hand soldered connections didn't lookvery reassuring but before I start to nitpickall day about other minor problems I insteadstarted following the traces of the circuitwith the help of my multimeter in order tocome up with this reverse engineered schematic.To understand how it works you might be askingyourself what the job of the ICs is and Iwould have to say that I do not have a definitiveanswer because one of them is not labelledwhile for the other one you can find no informationabout it on the Internet.So I was forced to hook up all of my testequipment in order to find out how the circuitworks.The first thing I noticed was that even whilethe LEDs were turned on for quite some timeand thus obviously got hotter, the flowingcurrent through them did only barely change.In fact the voltage across them even decreasedwhich means that we are dealing with a constantcurrent driver here which is definitely theright way to drive LEDs.But if you have no idea what I am talkingabout then make sure to watch my video abouthow to drive LEDs properly.Anyway, in order to dim the brightness ofthe LEDs, the second IC comes into play whichbasically only lets this constant currentflow with a certain duty cycle which decreaseswhile going through the 4 dimming steps.That is why we get this ugly flickering oncamera because the LEDs actually turn on anoff rapidly with a frequency of around 280Hz.Last but not least we also got an RC timercircuit to let the system know if you wantto go to the next dimming step or restartwith max brightness.And that's it in a nutshell which is not abad concept but it can be executed way betterand we can find out how by opening up thenewer downlight of the exact same type.First off the main PCB is this time securedin place with screws instead of glue whichis awesome.Next they got rid of the wired connectionto the LED PCB and instead used such a headerconstruction which is way more reliable.Also the amount of used components on thePCB has decreased tremendously which meansthere are less sources for faults.And needless to say reverse engineering theschematic for the circuit was this time alsoway faster and easier to do.But on the the negative side, informationabout this new IC can still not be found onthe internet, but it seems like the systemstill uses a constant current driving method.This time though in order to dim the brightness,the constant current value and thus the appliedvoltage to the LEDs gets decreased insteadof pulsing the LEDs.Now you might be thinking that this methodwould be more inefficient since more voltagewould have to drop over the main electronicsinstead of the LEDs which would equal morepower losses and thus heat.But as you can see the temperature of thenew downlight PCB only reached around 50 degreeCelsius after 5 minutes while the old lightreached a temperature of 53 degree Celsiusafter the same time.The reason is the new LED PCB design whichuses less LEDs but each one requires a highervoltage than the old LEDs.This way the combined voltage drop of thenew LEDs is quite a bit higher than the olddesign and thus it wastes less power evenif we decrease the voltage down to the darkestdimming level.Of course I also calculated the efficiencyoff all the dimming steps just to be on thesafe side which proves my point.So all in all it is kind of crazy how a newhardware revision of the same product canchange so much.The new downlight comes with a better mechanicalconstruction, features less components, doesnot come with camera flickering and has ahigher efficiency and thus produces less heat.Needless to say I will happily be using thisnew version in case more of my old downlightsdecide to quit working.And I hope that you enjoyed this video andmaybe even learned something new along theway.If so don't forget to like, share, subscribeand hit the notification bell.Stay creative and I will see you next time.