Salvaging an automotive LED headlamp

[Kitchen Panda]

When I started driving, we'd change a $5 sealed beam in the Canadian Tire parking lot with the screwdriver on our Scout knife...in the dark...in a light rain...uphill both ways. Car headlamps have changed a LOT since those days.

<revised to fix some mistakes I made>

I recently had the misfortune to drop my Camry while changing a tire - in spite of Dad's warning to never let my hand go between tire and wheel well, I got my hand pinched. My hand was fine, but my Camry was severely wrinkled around the top of the wheel arch. Luckily MPI insurance covered it and all we had to pay was the deductible.

Parts finally came in last week - one item that had to be changed was the headlamp. Two mounts got snapped - the headlamp was loose. This carried a very high cost on the insurance estimate, over $1000 Canadian! Checking on-line confirms that headlamp assemblies, which include the side marker and turn signals, are very costly. So, when the body shop called to say all the parts were in, I asked them to save the wrecked headlamp for me.

Tonight I've started taking it apart. I'm impressed at the intricate design of the acrylic light pipes for the low beam, and the great effort at waterproofing - even the pressure equalization vents are protected by baffles to stop water from splashing in. There's a soft rubber gasket that holds the two parts of the assembly together and that is still soft, supple and watertight after 4 years and 100,000 km.

The side marker light is a single yellow LED running directly on 12 volts. But the turn signals and DRL have multiple LEDs in series, with a DC/DC converter for each one. The high/low beam is interesting - it's built like a projection lamp, with a big acrylic (not glass) lens, a single LED on a big heat sink - and a fan to cool the heat sink!

The DC/DC converter for the low beam array looks easy to work with, just put 12 V on either of two pins and get either low power or high power. I can turn that into some kind of reading lamp or something. And if I can figure out the high beam lamp, maybe turn that into a high-power flashlight?

Great fun satisfying my curiosity here.

 

[John_Galt]

If you have it apart, please post pictures. Always interesting to see how these are constructed and what LEDs they're using.

 

[Kitchen Panda]

If you have it apart, please post pictures. Always interesting to see how these are constructed and what LEDs they're using.

I've never uploaded pictures here but I'll take a few and see if I can send them to be visible here. If you look for a YouTube video titled "2019-2021 Toyota Camry LED Headlight Disassembly" someone has already shot a video, though he doesn't explain what we';re looking at. He also opens up the housing off camera, which is a lot more work than I had at first though it would be.

I can't see any markings on the individual LEDs. I did notice the side marker and turn signal LEDs are amber, even though they also have an amber lens. The main lamp (high beam/low beam) is on power LED on a fan cooled heat sink, with a shutter that operates to change the pattern - you can hear a "clunk" when you go to high beams. I was able to get the DRL/park light assembly out with its converter - the chip in the converter has a data sheet that's on-line, not a house numbered part. At full brightness it draws about 0.8 amps at 13.6 V, in DRL mode it's only about 50 mA. Changing the power supply voltage a lot seems to make no difference to the lights till you get down to about 6 volts - not like the old days when yellow headlamps were your first clue that the battery was going bad.

 

[Kitchen Panda]

Here are some pictures of the Camry XLE headlight parts - I didn't do a step by step disassembly series, unfortunately.

First photo: headlamp on messy bench. The housing is at the top. Just about everything is stamped "R" for "Right" headlamp. Bin on the mid left holds all the screws and small plastic pieces, including the light pipes for the daytime running light/park light. In the centre of the photo is the big lens of the main headlamp assembly - below it is the board carrying the single amber LED for the side marker (sorry, upside down in this pic so you can't see this LED), and below that is the LED strip for the amber turn signal lamps. Just above the main lamp is the DRL assembly, 12 series cool-white LEDs on fairly small heat sinks behind the white plastic reflector. Each LED is aligned with a slot in the light pipe. You can just make out the DC/DC converter above it on the cutting mat. The chip on this board has a data sheet on line - it's a boost regulator, I guess putting out about 35 Volts.

Second photo: housing, optics, and electronics. The housing has a lot of reflective plastic and light pipes. The back of the housing (not shown) has a screw adjustment for aiming the headlamp. Very waterproof, even the breather holes have baffles around them to protect from splashing, and snug-fitting caps with some foam. The headlamp lens really catches the camera flash and reflects it back. To the right of the lens is the reflector that bounces the light from the upward-facing LED toward the front of the car. Above that is the main headlamp LED, a single diode on a big heat sink with a fan to cool it - it's facing backward in this photo. There's a solenoid underneath and a shutter that pops down when energized for h igh beam - I never noticed before but you can hear the shutters thump when you change to high beam. On the right is the DRL and its driver board, then the driver and marker lamp, and at the bottom is the single LED side marker. The DRL has wires for "DRL" and "park light" so you can pick high power (about 10 watts) or low power (about 1 watt).

Third photo is close-up on the main headlamp. The metal shield covers the "computer" - I wonder what chip they use? Looks like the same lamp gets used for Lexus, too. To the right of that you can see the LED chip. Underneath this is a big heat sink with a fan. I tried putting 12 V directly on these terminals with a small bulb to limit current and the LED came on - and the fan, too. I sorta want to take this cover off and see what's inside but I also sorta want to use this as an uber flashlight. We'll see if curiousity overcomes me.

 

[EJR]

This lamp uses the very first bi-functional LED projector (1st gen) ever on a mass produced vehicle (originally introduced on the 2016 Prius). Its a very good performing lamp. And yes, its used in many different vehicles but has since been succeeded by newer versions.

You can google "koito biled" or "koito dm008".

Devices that regulate power to LEDs are not called "computers", they are called drivers. The LED package used in this projector is a custom type of COB specially made for Koito by Nichia.

 

[Kitchen Panda]

This lamp uses the very first bi-functional LED projector (1st gen) ever on a mass produced vehicle (originally introduced on the 2016 Prius). Its a very good performing lamp. And yes, its used in many different vehicles but has since been succeeded by newer versions.

You can google "koito biled" or "koito dm008".

Devices that regulate power to LEDs are not called "computers", they are called drivers. The LED package used in this projector is a custom type of COB specially made for Koito by Nichia.

<edited to avoid multiplying posts needlessly>

Thanks for these details, I will look them up. I found lots of stuff out there related to this, looks like it was quite an innovation back around 2014 or 2015.

If you look at the third photo you can see what the maker printed on the cover. I don't imagine it runs Windows, but I expect there's some kind of microprocessor in there - probably to monitor the heat sink? There are a lot of wires coming off the headlamp control, perhaps it communicates back to some other system to give a fault message if the headlamp detects a problem? I can see that this would be a specialized LED custom-built for this job. It looks like one job of this LED driver "computer" is to monitor the heat sink fan and step down the lamp brightness if the fan fails. I also didn't know that the LED power changes from 15 to 35 watts when switching to high beam.

 

[EJR]

If you look at the third photo you can see what the maker printed on the cover. I don't imagine it runs Windows, but I expect there's some kind of microprocessor in there - probably to manage the heat sink?

Yeah, I see it and while it may be kinda sorta an accurate name and kinda sorta not (by true definition), I was just saying that these devices are always referred to as a driver.

There are a lot of wires coming off the headlamp control, perhaps it communicates back to some other system to give a fault message if the headlamp detects a problem? I can see that this would be a specialized LED custom-built for this job.

No communication. Just regulates power to the chip package and fan.

 

[Kitchen Panda]

Thanks for the internal shot and diagrams! Now I don't have to unsolder the cover. That 14-pin chip at the top right of the board might have some smarts in it (conformal coating makes the part number illegible, and it might be a proprietary house numbered item anyway). On the one hand, I'm amazed that a surface-mount inductor can be part of a driver that handles 35 watts. On the other hand, I'm amazed that this LED probably delivers more lumens on about half the power of a standard incandescent headlamp bulb.

 

[EJR]

On the one hand, I'm amazed that a surface-mount inductor can be part of a driver that handles 35 watts. On the other hand, I'm amazed that this LED probably delivers more lumens on about half the power of a standard incandescent headlamp bulb.

Welcome to the world of high luminance LEDs!

Technology has advanced (and continues to evolve every day) to the point where very small sources (smaller than a filament coil) can emit insane levels of luminance that previously were unimaginable.