Odd observation.. A XR-E, a MT-G2 and a XM-L in series and 2 are dark

with a 12 V 2,5A power supply from an old externall harddrive.

The only one that lights up is the MT-G2.

Why is that?

Maybe because it has much higher Vf than the other two?

Check all the LEDs individually to see if they still work. With a unregulated power source like that, unless there's something else in the circuit you didn't mention, it's easy to fry stuff.

In series the Vf for each LED adds, but they all get the same current. In parallel they all get the same voltage but the current is divided. Nothing inherently wrong with using LEDs with different Vf's in a single series string as long as each of them can survive the drive current they're given.

No, in series means that all leds see the same current, if one lights up, all should light up.

Btw, funny you made this set-up, one of my last year's builds was a xml-mtg2-xre in series too :-)

https://budgetlightforum.com/t/-/20550

I had never seen that before, thats really cool. If you lived in the US I would send you a bunch of 9v NiMH’s I just got for free out of the battery recycling bin, instead I may just have to make something similar

:-)

The 9V NiMh's have endless possibilities as long as high drain and long runtime are not needed at the same time.

I found out that the XM-L and XR-E have failed. So the chain of events were probably like this...

XR-E overheats and fails in open condition du to too high amperage.

XM-L overheats and fails due to too high voltage.

MT-G2 suvives due to emitter on noctigon soldered to copper and the voltage drops across the now failed XR-E and XM-L.

Ohh well. Back to the drawing board... :-)

You have to use something between the wall wart and the LEDs. Just because it says "12V 2.5A" on the sticker doesn't mean that is what it will actually do.

I know. But the 2 leds died before I could measure anything and I switched it off before the MT-G2 died too.

Will report back a little later...

During my last year's scratch build I found it odd that the above mentioned string of leds lighted up at all at 9V. If you add up the minimum voltages of the three leds separately (MT-G2: ~5.4V , XM-L ~2.5V, XR-E ~2.8V , these are extrapolations of my own measurements) you end up with more than 9V. And still they all light up, so something unpredictable is happening at low currents.

Something is not wired in series. If the XM-L and XR-E are open, there can be no current, yet you said the MT-G2 was lit?

True. It sounds like they were wired in parallel and the XR-E and XM-L popped immediately due to the insanely high voltage but the MT-G2, being as tough as they are, managed to survive the 12V hammering.

Update: ( and they were in series .. Come on guys. That daft I am not)

Turns out the psu does voltage adjustment on its own. It will deliver ~2,45 A relentlessly up to somewhere between 13 and 16 volts. Then the voltage is so hight that the amps drop.

And the XR-E is dead. As a doornail. But it died oddly. No light from it. Very little resistance (forgot what is was, less than 0,1 ohm). Desoldered it from the start and tested it with DMM and no light but still very little resistance. Never had one of these fail with the connection not being broken and actually thought it could not happen. The bond wires were intact as far as I could tell BTW.

The XM-L2 lives. There was a short on the star (not to self: Do not use the stars that wery cheap emitters from ali-express comes on. Or at least check the soldermasking under a loupe. )

Soo I changed the xm-l2 star and threw on another xm-l2 on another star instead of the original XR-E star. And now my project " 1600+ lumen worktable light is working like it should. Will post a few pictures a little later.

Here is a little something about what I was up to.

I needed a worklight. Plenty bright. Overhead. Cheap. Led.

Enter an old recycled lamp.

And here I am testing some anti flickering hardware... A capacitor :-)

Proper cooling...

Will it fit... Yes :-)

Then drilling holes for the rivets.

This project fought me at every turn it felt like at times. Here I was using a XP-G something or other. That was dead. I dont even think it had 5 minutes of runtime in the light it came in. And a rivet stem snapped off at the wrong place. Had to cut that off using a dremel and cut off disc.

That happened 3 times during this project. I´ll never skimp on rivets again. Ever!

Here is the emitters I ended up using. The warm XM-L is the one I thought died earlier.

Apparently I did not take any photos of the old setup where the XR-E was still being used. Sorry.

The above picture has the lead for the white star removed because that is a star from a batch of ali express emitters that makes a short when I solder it. Thats the first oneused in this project :-( I hate bad stars now.

This next one shows it after the removal of that star. And me being tired of changing stars so i took something that just works. A Sinkpad. Soldered to the copper cross.

Business end...

Tell tale rivets are the only thing that shows this is not how it left the factory. And the fact that the wire ends in a wall wart.

All working...

Mess on the table is for artistic impression only ;-)

The light is cool white and obviously casts three shadows albeit they are at a narrow angle.

On the wall you can see the three light tints from the top down:

XM-L2 A1 cool white on the top.

MT-G2 something or other from Intl-outdoor ( I never really cared for this emitter. Still don't. But Now I can open my parts box without that big ugly yellow dome lóoking up at me. )

XM-L T4 C7 Warm white

And here I am just playing with a magnifying glass :-)

Crap on the table is for artistic impression only ;-)

This is the wall wart I used. It is for an external harddrive and has excellent performance and requires no anti flicker hardware (capacitor)

Nice build! Good that you got it working, the lamp looks very useful to me.

Perhaps you can fabricate a diffuser in front of the emitters to soften the shadows, for a work lamp that might be an improvement.

Nice job! Happy to see you got it working.

I've had it on for some hours now and I am a little surprised at how cool running it is. There is only one place where the temperature is so high it is unpleasant to hold your finger there and that is on the alu mcpcb.

I am considering to change the cool white xm-l2 for a warm white xm-l. May be too cool for my liking.

@ Djozz: I'll try to use some ordinary scotch tape over them just to see if it makes any worthwhile difference.

the further away from the led, the better the softening works, so if you stick the scotchtape on a piece of glass or acrylic glas and mount it a few cm away from the led, the diffusing effect gets better (actually you are creating a traditional matt light bulb like that).

But just the piece of tape is much easier of course :-)