EEVblog #67 - Hacking the Princeton Tec EOS LED Headlamp with a Cree XPG

Dave does a teardown of the Princeton Tec EOS headlamp and mods it with a new Cree XPG LED.
Throw in a quick reverse engineer of the circuit, gratuitous scope shots, torturing a thermistor, a practical demonstration of why you really do need 5 multimeters on your bench, and as usual Dave finds no problems filling up 25 minutes.

[EEVblog]

I changed the 0R33 1206 resistor by putting a 0R47 in parallel. I did not change the other ranges. I used an R4 bin XPG.
The photos at the end though are from another one that I modded were I didn't change the values.
So the comparisons are bit over the shop, but it gives you the idea about the light increase.

[EEVblog]

@exnol The star mount one I used is not from Cree, Cree only sell the bare LED AFAIK, the Cutter Electronics version that has the Cree LED soldered to the Star mount mound already.

[gitargr]

My EOS took a dump recently and it doesn't seem like PrincetonTec offers much, if anything, in the realm of support. I couldn't for the life of me figure out how to disassemble my light. Found your video and wanted to say thanks for the great tear-down/circuit schematic. Should make troubleshooting my lamp much easier. I definitely owe you a pint.

[chukchee]

Finally, something YEAH! You should do more stuff like this. This is what its all about.

[reddoguk]

WoW!! I just sat through all that vid. It kept me amazed and entertained probably because i use head lamps for work and my favourite is the Petzl Tikka XP Atex, I can't wait for them to start using the xpg led, As i'm not confident enough to change it myself. But this guy is the biz, Well done!!

[willg]

Very cool! Thank you from a person who knows nothing of circuits!

[Afrotechmods]

Great video. Power electronics is my crack.

[Mtaalas]

Great blog as always. Keep 'em coming :)
Yo have tough me a lot about engineering.

[jcreigh]

Another great video, thanks! One question: There is a diode and high-value (100K?) resistor in series between the battery and the IC. I'm guessing that the diode is to provide protection against the battery being installed with reversed polarity, but what is the resistor for?

[gitargr]

Don't know if you've figured it out yet, but you can add a resistor in series with either of the wires to trim the brightness. There's all kinds of resources on the net to figure out what size resistor is optimal, or you can get a large bag of resistors from RadioShack or the like and tinker away until you find the right one.

[RobertGallop]

Excellent work once again. Did you modify the current for the hack'd one though? Wasn't clear if you did or left it the same, if you did, what resistor did you change and from what value to what value. Thanks!

[Firstner]

the last test is a win, what a diffrence!!

[EEVblog]

@tecnolover2642 Because I had one of that value and it's quicker and faster to simply parallel another resistor than remove the old and solder in a new one.

[tecnolover]

Great video! You are amazing! My needs are the same as yours. I'd like more of a FLOOD type beam pattern. My question is: In your modded version what current draw did you acheive by changing out the R12 33ohm resistor?? 350, 400 mA?? Also, why did you put in a 47ohm ?? I thought you want a lower value resistor to get a higher current to the LED?? sorry, I'm not experienced in electronics but you said the low setting used the highest value resistor, so to incread the HIGH why use a lower?

[ukalafina]

Great video but we were so close to having analyzed the whole circuit and I regret it did not happen:
what exactly is the function of the IC. Just to divert the power to a specific resistor with each brightness setting?
what exactly does the sense circuitry do?
buck converters give a constant voltage. How exactly does the current regulation take place? thank you

[justinsn]

Very nice video. Thanks for the nice tutorial on how to do this!

[EEVblog]

@tranpulse It IS that easy. You don't have to modify the circuit if you don't want to.

[tecnolover]

Another question, with your mod using the XP-G LED and a 350-400mA current what is the LUMEN output on HIGH now??? Also, do the cree led's come with a star mount?? do I need to buy a star mount or can I use the stock one already in there and just remove the old LED and put the new LED on?? also, , is heat going to be an issue with 350-400 mA ???

[sehsuan]

gosh. I'm way behind time on this video. I have 3 units Princeton Tec Quad headlamp, one of which is dead (given by a friend) - I think what David is saying is correct. Princeton Tec decouples the LED so that they could use the same circuitry of the Quad (4x wide beam LEDs), to fit the wide-angle throw market segment. Smart move!

[THESocialJusticeWarrior]

I have a cheapo Energizer one (like $15 US). It has a more even beam than either your std one or the mod but it isn't as bright as the mod, nor is it water proof. It does the job for me, I only use it around the house, like when I need to work on the AC lines with the relay off.