# PT Eos + Cree XP-G



## vtunderground (Jul 2, 2010)

I figured it'd be nice to have a headlamp with a warmer tint, so the other day I picked up a new 70-lumen Princeton Tec Eos, and a Cree XP-G R4 "neutral white" LED on a 20mm star from Cutter. 

The mod was easy (like most Eos mods). The Eos optic holder has a hole in the base just large enough to fit around a Luxeon Rebel emitter... because the XP-G emitter is a little wider, this hole needed to be widened slightly with a razor blade. Past that, it's just soldering & putting everything back together. In stock form, the Rebel is on an Opulent star that's pretty thin - mine wasn't even touching the heat sensor! Fortunately the Cutter star is noticeably thicker, so things fit together better (and the heat sinking should be a little better too).

Assuming that the stock Eos' output is 70 lumens, replacing the Rebel 100 with an R4 XP-G should increase the output to 91-97 lumens (and an R5 XP-G should give you 97-104 lumens). Not to shabby. I can see a slight increase in output. Also, the beam is improved! It's now smoother than with the Rebel - more of a smooth wide spot (or smooth narrow flood, depending on how you look at it). The beam will light up the entire back of my house at 100'.

I've owned (& modded) a number of Eos, but with the increased brightness, warm tint, and improved beam, this is definitely my favorite.


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## luckybucket (Jul 2, 2010)

Nice mod. I've been waiting on headlamps to catch up with flashlights and start using warm emitters, but it seems to be taking a lot longer. The only headlamp i've ever owned is a quad by PT. It's good to see an upgrade that improves beam at the same time. I think this will be my next purchase and mod.


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## Offroad'Bent (Sep 24, 2010)

vtunderground said:


> I figured it'd be nice to have a headlamp with a warmer tint, so the other day I picked up a new 70-lumen Princeton Tec Eos, and a Cree XP-G R4 "neutral white" LED on a 20mm star from Cutter.
> 
> The mod was easy (like most Eos mods). The Eos optic holder has a hole in the base just large enough to fit around a Luxeon Rebel emitter... because the XP-G emitter is a little wider, this hole needed to be widened slightly with a razor blade. Past that, it's just soldering & putting everything back together.
> 
> I've owned (& modded) a number of Eos, but with the increased brightness, warm tint, and improved beam, this is definitely my favorite.



Thanks for the info. Would this mod work on the older Eos, or will there be beam issues?
Also, which cutter R5 emitter and base would you suggest?


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## vtunderground (Sep 24, 2010)

This mod will work fine on an older Eos, however I don't think that the stock optic and optic holder will work (because the XP-G is so much shorter than a Luxeon I or SSC P4). I would use Cutter's XPG20STR (XP-G on a standard 20mm star PCB), and epoxy it in place. Most any 20mm optic w/holder should work. I think the Regina reflector would work well too, but you might have to file the wide end down to get it to fit (I've never tried it, I'm just looking at the dimensions).


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## gcbryan (May 24, 2011)

I know this is an old thread but perhaps someone will answer my questions anyway 

I understand the EOS (70 lumen version) has a frosted optic so assuming the emitter that was in there was more or less like a Cree XR-E (I don't know much about the Rebel) then wouldn't throw be better with the original emitter? If there was no frosted optic I can understand why the larger hotspot of the XP-G would be more desirable.

I'm just asking if since the optic is frosted if it wouldn't be better to use an emitter with the greatest throw since the frosting is going to reduce that throw anyway.

(I understand you were doing this partly to get a warm tint). I'm just trying to understand how this works in general.

Another question, doesn't the XP-G have a lower vf than the original emitter and doesn't this cause problems or is it OK because the emitter isn't being driven hard in the first place.

Lastly, I'm not sure if the EOS has light level memory but since most headlamps in this price range don't and since most seem to start on high (let me know if this isn't the case with the EOS) is it easy to swap resistors and have the light start in low instead of high?

Thanks.


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## robostudent5000 (May 24, 2011)

gcbryan said:


> I know this is an old thread but perhaps someone will answer my questions anyway
> 
> I understand the EOS (70 lumen version) has a frosted optic so assuming the emitter that was in there was more or less like a Cree XR-E (I don't know much about the Rebel) then wouldn't throw be better with the original emitter? If there was no frosted optic I can understand why the larger hotspot of the XP-G would be more desirable.
> 
> ...


 
i'm working on a Eos Xp-g mod right now. i'm using a 25 lumen Eos with a Luxeon optic so i had to buy a new optic and optic holder that work with the Xp-g. the thing i've learned is that you have to match the optic and holder to the emitter for it to really work properly. the optic has to fit the size and beam pattern of the emitter and the holder has to maintain the correct distance from emitter to optic for the setup to work like it's supposed to. if not, you get a really funky looking beam. if the emitters are similar in size and beam angle - the Rebel has a 120 degree viewing angle, the Xp-g has a 125 degree viewing angle, the Xp-e has a 115 degree viewing angle, and they're all about the same size - then you can get away with using the same optic and holder, although results may not be ideal. looking through the Carclo catalog, it looks like their Rebel and Xp-e optics have the same part numbers, so they must be interchangeable. the Xp-g optics have different part numbers though. if you use a larger emitter, like an Xr-e or Xm-l, you'll need a different holder, and a different optic altogther. given the specs of the Rebel, replacing it with the Xp-e may give you a little more throw, maybe... or you could just get a clear optic, or an optic with a narrower angle. i think 20mm Carclo optics go from 7.5 to 45 degrees and come in a variety of finishes (clear, frosted, rippled, etc). the optics i got are frosted 31 degree optics with the Xp-g compatible holder. i haven't put mine together yet, so i can't quite speak to the real world results just yet.

regarding the Vf, i think they're about the same. spec sheets say 3 V at 350 mA for both the Rebel and the Xp-g. 

regarding the UI, it does start on high and has no memory. don't know how hard that would be to change.


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## gcbryan (May 24, 2011)

I think adding memory isn't going to happen but I read somewhere that changing start up from high to low was just a matter of swapping the correct resistors on the circuit board if you know which one's to swap.

I don't know if it's really that straightforward though as I haven't seen anyone actually do it.


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## vtunderground (May 24, 2011)

gcbryan said:


> ...wouldn't throw be better with the original emitter?



Possibly. But with the frosted optic, I'm not sure you could really tell a difference in throw between the Rebel and XP-G (I couldn't).



> Another question, doesn't the XP-G have a lower vf than the original emitter and doesn't this cause problems or is it OK because the emitter isn't being driven hard in the first place.



Using an emitter with lower vf usually works well in a current regulated light like the Eos, because it increases runtime with no loss of output.



> Lastly, I'm not sure if the EOS has light level memory but since most headlamps in this price range don't and since most seem to start on high (let me know if this isn't the case with the EOS) is it easy to swap resistors and have the light start in low instead of high?



Maybe? It might work, but those resistors are too small for my twitchy hands to unsolder! I'll let someone else try this out.


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## gcbryan (May 24, 2011)

vtunderground said:


> Using an emitter with lower vf usually works well in a current regulated light like the Eos, because it increases runtime with no loss of output.



I guess current regulation is the key here. I was thinking of what would happen for instance in a direct drive situation if you switched in a much lower vf emitter...current would go way up and burn up the emitter. Or even in a light with a driver, the driver would have to be changed when changing to a much lower vf emitter.

Regarding switching out those resistors...I certainly couldn't do it! My hands are too clumsy for what you are doing just in replacing the emitter


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## robostudent5000 (Jun 15, 2011)

wanted to add pics of my Eos XP-G mod. the mod started out as a Seoul mod of a 25 lumen Eos. but then i had some problems with the original optic and the mod morphed into a neutral XP-G, flood optic mod. 

here are the guts of the mod. XP-G R2 5C1 (4000k) sits on 2mm aluminum spacers. the optic is a Carclo 20mm 31 degree frosted XP-G optic. everything is held together with thermal adhesive tape and epoxy. the spacers are needed because the new optic and holder are shorter than the stock optic and holder.

Edit (6/28): also, the new holder is a little bit wider than the stock holder and this required trimming of some inside bits. this also made centering the optic somewhat challenging. all in all, this is not the cleanest of mods, and if you want to mod a 25 lumen Eos and can get a hold of a good Seoul, you might be better off doing some variation of a Seoul mod.
_(dead pic link removed)
_
here is a stock 70 lumen Eos and the modded Eos side by side. the frosting on the mod's optic is pretty heavy. in comparison, the optic on the stock Eos barely looks frosted at all.
_(dead pic link removed)
_
beamshots, stock on the left, mod on the right - warm, floody perfection. on the mod, there's no hotspot at all, the beam is perfectly even inside of 40 degrees, and there's soft spill that extends pretty wide. a lot of throw is lost. instead, the headlamp evenly lights up a wide chunk of land from my feet to 50+ feet, which is what i was hoping for. i'm pretty happy with the results.
_(dead pic link removed)_

thanks to vtunderground who's post (this one) got me looking for the replacement optic.


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## gcbryan (Jun 15, 2011)

Nice work!

Do the 25 lumen models still have high,medium and low settings? If so what do you think the lumen output on low is?

Also, do you think the 25 lumen model (unmodified) is reasonably efficient and just 25 lumens or does the lumen output go way up when you swap in a more modern emitter?


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## robostudent5000 (Jun 15, 2011)

gcbryan said:


> Do the 25 lumen models still have high,medium and low settings? If so what do you think the lumen output on low is?
> 
> Also, do you think the 25 lumen model (unmodified) is reasonably efficient and just 25 lumens or does the lumen output go way up when you swap in a more modern emitter?



the 25 lumen model is pretty much the same as the newer model except for the emitter. the UI is the same and the current on each level is about the same. the original 25 lumen Eos used a Luxeon 1 R bin emitter that was rated at ~40-50 lumens @350mA. the newer Eos uses, i think, a Rebel N bin emitter which is rated at 100-120 lumens @350mA. i used an XP-G R2 bin emitter which is rated at ~110-120 lumens @350mA. if you look at my beamshot, you'll see that the output for the stock Rebel Eos and the 25 lumen Eos modded with the XP-G R2 are about the same. the output on low is about the same for both. i'd guess around 10 lumens.

Edit (6/28): CORRECTION! it took me a while to notice this. but it turns out that the low on the modded Eos is actually not as bright as the low on the stock Eos 70. the high of the mod is a little bit brighter, the medium is about the same, but the low is definitely dimmer than the low of the stock Eos 70. i don't know if it's because the driver is different or if it's because the Xp-g has lower luminous flux at lower currents. but the low is definitely not as bright. it's still not as low as i would like, but it's nice. it's not bad.


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## gcbryan (Jun 17, 2011)

What I meant was if you hadn't modified the 25 lumen EOS what was its lumen output on low do you think? If it had 3 brightness levels and was 25 on high then wouldn't it be something like 5 lumens on low?

My second question I've asked elsewhere (not to you) but I'll ask you as I'd like to hear your viewpoint...the warm tint in your modified EOS looks nice however what I generally hear regarding warm emitters is that it makes grass, trees, and leaves look more natural. The logic is that a warm emitter is more like the sun.

I don't see that however. A warm emitter looks more like sunset rather than the natural light for most of the day. It's true a warm emitter looks more like incan lighting but it doesn't look more like the natural sunlight to me and I don't see how it could make grass, trees, and leaves more natural looking. Incan lighting doesn't look natural to me even though it's pleasing in my living room. What is your take on this?


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## robostudent5000 (Jun 17, 2011)

gcbryan said:


> What I meant was if you hadn't modified the 25 lumen EOS what was its lumen output on low do you think? If it had 3 brightness levels and was 25 on high then wouldn't it be something like 5 lumens on low?



it was around 5 lumens on low, around 15 lumens on medium, and 25-30 on high.



gcbryan said:


> My second question I've asked elsewhere (not to you) but I'll ask you as I'd like to hear your viewpoint...the warm tint in your modified EOS looks nice however what I generally hear regarding warm emitters is that it makes grass, trees, and leaves look more natural. The logic is that a warm emitter is more like the sun.
> 
> I don't see that however. A warm emitter looks more like sunset rather than the natural light for most of the day. It's true a warm emitter looks more like incan lighting but it doesn't look more like the natural sunlight to me and I don't see how it could make grass, trees, and leaves more natural looking. Incan lighting doesn't look natural to me even though it's pleasing in my living room. What is your take on this?



i think this is a matter of personal preference. in my case, rather than trying to replicate daylight, i was looking for better contrast. since warmer light makes greens and browns stand out better, and i hike in mostly green and brown environs, warm tints help me see where i'm going better. 

the emitter i used here has a 4000k max color temperature. it's categorized as neutral white, but is bordering on warm white. i have 4700k emitters (xp-g r4 4b) in other lights, and the 4000k emitters are much warmer, and i think it's about as warm as i would go.


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## gcbryan (Jun 17, 2011)

Thanks for the feedback on the tint issue and I think I'd like to find a used 25 lumen EOS cheap just to try out hiking for conditions when 25 lumens might do and then the 5 lumen low would be welcome.


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## robostudent5000 (Jun 17, 2011)

gcbryan said:


> Thanks for the feedback on the tint issue and I think I'd like to find a used 25 lumen EOS cheap just to try out hiking for conditions when 25 lumens might do and then the 5 lumen low would be welcome.



the stock 25 lumen Eos wasn't bright enough for hiking IMO. if i could have run it on high for more than two hours, it might have been okay, but runtimes being what they were, i had to run it on medium a lot, and the medium wasn't bright enough for me to hike by. there was very little spill with the stock optic. on the medium and low settings, there was virtually no usable spill, so i had to move the lamp constantly to see where i was going.


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## gcbryan (Jun 17, 2011)

robostudent5000 said:


> the stock 25 lumen Eos wasn't bright enough for hiking IMO. if i could have run it on high for more than two hours, it might have been okay, but runtimes being what they were, i had to run it on medium a lot, and the medium wasn't bright enough for me to hike by. there was very little spill with the stock optic. on the medium and low settings, there was virtually no usable spill, so i had to move the lamp constantly to see where i was going.


 
Ah! Good to know. Then I guess I don't want a 25 lumens EOS  I guess a diffuser wouldn't work either since it would rob some lumens and then would be even dimmer.

That's the only problem with the newer 70 lumens EOS. The beam is just too narrow even though it is fairly diffuse. Your suggestion of tape helps a bit and at least it's bright enough but either a wider optic or one with more spill would be optimum.


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## robostudent5000 (Jun 17, 2011)

gcbryan said:


> That's the only problem with the newer 70 lumens EOS. The beam is just too narrow even though it is fairly diffuse. Your suggestion of tape helps a bit and at least it's bright enough but either a wider optic or one with more spill would be optimum.



you know, i wonder if a more transparent diffusion material like DC Fix would help more. i just tried scotch tape on my stock Eos too and the tape seems to diffuse the beam a bit too much. DC Fix is supposed to let more light through and retains some of the throw. and it's supposed to go on and come off clean and easy. Phaserburn was selling pieces in the Marketplace for a reasonable price IIRC.


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## vtunderground (Jun 17, 2011)

If you do end up buying a 25-lumen Eos, I recommend replacing the stock optic with an IMS 17mm reflector. I found the extra spill to be welcome.


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## gcbryan (Jun 18, 2011)

robostudent5000 said:


> you know, i wonder if a more transparent diffusion material like DC Fix would help more. i just tried scotch tape on my stock Eos too and the tape seems to diffuse the beam a bit too much. DC Fix is supposed to let more light through and retains some of the throw. and it's supposed to go on and come off clean and easy. Phaserburn was selling pieces in the Marketplace for a reasonable price IIRC.


 
Everyones preferences are unique I guess  I just added a second piece of tape on my EOS and I like the result better. The EOS optic is just too narrow and two pieces of tape were needed to make it so it's not so narrow. It throws the equivalent of my backyard and doesn't have an edge anymore. I can't really tell that the lumen output is less.

It must be but since it also changes the shape of the beam it's not easy to tell lumen decline unless it's large. Just changing from a narrower spot to a wider flood makes lux go down but lumens would change only if some output is being blocked. Scotch "Magic" tape is pretty clear since that's the whole point.

A perfect beam would be a noticeably brighter area in the center with it gradually diffusing out to edges that disappear. However the EOS never had that kind of beam anyway. Shinning on the wall in my house I could detect a slight hotspot (before any tape) but outside it never looked like it had a hotspot. It was just a smooth but narrow overall beam (30-40 degrees) That's more like those flood to throw lights in flood mode where there is no hotspot but the overall beam is still narrow and comes to an abrupt edge of darkness. The tape makes it more like the Storm (although the Storm with one piece of tape still has a nicer beam).

So, the way I look at it you start with the EOS and whatever you do should make it better than the EOS was. Two pieces of tape does that for me. It definitely helps bring extra light around my feet which was a problem with the original beam. It just got dark here and I was able to test it out a bit. I'll go out again later when it's really dark.


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## CyberCT (Jan 17, 2012)

gcbryan said:


> Everyones preferences are unique I guess  I just added a second piece of tape on my EOS and I like the result better. The EOS optic is just too narrow and two pieces of tape were needed to make it so it's not so narrow. It throws the equivalent of my backyard and doesn't have an edge anymore. I can't really tell that the lumen output is less.
> 
> It must be but since it also changes the shape of the beam it's not easy to tell lumen decline unless it's large. Just changing from a narrower spot to a wider flood makes lux go down but lumens would change only if some output is being blocked. Scotch "Magic" tape is pretty clear since that's the whole point.
> 
> ...



I have a neutral XPG-R5 emitter on a 16mm board. I wonder how hard it would be to make it fit. Should I epoxy a penny to the back of the R5 for a little better heatsinking? I'll have to mess around with it when I get home.

How hot does the XPG get inside the EOS? Did anyone's light step down due to temperature from the sensor? I broke my temp sensor trying to pry it off the LED in my EOS so I guess it won't be working. The light still works though.


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## Illum (Jul 31, 2012)

Given the design of the EOS, is it possible to place a slug of heatsink into the body and operate an LED without an optic or a reflector? Will it maintain water resistance? Or is the optic itself part of the weather barrier?

I ask because I recently bought one is is currently trying to devise a modification for it to perform just like my lost Zebralight H50, the difficult side is my zebralight... while it was in my possession... is frequently drowned by the weather. A headlamp that waterlogs during the occiasional rainstorm is not going to work for me :thinking:


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## rojos (Aug 1, 2012)

Illum said:


> Given the design of the EOS, is it possible to place a slug of heatsink into the body and operate an LED without an optic or a reflector? Will it maintain water resistance? Or is the optic itself part of the weather barrier?



Yes, it is possible. The front lens is a part of the body. The optic is a separate piece wholly enclosed by the body. Removing the optic does not compromise waterproofing. 

If you have an Eos that does not have a thermistor, there should be enough room for an 18mm diameter, round slug. An 18mm slug should slide in almost perfectly between the plastic support arms for the optic holder.


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