# SST-90 Mag 2D aspheric build, low resistance, direct drive



## Techjunkie (Jan 6, 2010)

I received my 4500K SST-90 emitter from Avnet today. The packaging was laughable. It came in a box about the size of a shoe box. Buried under much bubble wrap was an anti moisture bag with very specific handling instrutions. Within that was a large bag of dessicant, a moisture indicator card and finally what I'd call a jewelry box if it was designed by the military.

I used Jo's BrightLumens deluxe SST-90 Mag D heatsink. It does the trick, but having done it once, I'm not looking forward to doing it again. I can't think of a better way to mount the emitter, but it was nerve racking working on a $50 LED that's so delicate and so hard to mount.

I used the fattest wire that would possibly fit through the holes, 20 gauge stranded copper, and ran into trouble getting the fitment right. I had the emitter heatsinked by resting it upside down on top of the jaws of my vise, and that made the solder cool immediately on the pads. The thick pos wire was encroaching on the space of the center just a hair, but it was enough to cause it to sit improperly in the heatsink. My iron wasn't hot enough to melt the solder again and in the end I carfully used a dremel with a cut-off disc to shave back some of the solder so it would sit right. The other complication is getting the thick wire laden with solder bent just the right way to position it so it goes straight down the hole from the corner of the LED. Pics below explain it better than I can here.

I used AAA in the wire troths and Arctic silver thermal adhesive under the main pad. Adding the AAA to heatsink the wires to the HS is something I always do to improve thermal management. It's that much more surface area to transfer heat with.








As for reflectors, I did what I usually do and searched for the cheapest possilble solution. I experimented with the DX P7 reflector (sku 12229) and managed to make quite a mess of it with the dremel. Even more scary than the soldering, I had to use the dremel to cut a camphered edge to the inside of the heatsink after the emitter was already monunted.






The DX P7 reflector actually gave a much better (tighter / more intense) spot than the KD V2 reflector that I opened to 16mm. I had to raise the heatsink about 2mm to get the short DX reflector to focus properly. I was surprised to see a spot about the same size as given to the smaller MC-E emitter by other 53mm reflectors I've used for MC-Es.






I played around with some other refelctor/optic options, but I'm not done yet. I tried the 40mm+ deep reflector that comes inside the Mag 2D LED after cutting off the cam and opening the hole to 16mm. That gave the best focus yet, but I couldn't screw the head down passed the O-ring. If I cut the lip off the heatsink, I might be able to drop it down the tube until it sits on the Mag switch. That's about a half an inch, which might be just enough to make that reflector fit.

I tried the KD aspheric but what I found to be even better (much to my surprise/delight) was the $4 DX aspheric sku 12834. It's glass, not plastic, only 18mm deep and while it does not perform as well with the CREE XR-E, it seems to be better suited to the SST-90. Perhaps the difference in the domes affects the performance with the optic.






Oh, by the way, until the Sector_Cleared driver is available, I'm running the emitter direct drive on 2 parallel Sony 26650VT with a slapped together carrier that I described here.






I had to add copper braid to the tail spring. Tailcap mearurements were only ~3.5A on the bare spring, but over 7A on the braid. The Vf of the emitter drops as it heats up, but the batteries sag after use. The highest I've measured so far at the tail was 7.95A. The warmer color SST-90 must have a pretty high Vf. Also, I tried some slightly used NiMH C cells. Three yielded a 5-6 amp draw and with four cells current draw shot up to 11A before I quickly disconnected the leads. Maybe a 4s2p pack of AAs might be the direct draw sweet spot for the SST-90, assuming 2pAA sags more than 1C. I may just have to find out.

(update: after replacing the spring/braid with a cut down "golden" mag spring from KD and using deoxit on all the contacts, I'm measuring 8.5A draw at the tail and 8+ through the spring)

Until some of my other cheap reflectors come in, I'm keeping th DX aspheric in it. It's freaky fun - much larger and also more intense than the KD Q5 + Aspheric kit. I'll add beamshots later this week.

Update: finally experimented with 4s2p AA - see post # 25 below
Update #2: New reflector experiments. Stopped-down photos show improvement with a reflector that actually fits, post #28
Update #3: the experimentation and aggressive burn-in has significantly reduced the Vf of the emitter see post #31


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## Dioni (Jan 6, 2010)

*Re: SST-90 Mag 2D build in progress*

Great!


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## supasizefries (Jan 7, 2010)

*Re: SST-90 Mag 2D build in progress*

Can't wait for some beam shots.


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## netprince (Jan 7, 2010)

*Re: SST-90 Mag 2D build in progress*

beamshots!  

I'm hoping to build something similar when my parts come in. I'm a little nervous about not using a driver...


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## Linger (Jan 7, 2010)

*Re: SST-90 Mag 2D build in progress*



netprince said:


> I'm a little nervous about not using a driver...


Practice man, practice. Try it out a few times with cheaper emitters and it may easy your mind.
What might also be helpful is to deliberately sacrafice one, overheat it and see it turn blue and ... depart this land of lumens :candle:
YYMV
experience is great if you can afford it


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## Fulgeo (Jan 8, 2010)

*Re: SST-90 Mag 2D build in progress*



Techjunkie said:


> I tried the KD aspheric but what I found to be even better (much to my surprise/delight) was the $4 DX aspheric sku 12834. It's glass, not plastic, only 18mm deep and while it does not perform as well with the CREE XR-E, it seems to be better suited to the SST-90. Perhaps the difference in the domes affects the performance with the optic.
> 
> Until some of my other cheap reflectors come in, I'm keeping th DX aspheric in it. It's freaky fun - much larger and also more intense than the KD Q5 + Aspheric kit. I'll add beamshots later this week.



Hey Techjunkie, Just wanted to say I am also a big fan of the inexpensive DX aspheric lens. I also prefer it over the no longer available KD aspheric. The image that the DX lens throws up is a bit brighter and to my eyes a bit warming as if there is a slight color shift? I even prefer using it with the CREE Q5 R2. The DX lens also has less side spill ( I wanted to call it flood but that is really not what it is ) than the KD lens. Currently I am working on a SST-50 build. When complete it will be time to play with the aspherical lenses again.:thumbsup:


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## wquiles (Jan 8, 2010)

*Re: SST-90 Mag 2D build in progress*

Cool project. Looking forward to beamshots as well :thumbsup:


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## Techjunkie (Jan 8, 2010)

*Re: SST-90 Mag 2D build in progress*

The contestants (again). This time with a new addition, the WF-008 recoil thrower. It seemed only fair to include it, considering the aspherics here and the 450ft target tree in the distance shots.







This time, white balance is set to Sunlight aprox. 5200K for all shots.

Indoor settings: ISO 200, 0.4 Sec, F4
Outdoor settings: ISO 200, 4.0 Sec, F4

00. 

 




01. 

 



02. 

 

 <--This is the 4500K SST-90 being discussed here.

03. 

 



04. 

 



05. 

 



06. 

 



07.


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## moviles (Jan 8, 2010)

*Re: SST-90 Mag 2D build in progress*

the dx 50 mm lens are true aspheric lens or are sferic lens?


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## netprince (Jan 8, 2010)

*Re: SST-90 Mag 2D build in progress*

Hey Techjunkie,

How's the color on that emitter?? Compared to the MCE, is it closer to 5A tint or WH?


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## vestureofblood (Jan 8, 2010)

*Re: SST-90 Mag 2D build in progress*

Hi Teckjunkie,

Nice work, I lile the 2 imr cells to boost the amperage. 

I realize this thread is mostly about your SST mod, but what is PVC on the end of your first light for? A coupler I am guessing, did it fit right on or did you sleeve it somehow?

Thanks for sharing.


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## Techjunkie (Jan 8, 2010)

*Re: SST-90 Mag 2D build in progress*



netprince said:


> Hey Techjunkie,
> 
> How's the color on that emitter?? Compared to the MCE, is it closer to 5A tint or WH?


 
Closer to 5A. The closest I've got to it tint-wise is my XX-Ray, which uses 4B tint MCE. That's exactly what I was expecting, because the 4B is in CREE's neutral white group (adjacent to 4500K on that chart) whereas 5A is more toward their warm white group (although not quite in the 3000K range of 7A) whereas WH is at the warm end of their cool white group (~5500K).

I expect that the 5700K SST-90 is a pretty close match to CREE's WH tint.

After experimenting with neutral white tints, I was immediatlely hooked, which is why I went straight for the highest bin 4500K (GM400) instead of the 5700K or 6500K tints.


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## Techjunkie (Jan 8, 2010)

*Re: SST-90 Mag 2D build in progress*



vestureofblood said:


> Hi Teckjunkie,
> 
> Nice work, I lile the 2 imr cells to boost the amperage.
> 
> ...


 
Ha! That was to eliminate the laser like corona produced by the KD aspheric kit. (And also allow the torch to headstand in my cabinet.) It's a 2.5" PVC coupler with a slice of 2.5" PVC in it and bound to the Mag bezel with electrical tape. I was too cheap to spend $50 on a custom bezel. I call it my redneck aspheric bezel.


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## Techjunkie (Jan 8, 2010)

*Re: SST-90 Mag 2D build in progress*

I just replaced the beamshot post with a revised post with better beamshots. I decreased the shutter speed for the outdoor night shots, but I also used a lower ISO setting of 200 to match the indoor shots, so the longer shutter lag only brightened things up a litte. I should have gone for longer exposure still, or higher ISO.

More imporantly (to me) is that the fixed white balance setting of "Sunlight ~5200K" really does an awesome job of differentiating the emitter tints. You can even tell the difference between the 4B MCE tint of #5 versus the rosier 4A MCE tint of #3.


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## wquiles (Jan 9, 2010)

*Re: SST-90 Mag 2D build in progress (better beamshots)*

Nice job with the beamshots :thumbsup:


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## Fulgeo (Jan 9, 2010)

*Re: SST-90 Mag 2D build in progress*



Techjunkie said:


> I just replaced the beamshot post with a revised post with better beamshots. I decreased the shutter speed for the outdoor night shots, but I also used a lower ISO setting of 200 to match the indoor shots, so the longer shutter lag only brightened things up a litte. I should have gone for longer exposure still, or higher ISO.


 
Hey what brand and model of camera are you using to take your pics?


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## Techjunkie (Jan 9, 2010)

*Re: SST-90 Mag 2D build in progress*



Fulgeo said:


> Hey what brand and model of camera are you using to take your pics?


 
It's a digital SLR, a Canon Digital Rebel XTi.


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## Techjunkie (Jan 11, 2010)

*Re: SST-90 Mag 2D build in progress (better beamshots)*

I realize that the distance shots dull down the appearance of the beamshots. I purpously didn't zoom in to perserve the perspective of the distance, but I wish I had used a higher ISO. The fact that the tree has no foliage really hurt. Lessons learned.

Here's an animated .gif showing the difference between the three throwers. First the recoil XRE Q5, then the KD Aspheric Q5 kit and then finally the SST-90 aspheric. I think it tells a better story than the pics do by themselves:






Also...

I'd performed most of the resistance reduction rituals on my direct drive torches in the past, but for a long time, felt like that's all they were, just rituals. Reducing resistance by milliohms seemed like a fanatic's obsession even to me. That was until I saw what a huge difference that shorting the tailspring of my carrier with copper braid made. I began to consider the drastic effect of every milliohm of resistance on a device that draws 9 Amps at only 3.6 Volts input, and how much voltage drop is caused by the slightest resistance at that current.

Tonight I bit the bullet and bought the Deoxit/DeoxitGold kit from RadioShack for $15 and, 
*now I am a believer!*
On half spent batteries, this torch was only pulling 4A at the tail. After using Doxit and Deoxit Gold on the internals (and externals) of the Mag switch all contact points on the carrier the Mag tailcap, end of tube and even the battery contacts themselves, the same batteries without additional charging measured a 6A draw. 

I repeated this excercize on my Lil' Giant and the result was identical. This deoxit stuff is a fortune, but for a high current, low voltage direct draw application, it's worth every penny. I might just try some of this stuff on the only hotwire I have that doesn't require conditioning the batteries to avoid popping the bulb.


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## toby_pra (Jan 12, 2010)

*Re: SST-90 Mag 2D build in progress (better beamshots)*

Very awesome beamshots!


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## supasizefries (Jan 12, 2010)

*Re: SST-90 Mag 2D build in progress (better beamshots)*

Very cool animated gif shot. Thanks!


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## waddup (Jan 12, 2010)

*Re: SST-90 Mag 2D build in progress (better beamshots)*



Techjunkie said:


> Tonight I bit the bullet and bought the Deoxit/DeoxitGold kit from RadioShack for $15 and,
> *now I am a believer!*
> On half spent batteries, this torch was only pulling 4A at the tail. After using Doxit and Deoxit Gold on the internals (and externals) of the Mag switch all contact points on the carrier the Mag tailcap, end of tube and even the battery contacts themselves, the same batteries without additional charging measured a 6A draw.
> 
> ...



1.4A-6A with a couple squirts? AMAZING!

2. sais the guy that drops $50 into a single led.


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## Techjunkie (Jan 12, 2010)

*Re: SST-90 Mag 2D build in progress (better beamshots)*



waddup said:


> 1.4A-6A with a couple squirts? AMAZING!
> 
> 2. sais the guy that drops $50 into a single led.


 
As the emitter heats up, Vf drops and current draw increases. I just measured 8.48A draw on a freshly charged pack (post deoxit).

2. I'm penny-wise, pound foolish that way. Some stuff you just can't do without or economize on. The emitter falls into that category. Besides, I rationalized it this way: It takes 3 MCE to generate as many lumens and three of those in one torch = floody. I've been there and done that.

On the other hand, I also discovered a $1 bulb that cranks out just as many lumens as this $50 LED, and it's easier to drive and focus. :shrug:


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## waddup (Jan 13, 2010)

*Re: SST-90 Mag 2D build in progress (better beamshots)*

i spent $15 on some deoxit about 2 years ago, ANYTHING electrical that is quirky is improved with a squirt 

ime.:thumbsup:


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## Techjunkie (Jan 17, 2010)

*Re: SST-90 Mag 2D build in progress (better beamshots)*

I removed the spring+braid from my "carrier" and cut down a KD "Mag shorty golden tailspring" that I had in my pile-o-parts to recess it within the tailcap.

Holding the spring in place while mearuing with my DMM, I measured an 8A draw from the 2p26650 carrier through this new spring. That's a very small improvement in current at best, but I think the added force of using this spring instead of the old one with braid has improved the connection when the flashlight is fully assembled. (The other spring was weaker.) It seems a small bit brighter to my eyes this way and the installation looks cleaner.

I'm also noticing more heat from the neck, but that might also be because I wrapped the neck threads with teflon tape to make it harder to defocus the lens. The tape might be thermally insulating the neck from the head. I think I'll change that tape to aluminum foil to avoid thermal insulation at the threads.

Using the same "golden spring" I measured 10.5A draw from four AccuPower Evolution LSD NiMH C cells that each measured 1.26v open. I briefly considered changing the host to a Mag 3D and using this combination of cells and a resistor to get curent draw down to 9A. Runtime would increase a little, but I don't care for the added length or weight.

This got me thinking once again about direct driving this emitter from a 4s2p AA pack. I might just bore out another 2D host I have laying around to experiment with a little more. I might not need a driver for this torch after all.


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## Techjunkie (Jan 18, 2010)

*Re: SST-90 Mag 2D build in progress - Updated*

After reading of someone else's near perfect 9A draw from a FM 4s carrier in a Mag 1.5D and 4 German generic NiMH cells, I finally got around to experimenting with that 4s2p config of AAs that I mentioned on day one.

Long story short - it's a no-go for me. It can be done, but there's a delicate balance between carrier resistance and brand of cells. I built my carrier into the torch for minimal resistance and I used white topped Duraloops. The result was an instant-blue of the emitter. After adding some resistance by introducing the Mag tailspring as a conductor, I was able to keep the emitter from instantly turning blue to slowly turning blue. I measured current rising from 12A to 14A as the emitter changed tint.

I could have played with resistors and different cells, but in the end this grand experiment taught me a few things that made me decide to reassemble the torch as I originally had it with 2p26650.

1. The DMM itself adds enough resistance to drop current significantly at this amperage. As proof I offer that once the emitter had been heated up from the over driving, the emitter would still slowly turn blue using batteries measuring 4.1V open only when not using the DMM to measure current. Using the DMM, I'd measure 8.5A and no color shift would occur. This leads me to believe that without the DMM, I'm delivering 9+ A to the emitter on 4.1V open when the emitter is this hot (and Vf drops).

2. Nine amps is perhaps too much for this method of emitter mounting and cooling to run constantly. Possibly, I have too much Arctic Silver Thermal Adhesive between the emitter pad and the heatsink, but I don't think that's the case as the torch is getting pretty damn hot at these currents, which indicates that there is good thermal transfer from emitter to heatsink. Perhaps a surface mount solder to an MCPCB and a good silver thermal compound (not adhesive) between that and a heatsink slab to which the MCPCB is mounted with screws would be better. I know some would argue that's two thermal junctions from emitter to heatsink instead of one, but I argue that thermal adhesive is not nearly as good a conductor of heat as is the combination of separate junctions of solder and silver thermal compound.

Enough blah, blah, blah, here's the pretty pics. Notice the tint shift at the higher current on the indoor shot. Also, unfortunately, the ambient light changed between the 8A shot and the 12.5A shot several hours apart, so the sky does not look the same, but I assure you, camera settings were the same. (Click thumbnails for larger pics.):


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## Codiak (Jan 19, 2010)

*Re: SST-90 Mag 2D build in progress (better beamshots)*



Techjunkie said:


> On the other hand, I also discovered a $1 bulb that cranks out just as many lumens as this $50 LED, and it's easier to drive and focus. :shrug:


 

Do tell?!


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## Techjunkie (Jan 19, 2010)

*Re: SST-90 Mag 2D build in progress (better beamshots)*



Codiak said:


> Do tell?!


 
Here you go.


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## Techjunkie (Jan 19, 2010)

*Re: SST-90 white wall hunting*

I played with a new reflector tonight, the 53mm wide by 30mm deep XRE reflector from DX. I ground off the threads and opened the hole to 16mm. By pure coincidence the perfect focal point is exactly the same as the aspheric that I'm using. That's pretty nice, considering the other reflectors I've tried required the Brightlumens heatsink to be raised a few mm and even have a beveled edge cut to allow the reflector to drop inside it a bit. Also, that P7 reflector cast a yellowish beam, this XRE reflector looks surprisingly white. I had to compare to a cool white emitter to make sure I wasn't overdrivng the 4500K SST-90.

Below, I've compared that reflector to the DX P7 reflector which received the same treatment, the aspheric, and two MCE's in DX 53mm reflector with brass pill combos. All beamshots taken at ISO 200, 0.4 sec, WB=5200K. First shot at F4, second at F22. (clickable thumbnails for bigger shots):

New 30mm deep XRE___same focal point as asph.__old DX P7 MOP


 

 



Cool white MC-E in WF502B w/WF500 head, KD 3A driver


 



Neut. Wht. MCE 2p+2p w/ 2x DX 20330 Mag 2C


 



Cool white MCE F4______F22


 



NW MCE F4____________F22


 



4500K SST-90:

30mm XRE MOP F4______F22


 



Aspheric F4____________F22


 



DX P7 MOP F4_________F22http://s255.photobucket.com/albums/...action=view&current=IMG_1518SSTAsphericF4.jpg


 



http://s255.photobucket.com/albums/...hunting/?action=view&current=IMG_1521DXP7.jpg 
Reflectors compared:


 


http://s255.photobucket.com/albums/...n=view&current=IMG_1529reflectorscompared.jpg 
http://s255.photobucket.com/albums/...n=view&current=IMG_1529reflectorscompared.jpg


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## Techjunkie (Jan 19, 2010)

*Re: SST-90 Mag 2D build in progress - Updated*

OK, I'm officially obsessed with this one torch. I realize at this point that I'm basically blogging here... hopefully the stuff I'm learning will be of use to someone else.

I had company over tonight (for my birthday) and I wanted to show off this new masterpiece. Before the guests arrived, I tested battery voltage, saw that the cells were only 3.85V at rest and popped them in the charger. Several hours later, hot off the charger at 4.15V at rest, I loaded them and handed the torch to my brother-in-law to take for a spin.

59 seconds later I was yelling, "turn it off", racing toward him to do it myself. The SST-90 was turning blue.

A quick test with the in-line DMM returned a near 10A current draw, but no blue. I switched to the clamp meter and one of the test leads and measured a 12.5A draw slight tint shift. I screwed the tail cap back on and instant blue. This is nuts.

Out go the 2P26650, into an incan torch and used down to 4.0V open. Same results as above - test lead held in place and 12A+ draw. Cap on, instant blue.

In go 3 somewhat used AccuPower Evolution LSD NiMH C cells. Remember these from before? They still haven't been charged, but now when I attach the lead at the tail and measure with the clamp meter, current draw starts up at ~6A and scales up over 10 seconds or so to 8A. Based on the observation with the tailcap vs. the DMM lead, I'm guessing that with the tailcap in place, the emitter is pulling almost 9A from the 3 NiMH C cells.

So what happened? Do giant LEDs like this one need some burn-in time like overclocked CPUs do? Did the Vf of this emitter drop since it was installed after burning-in? Or, Is this just the Arctic epoxy failing to move heat away fast enough and thermal runaway is lowering the Vf drastically?

Changing the way the emitter is mounted is not an option as it would surely be destroyed.

As I see it, my options for this particular torch are:
1) only run it in short bursts on the Li cells (not loving that one)
2) add some resistance between the batteries and the switch or the switch and the emitter (maybe just changing the spring would be enough)
3) just use the NiMH C cells (once it's hot it's at or near enough to 9A)
4) bet on sector_cleared's 9A CC driver to lower Vout as Vf drops from heat production and get one of those.

I was kind of hoping to avoid the driver and just go with a direct drive solution.

This emitter is a tricky sucker. I thought I had it licked but it keeps throwing curves at me.


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## ma_sha1 (Jan 20, 2010)

*Re: SST-90 Mag 2D build in progress - Updated*

"So what happened? Do giant LEDs like this one need some burn-in time like overclocked CPUs do? Did the Vf of this emitter drop since it was installed after burning-in? Or, Is this just the Arctic epoxy failing to move heat away fast enough and thermal runaway is lowering the Vf drastically?"

Interesting finding,

Since vf drops with increasing temp, perhaps you "cooked it" enough that made a perminant drop of vf? 

Can I send you my SSR for cooking? as my uncooked SSR seemed to have too high vf to be driven to spec with single Li-ion or even IMR 26650 

Too bad they don't sell SSR by vf bin like the P7. 
I took a P7 I bin vf & drove it with 1x IMR 26650 DD & It looked brighter than SSR-50 DD with 1x26650. So, my SSR vf. got be be higher than the 
I bin P7 (3.5v to 3.7v) or maybe even J Bin P7. >3.7v.


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## Techjunkie (Jan 20, 2010)

*Re: SST-90 Mag 2D build in progress - Updated*



ma_sha1 said:


> "So what happened? Do giant LEDs like this one need some burn-in time like overclocked CPUs do? Did the Vf of this emitter drop since it was installed after burning-in? Or, Is this just the Arctic epoxy failing to move heat away fast enough and thermal runaway is lowering the Vf drastically?"
> 
> Interesting finding,
> 
> ...


 
Keep cooking it, it's not done yet 
Without letting it continue to run while "blue", if you run it for a little while as near to tint-shift heat as you can get it, I think that's the fastest way to "burn-in" the emitter to effectively lower the Vf. I'm sure it also shortens the life span, or the service life to 80% of original brightness, but I look at it this way, even 80% of original brightness at 9A is brigher than 100% of original brightness at 6A.

Post-burn-in current draw video demonstration here.


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## Fulgeo (Jan 20, 2010)

*Re: SST-90 Mag 2D build in progress - Updated*



Techjunkie said:


> Keep cooking it, it's not done yet
> Without letting it continue to run while "blue", if you run it for a little while as near to tint-shift heat as you can get it, I think that's the fastest way to "burn-in" the emitter to effectively lower the Vf. I'm sure it also shortens the life span, or the service life to 80% of original brightness, but I look at it this way, even 80% of original brightness at 9A is brigher than 100% of original brightness at 6A.



Hey Techjunkie I wanted to chime in say I suspect that your emitter is experiencing thermal runaway. I have made a SST-90 build using 20 gauge silver-plated wire and a BrightLumens SST-90 heatsink. I was real careful and probably a bit lucky and did a clean solder job on my emitter's lead wires. I used Arctic Alumina Adhesive to secure the emitter to the heatsink. I also painted a bit on the exposed part of the lead wires to insure that they would not short on the heatsink especially in the holes. There is some scuttlebutt wether the anodizing layer is a bit thin on the inside of the holes. Anyway I was trying to work out an 12xAMC7135 4.2 amp driver low circuit and then was going to use a reed switch driven FET for a 9 amp high circuit. I was going to use 3 ACCUPOWER Evolution D cells to drive it. In the process of playing with the build I discovered that I could not drive the SST-90 for more than 4.17 amps direct drive with my 3 D cells. Others have gotten similar results with their SST-90. When I tried 4 D cells the draw within 2 seconds went from 9.6 amps to 12.5 amps before I chickened out and broke the circuit. So I would say definitely a Vf issue. So I left my build direct drive with 3 D cells for now until some of the 9 amp driver solutions currently being work on in this forum come to fruition. Btw the 12xAMC7135 4.2 amp driver solution with the 3 D cells worked perfectly for my SST-50 build, but thats another story. Here is some speculation on my part on what is happening. 

1.) I think that your emitter is not securely potted to your heatsink and as you have speculated I think that once it heats up a bit Vf drops and it starts to draw current in a runaway fashion. This is my best guess and it is only a guess.

2.) Now here is some really strange speculation on my part but bear with me. You used Arctic Silver Adhesive in your build where I used Arctic Alumina Adhesive. Arctic Alumina is supposed to be completely inert where as Arctic Silver is electrically inert but not capacitive. The following quote is from their website. "NOTE: Even though Arctic Silver Thermal Adhesive is specifically engineered for high electrical resistance, it should be keep away from electrical traces, pins, and leads. The cured adhesive is slightly capacitive and could potentially cause problems if it bridged two close-proximity electrical paths." I know that other guys have used Arctic Silver Adhesive with good results. I think most of those builds thou were lower power builds. Arctic Silver has better thermal properties than Arctic Alumina but this note always made me apprehensive. It could be that the Arctic Silver Adhesive on the bottom of your SST-90 is acting like a resister and is in effect a heating pad. Far fetched I know but hey you asked for it. You could conduct an experiment. Take a bit of metal say a pre 1982 US penny( 95% copper), smear a light layer of Arctic Silver on it. Place two lightly tinned 20 gauge wires about 2mm apart (same distance apart the electrical pads on the bottom of the SST-90 emitter are) and glue them down with a dollop of Arctic Silver about the same size and thickness you figure is under your SST-90. Let dry and then apply your 3 C or lithium power pack. Does the penny stay room temperature? Does it get warm or too hot to touch? If it stays room temperature then continue the experiment by cooking your adhesive a bit by applying a small flame to the back side of your penny away from the adhesive. Get it hot for a bit and then let it cool and repeat your test. It if stays room temperature I think we can say its not the Arctic Silver itself. I do not have the Arctics Silver myself or I would conduct this experiment. I have three tubes of Arctic Alumina to go thru before I buy more. Hope this helped. Happy Mods!


----------



## Techjunkie (Jan 20, 2010)

*Re: SST-90 Mag 2D build in progress - Updated*



Fulgeo said:


> Hey Techjunkie I wanted to chime in say I suspect that your emitter is experiencing thermal runaway. I have made a SST-90 build using 20 gauge silver-plated wire and a BrightLumens SST-90 heatsink. I was real careful and probably a bit lucky and did a clean solder job on my emitter's lead wires. I used Arctic Alumina Adhesive to secure the emitter to the heatsink. I also painted a bit on the exposed part of the lead wires to insure that they would not short on the heatsink especially in the holes. There is some scuttlebutt wether the anodizing layer is a bit thin on the inside of the holes. Anyway I was trying to work out an 12xAMC7135 4.2 amp driver low circuit and then was going to use a reed switch driven FET for a 9 amp high circuit. I was going to use 3 ACCUPOWER Evolution D cells to drive it. In the process of playing with the build I discovered that I could not drive the SST-90 for more than 4.17 amps direct drive with my 3 D cells. Others have gotten similar results with their SST-90. When I tried 4 D cells the draw within 2 seconds went from 9.6 amps to 12.5 amps before I chickened out and broke the circuit. So I would say definitely a Vf issue. So I left my build direct drive with 3 D cells for now until some of the 9 amp driver solutions currently being work on in this forum come to fruition. Btw the 12xAMC7135 4.2 amp driver solution with the 3 D cells worked perfectly for my SST-50 build, but thats another story. Here is some speculation on my part on what is happening.
> 
> 1.) I think that your emitter is not securely potted to your heatsink and as you have speculated I think that once it heats up a bit Vf drops and it starts to draw current in a runaway fashion. This is my best guess and it is only a guess.
> 
> 2.) Now here is some really strange speculation on my part but bear with me. You used Arctic Silver Adhesive in your build where I used Arctic Alumina Adhesive. Arctic Alumina is supposed to be completely inert where as Arctic Silver is electrically inert but not capacitive. The following quote is from their website. "NOTE: Even though Arctic Silver Thermal Adhesive is specifically engineered for high electrical resistance, it should be keep away from electrical traces, pins, and leads. The cured adhesive is slightly capacitive and could potentially cause problems if it bridged two close-proximity electrical paths." I know that other guys have used Arctic Silver Adhesive with good results. I think most of those builds thou were lower power builds. Arctic Silver has better thermal properties than Arctic Alumina but this note always made me apprehensive. It could be that the Arctic Silver Adhesive on the bottom of your SST-90 is acting like a resister and is in effect a heating pad. Far fetched I know but hey you asked for it. You could conduct an experiment. Take a bit of metal say a pre 1982 US penny( 95% copper), smear a light layer of Arctic Silver on it. Place two lightly tinned 20 gauge wires about 2mm apart (same distance apart the electrical pads on the bottom of the SST-90 emitter are) and glue them down with a dollop of Arctic Silver about the same size and thickness you figure is under your SST-90. Let dry and then apply your 3 C or lithium power pack. Does the penny stay room temperature? Does it get warm or too hot to touch? If it stays room temperature then continue the experiment by cooking your adhesive a bit by applying a small flame to the back side of your penny away from the adhesive. Get it hot for a bit and then let it cool and repeat your test. It if stays room temperature I think we can say its not the Arctic Silver itself. I do not have the Arctics Silver myself or I would conduct this experiment. I have three tubes of Arctic Alumina to go thru before I buy more. Hope this helped. Happy Mods!


 
Fulgeo, I think you overlooked a few things that I had mentioned:

1) I only used the silver adhesive on the electrically isolated center pad. On the wires themselves, I used the white alumina adhesive (see first pic, left side, middle shot). My motivation was exactly as you have pointed out, the capacitative property of the silver flavor.

2) The torch is able to maintain up to 12A current draw without the tint shifting to blue. I'd say that based on that, the heatsinking is doing it's job.

3) When I direct drive from only 3 AccuPower Evolution NiMH LSD C cells, the torch now pulls more current even when it's cold than it did on day one, which suggests a lower Vf than on day one. I allowed it to rest overnight to verify this (testing C cells first). When I allow it to get hot, it pulls more current than when cold, but never gets to the tint-shift stage, so I wouldn't label that thermal runaway.

In the end, I can't safely direct drive from the Sony cells unless I use only one at a time or change the spring to add more resistance, but I can direct drive from 3 NiMH cells. On a fesh charge those three NiMH cells direct drive the emitter right up to the max safe current and provide longer runtime than only one Li cell would. Even as the cells sag over the discharge cycle, the torch is still so bright at 6-7A that the decrease in brightness from 9A+ can only be perceived from stopped down beamshots.

For now, I'm happy to keep this as 3xNiMH DD and put the 9A CC driver on hold until it's a proven performer. Besides, I've got SST-50 projects to work on :devil:


----------



## Fulgeo (Jan 20, 2010)

*Re: SST-90 Mag 2D build in progress - Updated*

Techjunkie I see from your photograph where you used Arctic Alumina and where you used Arctic Silver. I was just curious if any of the Arctic Silver flowed the 2mm distance between the center emitter pad and where you attached the one wire that has opposite polarity. I was also curious if it really matters or not. It would be interesting if you discovered a way to lower the Vf of the emitter by "cooking" it. At $50.00 a pop I would be scared to try and repeat your results. Perhaps as more SST-90 builds are made this property may show itself again and we will have more data.

P.S. for your SST-50 build I have found that I get the brightest beam using a cut down stock plastic reflector and a 250 FL aspherical lens. Relatively artifact free. The 250 FL aspherical lens is a must. This combo is noticeably brighter than a 15mm MOP aluminum reflector plus a UCL lens. I would say 20-25% brighter! Also the stock plastic reflector can survive the heat of a SST-50 driven at 4 amps for long runs. I have done 2 hour tests runs and it did not deform.


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## Techjunkie (Jan 20, 2010)

*Re: SST-90 Mag 2D build in progress - Update #3*

Thanks for the tip. I have some long focal length aspherics that I put on an incan and a P7 on top of their reflectors to concentrate the spill and create a larger, rounder hotspot, but throw suffered. I'm going for throw with this one too. I think I've decided to keep the aspheric on the '90 and use a reflector on the '50. 

The 53x30mm XRE reflector did almost as good a job on the 90 as the de-cammed Mag LED reflector that was too deep (45mm) to allow the head to scew down, and I almost decided to keep it instead of the aspheric lens, until I aimed it at that tree 450 feet away and it was bested by a WF-600 incan. At 50ft range it was very impressive, but stomped by a 3xMC-E torch. So the aspheric stays. Because of the size of the die, it's actually somewhat practical. Unlike my other aspheric or recoil flashlight, the '90 lights up the whole tree top.

I have plans to recess a heatsink for the '50 into the neck of a Mag C so I can use the Mag LED reflector with it. My goal is to build a non-aspheric, single LED torch that throws like that WF-600 incan. I have my fingers crossed that one of those two reflectors and the SST-50 does the trick. I'll be building another '50 with the same 53x25mm MOP reflector that served me well in the two MC-E torches in the white wall shootout, so it might be time for me to liquidate some of my MC-E creations which will start to look a bit dim by comparison.


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## Fulgeo (Jan 20, 2010)

*Re: SST-90 Mag 2D build in progress - Update #3*

Oh I wanted to say the cut down decammed stock plastic reflector I used for my SST-50 build was from an incandescent Mag. I will need to get a Mag LED plastic reflector some day to do some comparisons.


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## Linger (Jan 21, 2010)

*Re: SST-90 Mag 2D build in progress - Update #3*

Techjunkie,
what would you say then to a -90 DD 4xRayovac 'C' hybrid nimh's then? Might the 'C' have enough internal resistance to keep it with-in spec? And the 4.8v vbatt isn't an issue? I guess I am asking you to expound on 3x and 4x configurations and your experience.


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## Techjunkie (Jan 22, 2010)

*Re: SST-90 Mag 2D build in progress - Update #3*



Linger said:


> Techjunkie,
> what would you say then to a -50 DD 3xRayovac 'C' hybrid nimh's


 
I wasn't aware that ROV was making the Hybrids in C size. I can't comment on those specifically, but I do know that the AA hybrids don't hold a candle to the Eneloop or white topped Duracell Pre-charged (Duraloops) when it comes to sustaining Vout under high current draw.

I think the SST-50 can be directly driven to 5A with 3 NiMH cells under the right conditions, but they would have to be high current capable, low internal resistance cells. If the C Hybrids are actually C's and not just AA's disguised as C's (as I hear that the Energizer 2500mAH C cells are), then they'll probably do fine. I have some cheap Tenergy 3000mAH C cells that perform very well, not nearly as well as the Accupower LSD C cells, but better than most generic NiMH AAs anyway.

My advice is that if you already have the Hybrid C's then build the torch and try them. If they disappoint you, get some Accupower Evolution C's. They're the most capable NiMH C cells that I know of and you can see how well they peform in my video.


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## Linger (Jan 22, 2010)

*Re: SST-90 Mag 2D build in progress - Update #3*

the Rayovac 'C''s are actually sub-C's but BlackRose verified their capacity ~3500ma. Reports have them as very decent.
The cells are new to me. I've used AA packs on the -50 and -90, but not C cells and I'm aware the possible current strength might be a bit different.


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## Techjunkie (Jan 22, 2010)

*Re: SST-90 Mag 2D build in progress - Update #3*



Linger said:


> the Rayovac 'C''s are actually sub-C's but BlackRose verified their capacity ~3500ma. Reports have them as very decent.
> The cells are new to me. I've used AA packs on the -50 and -90, but not C cells and I'm aware the possible current strength might be a bit different.


 
I rebuilt one of my Dewalt 18V tool packs with Tenergy 3500mAH sub-Cs and it now beats the pants off of both the OEM NiCd pack and an aftermarket 3000mAH NiMH pack that I bought a year before. Torque is stronger and rotational speed is faster. (Unfortunately the torque is so high that the "hi-amp" solder tabs the batteries came with failed under the load when using a 2.5" hole saw bit. I had to shorten and resolder the one that popped.)

If the ROV cells compare at all to the Tenergy cells I used, then I'm sure you'll be very pleased with their high current capability and low sag under load. I'm purely guessing here, but I assume that sub-c's are primarily marketed for high current applications like tool packs.


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## Techjunkie (Jan 27, 2010)

*Re: SST-90 Mag 2D build in progress - Update #3.5*

This time, with a new twist, I'm revisiting this extremely low resistance 4.8V battery configuration again:






I've ordered five of the 8X7135 2.8A boards from KD. If they continue to be back ordered by the end of the week, I'll just get the 10 pack of 4X 1.4A boards from DX and stack them myself. I plan to use 3 of the 8x boards (or 6 of the 4x boards) in parallel for a total of 24 AMC7135 chips and 8.4A of regulated current. (The other boards are for building an SST-50 torch the same way.)

I've run the 2.8A boards on 2X LiFePO4 batteries which is 6Vin+ without them overheating, but they were somewhat heatsinked the by way they were mounted. I'm hoping that if I can't figure out a good way to heatsink them that on ~4.6V input they wont overheat and fail on me.

If this works, I should have 30+ minutes of runtime, most of it regulated at 8.4A, and still keep the formfactor down to 2D. Mostly I'll be proud to have assembled the ultimate poor-man's SST-90 max current regulator/regulated torch. I wish I had chosen "The_Poor_Man" as my handle on CPF so I could write "The_Poor_Man's guide to...."

*Question:* Should I be concerned about abusing the Duraloops this way? In this two-parallel (four serial) configuration, each battery is splitting the 8.4A load and so constantly running at 4.2A current draw. Vout is sustained pretty well in these batteries (link to chart), about 1.15V at that draw, but will I be damaging them (quickly)? That could be a pretty expensive prospect for the poor man. (Oh, that poor man...) 

I suppose I could move everything to a 3D and squeeze in 16AA as I did in the LED USL, but this time configured as 4s4p. That would double runtime to an hour and reduce battery load to 2.1A each...


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## vestureofblood (Jan 29, 2010)

*Re: SST-90 Mag 2D build in progress - Updated*



Techjunkie said:


> 2) The torch is able to maintain up to 12A current draw without the tint shifting to blue. I'd say that based on that, the heatsinking is doing it's job.


 
+1

I realize these SST emitters are already a bit tougher than MCE an P7s, but IMO to say the heatsinking is "doing its job" is an understatement. 

I dont have any of the SST emitters, but I can tell you when the layer of epoxy between a bare emitter and heatisnk is even a little too thick, or insufficient in any way a quick is commonly the evidence. 

I am actualy surprised at how well this led has stood up to the torcher. 

When I first started using bare MCE emitters, I put one on a mag C heatsink with AA epoxy about .5mm thick ( I know I know ) but it didnt seem like much at the time. I put 3 rested Duraloops in and in less then 30 seconds got a very blue color and then death

This being said, if something is "wrong" (not saying there is) I dont think that your trouble lies there


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## Techjunkie (Jan 29, 2010)

*Re: SST-90 Mag 2D build in progress - Updated*

Thanks. I'm glad you agree. When I do use thermal epoxy instead of solder to mount bare emitters, I usually slide the emitter back and forth across the heatsink to spread the epoxy as thin as possible. This heatsink doesn't allow you to wiggle it at all. I had to push down firmly from the top while pulling the wires from the bottom to make sure as much epoxy as possible squished out from the wire turrets at the corners. I'm confident that I did the best job possible with these materials, and the proof is in the puddding - no 



vestureofblood said:


> +1
> 
> I realize these SST emitters are already a bit tougher than MCE an P7s, but IMO to say the heatsinking is "doing its job" is an understatement.
> 
> ...


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## mr.lumen (Mar 2, 2010)

*Re: SST-90 Mag 2D build in progress - Update #3*



Techjunkie said:


> I rebuilt one of my Dewalt 18V tool packs with Tenergy 3500mAH sub-Cs and it now beats the pants off of both the OEM NiCd pack and an aftermarket 3000mAH NiMH pack that I bought a year before. Torque is stronger and rotational speed is faster. (Unfortunately the torque is so high that the "hi-amp" solder tabs the batteries came with failed under the load when using a 2.5" hole saw bit. I had to shorten and resolder the one that popped.)
> 
> If the ROV cells compare at all to the Tenergy cells I used, then I'm sure you'll be very pleased with their high current capability and low sag under load. I'm purely guessing here, but I assume that sub-c's are primarily marketed for high current applications like tool packs.




hey techjunkie, very impressive builds. i am trying to make a thrower out of a sst-90. im new at this so i figured doing a mag mod would be easiest. do you think i should go with a C sized body or a D? (i dont mind the extra size, im concered with brgihtness of the light) im going for the brightest farthest throw, not long run time, so morer like a show light. just looking for some pointers. i was gonna get the britelumens sst-90 heatsink, the dx aspheric lense u recomended for the 90. so i was still curious about the batteries to use for maximum output and reflector, if u think one is needed with the aspheric lense. and possibly a new tailcap spring and switch. i would also need 3 drivers wouldnt i? thanks for your time and help.


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## vestureofblood (Mar 11, 2010)

*Re: SST-90 Mag 2D build in progress - Update #3*

Hi Tj,

How long did it take for your emitter to arrive from Avnetexpress?


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## Fulgeo (Mar 11, 2010)

*Re: SST-90 Mag 2D build in progress - Update #3*



vestureofblood said:


> Hi Tj,
> 
> How long did it take for your emitter to arrive from Avnetexpress?



When I first ordered a SST-50 and a SST-90 from them it only took about 5 days.


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## Techjunkie (Mar 11, 2010)

*Re: SST-90 Mag 2D build in progress - Update #3*



vestureofblood said:


> Hi Tj,
> 
> How long did it take for your emitter to arrive from Avnetexpress?


 
I checked to make sure they were in stock first, so it only took about a week by FedEx Ground. (I'm in NY)


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## vestureofblood (Mar 11, 2010)

*Re: SST-90 Mag 2D build in progress - Update #3*



Fulgeo said:


> When I first ordered a SST-50 and a SST-90 from them it only took about 5 days.


 


Techjunkie said:


> I checked to make sure they were in stock first, so it only took about a week by FedEx Ground. (I'm in NY)


 
Awesome thanks guys. I am thinking about the top bin 5700k myself. I have found the true neutral whites to be just a bit on the yellow side for me. I of course dislike the blue/purple of the 6500+ even worse. 

I just wanted to know for sure before I ordered. There was something about a "13 week factory lead time" written there that scared me, but I guess that's just if you order more that what is in stock.


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## Fulgeo (Mar 12, 2010)

Vestureofblood when I ordered my initial emitters I gave them a call to make sure that they actually had them in stock. They were very friendly and at the time they had the emitters in stock and ready to ship even thou their web page did not reflect this. Also for some reason my 5700K SST-50 WJ at 4.2 amps is noticeably brighter than my 6500K SST-50 WJ at 4.2 amps. I had an early conversation with a Luminus engineer on this subject and his opinion was that the 5700K might have a slight edge over the 6500K. I got myself a 6500K emitter and when I put it together and tested it I thought to myself "I'll be damned he was right!". The 5700K SST-50 emitter is defiantly a bit brighter. It also is a bit on the vanilla white side. The 6500K is a nice cold white. I prefer the "colder" shade emitters over the warm as long as there is no blue or green preservable. So I prefer the 6500K tint, but this is personnel preference. I have 3 of the 6500K SST-50 emitters. I have sent one of them to jtr1962. Hopefully in a few more weeks he will have the testing done and post the results in his "*White LED lumen testing"* thread.


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## Walterk (Apr 28, 2010)

Great thread and good work. 
Saw your 3 videos on Youtube today.

Hope 10A drivers are available soon!


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## gcbryan (Apr 28, 2010)

Nice thread. Can you address the question about why a reflector is needed with the aspheric?

Also, have you ever had the chance to compare your SST-90 with the Olight SSR-90? I'd say you just saved yourself $350 or so!


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## Techjunkie (Apr 28, 2010)

Walterk said:


> Great thread and good work.
> Saw your 3 videos on Youtube today.
> 
> Hope 10A drivers are available soon!


 
Thanks, Walter. I just realized that I never went back to post #41 to add a link to my Big Red build where I think I've found the best possible reflector option (Mag Rebel reflector with emitter mounted down in the neck). 

Both of my SST-90 Mag 2D builds make me very happy. I get maximum output from the amazing SST-90 emitter, very repspectable runtime with consistant output, and didn't have to use any exotic/expensive/unproven drivers to achieve either of them. I should quit while I'm ahead. (So I started experimenting with SST-50 emitters instead :naughty


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## Techjunkie (Apr 28, 2010)

gcbryan said:


> Nice thread. Can you address the question about why a reflector is needed with the aspheric?
> 
> Also, have you ever had the chance to compare your SST-90 with the Olight SSR-90? I'd say you just saved yourself $350 or so!


 
No reflector is needed with the aspheric. It's an either/or kind of a thing. I was experimenting with reflectors with this one, but only liked the Mag Rebel reflector which wouldn't fit with the BriteLumens heatsink, which is why I built another SST-90 torch where I sank the heatsink into the neck. That one is regulated and runs on AAs. This aspheric is direct drive and runs really, really damn well on Cs.

I'm not one for expensive name brands, but I certainly would enjoy comparing them. I'd rather mod a bunch of Maglites or cheap Chinese hosts than buy a single high priced light. I modded a Streamlight once, but it was a beater that I only paid $15 for.


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## gadagain (Apr 30, 2010)

I made a 4D nimh cells direct drive on a sst 90. Tail cap current was measuread at about 4 A, using the thin DMM standard probes. I was running before the emiter from 4 alkalines, no problem at all. Now, the emitter just  after some seconds when running at 4 NIMH´s D size.

I will rebuild this flashlight using two of these resistors, in paralel, to get 1 ohm resistance, to run this in 4 D NIMHs:

http://www.britelumens.com/images/930.jpg

Do you think guys, I will not fry again my expensive SST 90  ?


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## Techjunkie (Apr 30, 2010)

gadagain said:


> I made a 4D nimh cells direct drive on a sst 90. Tail cap current was measuread at about 4 A, using the thin DMM standard probes. I was running before the emiter from 4 alkalines, no problem at all. Now, the emitter just  after some seconds when running at 4 NIMH´s D size.
> 
> I will rebuild this flashlight using two of these resistors, in paralel, to get 1 ohm resistance, to run this in 4 D NIMHs:
> 
> ...


 
I think that because the SST-90 current draw scales so incredibly quickly with the smallest changes in voltage, and because proper heatsinking is so incredibly important to keep from destroying it at high currents, that SST-90 builds are not for novices. Four D-cell NiMH certainly produce enough power to kill an unregulated SST-90, but if it were heatsinked properly, you should have had some advance warning in the form of blue tint shift for at least two seconds before the emitter completely died.

If you decide to try again, a resistored setup is a possible way to go, but I do not recommend it. For starters, if you used two of the resistors that you linked to in parallel, you would likely kill the second SST-90. Those resistors are 0.1 ohm each. Two in parallel would yield 0.05 ohm of resistance. Your application calls for at least 0.15 ohms of resistance and the resistors would have to be able to handle at least 12W. (Your power source is 4.8V, the emitter calls for about 3.5V to run at 9A, so you would need the voltage drop across the resistor to be 1.3V. To cause a 1.3V drop at 9A, 0.1444 ohms resistance is needed using the formula 1.3/9. The resistors would have to disspate 9*1.3 or ~12W of heat.)

You could use 3 of the 5watt 0.47ohm resistors that RadioShack sells in parallel to achieve the right combination, but an even better solution would be three 2.8A 8*7135 regulators wired in parallel. With the regulators, you would have a constant 8.4A current over a very large voltage range and as Vbatt drops below 3.5A, the regulators would maintain a higher current than the resistored setup would.


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## gadagain (Apr 30, 2010)

Techjunkie said:


> I think that because the SST-90 current draw scales so incredibly quickly with the smallest changes in voltage, and because proper heatsinking is so incredibly important to keep from destroying it at high currents, that SST-90 builds are not for novices. Four D-cell NiMH certainly produce enough power to kill an unregulated SST-90, but if it were heatsinked properly, you should have had some advance warning in the form of blue tint shift for at least two seconds before the emitter completely died.
> 
> If you decide to try again, a resistored setup is a possible way to go, but I do not recommend it. For starters, if you used two of the resistors that you linked to in parallel, you would likely kill the second SST-90. Those resistors are 0.1 ohm each. Two in parallel would yield 0.05 ohm of resistance. Your application calls for at least 0.15 ohms of resistance and the resistors would have to be able to handle at least 12W. (Your power source is 4.8V, the emitter calls for about 3.5V to run at 9A, so you would need the voltage drop across the resistor to be 1.3V. To cause a 1.3V drop at 9A, 0.1444 ohms resistance is needed using the formula 1.3/9. The resistors would have to disspate 9*1.3 or ~12W of heat.)
> 
> You could use 3 of the 5watt 0.47ohm resistors that RadioShack sells in parallel to achieve the right combination, but an even better solution would be three 2.8A 8*7135 regulators wired in parallel. With the regulators, you would have a constant 8.4A current over a very large voltage range and as Vbatt drops below 3.5A, the regulators would maintain a higher current than the resistored setup would.


 
Thanks for the tip. Are you refering the regulators from dealextreme or kaidomain ?


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## Techjunkie (May 1, 2010)

gadagain said:


> Thanks for the tip. Are you refering the regulators from dealextreme or kaidomain ?


 
I used the KD regulators becuase it was less work to wire up 3 of the double 1.4A boards than 6 individual 1.4A boards (DX doesn't have 2.8A doubled boards). You could go either way though. I think DX is sold out on the 10 pack of 1400mA 4xAMC8135 boads, so if you don't need 20, then KD is your next best option (they still sell them 10 at a time).


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## NeSSuS-GTE (Jun 17, 2010)

Techjunkie! Thanks so much for all your effort put into this thread!

I have finally decided to begin playing with the SST-90 and found your experiences in this thread to be most valuable! You have definitely inspired me to work towards an aspheric mod.

So, if you were to summarize the battery configuration you found preferential in direct driving these SST-90s, would it be three C NiMHs?

If you decided to start again from scratch (like I am) how would you build your SST-90 mag now?

Thanks again for so much good info!


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## Techjunkie (Jun 17, 2010)

NeSSuS-GTE said:


> Techjunkie! Thanks so much for all your effort put into this thread!
> 
> I have finally decided to begin playing with the SST-90 and found your experiences in this thread to be most valuable! You have definitely inspired me to work towards an aspheric mod.
> 
> ...


 
NeSSuS-GTE, If I were to do another SST-90, I'd probably go the same host (Mag 2D) and battery (3x NiMH C direct drive) route again, with the same resistance mods, and only change the heatsink to a pedistal-less one recessed into the neck and use an SSR-90 on star, mounted not with epoxy but with thermal grease and screws. Basically, design-wise, I'd combine this torch with my Big Red torch that I described in post #41. I think it would provide the best bang for the buck and would be the least risky design for many reasons.


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