Do you mean half of the original (2 x R180) resistance, i.e., so the equivalent of R045 resistance (total)?
So, if I completely remove the original stack of resistors and replace with, say, a single R050, that would be “it”, right?
Thanks,
Jim
The math sounds right to me (but!). The problem with doing that is what you’re doing to that resistor. ~5A with 0.25v drop through a single 1206 is 1.25W. Assuming you’ve got 1/2W parts (the most popular rating for 1206 current sense on Mouser) then you’re at 250% of the rated dissipation.
Ahh! Ok, thanks for confirmation re. the resistance, and I understand the potential issue re. rating for the resistor. I’ll see if I can find some correctly (physically) sized resistors with the correct values so I can stack on top of the original 2xR180 to get down to about total R050.
The higher the resistance, the less current that will flow throw a resistor. So two R200 1/4W resistors will be equivant in power handing to a single 1/2W R100 resistor.
Well, I think that I “did a bdiddle”, or maybe “worse than a biddle” (or “better”, depending on your viewpoint :laughing:….
I stacked 2 R200s on top of the 2 R180s, and I measured tailcap on high, and got……
~8.79 amps!!!
that only lasted a few seconds though, until the light died :(…
I inspected the driver, and nothing looked like it burned or popped, so I took the whole head/pill apart.
Then, I tested the emitter (the original XM-L on the big 20+mm star) and, that was dead.
So then, I wanted to check if the driver was still working, but I didn’t want to pop another emitter, so I removed the 2 R200s, and hooked up a new (old) XM-L on a Noctigon, and fired it up connected to my bench supply, and got LIGHT!! And modes even :)!!
So, I added 1 R200 back on top (so I was at 2 x R180 + 1 x R200, or about equivalent to R069), and put it back into the light, and tested tailcap and got ~2.21 amps, or about 17.68 watts (into the driver). That would be about 5.89 amps (17.68/3) to the emitter at 100% efficiency or ~4.71 amps to the emitter at 80% efficiency.
Seems like that’s probably a safe place to be for this light?
Now, going tangentially: I’m wondering how this light would do with an XP-G2 instead of an XM-L? Would this be a good thrower? It seems like the head/reflector, while not huge diameter, isn’t bad, but would an XP-G2 do ok at ~4.71 amps?
Also, would it work with this reflector? Or maybe I’d need to use something like this:
http://www.fasttech.com/product/1576101
??
Jim
EDIT: Corrected typo, per wight :)…
[You typed amps where you meant to say watts in one place.]
Sorry about the emitter, not sure why things went bad - maybe the inductor as mentioned earlier?
The XP-G2 should be able to take whatever the XM-L2 can, and the peak output is just over 6A, so that sounds fine to me… Crash-testing a XM-L2 and a XP-G2 on copper Sinkpads
Remember that new XM-L2’s die at low current, around 5-7A or something, I don’t know. (Fish around BLF to get actual info.) New XP-G2s may eventually pickup that flaw as well.
No need to apologize about the emitter… wasn’t your fault, and it was a risk that I knew going in…
This light just looks like a thrower, doesn’t it? So, I think that I’ll try going with an XP-G2 and see what it does.
The vF scales as amps goes up, so you are not at 4.7 amps, closer to 4 at 80%.
(17 watt * .8 ) /vF (~3.5)
Hi,
So, are you going to keep yours with the 2 x R180 and the 1 x R150 stacked and going with an XM-L2? When you do, can you post your tailcap current?
Jim
I have an r120, and tail current was in the 2.85 range. I don’t have a way to measure lumens or emitter current, but output was not good.
You can measure emitter current the same way you measure tailcap current. Replace one of the emitter wires with a pair of wires and put the DMM in the middle…
Hi,
I’m assuming that you meant an R120 stacked on top of the original 2 x R180? That would give like the equivalent of an R051.
Also, 2.85 amps at the tailcap would mean about 22.8 watts into the driver.
So, assuming ~3V emitter voltage and 100% efficiency, that would be 7.6 amps into the emitter, so I don’t understand how output would be “not good”?
At 3.5V emitter voltage and 80% efficiency, that would still be 5.21 amps into the emitter, which should be plenty (may be too much) for an XM-L/XM-L2 emitter?
Just keeping track of things:
180 mOhms (1 x R180): 0.41 amps (ohaya)
90 mOhms (stock 2 x R180): 1.46 amps (ohaya)
69 mOhms (stock 2 x R180 + 1 R200): 2.21 amps (ohaya)
56.25 mOhms (2 x R180 + 1 x R150): 2.8 amps (bdiddle)
51.4 mOhms (2 x R180 + 1 x R120): 2.85 amps (bdiddle)
47.36 mOhms (2 x R180 + 2 x R200): ?? amps (ohaya - Measure freaky 8.79 amps - must’ve been something wrong!)
Hi,
Hmm… The problem I have with trying an XP-G2 in this light is that the original star was for XM-L, and it’s LARGER diameter than 20mm.
I have some XP-G2s on 20mm stars, but using them presents some problems:
- The solder “bumps”: The light originally comes with a white plastic centering ring/insulator that goes over the star, and prevents shorting the soldering points to the reflector. With the large original star, I think the solder joints for the +/- wires are near the edge, and the white disk is raised at the edge. However, if I use a 20mm star, the solder joints are not at the edge, so they will push the white disk up and not allow it to seat.
- Obviously, the 20mm star is smaller diameter than the original one, so I’m not quite sure how I’ll center it.
I’m thinking that with the XP-G2, I won’t use that white plastic disk, but rather, just file the joints as flat as possible, and then put some Kapton tape on the joints. That will insulate the joints from the reflector, but I’m still not quite sure how to center the emitter, and keep it centered?
Jim
Does Maxtorch make a 25mm XP copper mcpcb?
There are 26mm copper stars.
http://www.mtnelectronics.com/index.php?route=product/product&path=63_65&product_id=348
Ohaya, get one of those 26mm Maxtoch stars. Mine took about 30 minutes of filing to make it fit.
In terms of driver efficiency, I think it is going down to ~70% efficiency. If I can find the time tonight I’ll try and take emitter current. Maybe I had a bad reflow on the MCPCB.
I may do that eventually, but (a) I want to try to see if I can “make do” with parts that I already have for this light/mod and (b) RMM isn’t shipping until 12/1.
I can say that the stock LED was not turning blue at the 2.58 amp tail cap draw.
I assume you still have old XML’s lying around, play with it and if you kill one just reflow another gen 1 emitter on it.
I already did that (killed an old XM-L in this light). That was what I meant by I “did a bdiddle” earlier :)…