Doesn’t require breaking connection? If the Vf is known, can the emitter amperage be reliably tracked on the charts? Or semi-reliably? I was just double checking the temperature range of the Arctic Silver Thermal Adhesive. It’s top end says 150C. With the 32mm copper star and thick aluminum shelf on the pill, and another 1/4” of copper under that, it takes a setting up around 850º on my Hakko 888 station to solder a lead on, and even then it takes remarkably long under contact before the solder softens…it doesn’t go full liquid like I’m used to seeing so it’s barely making the bond as it is. This can’t be good for the thermal adhesive.
I’ve got a narrow bevel tip on that I used to stack the chips, would this be why? Need to switch tips back I guess.
I can’t believe this! I did it over and over, and it’s freakin unbelievable! I kept getting 4.40A, but wasn’t sure that was high. So I had my wife actuate the clicky to run through the modes and OMG! 8.50A!!! At the emitter! Yowza, there was some serious heat coming off that bad boy and I was almost in contact with it!
This is with 2” long 12 ga Romex wire at the negative lead on the emitter. I clamped the negative or common with hemostats, then held the positive in place ready to bail if need be.
I thought that I knew the answer to your question “If the Vf is known, can the emitter amperage be reliably tracked on the charts?”, but I had already been doing some testing, and now, I don’t know the answer.
The testing I’m doing is with just an XM-L emitter on a PCB. I don’t have a bench power supply, so I’m using an Accucel 6 hobby charger instead, which may be the problem.
I’m using a new DMM (Ideal Pro) for measuring the emitter voltage (voltage across the emitter) and a clamp meter to measure current. The Accucel also shows current and voltage output.
The thing that is puzzling is that as I increase the current from the Accucel (say from 1 amp to 1.5 amps), the voltage across the XM-L is dropping, from about 2.87V to like 2.7V.
One issue with doing that is you probably won’t be able to re-program the driver. The PWM pin on the processor chip is one of the pins used to program the chip. The polarity diode isolates the power on the processor chip from the emitter power. Without that series diode, your poor little AVR programmer will try to also power up the LED (s), and won’t be able to supply the 3+ amps. You would need to remove the 200 ohm resistor to re-program the processor.
Could the Zener be clipping the led voltage as well as the mcu input? An XML will certainly hit 3A at 4.2V in but not a 6V mtg. Can you measure the led Vf at the 1.65 drive current? Cree specs that ~5.8+V so even a little clipping or host resistance could increase sag.
Hint: solder the leads to the star before mounting it to the light/heatsink… Also pre-tin the star and leads with solder before going in for the kill…
Double hint: make SURE that the wires to the star do not short to it and the insulation is intact, particularly where it crosses the edge of the star. Make sure there is insulation there!. Otherwise, you can get a dead-short on the battery(ies) when you install them.
Depending on the cells used, I get anywhere for 3.5 to 6.3 using 2S 18650’s. Relic38 has been getting up to 7 amps in some of his reports to this thread.
Let me start at the end. When it was all back together I took a Voltage reading across the emitter and got 6.42V when on high.
Now, back up. With the leads on the DMM I got…at the tail….07, .74, 2.72A at the emitter….04, .69, 2.56A. With the short solid 12ga wires at the tail….07, 1.19, 4.41A and at the emitter….07, 4.40, and 8.50A. Somebody please tell me what all this means!
Edit: All tail readings were taken last, with light reassembled.
No, that 200 ohm resistor limits the current the zener draws from the battery. Without it, the zener will probably vaporize with a satisfying BANG followed very shortly by the processor!
A grand total of zero times. So that is not a concern for me.
When I was using the solid short wires on the emitter, I couldn’t activate the modes myself and kept hitting medium. Taking the leads off, starting over, every time it was a solid 4.40 on medium. Then my wife came in and she pressed the clicky and got the low low, then the 4.40 and then 7’s scrambling up into 8’s and stopped at 8.50. Had to stop, the emitter was scorching my fingers.
I’ve been using the short solid wires for quite some time on tailcap readings, as that’s the only way my DMM comes anywhere near known readings. I even bought new leads, paid like 12 bucks for leads when my DMM was 20 to begin with! lol
Looking at djozz’s chart (hope my memory is working there) the Vf would indicate around 3A. I don’t know much of anything about all this, but I remember y’all talking about the cells sagging shortly after start…I took the Vf reading some 30 seconds after turning the light on High. For whatever that’s worth. Scrambling to hold everything, then trying to stare into the sun to find the contacts without shorting anything out. Repeated it to be sure. By the time I got the 6.42V solidified, the light was pretty hot!
That’s what I thought it was supposed to do. Just wondering why the different output for the mtg. It’s not the chips or mcu apparently so something is dropping the led voltage, sag, host resistance, grease on the extension threads, something.
Sorry I’ve been confusing things DBCstm. 4.4A sounds spot on for a 3A driver with 4 extra chips and is why I wonder about a short. If the led - wire solder point contacts any part of the host the chips get bypassed resulting in dd. 8.5A is just not right for 12 chips. What’s odd is that you still have any modes.
The request for emitter Vf was directed towards comfychair to find out why 3A with XML but not with mtg. Could it be a mis binned 9V mtg?
Good point Rufus. He probably had the reflector off for the emitter current test and on for the tail current test. If that is the case, the first place to search for a short is the reflector. Or the emitter base may be pushed into a position by the reflector that causes short on pill.
The reflector on the K3 pill screws on. There’s a nice thick centering ring it makes contact with. Yes, I took that off and put the pill into the L2P host with no head at all. And yes, if I did manage to short it out and go direct drive there would be no modes. But there were modes! My wife ran through them. 3 times. By the time she left it on that blazing Hi the last time, my fingers were about toasted and I had to quit. I clamped the loosened negative lead to the wire from the DMM with hemostats, upward and onto my hand with the back of the stats. Visibly making no contact with the side of the pill. I then hand pressed the other wire from the DMM to the pad on the copper star. This star is glued to the pill, no movement whatsoever. Visibly keeping the contacts clear of each other, scared shirtless I was gonna see blue arcs and smell doom. We repeated the reading 3 times. Running up through the modes. I got that 4.40 on medium at least 7 times. Yeah, I was kinda stoked.
Mind you, pointing my S2200 at a white Styrofoam ceiling lights the room up like the overhead lights are on. Clicking the K3 on eliminates the results of the S2200. Noticeably brighter, and not by a little bit. Same thing with my Triple XM-L2 from Elektrolumens. It fires up the room, big time. But not as much as the K3. The Triple XM-L2 was estimated at 3000-3500 lumens. And the K3 is brighter. Figure it out, I can’t.
The discussion in this thread convinced me I should try removing the 0.5 ohm resistor from my short DST. Just for the record here’s what it looked like before, with the resistor:
So now, it’s true direct drive, and still dedomed MT-G2, and here’re the new numbers:
Tailcap current: 3.46 amps
Lux at 1 meter: 60477 (60.47 Klux, measured at 39 feet and calculated to 1 meter)
Batteries: 2xSibeile IMR 18350, fully-charged
I think it's impossible to kill a MTG2 with only two cells, even with a bare star not attached to anything the solder will melt and the LED slide off onto the floor before the LED itself is damaged.
Ohaya. Looks like you might get a very respectable 120kcd at 7 amps. I updated the OP in the throw measurement thread. Do you have a post that shows the dedomed emitter in the reflector? I would like to see the emitter height and placement.
Only 3.5 amps with IMR’s? I’ve never used 18350’s, but that sounds low. I find myself struggling getting rid of all resistance with all the connections that electricity has to cross in that light. I currently have some somewhere in that light that I need to find. I’m thinking you have some resistance somewhere too.
