Shorting the negative emitter lead against the reflector would do that. (Almost any short along the negative path could do that.) FYI this applies to many of the buck drivers we deal with, but not necessarily all.
What emitter current are you seeing with the IOS version?
I used this LD-40 in my Uniquefire 1405 - it is an aspherical lens flashlight. 
I didn’t measure the emitter current reading, didn’t think about this. I will measure it and post it here again.
How hard has this driver been pushed into an MT-G2?
Hi guys. I’m thinking that this (these) drivers can work for multiple alkaline lights. Would anyone be willing to replace R100with an R200 to see how much output is reduced to? (1.2A?) Thanks
You mean for 4xAA lights?
I might have to mod a couple 4D mags and don’t want the current more than 1400mA. 4AA is a possibility too since I have a 4 AA headlamp to mod.
I think it’s safe to assume that you’ll be in that ballpark, output wise. Input will be lower of course since you’re talking about stepping down 4v-6v to ~3-3.4v or something.
I have some more testing to do with this driver so I’ll do my best to do a quick test with R200 for you. If you see me start posting results at some point and I don’t mention it just remind me.
Thank you. I have one driver arriving in about two weeks. No smd components down here so will have to visit digikey too when the money makes itself available. That’s another month wait. Lol.
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I’m slightly confused about something. I thought current controlled means no PWM yet, whining is mentioned. Is this whining seen in the output or is it in a different section of the driver?
The sense resistors are 1206 size, but I think you can get away with 0805 size. FT carries 3 values of sense resistor for 01206 and many more for 0805. I assume you’ll save a lot of money over Digikey? Use the dropdown menus.
1206 - http://www.fasttech.com/products/0/10007371/1615805-1206-0-12r-smd-precision-resistors-100-piece
0805 - http://www.fasttech.com/products/1002/10003143/1234404
That’s a common misunderstanding. The buck section is CC and like most drivers has only a single set current. We feed PWM into the buck controller for all lower modes, it just turns the entire buck section off and on. It’s exactly the same setup as using 7135’s, which are also CC. Some much more rare drivers have the ability to change the set current, those are also referred to as CC but they are PWM free.
So one uses pwm to control how much current the buck section supplies and one uses pwm to pulse a fixed buck current.
Mmm. Depends on the scenario probably.
"and one uses pwm to pulse a fixed buck current." - This is the common setup. That's how the LD40 and most other CC (current controlled) drivers operate.
"one uses pwm to control how much current the buck section supplies" - The LD29 definitely seems to work the way you describe. I'm not sure that all other "PWM free" drivers work that way. The DQG 26650 driver for instance does not, although it is appears to be a CC (current controlled) boost driver. It actually has transistors which bring in different arrays of sense resistors depending on the mode.
Ok, so which category would a synchronous buck converter fall under? The one that changes buck current? ( I assume the first type Rufus mentioned?)
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. Thanks guys. I have one more question but will have to go through the thread again first.
Synchronous/asynchronous has nothing to do with this.
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The resistance value of the ones in that first link .120 ohm correct?
Also I have something I've not seen mentioned yet. I bought several of these from mountan electronics which I assume are hanks 2.4A always start on high. All of them looked normal accept for one. The sense resistor on it is different. Rather than the R100 it has a pair of shorter resistors that say 1R2. Is this just a different shape of resistor? A pair of 200s rather than a single 100?
Also If I am reading this thread correctly using a .180 resistor stacked on top of the .100 should get me to around the 3.5A mark right?
If anyone happens to have a source for cheap 1206 size resistors in that value I would also appreciate it :)
1.2 Ω vs 0.1 Ω
What resistor is underneath the 1.2 ohm? They probably ran out of R100 and stacked some others to get the equivalent (or close to it) resistance.
No, 1R2 is 1.2 Ohm, the R represents the decimal point.
Yes I bought my LD-40 (or LD-4B) from IOS and it does always start on high.
If the stock output current is 2.4A with an R100, you should probably get 3.73A by stacking an R180 resistor on top of it.
Can anyone please kindly help me to confirm what is the height of this LD-40 (or LD-4B)? From the top of the toroid to the PCB surface (excluding the thickness of the PCB itself) as illustrated in the sketch below.
It was reported as 10mm in both IOS and CNQ websites, but I doubt about that and they did not state 10mm is from where to where.
Much appreciated.
I just pulled out the unit I used for some testing earlier in this thread. On my sample (which has been used some for testing on the bench) it’s ~11mm overall (including PCB) without compressing the driver. Compressing it brings it down to about 10mm overall.
The soldering job holding the toroid in place is not perfect. It does not look like I ever reworked those solder joints, I think it’s safe to say it’s the factory job. That’s where the extra height on the one I have comes from.
I think if you were very careful in reworking this board you could get the total height down to 9.5mm or 9.4mm. So in a best case scenario the height above the board could be reduced to 8mm… maybe.