LD-40! (17mm Buck driver, 3-16.8v!)

Flashlight Modding and DIY Parts
72

I’d assume it was the protection circuit.

73

ANNNND, with that, you’d be correct :)!!

I removed the protection circuit, and re-wrapped the battery, and now I get modes when I use that battery :)!!

74

Re. 3) I’ve tried several different 14500s (paired with a dummy… NO COMMENTS PLEASE :)!!), i.e., with 1x14500, and I get consistent 1.43 - 1.44 amps at the tailcap.

I have been trying to measure tailcap current with 2 x 14500, but not having much luck… I’m not sure why. The light/host I have this in has female threads at the tailcap end of the tube, so I’m having a hard time making contact with the threads because they’re inside the battery tube, I think.

EDIT: I don’t know what current the stock driver does with 1x14500.

75

I hated doing it, but FYI, I decided to sand off the ano on a (small) area of the end of the battery tube, so that I could just use a test cable with alligator clips with the meter. I then measured tail cap current with 2x14500 (Efest IMRs) and remember this is with 3 x XP-G2 emitters.

Anyway, tailcap was about 0.92 amps. I guess “theoretically” and not taking any loss into account, that should give about 2.45 amps at the emitters, or ~0.81 amps per XP-G2?

The measurement was a quick one, less than 5 secs, I guess. Should I run it longer on high to see if something smokes?

EDIT: My test cable is one of my “regular” ones, from Radioshack, about 18” with alligator clips at both ends. I was also just using my normal test leads on the meter, probably a meter each:

EDIT 2: My “theoretical” calculation:

Power in = 0.92 amps x ~8 volts = 7.36 watts

Total Emitter current = Power/Vemitter = 7.36 watts/3 volts = 2.45 amps

Per emitter current = 2.45 amps/3 = 0.816 amps

76

I don’t see why anything would smoke. I also don’t see why output is so pitiful if you’ve still got a stack with R200/R200/R100 on there. I’d expect efficiency to drop but output to go up. Something is limiting performance and I doubt that it’s the batteries. I don’t really know what is doing it. Possibly the TOFF cap needs to be adjusted for higher currents?

BTW what host is that?

EDIT:

I note that you did not include losses in the driver. As usual, I’d say 80% is a good number. So we’re actually looking at about 5.89W/3xEmitters = 1.96W per emitter. So maybe more like 2A output. Odd.

77

This is the host:

Also an RC-G2 W/quad…right now limited to 1 x 14500 or 2 x 14250, but waiting to get an extension made.

78

BTW re the current calculations, that’s why I wrote “theoretical” and put that in quotes :)…

EDIT: Corrected mispelling (my tablet keyboard’s auto-suggest :laughing:.

79

Just to eliminate possibilities, I re-tested the 2x14500, but with a pair of short (less than 12”) 20 AWG cables, and got exactly the same current at the tailcap, ~0.92 amps.

Kind of strange :(!!!

80

I’m starting to think that what you said about there being SOMETHING on this driver that is limiting the current may be right. It’s acting almost like a current regulator?

81

I think that there must be some fundamental thing that is different with this CNQ driver, vs., say the LM driver.

I just went back to a light (an RC-G2) that has the LM driver, resistor-modded with an R100 stacked, and a new/upgraded Schottky diode and FET (only the one nearer the diode). The light has a quad XP-G2. I had to jury-rig to get 2 x 14500, and here’s a pic:

So that was 3.042 amps at the tailcap with 2x14500, so “theoretical” (not counting efficiency losses):

Power = 3.042 x ~8 = ~24.336 watts

So, the Iemitter (total) would be approximately:

24.336 watts / ~3 volts = ~8.112 amps

and Iemitter (per emitter) would be:

~8.112 amps / 4 = 2.028 amps / emitter

The thing here is that the LM driver seems to be behaving “correctly” with respect to output, whereas the CNQ driver seems to be constraining output?

82

My suspicion still lays with the TOFF cap.

Page 4 of the datasheet discusses the effect of the offtime cap (they call the cap Coff, not Toff. oops.)

I’m having a trouble figuring out how I’m supposed to handle units, and since Roff isn’t present I’m assuming that the Roff fraction just cancels out… yeah I don’t know where I’m going with this.

Where I’m really going with this, is would you be willing to strip the Coff/Toff cap off of your board ohaya? I think that output may get much, much dimmer without the cap present. Or something could blow up. Like I said, I’m having trouble figuring this section out. From what I can figure the offtime without that cap should go way up. So a higher value cap could reduce offtime.

Or all that could be wrong and Toff actually (sort of) sets the period. I don’t know. I’d like to know what happens when you take it off, but if it increases the period a lot (which it might do by a few orders of magnitude… like 3 or 4 orders of magnitude) it could make the output so rough that it kills LEDs.

83

PMs sent…

84

Purchased 3 of these to play around with. I think I will stack it with an R150 instead of an R100 to get a theoretical 4.16A vs 5A. I’ll be pairing this up with an MT-G2 in a Dipper D19 (L2 clone).

I prefer stacking resistor chips as I am better at it than stacking 7135s, so no zener modded driver for me. :smiley:

85

Please post your results when you do that?

Thanks,
Jim

86

I now have an LD40 and one of the LM drivers (extensive thread here) in hand for testing and comparison thanks to another BLF’er.

So far I haven’t learned a ton, but I’m working on it.

Here are the connections for the pads on the bottom of the LD40:
V+ = The zener-regulated voltage supplied to the modes chip (00VM) and the QX9920 (LEDA)
GND = having a little trouble here. It beeps out to Pin 1 & 3 on each MOSFET package… which the datasheet says is Gate? Really? GND for the logic section.
3 = Pin 6 on the modes chip (00VM)
1 = Pin 3 on the modes chip (00VM)
0 = Pin 1 on the modes chip (00VM)

When the driver is powered Pin 6 is pulled up to V+ and Pin 3 and Pin 1 are pulled low.

  • In the stock configuration the mode order is L/M/H (at least for the 3-mode one I’ve got). The modes chip does not give a 100% duty cycle. The duty cycle of each mode is: ~0.5% (L), ~17% (M), ~84% (H ).
  • When Pads 3 & 1 (Pin 6 & 3) are connected the driver appears to be locked in High. Duty cycle appears to go up a smidgen to 85%.
  • When Pads 3 & 0 (Pin 6 & 1) are connected the driver appears to be locked in Medium. Duty cycle is still ~17%.

EDIT: be sure to see updated info 2 posts below this one.

87

Maybe the pinouts for some 8205S chips are different?

This one:

http://www.ic-on-line.cn/view_download.php?id=1461919&file=0231\gtt8205s_4934460.pdf

shows pins 1 and 3 of the GTT8205S as “S1” and “S2” (i.e., “source1” and “source2”), respectively.

88

You hit the nail on the head.

I was about to post that these 8205s chips are certainly marked upside down as compared to the datasheet I used. More likely is that they are just a different 8205S as you’ve shown. That datasheet turns the pin configuration inside out!

The connections are as I stated. Pins 1 & 3 connect to the “GND” pad as well as VSS/GND on the QX9920 and to VSS/GND on the modes chip (00VM). Pins 5 & 6 of the 8205S next to the QX9920 (LEDA) chip connect to DRV from the QX9920. The other 8205S is no doubt hooked up in a convoluted fashion, as usual (it’s also the one which connects the GND net hooked up to QX9920 and “00VM” to battery GND).

The pinout for “00VM” is:

  1. Pad 0 (Connect to Pad V+ or Pad 3 for Fixed MEDIUM mode (~17.65% duty cycle))
  2. Vss (GND) (Pad GND)
  3. Pad 1 (Connect only to Pad 3 for Fixed HIGH mode (~85% duty cycle))
  4. PWM (PWM output)
  5. VDD (regulated voltage input from Zener diode) (Pad V+)
  6. Pad 3 (Connect to GND pad for Fixed LOW mode (~0.5% duty cycle))
89

I measured 2.0 Amps output to my XM-L2 on a Noctigon. (2.00 - 2.05A) I used my modded HF meter. This corresponds pretty well with the R100 current sense resistor, which sets 100% duty cycle at approximately 2.5A. Since we only operate at 85% duty cycle we’re getting about the right current reading.

The IOS version may be using a modes chip with a higher duty cycle.

EDIT:

Input:
7.10v @ 1.08A

Output:
3.10v @ 2.00A

Efficiency:
~80.85%

90

Thanks for that info, wight! Did you have a chance to test with an R200 stacked on the R100?

91

Unfortunately my measly 3A CC buck PSU gets upset with the driver when I do that. The PSU claims that it’s outputting ~2.4A and something like 4-5v (when set to 7.1v). The CC light flickers. I tried turning the voltage up, but it still does it. It seems that the driver’s inrush or whatever must spike above 3A with the R200 stacked on top of the stock R100. I got almost exactly 3A output from doing this. I should get a bigger, better PSU.