comfychair-inspired quick+cheap+lazy single-sided 17DD FET-driver (poor man's nanjg92)

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Major
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Update! And a bump!!!!
As the original FET seller sold out I ordered 20 from ebay seller E-best_trade Link they arrived in 8 days from Hong Kong. And test good, genuine original.
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I decided to build a Fet+1 driver. This turned out to be really easy with just a wire link from pin 5 to FET gate.
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I used Dr jones basic MiniDrv firmware and added a couple of lines to make it duel PWM. Sorry about the screen shot don’t have any other way of showing.
The output is low(2ma), medium (350ma), high (1.2A), turbo (4.5A), with a 20 second turbo step down and no memory always starts on low.

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FmC
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Nice work.

What battery were you using?

Major
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FmC wrote:
Nice work.

What battery were you using?

Thanks.
A LG HE2 but with a multimeter in series so probably will have higher amps than measured as leads aren’t great.
djozz
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Great work Major! Love it that you got the FET+7135 option working! I'm jealous of your skills too, I will never go into the coding/flashing direction I'm afraid, and the UI you made is close to my perfect one Smile

bibihang
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Yeah nice job Major! And thank you for letting us know that the new buying source of the FET is good. Smile

djozz
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Major, for the record, I take it that the FET-drain is connected to the led-minus pad, it is not clear in your picture, I have drawn a yellow line to show it:

Major
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.Yes that line is correct, I soldered the FET-drain to the pad where the 7135 used to be.
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djozz wrote:

Great work Major! Love it that you got the FET+7135 option working! I’m jealous of your skills too, I will never go into the coding/flashing direction I’m afraid, and the UI you made is close to my perfect one Smile


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Thanks, I’ve been looking for a cheap and easy Fet+1 driver for ages. Cheers but im no programmer I just copy what the clever people on here write and alter it until it works!
nofear87
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My driver mod shows only 3,3A at the tailcap. Did there something went wrong? I have tested with different cells.

I soldered all like shown in the first post. I soldered the LED – to the top of the fet…the old minus isnt soldered to the fet

bibihang
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What batteries have you use? Are they fully charged? What is the gauge of your DMM probes? Did you do spring-mod? What LED are you running with?

Rufusbduck
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nofear87 wrote:
My driver mod shows only 3,3A at the tailcap. Did there something went wrong? I have tested with different cells.

I soldered all like shown in the first post. I soldered the LED – to the top of the fet…the old minus isnt soldered to the fet


Pictures really help. What FET are you using? Many won’t turn on fully at battery voltage and can limit current.

Three Tanna leaves to give him life, nine to give him movement. But what if he eats the whole bag?

Scott

nofear87
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Thanks! The Led is a Cree XM-L2. I use fully loaded LG MH1 Cells….there should’nt be any problem.

I used these Mosfets from MTN: http://www.mtnelectronics.com/index.php?route=product/product&path=25_76...

I’m at holiday..so I have’nt any pictures actually Smile But I soldered it like the first post!

What are DMM probes? Spring is’nt modded right now.

Robert

prisma
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An additional spring bypass should help a lot especially in a 1 cell configuration.
If you are using standard DMM probes, they are probably too thin, you should use short and thick ones (Messleitungen) Wink

cajampa
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Yeah if you are using stock DMM probes & have not bypassed the springs, that is probably it. Bypass the spring & use fat short wires from the DMM & i am sure you will get higher amps.

nofear87
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Which dmm probes you prefer? I will do the Bypass as fast as possible.

cajampa
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Just try some short fat electrical wire you have, almost anything shorter & fatter than the normal thin DMM wires is better for measuring high amps.

Rufusbduck
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DMM, digital multimeter. The probes are the metal bits at the end of the wires that plug into the meter. LEDs are voltage sensitive and maintaining high current through them extremely dependent on eliminating voltage drops in the circuit which the meter is now part of. Other voltage drops occur in the switch and springs. Minimizing all 3 should result in a dramatic measured difference.

Three Tanna leaves to give him life, nine to give him movement. But what if he eats the whole bag?

Scott

nofear87
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Very well explained. Thank you very much.

So I should use the wires without probes? And replace them against fatter and shorter ones. But how the wires fits into the meter without probes?

And what’s with the dmm wires at the led. You soulder them for measuring?

bibihang
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nofear87 wrote:
But how the wires fits into the meter without probes?

Use banana plug, just solder your 22awg (or thicker) wires onto the banana plug and you have a pair of good test leads.
djozz
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I even have solid copper clamps soldered to my (short, thick) DMM-leads, because I found a considerable voltage loss over the iron clamps I used before. I could not find solid copper banana plugs btw.

mozart.f
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Congrats for djozz and Major.
Just ordered the banggood driver and eBay fet. As soon as they arrive wil try this in my Uniquefire 1504 host that I just received.
I really hope that this thread receives much more attention and participation from BLF members. This mod has a fantastic cost benefit ratio.
Keep the good work djozz/Major….

M4D M4X
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I did that with a 105c today. ..
stripped the 8 7135 and mounted the fet (taken from a computer Mainboard )

low and high work bit mid does not…
could it be that a fet has problems with a specific pwm ratio?

amps are nearly DD Wink

PLEASE NOTE
i do not work in "reviews, deals and codes" for the time being
maybe M4D M4X will return one day, but until then:

THANK YOU FOR YEARS OF YOUR SUPPORT AND FRIENDLY CONTACTS!

djozz
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M4D M4X wrote:
I did that with a 105c today. .. stripped the 8 7135 and mounted the fet (taken from a computer Mainboard ) low and high work bit mid does not... could it be that a fet has problems with a specific pwm ratio? amps are nearly DD ;)

I know not enough about FET's to know what happened to your med mode, I just know that there are several types, some work as a discrete on/off switch, others allow intermediate currents (like the FET on the LD1 and LD2).

djozz
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mozart.f wrote:
Congrats for djozz and Major. Just ordered the banggood driver and eBay fet. As soon as they arrive wil try this in my Uniquefire 1504 host that I just received. I really hope that this thread receives much more attention and participation from BLF members. This mod has a fantastic cost benefit ratio. Keep the good work djozz/Major....

thanks mozart. Note that in post #10 there's a link to an even cheaper ak-47 driver (set of 2 for $2.89) , from dx. Dx does not mention the type but they are genuine ak-47A drivers.

edit: dx is sold out at the moment Sad

Rufusbduck
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A common issue is that output in each mode is a fixed percentage of maximum so when you up the maximum by replacing the 7135’s with an FET the middle and low modes get boosted as well so low mode might be brighter than one might wish. This is normally corrected by adjusting the firmware to lower percentages.

Another is that if the input capacitor is in the wrong place voltage spikes can cause malfunctions.

Three Tanna leaves to give him life, nine to give him movement. But what if he eats the whole bag?

Scott

nofear87
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I have bypassed the springs at switch and driver. Know the xm-l get burned Sad I think thats to much current. Is that possible? It is hard to measure without destroying another led.

FmC
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nofear87 wrote:
I have bypassed the springs at switch and driver. Know the xm-l get burned Sad I think thats to much current. Is that possible? It is hard to measure without destroying another led.

LED mounted on DTP board, & attached to a light/heatsink, you should not be burning them.

mozart.f
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djozz
Is it possible to mod a QLITE REV.A in the same way as the Ak47, i.e., taking out the 7135s and mounting the fet?
I appreciate the QLITE modes, and have 1 driver that is currently not used that could be modded.
Thanks for the help.
Mozart

ImA4Wheelr
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^ Answer is yes.  First sentence of OP has a link to where that was first done (Qlite and Nanjg have the same circuits, just higher "binned" 7135's in the Qlite).

djozz
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ImA4Wheelr wrote:

^ Answer is yes.  First sentence of OP has a link to where that was first done (Qlite and Nanjg have the same circuits, just higher "binned" 7135's in the Qlite).

yes indeed, hence the title of this thread referring to comfychair, this is just his mod with a smaller FET that fits easier, and cheaper driver.

mozart.f
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Thanks for the replys.
Tried to find some one that used the QLITE in this thread but didn’t find. Excuse my noobness. Trying to learn the basics yet.
I’m in my second led flashlight mod. The first was an Convoy S2+, that was accidently dedomed when received 2 7135s to its driver. Now mounting a Uniquefire 1504 host, that will receive a dedomed XP-G2 S4 2b and a fet driver.
Cant wait the parts arrive to mount a fet hot rod thrower.

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