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

Thanks.
A LG HE2 but with a multimeter in series so probably will have higher amps than measured as leads aren’t great.

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 :-)

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

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:

.Yes that line is correct, I soldered the FET-drain to the pad where the 7135 used to be.
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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!

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

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?

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

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&product_id=439

I’m at holiday…so I have’nt any pictures actually :slight_smile: But I soldered it like the first post!

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

Robert

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:

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.

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

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.

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.

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?

Use banana plug, just solder your 22awg (or thicker) wires onto the banana plug and you have a pair of good test leads.

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.

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….

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:

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).