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

So that would help to reduce the overall resistance (higher current to the LED)?

+350 мА

that is only true for an ideal powersource. In reality the extra current via the 7135 will cause a slight voltage drop over the driver (which in total is the good thing) which will lower the current through the FET a bit. ...or not quite like this but someway like this

Hmm, how would that be considered a good thing?

I still think that a poor FET + 1 or 2*7135 is still better than 12*7135?

[quote=bibihang]

You can connect two FET in parallel

Good idea, thanks!

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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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.

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.