The part was marked D7136, but searching for that revealed no datasheet from either the google or the yahoo.

Thanks for the schematic re-sizing, what value works for the image width—the original was too big to post. Thru trial and error i found 560 works for this image.

Huh… first I’m seeing of a 7136. Nice! I can use that puppy…

DrJones used them here: http://budgetlightforum.com/node/44674
They are hard to find as AMC7136. To my knowledge they are sold as QX7136 which show up as being much more available. I think they are the same, but I’m not %100 sure. What I have troubles finding out is what size range the current setting resistor Rext has to be when using it without an external FET.

The 7136 can sink a maximum of 500 mA, but the typical range for use is 10 to 400 mA.

So to calculate the proper resistor, Rext, first you must select at what current you wish to drive the lamp, for example let’s pick 200 mA. The cutoff voltage of the current sense is 50mV, so the Rext = V/I = .05/.2 = 0.25 Ohms, and it would dissipate .01W, so i would pick a higher power rating such as 0.1 Watts.

If you wanted the highest current 400 mA, then Rext = .05/.4 = 0.125 Ohms, power is .02 W so pick 0.1 Watt resistor to cover.

For the lowest current, Rext= .05/.01 = 5 Ohms, power is .5 mW.

So to cover the full current range from 10 to 400 mA, Rext ranges from 5 to 0.125 Ohms rated at 0.1 Watts.

The Husky spotlight uses 2 parallel 0.04 Ohms resistors to regulate the maximum current to I = V/R = .05/.02 = 2.5 Amps. The N-channel FET is rated 60 Amps and can easily handle that current. The Rext must handle 1/8W, which is why they used two 1206 SMD resistors, which have a 1/4W rating.

Thanks for explaining. I know that is the typical current sense formula when the current sense resistor is inline with the LED. I was hoping that with current sense resistor from CS to ground without being inline would’t need higher rated resistors.

That was me! Can anyone tell what it is? Looks like a XP-L to me. I swapped it out for a spare XP-L HI I had and it works great with a 18650 for power. I noticed that the current drops slowly after the light is turned on for a bit, but if I unplug it and plug it back in it jumps back up to ~2.5a. I was thinking this might be thermal protection kicking in, but it shouldn’t jump back up to 2.5a then. Or maybe that quick moment it is off is enough to shed some heat.

There! Now I can read it

Huh… first I’m seeing of a 7136. Nice! I can use that puppy…

09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0

The part was marked D7136, but searching for that revealed no datasheet from either the google or the yahoo.

Thanks for the schematic re-sizing, what value works for the image width—the original was too big to post. Thru trial and error i found 560 works for this image.

DrJones used them here: http://budgetlightforum.com/node/44674

They are hard to find as AMC7136. To my knowledge they are sold as QX7136 which show up as being much more available. I think they are the same, but I’m not %100 sure. What I have troubles finding out is what size range the current setting resistor Rext has to be when using it without an external FET.

https://www.flickr.com/photos/akrylamid/sets/

The 7136 can sink a maximum of 500 mA, but the typical range for use is 10 to 400 mA.

So to calculate the proper resistor, Rext, first you must select at what current you wish to drive the lamp, for example let’s pick 200 mA. The cutoff voltage of the current sense is 50mV, so the Rext = V/I = .05/.2 = 0.25 Ohms, and it would dissipate .01W, so i would pick a higher power rating such as 0.1 Watts.

If you wanted the highest current 400 mA, then Rext = .05/.4 = 0.125 Ohms, power is .02 W so pick 0.1 Watt resistor to cover.

For the lowest current, Rext= .05/.01 = 5 Ohms, power is .5 mW.

So to cover the full current range from 10 to 400 mA, Rext ranges from 5 to 0.125 Ohms rated at 0.1 Watts.

The Husky spotlight uses 2 parallel 0.04 Ohms resistors to regulate the maximum current to I = V/R = .05/.02 = 2.5 Amps. The N-channel FET is rated 60 Amps and can easily handle that current. The Rext must handle 1/8W, which is why they used two 1206 SMD resistors, which have a 1/4W rating.

Thanks for explaining. I know that is the typical current sense formula when the current sense resistor is inline with the LED. I was hoping that with current sense resistor from CS to ground without being inline would’t need higher rated resistors.

https://www.flickr.com/photos/akrylamid/sets/

Yes you are right Mike, the resistors don’t need to be power-rated as high to use the internal FET.

But the resistor values need to be the same? 5 to 0.125 Ohms?

https://www.flickr.com/photos/akrylamid/sets/

Yes that’s right, to regulate the internal FET current from 10 to 400 mA, those are the range of resistor values.

So 0603 or 0402 SMD resistors could be used since they are rated 1/16W.

Picture of the LED used is linked HERE

That was me! Can anyone tell what it is? Looks like a XP-L to me. I swapped it out for a spare XP-L HI I had and it works great with a 18650 for power. I noticed that the current drops slowly after the light is turned on for a bit, but if I unplug it and plug it back in it jumps back up to ~2.5a. I was thinking this might be thermal protection kicking in, but it shouldn’t jump back up to 2.5a then. Or maybe that quick moment it is off is enough to shed some heat.

S8 Triple - 219c, MTN-17DDm

M1 - XP-L 7a, 105c

C8 - XP-L HI, A17DD-L