# Need help with buck driver

I am trying to bump up the amps on this Ultrafire 2 x 18650 flashlight that looks like a Big C8.

The driver says TR-0010
I think the resistor I want to piggyback onto is R082 in the picture.

I am going to put a R33 like this;
https://www.fasttech.com/p/1615806
on top of it.

How many can I add before the voltage to the emitter is too high?
Thanks!
Keith

Hi!
Usually the formula is something like Iled=0.250/Rcs.
And there is no voltage regulation/limiting , but current.
So for about 5A you would need 0.05Ohm.
And you would loose 5A*0.25V=1.25W at this resistor (so it should be big enough to spread that power).
If you add 0.33Ohm resistor in parallel, you would get total 0.0657Ohm, if you add two - total 0.0548 Ohm —> 4.56A
However all these values are approximate.

I'm not familiar with the components on that driver, but it appears that the driver may be capable of delivering a decent amount of current. Just going by the size of the inductor and flyback diode.

The way I like to do it is set up the driver out side of the light so that you can measure current to the emitter. Then do the following:

• Measure current at the Low and High modes and write it down.
• Connect two short wires, one on each side of the R082 resistor.
• Than solder a resistor to the wire ends and remeasure current at the 2 modes.
• Add another resister and remeasure again. Do this until:
• You get the desired current on High or you get to a point that current no longer increases on High or Low starts to get closer to the High mode, you have gone to far.
• Note how many resistors were needed before that point.
• Unsolder the wires from the board and solder on a stack of the number of resistors needed.
• Remeasure current to confirm resistors are working properly.

Good tips.

The members above have explained it pretty clearly.

I can also estimate the value/number of resistor that you need to stack on top of the stock R082 by providing me the two information below:

1. What is the LED current on High mode now (stock)?
2. What is your desired maximum LED current?

It didn’t like the 2 r33’s on there.
Tailcap amps only showed like 1.89 but I forgot, that doesn’t mean that the emitter isn’t getting more than twice that being a buck.
Stock it was around 1.45 at tail, should have left it alone I guess.

Then to matters more fun, the solder I found in the basement must have gone bad over the years? as it is all slag, dirty as heck and doesn’t seem to have any rosin left in it.
Think I cooked the orig resistor or at least changed it’s value because after pulling the piggybacked R33’s and installing another T6 Emitter, I am now only getting 1.15 at the tailcap.

Tried to get some solder at Radio Shack today, guess what?
I mean, call me crazy, but isn’t that like a craft store not selling glue?

I laughed out loud and then said “Radio Shack, we don’t sell solder!”

Amazing! Why don’t they just go away already? All they want ot do is sell Sprint phones, R/C cars and little else.
Troubling times my friends.

Later,
Keith

Radio Shack is actually going out of business. They won’t be restocking things like solder.

The solder you found might not even be electrical solder. The flux core doesn’t go away but if it was dirty outside it would not wet properly even if it was electrical solder. You should be able to find 60/40 flux core solder either at a local hardware store or online. .032”-.06” diameter.

Sn63/Pb37 may be slightly better than 60/40. It melts not quite as hot and more all at once. It might also be slightly better in other ways. 63% tin 37% lead is the eutectic, the mixture with the lowest melting point.