Help with 8a driver and load

[RedCowboy]

With NUBM44 diodes I check the setting of my drivers with a 100w 1 ohm resistor and an INDUCTIVE meter, not in-line but inductive and that works just fine for a short ( few seconds long ) test ( room temp ) I have also dialed in the BB8 using the same 100w 1 ohm resistor, at room temp and in 10 seconds or less just set it up heat sinked and set to 4.5a, no problem.

 

[Alaskan]

Agreed, For the NUBM44 diode with it's relatively high forward bias voltage that will work great if you have two Li-ion batteries producing 8.4 volts. The 1 ohm resistor will pull 8.4 amps short circuit current and you can adjust down from there, as long as your lead resistance in the circuit isn't adding another ohm.

If setting up the current for a lower forward bias voltage laser diode and just one 4.2 volt battery you would need a lower resistance, or you would never be able to reach above 4.2 amps using the 100 ohm resistor. Not very often you would need that though. I like your method.

 

[RedCowboy]

I typically use 3 cells for a nubm44 but 2 is the absolute minimum and only good IMR such as EFEST, I remember someone attempting a boost driven nubm44 and having trouble even with a good 26650 battery.
The nubm44 draws 4.5a when limited to 4.75v including lead wires so the 1 ohm load is a reasonable analog for the nubm44 and I have looked at the draw of an SXD driver driving a nubm44 @ 4.5a, it's basically 2a @ 12v or 3a @ 8v ( 24w ) into the driver so a single cell powering a boost driver which is also less efficient would mean a 7a draw with the cell sagging to about 3.5v, I don't think anyone has been able to get to 4.5a with a boost driver, granted a good 26650 will do 7a but the driver/wires/switch/battery contacts would all have to add up to 1/2 an ohm or less which is possible but I haven't seen it work very well.
Again I just use the 100w 1 ohm resistor in place of a nubm44 to verify my driver is putting out 4.5a for 10 seconds or less, I don't run it long enough to get the resistor hot, not heating it up at all in just a few seconds and I don't use an inline meter but I use an inductive meter that won't add any resistance.

 

[diachi]

With NUBM44 diodes I check the setting of my drivers with a 100w 1 ohm resistor and an INDUCTIVE meter, not in-line but inductive and that works just fine for a short ( few seconds long ) test ( room temp ) I have also dialed in the BB8 using the same 100w 1 ohm resistor, at room temp and in 10 seconds or less just set it up heat sinked and set to 4.5a, no problem.

By inductive meter I assume you mean a current clamp? If so, why are you using a current clamp and a current shunt? There's no need for a shunt if you're using a current clamp. All you're doing is turning electricity into heat and increasing your voltage drop by 1V/A... Are you just using the 1ohm resistor with no diodes...?

 

[Alaskan]

He's using that 1 ohm resistor as a load, I don't believe it is a precision resistor to use as a shunt. If his current meter is precision, he doesn't need a precision resistor for the load.

 

[RedCowboy]

Here's one of many drivers I have bought from DTR pre set by Jordan to 4.5a and it was in a build that I tore down to repurpose the laser diode, I had checked the driver before installing it and here it is tonight still putting out 4.5a with two 2 ohm wire wound resistors in parallel as the load and 2 x 26650's powering it, it reads the same driving a nubm44.
I have also verified 3.5a and 4.0a pre set drivers and set up some to 4.5 - 5.0a which is reflected by the diodes output seen on my LPM, for this application 1 ohm works just fine as the driver doesn't know the difference between the resistor and the nubm44 which draws 4.5a when voltage is limited to 4.75
Tonight I tested this for 20 seconds and it toggled between 4.4 - 4.5a, I also have other inductive meters that reflect the same.
Checking these resistors with my Fluke meter and zeroing out for my meters leads I get 0.96 for these resistors with lead wires.