NJG-18, multimode boost driver for 445nm.. and possibly 650nm

[steviedezie]

well since you got 10 of them, when they get here you should run 2 in parallel with a test load to see.

 

[bhwollen]

I don't have a reliable test load. Want to help me? It could be like a month cause I ordered them from dx *facepalm*

 

[steviedezie]

sure... i can whip up a 3A testload easy.

 

[HIMNL9]

That what i meant in my previous post, is that, basically, this driver is a constant voltage driver, so is not good for LDs ..... you know that, with the low internal resistance of a LD in lasing state, is enough a very low increase of voltage, for increase a lot the current ..... and also, the current and internal resistance of the LD changes when it become more hot .....

Also, the manufacturer itself state 2,5% instability, for these chips

Is probably this that fried Asherz LD ..... you set your driver for, say, 1500mA, with the LD cold, then hook the LD ..... it increase temperature, internal resistance fall, and current can go "avalanche" to 2 or more A in seconds ..... is this the basical reason for which we use current drivers for LDs, instead voltage drivers.

Modifying this one, can be done but it don't worth the effort, imho ..... you can try to use it as "fixed current" drivers, changing the circuit so the LD go directly from +Vout to the set pin, and a low value resistor hooked from the set pin and GND ..... you can calculate the current in the same way you use for linear drivers, but with this IC, the pin that "sense" the output is the same pin that power the IC itself, and for stable operations, it MUST be at more than 1.5V (usually it work with a minimum voltage of 1.8V) ..... this means, in poor words, that for get, say, 1A, you need to use 1.8 ohm resistor, and this means, first, a drop of 1.8V, and second, a power dissipation, on the resistor only, of 1.8W

And due to its internal configuration, there's no way for modify it adding an external current sense IC, as it was made for flexdrive ..... it cannot simply be done, with this IC.

Under 1.5V on the Vout pin, it become unstable, and under 0.9V, it start to oscillate without any regulation.

It's a good driver for LEDs, that are much more resistant and tolerant than LDs, but not for LDs, imho.

 

[rocket689]

well its been like what... 2 months now that the flex's have been out. damn, how long does the manufacturer take to make these.

Dr Lava is claiming to be able to start shipping flexdrives in about 15 days. He's been busy working on his defense for his degree. We'll see :undecided: Here's the thread http://laserpointerforums.com/f57/dear-dr-lava-62853-2.html

 

[Asherz]

That what i meant in my previous post, is that, basically, this driver is a constant voltage driver, so is not good for LDs ..... you know that, with the low internal resistance of a LD in lasing state, is enough a very low increase of voltage, for increase a lot the current ..... and also, the current and internal resistance of the LD changes when it become more hot .....

Also, the manufacturer itself state 2,5% instability, for these chips

Is probably this that fried Asherz LD ..... you set your driver for, say, 1500mA, with the LD cold, then hook the LD ..... it increase temperature, internal resistance fall, and current can go "avalanche" to 2 or more A in seconds ..... is this the basical reason for which we use current drivers for LDs, instead voltage drivers.

Modifying this one, can be done but it don't worth the effort, imho ..... you can try to use it as "fixed current" drivers, changing the circuit so the LD go directly from +Vout to the set pin, and a low value resistor hooked from the set pin and GND ..... you can calculate the current in the same way you use for linear drivers, but with this IC, the pin that "sense" the output is the same pin that power the IC itself, and for stable operations, it MUST be at more than 1.5V (usually it work with a minimum voltage of 1.8V) ..... this means, in poor words, that for get, say, 1A, you need to use 1.8 ohm resistor, and this means, first, a drop of 1.8V, and second, a power dissipation, on the resistor only, of 1.8W

And due to its internal configuration, there's no way for modify it adding an external current sense IC, as it was made for flexdrive ..... it cannot simply be done, with this IC.

Under 1.5V on the Vout pin, it become unstable, and under 0.9V, it start to oscillate without any regulation.

It's a good driver for LEDs, that are much more resistant and tolerant than LDs, but not for LDs, imho.

Thanks for the info, always good to learn more That cleared up some stuff that I was wandering about, but I think the reason my diode blew was down to my current setting to begin with, I'm going to get a powersupply soon so I can try and set these drivers properly with a test load.

I think the reason my diode blew, was my test loads resistor was a low wattage one, so that meant heat increasing quickly and as you said above resistance dropping, thus meaning a higher current than I was reading on my DMM.

I think if I build a decent high current test load, a constant 4.2V power supply I can get the current set a lot easier, then I'll just make sure both the driver and diode are well heatsinked, keep duty cycles to a minimum and then it should be fine, I think heat is the main issue as you said for throwing these drivers current haywire

 

[steviedezie]

awesome news rocket!! good to know that the tried and true flex's are coming back. microboosts too. no way in hell was i going to pay $38 dollars for a flex on ebay.

 

[rocket689]

Yea, I almost splurged and bought one of those $38 ones a while ago when I was in need of one. Those aren't even around anymore. You literally can't find a source for a flex on the net as of right now. Thank goodness he's bringing them back in stock..

 

[joebob]

Is there a troubleshooting guide to a micro flex drive v5? I had it working then one end of my diode came off and it no longer works. I remember reading somewhere where it said do not hook up power with no load on it as it will break it. So i think that it the cause of my problem. But Dr. Lava hasn't been on much at all so was hoping if another member could help out.

 

[steviedezie]

Look for any immediate signs of damage...missing components, charred or burnt components, etc. I'd say you blew the output cap when it was powered on without a load. check that to see if it still is good. other than that...the IC itself might have fried...but i hardly think that could be the case.

 

[SHIN]

I tried to MOD NJG-18.

I stacked 82K ohm resistor over R1(10K ohm).
This reaches 1.8A output.

After connecting A140 diode (from DTR) and 32600, the power of Hi mode is max 2070mW then stabled at 1850-1900mW.

But some protected 18650 shut the power like when shorted.
The only protected 18650 was Samsung 2600.

I planned this for 18650 host but now I should change the host and the heatsink for bigger Li-ion....

SHIN

 

[LarryDFW]

This reaches 1.8A output.

After connecting A140 diode (from DTR) and 32600, the power of Hi mode is max 2070mW then stabled at 1850-1900mA.

But some protected 18650 shut the power like when shorted.
The only protected 18650 was Samsung 2600.

I planned this for 18650 host but now I should change the host and the heatsink for bigger Li-ion....

SHIN

I have lots of Samsung 2600s cells . . .
and NONE of them are protected.

They should easily handle 4-5 amps current draw.

LarryDFW

 

[rhd]

You likely wouldn't ever expect Samsung/Sanyo/Panasonic cells to be protected. Since they are generally not intended for individual sale as cells for flashlights, lasers, etc, they would normally be incorporated into multi-cell packs, with one main protection circuit (ie, for laptops, etc)

I don't think I've ever seen cells from those manufacturers sold "retail" on their own. Has anyone else?

 

[SHIN]

I use this:

LiteMania - P18650 (2,600mA Samsung)

edit] He is a CPF member.

 

[joebob]

Look for any immediate signs of damage...missing components, charred or burnt components, etc. I'd say you blew the output cap when it was powered on without a load. check that to see if it still is good. other than that...the IC itself might have fried...but i hardly think that could be the case.

I looked to see if there were any burn marks or pieces missing but I really couldn't tell to much. What is the output cap? I'm looking on the internet for a blown up picture of a new v5 to compare it to.

 

[steviedezie]

I looked to see if there were any burn marks or pieces missing but I really couldn't tell to much. What is the output cap? I'm looking on the internet for a blown up picture of a new v5 to compare it to.

the output cap is the black thing with a white line on one side and it theres two lines of reading 100 and 6V. you usually blow the cap when theres power applied to the driver without a load.