Promising Looking Buck Driver (17mm and 22mm)

[TaterMay]

Do you guys actually want or need modes? Are most laser diode drivers constant current, or constant voltage?

I really love having multiple modes. For example, having a 3+ watt/1+ watt/50 to 100mW laser is much better, in my opinion, than having to go grab three different lasers. I've owned and built lasers with 4 modes before, and I really do miss them. Don't care for the Strobe at all, if it's even safe for laser diodes.

 

[ImA4Wheelr]

^ Same here.

I received all the parts yesterday (well, the package arrived. Haven't opened it up yet). It may be a bit before I put everything together though. Have a lot of time demands right now and still need to pick a host and mod it to hold the emitter.

 

[tungsten2k]

I really love having multiple modes. For example, having a 3+ watt/1+ watt/50 to 100mW laser is much better, in my opinion, than having to go grab three different lasers.

When using a multi-mode driver, isn't the beam just as dangerous to the eye as the full-power mode ? I just did an NDG7475 and an NUBM44 build with the simple C6 generic hosts from Gary and one of the adjustable drivers he sent was bad, so I tossed a cheap linear in for now to get it working / tested: 17mm 2800mA 5-Mode Memory Regulated LED Driver Circuit Board for Flashlight (DC 3~4.5V) - Free Shipping - DealExtreme

The low mode seems deceivingly "safe" but isn't it literally as dangerous as full power, because it's just strobing full-bore on a low duty cycle so our eye/brain is giving the impression it's ~50mW ? That said, I do agree that the multi-mode feels like a game-changer - its awesome - I just wish it were slightly safer, because at full power, even the reflection off gray or darker materials could potentially be weapon-levels of radiated power; couldn't it ?

If my theory is correct, I would imagine a driver that actually could change drive currents (even if just 2 modes) would be a huge boon for us. Or am I completely off-base here ? Does such a driver exist ?

While waiting for my IMR 18350s to arrive, I took these shots with a single 4.30v 18650 - the NDG7475 is awesome, and the NUBM44 seems almost as bright as my old M140, when running on JUST ONE CELL :shhh:



So, the reason I ask all this is if these multi-mode drivers do smooth the peak output down (perhaps through a smoothing cap on the driver output ?) then they seem the ideal solution. Looks like these out of stock though.

Thanks,

-=dave

 

[RMM]

I'm not sure if what you're looking for exists, maybe it does. What you're talking about is true constant-current dimming instead of PWM dimming like my driver uses. PWM works great for LEDs because there isn't any tint shift, but if you're talking about laser safety (I'm no expert here), it probably doesn't help because you're just delivering smaller pulses of the same high-power output.

Constant-current dimming can be accomplished by offsetting the current sense voltage, which can be accomplished by several different methods. If you only need two or three set modes, it isn't too bad because you can just bring different resistors or resistor networks into play, but if you want infinite dimming then you have can use an opamp to make and RC/LC circuit (rough DAC) to filter the micro controller's PWM signal into a usable analog signal which is then used to bias the feedback circuit on the buck or boost converter. It sounds easy, but it is hard to get one that works stable across the wide temperature and voltage inputs that you get in these tiny drivers, as well as the usual packaging issues. I believe that the LD-1 flashlight driver uses a similar method to accomplish its constant-current dimming (although it is a linear driver).

 

[tungsten2k]

I'm not sure if what you're looking for exists, maybe it does.
[...]
I believe that the LD-1 flashlight driver uses a similar method to accomplish its constant-current dimming (although it is a linear driver).

Thanks for the tip RMM. I've contacted LED4Power to discuss using the LD-2 linear driver for this, but it doesn't have sufficient power handling for the Vf and power envelope of our high-powered diodes when driven from 2S. I'm researching some suggestions from LED4Power on how to work-around and will update here if successful.