Variable laser power?

sinner · Mar 18, 2012

I just did something like that but i am not a potentiometer fan , I had time to kill anyways!!
I used a DDL design based on LM1086,
Using 4x 10-Ohm 5W Resistors, in parallel with a small switch soldered to the later 3 Resistors. Sounds Stupid ?! eH!
Well the design is funny, maybe not if u must need this kind of adjustable power laser..

1. 1x 10-Ohm + 3x Disconnected via Switch ~125mA
2. 2x 10-Ohm Connected & 2x Disconnected ~250mA
3. 3x 10-Ohm Connected & 1x Disconnected ~375mA
4. All Resistors Connected (Paralleled) ~450mA

That is not the best option there is, but i was planning ultra-ghetto 405nm build this time..
Had a fun time though !!!

foulmist · Mar 20, 2012

I just did something that might interest you

Add-On Dimming Circuit

Hiemal · Mar 20, 2012

Why are you guys overcomplicating this so much?

Just put the potentiometer where the adjustment pot goes. Really doesn't get simpler than that...

foulmist · Mar 20, 2012

Le Quack said:
Why are you guys overcomplicating this so much?

Just put the potentiometer where the adjustment pot goes. Really doesn't get simpler than that...

Ok, find me a 0.28ohm potentiometer to regulate my buck/boost driver please I will take 50pcs

this is not complication at all, it's just the RIGHT WAY

sinner · Mar 20, 2012

Le Quack said:
Why are you guys overcomplicating this so much?

Just put the potentiometer where the adjustment pot goes. Really doesn't get simpler than that...

You sure didnt check the Add-On from foulmist!!
Smartswitch bites the dust

Hiemal · Mar 21, 2012

foulmist said:
Ok, find me a 0.28ohm potentiometer to regulate my buck/boost driver please I will take 50pcs

this is not complication at all, it's just the RIGHT WAY

You wouldn't need that low of a potentiometer actually....you can use a standard pot, with a voltage divider.

It would work by dividing the voltage given by the pot so that you can give it a degree of adjustment.

foulmist · Mar 21, 2012

Le Quack said:
You wouldn't need that low of a potentiometer actually....you can use a standard pot, with a voltage divider.

It would work by dividing the voltage given by the pot so that you can give it a degree of adjustment.

If I do that the pot will be away from the PCB which break the design of the driver and pcb layout is crucial for boost/buck drivers ... I don't think it will work...

Bionic-Badger · Mar 21, 2012

Here is the current regulating circuit I use for all my analog power control. Do note that it has terrible efficiency because I'm basically using the MOSFET as a voltage-controlled resistor. The mosfet gets hot depending on how much current goes through it, so be sure to heatsink it. I was literally causing the packaging and protoboard of my circuit to cook when I tried using such a circuit as a test for one of those 30W red diodes (8A or so). It should be okay for 1-2A however, provided there is heatsinking and you don't touch it, lest you get burned.

Tech_Junkie · Mar 22, 2012

I have an older flexmod. I should be able to Pot the input to the driver, no?

Sorry, I'm an uber noob with electronics.

Sigurthr · Mar 22, 2012

Nice circuit there, BB! Ya, mosfet is the way to go for easy dimming when you don't want to route a lot of power through a pot. With the mosfet as the voltage controlled resistor you determine the output current by the input voltage, and since you can use very very low currents at the right voltages to drive the mosfet, you can use very low power high resistance pots to control a high power low resistance output. Plus, a mosfet doesn't drop 1.5V like a NPN BJT will.

foulmist · Mar 22, 2012

I still think a PWM at the enable pin is better (for ICs that have it) to control the output, it takes almost zero current to run and doesn't heat AT ALL and can be programmed as you please, and external components are very few.

and pots aren't that accurate and can't be held in position very well, not to mention the wipers wear off pretty easily. that's just my opinion, I am not trying to force it on someone

:beer:

Bionic-Badger · Mar 22, 2012

foulmist: The problem with PWM is that unless it's very high frequency it isn't very good for stuff like laser shows because you can see the PWM in the output. Also, some PWM circuits aren't very high resolution, like those Arduinos and their 10-bit PWM. Also, the full-on output of the driver would need to be clamped to the max pulse current, or even the constant current level depending on expected duty cycles.

foulmist · Mar 22, 2012

Bionic-Badger said:
foulmist: The problem with PWM is that unless it's very high frequency it isn't very good for stuff like laser shows because you can see the PWM in the output. Also, some PWM circuits aren't very high resolution, like those Arduinos and their 10-bit PWM. Also, the full-on output of the driver would need to be clamped to the max pulse current, or even the constant current level depending on expected duty cycles.

I wasn't thinking about laser shows but handheld lasers, I will try it on my laser diode when I receive it, and only 1% is lost out of the max output current. I will post a video once I am ready. I might try it on a LPC-826 i have lying somewhere I wanted a 445nm but I will wait for a while

TacoHerder · Apr 1, 2012

I noticed there was a 1W 445nm laser on ebay. It uses the big UltraFire flashlight for the host. Looks like he used the flashlight driver for his diode. I noticed it has 5 modes just like the flashlight. Would that actually work, or will the diode die sooner than later? Here is the link btw 1w 445nm blue laser parts kit module and host driver/mount batteries /chager | eBay

Tech_Junkie · Apr 1, 2012

Yes, as long as the current settings work with the 445nm diodes.

Lazeere put a mode driver in my 1.5W build. It has low, high, and high strobe.

TacoHerder · Apr 1, 2012

Cool. I might have to make one like that. I have the TrustFire TR-3T6 "3800" lumen flashlight. It only cost $38, but is freaking super bright. I feel kinda bad wanting to buy another one just to take apart and turn into a laser. Eh, i think i'll be able to live with that sacrifice though

Maybe add a thermal switch and some power led lights...somewhere on it.

Variable laser power?

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