Who wants a variable power laser?

[clansley]

In another thread I came to the conclusion that I would love a variable power laser. That would mean I could buy the readily available 1W+ 445nm, but turn it down to just 200mW (which for me would used more than at the high setting).

I wondered how many others would be interested in such a laser? It may be if there are enough of us, that one of the well known builders may be willing to build them. Builders: If you would be interested please tell us!

From researching on the forums, such a laser is unlikely to go all the way down to 1mW; as some diodes start lasing at a higher figure such as 200mW.

Advantages (as I see them; I'll add more as others give them):

• Needing only 1 laser for both inside / outside uses (i.e. avoid getting both a 2W and a 200mW)
• For photography; matching the brightness of the lasers
• Obtaining a mid-range power laser; it's hard to get some wavelengths in mid-range powers (200-300mW)

Gauge of interest:

• clansley: a variable power (non-PWM based/LED driver) 1W 405nm in a handheld/portable host. [And later 445/520/650]

P.s. Blord's Dominator has multiple power levels (100%/50%/10%/flashing) and can take 445nm and 520nm diodes. It's PWM based but this may be an options for some! (100%=3W+, 50%=1.5W+, 10%=300mW+)

 

[crazyspaz]

Cool idea, definitely not difficult to do. What would you think of using a linear pot instead of having a knob on the outside of the host?

 

[bdgreenb]

25 ohm rheostats work really well for this, also if you want just 2 or 3 powers you can look into led drivers with high, med and low

 

[BodhiSci]

I'd be very interested. I have been wanting to make one with an outside adjustment. My wish list is

Outside Variable Adjustment or Hi Lo Switch
Pulse (Varrable Freq would be awesome)
Modular design with connectors to plug wires in (swap driver or diode easily)

25 ohm rheostats work really well for this, also if you want just 2 or 3 powers you can look into led drivers with high, med and low

Cool idea, definitely not difficult to do. What would you think of using a linear pot instead of having a knob on the outside of the host?

Would you use these with adjustable driver or to change Vin to same?

 

[clansley]

Cool idea, definitely not difficult to do. What would you think of using a linear pot instead of having a knob on the outside of the host?

Sounds like you've done this before I'm a complete electronics noob, is the linear pot a slider? IMHO being able to do it is more than important than the interface. A slider seems better as you can easily tell what the current setting is.

25 ohm rheostats work really well for this, also if you want just 2 or 3 powers you can look into led drivers with high, med and low

Sounds like you've also done this before The ultimate is it being completely variable - but 2 or 3 powers is much better than just 1
Would led drivers be PWM, would that work with a laser; wouldn't the laser be pumping out max power for long enough when say at 50% that it would still be as dangerous as if it was at max power all the time? [remember I'm speaking as a complete noob!]


When I did my initial research (googling LPF), I got worried that this might be something hard to do as there are many threads of people saying "it's simple just do X" then somebody else comes along and says it's a lot harder than that! I think (as a electronics noob) the main issues were centered around:

• the high watts - required an expensive/bulkly component
• some drivers try to compensate for the increased resistance.
• the robustness of the component (as it's likely to be changed a lot)

I'm glad that it sounds like you guys have already done this kind of thing

 

[crazyspaz]

Well, it is fairly simple, just have to have a special host for it. Instead lf using a small SMD trimpot you would jist have 2 contact points for a larger pot. I can think of a few possible problems but I think they are highly unlikely. Worth trying, though.

 

[USAbro]

If it's just for experimenting, not for beauty pvc pipe is a good make shift host, because it can be so easily molded and cut for people like me, who only have a jig saw, circular, and hack saw and some hand machining tools.

 

[alessnilsen]

Hi! :yh:

In my 450nm laser I included a switch that can set the driver to 1,2A (1W) or 300mA (almost in the lasing threshold), this helps a lot, because I don't want 1W all the time!

When I need a real variable power I control the input voltage of the driver, for example, if you have a 450nm LD with 6.0V of forward voltage, the driver (lm317) will need 9V to drive it, but we know that the lasing threshold start at 4V, if we supply 7V to the driver, the current will be small and the LD should not lase, but if we starts to slowly increase the voltage to the driver, the current will slowly increase too, from 7V (the smallest power needed to the LD lase) to 9V (full power).

The theory is that the driver will try to compensate the lack of input tension, but when it tries to compensate, it fails, and the current drops, and if the current drops, the output power is reduced too, varying the input tension you can get from 0% to 100% of the power, without using any big rheostat or big potentiometers.

 

[Nute]

I would love it if my 1w 445nm had a hi/low mode. I was thinking about the idea of putting a potentiometer or a rheostat on my + wire between the diode and driver. Kind of like a dial-o-watt if you will. I wonder if this could work and be integrated into the host somehow.

 

[Moe Ron]

Greetings,


There are many builds available now with modes, Hi, Med, Low, Strobe, and S.O.S., using LED drivers. All my builds use drivers with modes as I refuse to build a laser that just turns on an off. Seems very lame to me to spend top dollar for a driver that just goes on and off, when there are many good drivers out there that work great.
I know there are many that prefer to use other drivers, and site all kinds of issues and problems LED drivers can cause. While there are some, I have yet to have any issue with any of the drivers I have used. The only downside I have found is that not all drivers output what they are rated at, other than that, ain't nothing wrong using an LED driver.
Using a variable adjustment would be cool, but why not just use what is currently available....


cheers,
Moe

 

[Pman]

It's not my place to say but hang onto your hats

 

[sellersmd]

This is a really interesting topic for me. I would love to use a multiple mode LED driver to be able to have multiple output intensities on a laser, but I haven't been able to ind a suitable driver for my needs. Trying to do the build with a PL520 diode, so I would like input voltage to be up to 4.2VDC (18650 battery) and I would like max current to be ~400mA. Just haven't been able to find the right driver.

 

[AMooMooCow]

Yeah, I love variable power. My friend asked me to build him a blue laser a year ago, and I put it in a plastic box from radio shack. Used an LM317 driver with 2 sets of resistors in series. When you push the big red button, it jumps the extra resistors and puts out 1.5A instead of 200mA. It made me so giddy to have a big red button.

 

[clansley]

I'm striking PWM based dimming off my wish list - which I believe is going to mean all LED based drivers.

From a past thread:

The main problem is that PWMing a laser gives the illusion of it being low power and thus safer. This is not what happens, our eyes only perceive it as being lower power. Thus you are more apt to be injured by a PWM'd laser than an analog modulated one.

Although, PWM based dimming may still be good for some people, one of it's advantages is it can make a laser even dimmer than the min lase threshold of the diode; i.e. if a diode will only lase at a minimum of 200mW, with PWM you can make it appear dimmer than that (presumably all the way down to 1mW) - but it will not be as safe as it looks.

 

[Ehgemus]

If there's any special machining for this project I would be in for that.

 

[Atomicrox]

I've wanted one for a very long time. Not sure why no one has come up with a "standard" solution so far.

I suppose it would require a buck driver with two pots - one on board for setting the maximum current and solder pads for an external pot to vary the current between 0-100%.

Would also require a custom or modified host with a hole for the pot.