Could a 445 9mm 3W Diode be run on lower power with one battery?

[BodhiSci]

Want to be able to go from higher power to lower power, by changing from 2x18650's to just 1. using an X-Drive driver.

Bad for the diode? driver? (it is within range but I don't know if their output is set based on the current # of batteries (voltage) or if it would or wouldn't work for some reason.


Thanks!

 

[andrewb]

You can't use a single 18650 with an x-drive for a 445 diode.

X-drives are 'buck mode' drivers, meaning they require a higher voltage than the voltage drop of the diode (and then they 'buck' the voltage down to the diode voltage.) For a 9mm 445 diode, the diode voltage is about 7V when running at max current of about 2.4A. Hence why you need two Li-Ions at 3.7V each for a buck driver.

This is why the X-boost (and other boost drivers) exist. A boost driver will boost the voltage from a single 3.7V battery to the necessary diode voltage of roughly 7V.

Search the forum for 'buck boost drivers' if you want to read more about the differences.

Also, you can see here for a compilation of voltage vs current vs power plots for a variety of popular diodes, using different lenses.

http://laserpointerforums.com/f52/updated-g9-vs-g2-vs-3-element-vs-acrylic-study-85334.html

 

[starlight]

Not sure if it is safe but I did it on accident. I had a home built lab style 445nm laser and was just using batteries hooked up with magnets off bare wire. After making a battery holder I wired it in series and couldn't figure out why my laser lost so much power until I seen my mistake and fixed it. Don't think anything was damaged as far as I can tell.

 

[BodhiSci]

You can't use a single 18650 with an x-drive for a 445 diode.

X-drives are 'buck mode' drivers, meaning they require a higher voltage than the voltage drop of the diode (and then they 'buck' the voltage down to the diode voltage.) For a 9mm 445 diode, the diode voltage is about 7V when running at max current of about 2.4A. Hence why you need two Li-Ions at 3.7V each for a buck driver.

This is why the X-boost (and other boost drivers) exist. A boost driver will boost the voltage from a single 3.7V battery to the necessary diode voltage of roughly 7V.

Search the forum for 'buck boost drivers' if you want to read more about the differences.

Also, you can see here for a compilation of voltage vs current vs power plots for a variety of popular diodes, using different lenses.

http://laserpointerforums.com/f52/updated-g9-vs-g2-vs-3-element-vs-acrylic-study-85334.html

Ok, that makes sense. After reading that, I found a PIV curve. I think it might have just enough power to turn on, at least while the battery is fresh the new 18650 I'm ordering are Panasonic 3400 mAh, they start at 4.2V I believe. Maybe that would help. It is really so that I can have low power sometimes on walks. Not sure how having a HP pointer would be in a neighborhood. Just be careful to not do it around people I suppose. I am careful even with my 303's now.

Check this out:

http://laserpointerforums.com/f65/new-9mm-445-diodes-73284-7.html

Not sure if it is safe but I did it on accident. I had a home built lab style 445nm laser and was just using batteries hooked up with magnets off bare wire. After making a battery holder I wired it in series and couldn't figure out why my laser lost so much power until I seen my mistake and fixed it. Don't think anything was damaged as far as I can tell.

Cool, Yeah, damage is a concern of mine

 

[DTR]

Yea it will work if you only use a single 18650 but you will probably only get a few hundred mW out of it.:beer:

 

[BodhiSci]

Yea it will work if you only use a single 18650 but you will probably only get a few hundred mW out of it.:beer:

Good! That's what I want. To be able to go from HP to lower (safer attention wise at times). Thanks.

 

[grainde]

You can't use a single 18650 with an x-drive for a 445 diode.

You can.

For a 9mm 445 diode, the diode voltage is about 7V when running at max current of about 2.4A.

Its actually only about 5 V @ 2.4 A?

Ive also measured them @ around 5 V too. The 405s and some 520s have Vfs in this range.


Anyway as its a buck and as the Vf is higher than the battery voltage, the driver is not in regulation ie there is no current regulation. This means the diode will be run at approx the voltage that the battery is at (minus losses), which as its a diode will be current limited. The exact current at this voltage can be taken from the IV curve. As the voltage cant increase there is no risk that the diode will receive more current. As you use the laser the voltage will drop (and so will the current) gradually reducing the output of the laser.

I actually use Lazeerer X-drives (bucks) in my kryton builds with 9 mm diodes and use 1 x 18650 to eg set the focus, or to simply have a lower power laser. With one battery the current at the tail cap is around 200 mA, which gives around 200 - 230 mA out. :beer:

 

[Atomicrox]

I do this all the time with lasers that use buck or linear drivers, but never tried with a 445nm 9mm diode (mine uses a boost). Never had any damage from it.

From my trials power will be somewhat different every time you turn the laser on, even with fresh batteries. Never figured out why that happens, but it does.

 

[grainde]

Power will be dependent on the actual Vf (or charge state) of the battery which will correspond to a certain current on the IV curve. Batteries have different internal resistances and so there will also be voltage drops associated with the current draw between different batteries ie the diode will see a lower bat voltage than under no load and hence the current draw and power will be less (and variable between batteries).:beer:

 

[Atomicrox]

That doesn't explain why the laser power will vary when you fire it up multiple times in a row without removing the battery. This happens with two of my lasers and the variation is so large that you can detect it without using an LPM (on the LPM I've seen up to 200% of variation).

Very strange stuff! :wtf:

 

[grainde]

Ok interesting? I did a comparison of 4 lasers all with Foulmist iDrv3 drivers and all gave within 40 mW of each other. IIRC The tail cap currents were all similar and around 200 mA. Later I measured an x- drive and got similar results. Ill try to dig up the data.:beer:

 

[DTR]

Power will be dependent on the actual Vf (or charge state) of the battery which will correspond to a certain current on the IV curve. Batteries have different internal resistances and so there will also be voltage drops associated with the current draw between different batteries ie the diode will see a lower bat voltage than under no load and hence the current draw and power will be less (and variable between batteries).:beer:

It will also depend on the temperature of the unit. Diodes draw more current at any given voltage the warmer they are.

 

[BodhiSci]

Sweet! So glad to hear all this. Really interesting to. I love this stuff. Can't wait to get an LPM. I'm going to go with the X-drive and a 2x18650 so I can do this with a spacer. (gotta get one now...) This place is such a great resource.

 

[Atomicrox]

Bump! Made a video showing the power variation I mentioned - this is with the 462nm in my sig, using a single panasonic 18650. Small variations during the same run are due to my hand not being 100% steady while holding the laser.

This also happens with the 445nm C6, but the variation is smaller.

My guess is that it has something to do with firing the laser very close to threshold.

 

[BodhiSci]

Bump! Made a video showing the power variation I mentioned - this is with the 462nm in my sig, using a single panasonic 18650. Small variations during the same run are due to my hand not being 100% steady while holding the laser.

This also happens with the 445nm C6, but the variation is smaller.

My guess is that it has something to do with firing the laser very close to threshold.

I have the same thing on my pen lasers.

 

[The Lightning Stalker]

My theory is that since it's right around
threshold, it's hopping around at different
modes. Some modes are more favorable than
others. If it is right near the threshold,
sometimes it will kick in and lase, but not
every time it hits the exact same current.
When they are on the edge of operation, all
simple oscillators exhibit instabilities
that are somewhat dependent on initial
conditions, such as stray electromagnetic
fields.