LPC-815 red module powered by single Li-ion + linear driver

[lazerov]

I'm working on a portable RGV build. One of the goals is to power all three laser modules by single Li-ion 3,7V battery (18650). This is the red laser module I'm going to use in it. It's a LPC-815 LOC diode, pressed in a custom machined aluminium heatsink, driven by low voltage drop linear driver. The lens is the one found in the LPC-815 sled (so it's free).
Picture of the experimental measurement setup (I know it looks bad ):

The driver used can easily provide 0,41A to the diode at only 3,6V. It can supply much more but I don't want to push the diode so far. Current remains stable at higher voltage.

Picture of the driver used:

This is a modified driver from the cheap "50mW" 2xAA green laser Focalprice sells. I changed the resistor from 1Ohm to 0,5Ohm (the big black resistor). A driver with the same design and different component values can be found in the green modules available on DX (here). Their driver can be used with no modification at all.

This module can light matches and cut black tape without focusing. Beam diameter at aperture is ~2mm. Divergence is not great, though, and the "wings" around the dot are quite big.
The violet module in the RGV build is going to use same heatsink, lens from the PHR sled and O-like BR LD driver. With these lenses I should have matching beam diameters of all three colours (the green module has 2mm thick beam).

 

[Eudaimonium]

And where exactly are the pictures?
WTH

And, if you don't mind me saying, AMC7135 from DX. cost 16.99$ for 20pcs
350mA constant current fixed output
Vdrop only 120mV , perfect for 2xAA, or 1x CR123 or so (with the rectifier diode shorted, if not, then 0.8 Vdrop, perfect for LIIon power)
I'm using these drivers for a year or so... Makes me able to pack my red LCC build into a fancy flashlight that uses 2x AAs, without need to buy expensive DC DC converters, like flex or so...
Can you give a link to the schematic of that driver you are using?

 

[lazerov]

And where exactly are the pictures?
WTH

Pictures are uploaded at Imageshack and work perfectly fine for me.

And, if you don't mind me saying, AMC7135 from DX. cost 16.99$ for 20pcs
350mA constant current fixed output

The 7135, of course. You cannot control the current at all. And those 350mA are not that fixed, according to datasheet (variation from 340 to 380mA)

Can you give a link to the schematic of that driver you are using?

I didn't make the driver myself. It's from a 50mW greenie. But I have the schematic of the driver in DX modules. As I said only component values are different.

 

[Eudaimonium]

Yes, I can see the pictures now... Sorry
What kind of module are you using to get 2mm beamt @ aperture exit?

Nice heatsink!

 

[lazerov]

What kind of module are you using to get 2mm beamt @ aperture exit?

I'm using the short focal length lens from the LPC sled. It's in a custom machined lens holder which screws directly in the heatsink. Diode is pressed directly in the heatsink as well.
This lens could be used in Aixiz module, too. Check this tutorial. It's about the lens in the PHR sled but its size is virtually the same as the LPC lens.

Nice heatsink!

Thanks! I had these machined locally for few $ each. Maybe I'm lucky there are some machinists in my city.

 

[Eudaimonium]

I'm using the short focal length lens from the LPC sled. It's in a custom machined lens holder which screws directly in the heatsink. Diode is pressed directly in the heatsink as well.
This lens could be used in Aixiz module, too. Check this tutorial. It's about the lens in the PHR sled but its size is virtually the same as the LPC lens.

Thanks! I had these machined locally for few $ each. Maybe I'm lucky there are some machinists in my city.

Well I get my done for free on CNC 3d machine...
School has one CNC and I know thw professor who is in charge of it so...
;D
If anyone needs something done on CNC... You know to talk to ME!
However since I cannot recieve paypal... Dont ask me to make you a V8 engine block....
If you know what i mean.

 

[LarryDFW]

lazerov;

I am using the same driver circuit in a couple of green lasers.

The circuit is designed for no more than 3 VDC with green IR diodes.

It can probably operate @ 3.6VDC with a Red diode. Use a 1N4006 diode in series with the #18650 battery.

At higher voltages, the Q3 pass transistor gets hot enough to fail.

If it fails, it will take out the laser diode.

LarryDFW

 

[Jimmymcjimthejim]

Check this tutorial. It's about the lens in the PHR sled but its size is virtually the same as the LPC lens.

Thanks for posting my tutorial. However it is currently outdated, I'm going to make a V2.0 of the tutorial soon once I get a working red laser (should be by this weekend, however the mod may not work with LCC diodes, the ones I am getting.) This newer version of the mod makes the beam diameter even smaller and without any scatter around the dot, but only for red lasers.
Even if it doesn't work I'll still post the mod anyway.

 

[lazerov]

@LarryDFW
Yes, the driver from DX modules (which is very similar to the one used) works fine in the 2,7 - 3,2V range when powering IR LD. But an IR LD has a voltage drop of about 2V. A red diode should have ~3V voltage drop at 400mA. So the power transistor has to dissipate about the same power.
It does not become excessively hot (at least at 3,6V, heat may be a problem at full charge of the Li-ion), but I'm going to use a small heatsink, just in case.

@Jimmymcjimthejim
Sounds promising. Especially the ''without any scatter around the dot'' part

 

[Eudaimonium]

@LarryDFW
Yes, the driver from DX modules (which is very similar to the one used) works fine in the 2,7 - 3,2V range when powering IR LD. But an IR LD has a voltage drop of about 2V. A red diode should have ~3V voltage drop at 400mA. So the power transistor has to dissipate about the same power.
It does not become excessively hot (at least at 3,6V, heat may be a problem at full charge of the Li-ion), but I'm going to use a small heatsink, just in case.

@Jimmymcjimthejim
Sounds promising. Especially the ''without any scatter around the dot'' part

Correct me if I'm wrong (and I probably am) but I think IR has 2.4 V forward voltage...

 

[lazerov]

Correct me if I'm wrong (and I probably am) but I think IR has 2.4 V forward voltage...

The 500mW, 9mm, IR laser diode used in DX100 and "DX200" green modules has a voltage drop of 1,916V at 570mA. I can measure 250mW one (from another module) this Saturday.

 

[Eudaimonium]

The 500mW, 9mm, IR laser diode used in DX100 and "DX200" green modules has a voltage drop of 1,916V at 570mA. I can measure 250mW one (from another module) this Saturday.

I 'accidentaly' came in posession of 9mm diodes of a power of 1W .
Current is about 1 to 1.4 A max. What would it's voltage drop be?
It's kinda important...

 

[laserdudephil]

I'm not sure if you're busting chops or not so I'll answer. Power(watts)=Potential difference(volts) * Current(amperes). So for an input power of 1W, 1W/1.4A=0.71V. If you're talking about 1W of photons, you first need to determine the lasing efficiency (say 10% for example) and divide the output power by it (1W/0.1=10W in) your votage would then be 10W/1.4A=7.1V

 

[lazerov]

I'm not sure if you're busting chops or not so I'll answer. Power(watts)=Potential difference(volts) * Current(amperes). So for an input power of 1W, 1W/1.4A=0.71V. If you're talking about 1W of photons, you first need to determine the lasing efficiency (say 10% for example) and divide the output power by it (1W/0.1=10W in) your votage would then be 10W/1.4A=7.1V

I already answered his question with a PM (as this thread was about something else).
Your method will work but you need to know the exact efficiency of the diode at the needed current. It's much easier to just measure the diode voltage drop at that current.

 

[Eudaimonium]

I already answered his question with a PM (as this thread was about something else).
Your method will work but you need to know the exact efficiency of the diode at the needed current. It's much easier to just measure the diode voltage drop at that current.

Precisely, thank you for that,
Lasing efficency of a common 808 IR diodes are about 45 %.

 

[laserdudephil]

Pictures are uploaded at Imageshack and work perfectly fine for me.

The 7135, of course. You cannot control the current at all. And those 350mA are not that fixed, according to datasheet (variation from 340 to 380mA)

I didn't make the driver myself. It's from a 50mW greenie. But I have the schematic of the driver in DX modules. As I said only component values are different.

There's something very wrong with this picture (schematic.) If you're not providing more than 4.3V then that 4.3V zener in the reference divider is not regulating. What that means in plain english is that the laserdiode power varies with battery voltage and that's no longer a constant current regulator. You should use this circuit with a minimum of 6V (2 x 3.0V Lith. cells)