Advice on the LM1117?

[Djakkennaia]

So for my second laser build, I am going to build a 300mW red laser, using the LPC-815 diode. I want to mod it into an old LED flashlight that is powered by 3 AA batteries, and regulated by an LM317 current driver. The problem is, The voltage drop on the LM317 is ~3v, and the voltage drop on the LPC-815 is ~3v, meaning that I need >6v of energy from the batteries. AAs only output 1.5v each, or 4.5v for the 3 of them. I see two solutions to this problem.
1: Buy a set of 14500 AA size batteries and a charger, which would be costlier than I want this laser to be, or
2: I have heard of a 'low-dropout' LM1117 regulator said to have a dropout of ~1.2v. This would be my choice, except for that I do not have any idea about the LM1117. Can it even be used in the same application as the LM317? And if so, what is the reference voltage on this one, so that I don't 'blow' the diode? thanks in advance!

 

[benmwv]

Lm1117 basically does the exact same thing as a 317 with a lower dropout. Ref voltage is the same.

Here is a lm1117 board I made for SOC red pen build set at 380ma with 3 parallel 10 ohm resistors:

There is a 22uf smd cap under the smd diode case you were wondering why you can't see a cap. Most people say use an input cap with lm1117 but I didn't mostly cause I didn't mave any room and on the datasheet it says you only need it if it is more than 3 inches (I think it was 3) from the batts.

 

[jib77]

Same as LM317 ***EXCEPT*** because it is a low drop out type of regulator it needs input and output caps for stability ... 10uF ceramics to be exact, do not use electrolytics as they have high ESR and will make the driver unstable. If you want a ready made LM1117 driver check the link in my sig, I have a version for LPCs (379mA). They work with 2x Li-Ion.

 

[Djakkennaia]

@benmwv
Is it just me, or that a small LM1117? or are the LM1117s smaller than the LM317s? and is that veroboard that you built the driver on?

 

[benmwv]

Yeah it is a pretty small lm1117. I believe lm1117 and lm317 come in all the same package types. I haven't looked up the specs on this package as I just found it in a drive I was harvesting but I'm sure it's not rated for as much output as the bigger ones on jibs drivers.

I'm not sure exactly which veroboard is but this is the one with a circle around each hole not the "rails".

Jib really is the master on all things lm1117, but just in my experience this driver seems to work fine (at least for my purposes) with no input cap.

 

[Juniortore1]

PLEASE HELP

Hey, I have a few linear drivers (2x Groove2 lava drive) and one rckstr (<<spelling?) I have had terrible luck with heatsinking these little F*****'s neatly inside an aixiz module and inside the pill.

Is it okay to run either of these drivers for minutes at 350ma with no heatsinking? If yes, my life would be a lot easier and I can finish this SOC red build that has been sitting in front of me for the last month.

If I can sell this SOC build, I will use flex/ boost drives for anything over 200ma due to linear heating.

I may get a few of those jib drivers sometime just because they look cool anyhow

 

[Djakkennaia]

@benmwv
Veroboard is also known as stripboard. Stripboard is the one with the 'rails' running along it, similar to breadboard.

@Juniortore1
If you REALLY wanted to, you could throw a 2 Amp board into a Aixiz, and it work flawlessly, as long as you use a VERY short duty cycle. I run my first laser, the PHR803T, at 200mA, and it never really gets that hot, especially since I only run it for about 15 seconds at a time. I'm still waiting on the parts for the laser I am building right now, but I feel that the 350mA driver won't cause any problems as long as you keep in mind to shut it off every now and then.