LM317 driver help! I am a noob!

[jsteg1981]

Brief update to my findings today.

LD is healthy and burning. I used a 9V battery and 5 ohms of resistance.

I ended up with 3.8V and 230ma for a whopping 874mW. It did slowly burn electrical tape. I ran it for about a minute. Nothing got very hot (ie the driver and LD well the housing at least).

Now if I did purchase a premade driver, which one would you recommend for 1.5W while using three 10440s? I ask because someone has recommended against the LM317 driver I am using...

 

[Cyparagon]

I ended up with 3.8V and 230ma for a whopping 874mW.

You're confusing input power with output power. You've calculated input power - we rate lasers by their output power, and I think you'll be getting less than 100mW at that current.

 

[jsteg1981]

Haha yeah. I figured that one out earlier on a different thread. I found a graph that is supposedly an estimate that compares the amperage to the estimated wattage output. Based on that graph you are correct. It is aproximately 100mW which would explain the extremely slow burn.

I greatly appreciate all you guys' help. Someone also suggested using only two 10440s and getting a AAA spacer so that I do not have to dissipate so much heat.

Also, at what amperage should I move away from the LM317 as the driver?

 

[jsteg1981]

Ok here is an update on my laser.

I have made a driver circuit with the LM317, two 2.2 ohm 2W resistors and a 16V 10uF capacitor. I have soldered all that on to a small circuit board. The resistors are parallel.

When the laser is first powered on, it is at 1.05A for about a half of a second then drops to about 300-350mA. After about 15 seconds, it jumps back up to about 600mA. It is also pulsing. You can only tell it is pulsing by quickly moving it around. As in it looks like the laser is jumping and not fluid lines.

Any ideas?

 

[Blord]

Did you heatsink the LM317 ? They get hot at 1A. The pulsing is a sign of overheating driver.

 

[jsteg1981]

Yes it has a heatsink. Should I rebuild the driver with a new LM317?

 

[jsteg1981]

Also what about the jump in current?

 

[Blord]

Picture of the setup would help. Now it is only guessing what is wrong.

 

[jsteg1981]

I forgot I removed the capacitor thinking it had something to do with the current jumping.

 

[darkmagic89]

View attachment 40553

I forgot I removed the capacitor thinking it had something to do with the current jumping.

That heatsink is too small (the one on the LM317) the LM317 can handle on its own only 0.25W of power but whit proper heatsink can go up high to 1.5A (heavy duty 3x3x4cm heatsink and overflow of air forced by a cooling fan).

When the laser is first powered on, it is at 1.05A for about a half of a second then drops to about 300-350mA. After about 15 seconds, it jumps back up to about 600mA. It is also pulsing. You can only tell it is pulsing by quickly moving it around. As in it looks like the laser is jumping and not fluid lines.

the LM317 IC has an internal shutdown sistem that is trigered when it reaches about 125,4°c then when the temperature less than 125,4°c it goes up again delivering full power until reaches again 125,4°c and shutoff and then over and over again, in the datasheet of the semiconductor you can find these usefull information that you can use at your advantage knowing the tipe of LM317

OPERATING TEMPERATURE RANGE
_________________________________
LM117 −55°C ≤ TJ ≤ +150°C
_________________________________
LM317A −40°C ≤ TJ ≤ +125°C
_________________________________
LM317-N 0°C ≤ TJ ≤ +125°C
_________________________________
Preconditioning
---------------
Thermal Limit Burn-In All Devices 100%
_________________________________

hope that this will help you


P.S.
@DTR since my first baby died for overheating diode( :banghead: my mistake since i forgot it on for about the entire night..now is a cheap chineese laser pointer) searching online for diodes i found this strange ebayer guy that sell's M140 for less than 100$ :drool: and has all 3489 feedback's positive so now, the next diode i will buy in the future is one of yours (waiting for payout from the boss) , the question is, since my option is a M140 diode in copper aixis module whith 3 element glass lenses, can i power the diode in the aixis module without a heatsink/host for couple of minutes at 330mA and 610mA whitout damaging the diode?
my second question is, the 3 element glass lens are coated for the 445nm or is a bare 3 element lens?

thank you very much and to all please excuse my very bad english

Alex

 

[Cyparagon]

the LM317 can handle on its own only 0.25W

It's true the heat sink is too small, but this figure of yours is wrong. According to the datasheet, thermal resistance from junction to air is 80C/W, and the max junction temp is 125C. Therefore it can handle at least 1W of dissipated power if the ambient air is less than 45C.

 

[darkmagic89]

It's true the heat sink is too small, but this figure of yours is wrong. According to the datasheet, thermal resistance from junction to air is 80C/W, and the max junction temp is 125C. Therefore it can handle at least 1W of dissipated power if the ambient air is less than 45C.

hi there Cyparagon,

maybe you are right, my idea was only pure logic seeyng the photo of the LM317,if you notice there is a treathed tube on the right, so i was thinking about the laser being mounted and that air inside the tube (spacing betwen laser diode module and heatsink of LM317) due to rapid incrementing temperature and irradiance heat of both module and heatsink and whitout air exchange inside the tube will rise untill all the exess heat not dissipated (because of saturation of air and laser module heatsink) will kill the diode after some litle time ...
so conclusion is of all of this logic thinking of myne is that if jsteg1981 maybe put's something thath can block the exess heat from the LM317 to the LD the laser wuoldnt have'd died,but this is only an idea.

please excuse my bad english hope you can understand :beer: