First Burning Laser/Lm317T Driver Issues

Didactic Discord · Jan 27, 2014

Hi everyone! After having some odd problems with my PHR-805T laser diode and Styropyro's 3$ laser driver build, I thought I would ask for some help (I need it badly DX). I began by using 8 AAs, using the positive wire to go to a switch. I then attached a positive to the other side of the switch, and attached that to the Vin on the 317. I then decided I wanted 125mA going to my diode, so I attached a 10 ohm resistor across the Vout and Adj pins. After that, I attached a positive wire to the positive pin on the diode. The negative pin and negative wire from the 8 AAs were then connected. Instead of getting 125mA, I got only 47. I tried using lower value resistors, but the current didn't change. So, now I would like to use a different laser diode with an LM317T driver, but I do not know how to get started. Please teach me o masters of the art of circuitry! I would like to know which diode I should use for my first burning laser, and how to build this gosh darn driver. Thanks!

ARG · Jan 27, 2014

Those 8 AA's, are they in parallel or series? Just checking

Also just to check, do you have your Vout in the right place?

A picture of the driver may help troubleshooting as well

Didactic Discord · Jan 27, 2014

ARG said:
Those 8 AA's, are they in parallel or series? Just checking

Also just to check, do you have your Vout in the right place?

A picture of the driver may help troubleshooting as well

Vout is the middle pin, right? I also think the AAs were in series.

Cyparagon · Jan 28, 2014

How are you measuring the current? What is the voltage across the set-resistor you've chosen?

Didactic Discord said:
I attached a positive wire to the positive pin on the diode.

From where? Vout or adj? you want it from adj.

ARG · Jan 28, 2014

Didactic Discord said:
Vout is the middle pin, right? I also think the AAs were in series.

Check the voltage output from the AA pack, just to make sure

Your Vout comes from the Adj pin.

As Cyp said, also check the voltage across the set resistor.

Didactic Discord · Jan 28, 2014

Cyparagon said:
How are you measuring the current? What is the voltage across the set-resistor you've chosen?

From where? Vout or adj? you want it from adj.

In the build I tried, I measured the current by inserting my Fluke multimeter in the circuit and used the 300mA setting. The current was 37-47mA. The voltage coming out of the 8 AAs was about 12.5V. The voltage going across the 10 ohm resistor was .35V.

Is it possible the PHR-805T was a little fried, and that's why it was drawing very little current?

I'm thinking I want to use a blue laser diode, but have no idea which one would work best with the LM317T driver. Does anyone have any suggestions?

Cyparagon · Jan 28, 2014

What is the voltage from adj to ground, and what is the voltage from Vin to ground?

Didactic Discord · Jan 28, 2014

Honestly, I can't remember a lot of those details. Also, the PHR-805T diode is broken. I want to start over, but with a completely different diode. I'm a little ambitious, so I want to build a blue laser that produces about 200-500mW. I still want to try to use the LM317T, but with a variable resistor (about 100 ohm pot) and a 1 ohm resistor. I don't want to use capacitors or anything like that. So, what if I attached a + wire to Vin, the 100 ohm pot to Vout and Adj, attach a 1 ohm resistor to the remaining pin on the pot, then used a + wire to go to the blue laser diode and finished the connection between the 8 AAs and the diode? Should I use an Osram blue laser diode? A Casio m140? If not, which one should I use with this driver?

Cyparagon · Jan 29, 2014

So your new stance is "f

ck it, let's try something bigger and harder and change all of the variables" instead of getting the easy thing to work first?

CheeseHasLeafs · Jan 30, 2014

I do have a question: why are you so set on using AAs? There are better options out there, that are more economical on space, too.

Didactic Discord · Jan 30, 2014

AAs can deliver more mAh than 9V batteries. I'm willing to use more space if it means more current.

CheeseHasLeafs · Jan 30, 2014

I wasn't really thinking about 9 volts. Don't get me wrong, I'm no expert (far from it) but I figure that if the majority of the laser community is using Li-ions those would be a better choice, wouldn't they?

BShanahan14rulz · Jan 30, 2014

Alkalines are easier to come by, safer, cheaper in the short run, safer, I don't see anything wrong with AA alkies.

Didactic Discord · Jan 30, 2014

CheeseHasLeafs said:
I wasn't really thinking about 9 volts. Don't get me wrong, I'm no expert (far from it) but I figure that if the majority of the laser community is using Li-ions those would be a better choice, wouldn't they?

I don't know, I'm just using what I have. Perhaps someone can explain what's so special about these other batteries?

CheeseHasLeafs · Jan 31, 2014

Well nothing against AAs. It just seems a PITA to me, that's all. I have an RC helicopter and the main reason I don't fly it often is because the controller uses something like 8 AAs (actually thinking of hooking that up to a 12v like you find in lamps).

CheeseHasLeafs · Jan 31, 2014

hah thanks. Good luck with that PL450. If I ever build a 450nm laser I'd go for that diode (nice and single mode).

First Burning Laser/Lm317T Driver Issues

Didactic Discord

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ARG

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Cyparagon

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ARG

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CheeseHasLeafs

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Didactic Discord

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