Need help with driver!!

[ossumguywill]

I made a driver with an LM317. It's the one you find all over the internet. I am using a test load "diode" with 4 1N4001 and a 1 ohm resistor. So, when I power it with 5 volts from a PSU, it puts out a max of 3.17 volts (right within spec) but only 45mA/mV over the resistor! WTF? the same happens when I power it at 12 volts, when I turn the pot so that it's putting right under max into the diode, I only get around 50mV over the 1 ohm resistor, but then when I get it right up to 3.4 volts (a bit over spec) on the diode, there are like 250mA. I mean I guess that makes sense electronically, but then how the F am I supposed to get enough voltage in the diode without burning it out? Can someone help me, am I doing it wrong? BTW my diode is a $10 red rohm from lasersurplus parts. I'm probably just being an idiot... I really have no idea what to do, what voltage should I get around the test load, and what voltage should I get over the resistor? Any help?

 

[Eudaimonium]

I believe you mistaken the polarity of your LM317 regulator chip. The right pin of it goes ti POSITIVE (+) of the power source.

In any case, you should calculate the resistance between the OUT and ADJ pins, and instead of a potenciometer, have a fixed resistance. If you want 200mA (good for short closed can diodes) you use 6 ohms. If you have long (open or closed) diode, you should use 3 ohm, which should give you 400 mA which is perfect for these diodes.
If you want something else, the formula is :
Current on diode = (1.25) / (resistance between out and adj)

1.25 is commonly refered to as Vref, reference voltage of the 317 regulator chip.

 

[lasersbee]

I made a driver with an LM317. It's the one you find all over the internet

There are quite a few different LM317 circuits on the internet...

An exact schematic or closeup photos of your actual circuit would make
trouble shooting a lot easier for the members....
You may have made a mistake in connecting the circuit...


Jerry

 

[HIMNL9]

Also

..... I power it with 5 volts from a PSU .....

Too few Vin, imho ..... try with 9V input, at least, just for see if the problem is this one.

BTW, as lasersbee said, schematic AND values helps a lot in figuring out what can be the problem

 

[billg519]

Yes, 5V might be a little low. I have tested reds with linear drivers using a variable voltage bench supply, and below 6V, proper operation is not guaranteed. Not enough voltage overhead for the regulator. The only voltage you need to be concerned with is the reading across the 1 ohm resistor in the test load. 1mV = 1 mA, so if you want 250mA for your rohm LD, you should read 250mV across the 1 ohm resistor. A current regulator will only allow it's load to receive enough voltage for the set current to be drawn by the load. Ensure that you have in fact built the LM317 Current Regulator, or DDL Driver as it's also known. For 250mA you are using a 5 ohm resistor between the output and adjust pins?

 

[ossumguywill]

Hey guys, I have decided I might just go with one of these, the $5 driver from laser surplus parts. And why is it bleeped out?:
http://www.*****************.com/index.php?main_page=product_info&cPath=3&products_id=78
It says they put out a max of 2.5v, that seems a bit low for a red driver.
Are they any good? In the mean time I will work on my driver.

 

[Eudaimonium]

Sorry but the link does not work.
Anyway, not all drivers are step down linear converters.
There are also a type of circuits that are called Boost converters, which does not have Vdrop at all, they can power a 5 V bluray diode off 3 V battery. They use extra current from the battery and 'transform' it to voltage.
If you want more info, punch in DC DC converter in wiki.
Most popular boost converter laser diode driver here is FlexDrive.

 

[HIMNL9]

I think this site hates the laser surplus parts links

(probably that name is in the list of the forbidden words)

Anyway, is this one

 

[Eudaimonium]

I prefer DealExtremes AMC7135 which gives 350mA, nice longlife current for LCC/LOC.
No pots, no trimming, no fuss, you can jump the diode, or not. That gives 0.1 or 0.8 Vdrop respecively, That respectively makes it perfect for 3V (2x AA(A) ) or 1x li ion 3.7 V.
Price is 16$ for 20pcs. Less than a dollar a piece, free shipping. What more can you ask for?

 

[ossumguywill]

I prefer DealExtremes AMC7135 which gives 350mA, nice longlife current for LCC/LOC.
No pots, no trimming, no fuss, you can jump the diode, or not. That gives 0.1 or 0.8 Vdrop respecively, That respectively makes it perfect for 3V (2x AA(A) ) or 1x li ion 3.7 V.
Price is 16$ for 20pcs. Less than a dollar a piece, free shipping. What more can you ask for?

cool, I'll keep it in mind.

 

[lasersbee]

I still have not seen any schematics... drawings or Photos of your circuit...
Have you tried it with 8 to 12 volts....

The Drivers on the link are O-Like drivers...

http://www.o-like.com/b2b_cpinfo.asp?id=987


Jerry

 

[ossumguywill]

I still have not seen any schematics... drawings or Photos of your circuit...
Have you tried it with 8 to 12 volts....

The Drivers on the link are O-Like drivers...

2pcs CC power supply driver£*>Laser Accessories£*>Laser&lighting products£*>www.0-like.com


Jerry

sorry for no pictures, I will upload right now, but I have actually just gone with the circuit I had and put it on a perfboard, I just gave it a 10 ohm resistor so it puts out exactly 3.2V and 135mA over the resistor when juiced at 12V (the idea behind this is longevity, not power, so ~100mW should work)

The driver is on one of those boards where everything except + and - are in groups of 3. It appears to operate stably and not get too hot when I attach a heatsink to the LM317. also included is the schematic I used. one of these shows the pin functions and stuff.

 

[lasersbee]

What are the color bands of your resistor...

Are you now saying that your circuit works for you
with 12 volts on the input...:thinking:

Jerry

 

[ossumguywill]

more pics, with some wiring

What are the color bands of your resistor...

Are you now saying that your circuit works for you
with 12 volts on the input...:thinking:

Jerry

brown black black gold

And with 12V it is very hard to get right is what I said, I have a feeling 9v would work better but my bench supply only does 5V to 12V, nothing in between. Although maybe the purple wire is negative 5.... I can try that later, but right now I think this will avoid instantly killing my diode.

 

[kiyoukan]

if you are using a pc psu the white wire is neg 5 volts and the orange is + 3.3 volts. that will give you 8.8volts check with volt meter.

 

[lasersbee]

more pics, with some wiring



brown black black gold

And with 12V it is very hard to get right is what I said, I have a feeling 9v would work better but my bench supply only does 5V to 12V, nothing in between. Although maybe the purple wire is negative 5.... I can try that later, but right now I think this will avoid instantly killing my diode.

I hope you are using a Test Load and NOT you Laser Diode for testing...:thinking:

Jerry
(4500-115-9595)