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Making a driver - help is needed

SeNNHeISeR

SeNNHeISeR

0
Joined
Oct 21, 2008
Messages
100
Points
18
Hello to all.Firstable i've read alot of topics for a driver but still i have to make this one.
I've found this It can be done - Laser driver
I went out buying parts and realized that i couldn't find the exact same ones.
i got:
1n4002 diode
11ohm resistor
LM317T chip
10mfd 16v capacitator
9v battery snap
9v battery
bare PCB for beginners

My qusetion is are those parts suitable for this driver(will they work).And i couldn't find a potentiometer, someone said something about fixed resistor so i'd like some help.Also i forgot to mention that i wanna build driver for a phr-803 diode
 





like i said i will be driving a blu-ray diode in the site which i posted says that i need one resistor 10ohm but i have an 11ohm thats ok.BUt i ask about an fixed resistor and how to calculate its resistance.because i couldn't found any 100ohm ones , but i dont'wanna mess with 100k ohm pots.
 
SeNNHeISeR said:
like i said i will be driving a blu-ray diode in the site which i posted says that i need one resistor 10ohm but i have an 11ohm thats ok.BUt i ask about an fixed resistor and how to calculate its resistance.because i couldn't found any 100ohm ones , but i dont'wanna mess with 100k ohm pots.
Click to expand...

The pot serves a purpose. You dont know how to calculate the resistance because diodes are all different. Even the same make and models will vary. This is the reason for the pot, to slowly turn it up untill the diode lases. By circumventing the pot you basically just defeat most of the purpose of a dirver circuit in the first place...
 
Actually, I am strongly discouraging a potentiometer use in DDL driver.

There is no point setting a pot with 6 ohm in series (Jerry?! :S ).
You will end up with 200 mA when pot is lowest, that is too low for red diode and too much for PHR diode.
So what is the point in that? Only complicated driver design.

OP, you need three components, LM317, capacitor (any in uF range will do, by any means) and a resistor that you need to use between OUT and ADJ pins to regulate the current.
11 ohm is perfect for PHR diode, it will provide around 110mA , which is very good current for these diodes.

So yes, it will work :D
 
To choose your resistor, just divide 1.25V/(desired current) for this circuit.
 
Good catch... Eud...

I just quickly went by this drawing on the Link supplied by the OP
for the Senkat Reds... (my mistake...:yabbem:)...

LM317%20components01.jpg


BTW... take the output to the LD from the Adjust pin (like shown on the
drawings) and not the Output pin of the LM317 or it will be a Voltage Driver
and not a Current Driver...


Jerry
 
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Flaminpyro said:
can you explain why 1.25 volts is used for this calculation :thinking:
:thanks:
Click to expand...
You serious or...?

Vref, Reference voltage is between OUT and ADJ, used to 'measure' the resistance, therefore to set the current.

Why is it 1.25, who knows, it was designed that way.
It just is.

And also, for OP, 10-12 ohms is good for PHR, lower resistance is higher current.
 
Just be sure to use a test load before you hook it all up. And remember after you have tested it short the cap THEN hook up the LD before you supply the juice to the driver ;).

Eudaman Eudaimonium :D
 
OK I'll restate my question, I know what the forumila dose, what I want to know is why is 1.25 volts used, why not 1.35672 volts ?


Eudaimonium said:
You serious or...?

Vref, Reference voltage is between OUT and ADJ, used to 'measure' the resistance, therefore to set the current.

Why is it 1.25, who knows, it was designed that way.
It just is.

And also, for OP, 10-12 ohms is good for PHR, lower resistance is higher current.
Click to expand...
 
KiLLrB said:
Just be sure to use a test load before you hook it all up. And remember after you have tested it short the cap THEN hook up the LD before you supply the juice to the driver ;).

Eudaman Eudaimonium :D
Click to expand...

Hey thanks dude :D Good one ALSO, everyone, if you think you will forget to short out the capacitor , changing the diodes often on one driver and all:

Solder one ~470 ohm resistor in parralel with output capacitor, it will serve as a cap bleeder, it will discharge the capacitor without affecting the operation of the driver.
 
now i ednded up using two 11ohm resistors one in place of the 10ohm in the schematic and one to replace the pot.everything else is wired up like on the drawing wich laserbee posted
now the question is "to solder or not to solder?" :) :D
 
Eudaimonium said:
You serious or...?

Oh I don't know, maybe because it says so in the datasheet? :D:wave
Click to expand...

Hey Eudaimonium,

There is no need to be a Smart A$$ answering question to a well
known member that has been on the Forum for a while...:tsk:

Just because you read Data Sheets does not mean that all other
members do or can...
A little respect goes a long way in our community.... IMO

@ SeNNHeISeR.... Soldeing connections is always the way to go
with Laser Diode circuits... especially the very sensitive Blu-Ray types..
As was posted above (1.25V /22 Ohms) will give you aporox. 59mA
of current from your driver... Be sure to test your driver with a Dummy
Test Load..


Jerry
 
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