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DIY Homemade laser diode driver

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Bluefan

Bluefan

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A LED makes a nice test load, it has practiaclly the same diode behaviour, just using a led should work just fine.

A few remarks when using an LED: They usually go up to 20mA max, which is usually too low for LD, and you wouldn't want to blow up your LED in testing. Also, LED's usually have a higher voltage drop than the average LD, they're usually more like a blu-ray diode in voltage drop. Take care that your driver can give a high enough voltage to reach the set current.
 





B

Beeko

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So, what is the entire parts list for Daedal's driver? Is this right?

- 1x LM317T
- 1x 47uF capacitor
- 1x 25ohm Pot.
- 1x 1N4001 Diode
- 2x 10ohm Resistors
I have everything but I really would like to know what kind of resistor to buy, the 10ohm 1/4 watt or 1 watt
 
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harryd

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thanks for all the useful information but i have a question. i have a red laser diode and i want to do an experiment at different output power. can i just use this circuit and change the pot to change the output power.


NOTE: i want the laser max output < 5mw and change it in that range.

NOTE 2: what values should i check in the datasheet to make sure i dont burn it or anything ?
 
lasersbee

lasersbee

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The Max allowable current for your specific LD is the most important Value....
followed closely behind by the Max voltage...
A Laser Diode is a Current device... Similar to an LED.. but not
the same..:cool:

Jerry
 
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lasersbee

lasersbee

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Bluefan said:
A LED makes a nice test load, it has practiaclly the same diode behaviour, just using a led should work just fine.

A few remarks when using an LED: They usually go up to 20mA max, which is usually too low for LD, and you wouldn't want to blow up your LED in testing. Also, LED's usually have a higher voltage drop than the average LD, they're usually more like a blu-ray diode in voltage drop. Take care that your driver can give a high enough voltage to reach the set current.
Click to expand...

wtf.gif
Where are you pulling these nuggets of wisdom from....:thinking:

You should not use an standard LED as a test load unless you want
your LD to DIE...:cryyy:
An LED does not have the same characteristics as a Laser Diode...
And if I want to adjust my Driver to (let's say) 200mA... a standard
LED will blow way before that current is reached...


@ harryd....

!!! USE A TEST LOAD !!!

There are circuits for Tests Loads all over the Forum...:cool:

[EDIT]

yes... but always verify/test your circuit values with a Test Load
and not your LD... Components have tolerances and mistakes
can be made...

harryd said:
and the resistance = 1.25/ max current value right ?
Click to expand...


Jerry
 
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lasersbee

lasersbee

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No ofence intended... but you are new here and you will
never learn how to find info on the Forum if we spoon feed
it to you...
This would be the perfect opportunity for you to do a some
research using our famous [Search] Button....

BTW... if you have trouble finding 1 Ohm 1/2 Watt resistors...
have a look in my Sig...:cool:


Jerry
 
Bluefan

Bluefan

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lasersbee said:
wtf.gif
Where are you pulling these nuggets of wisdom from....:thinking:
Click to expand...

Jerry,

The glorified test load around here is just a bunch of diodes, and now a small change in diode (one that emits light) suddenly doesn't work? An LED is closer to an LD than a diode in voltage drop and the fact that it emits light, that's why we use more than 1 normal diode to come close to an LD. I think in behaviour an LED isn't different from a normal diode or from a laser diode, that is an exponential relation between current and voltage.

But, as I said in the same post, the max current is different for each. Normal diodes usually go to 1A, LED's to 20mA and laser diodes for a few 10's of mA to several amps. Which of course only makes LED's usefull for LD's below 20mA, which is why we usually construct our test loads.
 
lasersbee

lasersbee

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Bluefan said:
Jerry,

The glorified test load around here is just a bunch of diodes, and now a small change in diode (one that emits light) suddenly doesn't work? An LED is closer to an LD than a diode in voltage drop and the fact that it emits light, that's why we use more than 1 normal diode to come close to an LD. I think in behaviour an LED isn't different from a normal diode or from a laser diode, that is an exponential relation between current and voltage.

But, as I said in the same post, the max current is different for each. Normal diodes usually go to 1A, LED's to 20mA and laser diodes for a few 10's of mA to several amps. Which of course only makes LED's usefull for LD's below 20mA, which is why we usually construct our test loads.
Click to expand...

Isn't that basically what I posted... :thinking:
Standard 20mA LEDs should not be used as Test Loads because they can't handle the currents that a 1000mA rectifier diode can...
And I don't see too many members using Laser Diode Drivers set at
under 20mA (in case they blow the LED)...

BTW.... the Test Load is not Glorified... it is a proven method to safely
adjust the current of one's Laser Diode Driver to avoid blowing one's Laser Diodes....:cool:

Jerry
 
Bluefan

Bluefan

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Then we agree :) And of course I put in a bit of sarcasm, the Test Load is indeed a good proven method.
 
GreenLaser

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hey guys will my diode driver work if i use a 1n4004 diode a 200 ohm pot and a 10ohm resistor instead of a 4ohm???
cheers
 
HIMNL9

HIMNL9

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GreenLaser said:
hey guys will my diode driver work if i use a 1n4004 diode a 200 ohm pot and a 10ohm resistor instead of a 4ohm???
cheers
Click to expand...

Sorry, what exactly do you mean ?

Driver schematic diagram ?

Type of driver ?

:thinking: :confused:
 
GreenLaser

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this ddl driver in stead of 100 ogm pot can i use 200ohm pot instead of 4 ohm resistor can i use 10ohm resistor and instead od 1n4001 can i use a 1n4004.
and i have a pack of blue 5 band resistors how do i find out if they are 0.25% 0.5% 1% 2% so then i could find out the ohm value.
cheers
 
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