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DIY Homemade laser diode driver

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ElektroFreak

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This forum's got a LOT of good info in it.. all you've got to do to get the answers to nearly any question you have is to look around the stickies and use the search function. Then if you still have questions, post 'em!
 





nikola tesla

nikola tesla

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still I need to ask about this guide:
Is it only about controlling current? I mean as far as I got it this circuit keeps the voltage constant and lets you control the current. Do I only need to control current in order to control the laser power output? doesnt the voltage affect this too?
 
Spyro

Spyro

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hm, i dont know how should i connect 2 2ohm rezistors in parallel. Could you PM me a painted photo? pretty please :3

*EDIT* - so if i would put 2 10 ohm rezistors like this
...........+
|| ||
''''''''''''''''''-
i would get like a 5ohm rezistor?
and how much R rezistors i should use?
 
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ElektroFreak

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nikola tesla said:
still I need to ask about this guide:
Is it only about controlling current? I mean as far as I got it this circuit keeps the voltage constant and lets you control the current. Do I only need to control current in order to control the laser power output? doesnt the voltage affect this too?
Click to expand...


This circuit configuration is current limiting. The basic circuit was NOT developed by Daedal here, in fact it can be found at the bottom of pg. 19 here in the device datasheet: http://www.ti.com/lit/ds/symlink/lm117.pdf

This configuration limits current, the laser diode sets it's own voltage by acting like a zener diode. Laser diodes are current driven devices, so I is the main parameter that concerns us.
 
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ElektroFreak

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Spyro said:
hm, i dont know how should i connect 2 2ohm rezistors in parallel. Could you PM me a painted photo? pretty please :3

*EDIT* - so if i would put 2 10 ohm rezistors like this
...........+
|| ||
''''''''''''''''''-
i would get like a 5ohm rezistor?
Click to expand...

That's correct!
 
Spyro

Spyro

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so i have now a LM317T driver here and 2 10 ohm rezistors! Need a pot a cap and a diode :)
 
Spyro

Spyro

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I found some potentiometers but i can't see anything about ohm.... only how much W, R and K...
 
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nikola tesla

nikola tesla

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So with the driver from this guide I can basically use any diode and an energysource with any voltage?
 
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ElektroFreak

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Any input voltage up to 40V IIRC, BUT the bigger the difference between the input and output voltage the hotter the LM317 will run.
 
nikola tesla

nikola tesla

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ok so the closer I stick to the voltage the diode needs the more efficient the whole circuit will be?
thanks for your responses you helped me a lot
 
Spyro

Spyro

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just build one, i actually bought 2 2ohm rezistors but they were 3.8 ohm XD what a luck :D
works preety well with my led'ed lazor diodes and my leds :)
 
nikola tesla

nikola tesla

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So when I want to build one that never exceeds the diodes max in ampere how can I calculate how much ohm the resistors and poti has to have?
 
Spyro

Spyro

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nikola tesla said:
So when I want to build one that never exceeds the diodes max in ampere how can I calculate how much ohm the resistors and poti has to have?
Click to expand...

Pot has to have about 100 ohm, your for your rezistor is quite difficult. Divide 1250 with how many amps you need. Example : i need 125mA so 1250:125=10 ohm rezistor.
 
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