Running a 445nm diode at 30mW

• Apr 2, 2011

• #1

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Grunff

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Hi all,

If I want to run a 445nm diode at a tiny 30mW, is there any need for a driver, or can I just use a current limiting resistor?

 

• Apr 2, 2011

• #2

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anselm

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If you want a stable 30mW, you will need a driver anyway.
Just using a limiting resistor your output starts at some value and continously
decreases from there as the batteries discharge.

 

• Apr 2, 2011

• #3

G

Grunff

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anselm said:

If you want a stable 30mW, you will need a driver anyway.
Just using a limiting resistor your output starts at some value and continously
decreases from there as the batteries discharge.

Click to expand...

Thanks - good point about the battery voltage dropping.

 

• Apr 2, 2011

• #4

chipdouglas

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you especially need adriver. if you direct drive it you get the batteries full power.

also i believe if you want 30 mw you need to set your driver around like 200ma. but search for that first, or if you have a laser power meter even better.,

michael

 

• Apr 3, 2011

• #5

Plan B

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I'm sure I read somewhere that the threshold for these diodes was around 220ma and would start to lase at about 10 mW. At these levels it was reported that they were VERY unstable.

 

• Apr 3, 2011

• #6

chipdouglas

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i think they are stable, albeit a high current and a low mw ratio. but i believe i have read that under 50mw these diodes are single mode which means you will get a better beam.

i have no experience with it at this low power though.

michael.

 

• Apr 3, 2011

• #7

Prototype

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Get one of the eBay ItemQuickShip 405nm pens for $8. Their drivers work and are 200mA max. There's a thread about low powered blue pens somewhere that talks about it a bit more, and has a pic of someone who made one in this way.


Edit: Found the thread: http://laserpointerforums.com/f65/cheap-aaa-powered-20-30mw-blue-pen-60753.html

 

Last edited: Apr 3, 2011

• Apr 4, 2011

• #8

LarryDFW

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Grunff said:

Hi all,

If I want to run a 445nm diode at a tiny 30mW, is there any need for a driver, or can I just use a current limiting resistor?

Click to expand...

A resistor will work fine with a #18650 battery.

You will have to test it to get the proper value of resistance.

LarryDFW