Welcome to Laser Pointer Forums - discuss green laser pointers, blue laser pointers, and all types of lasers

LPF Donation via Stripe | LPF Donation - Other Methods

Links below open in new window

ArcticMyst Security by Avery

Question- Simple circuit to test diode

Joined
Oct 9, 2010
Messages
66
Points
0
Hey all,

I was wondering if I use the information provided in the datasheet below for a 250mW laser diode, if I could just create a simple circuit insuring that the voltage and current was appropriate, just to test it out...

(Simple circuit includes 4x AA batteries in series with - + leads, 2x 51ohm resistors in parallel to = 25.5ohms total resistance, 1x 250mW diode)

This configuration should give the laser diode an estimated 2.685V, 130mA. What I don't understand though is that 2.685V x 0.130A = 0.349W

Can someone chime in and make corrections where needed?

Also can someone explain what threshold current is, and all those other little symbols and stuff?

datasheet.png
 
Last edited:





Joined
Oct 9, 2010
Messages
66
Points
0
Okay, so I looked up threshold current, and it's what I thought it was; minimum current, basically.

What I'm confused about, is why the Operating current AND operating voltage = 325mW
 

Toke

0
Joined
Jul 25, 2010
Messages
1,099
Points
0
Laser diodes are rated by output power, as efficiency vary (50-20%) the input power will be significantly higher.

(I have not checked your calculations, but the 6V from your batteries should be distributed between resistors and diode.)
 
Last edited:
Joined
Oct 9, 2010
Messages
66
Points
0
I see, thanks that helps.

So as far as testing the diode safely, this simple circuit should work?

Laser diodes are rated by output power, as efficiency vary 50-20% the input power will be significantly higher.
 
Joined
Oct 9, 2010
Messages
66
Points
0
As you can see the resistor should be about 27 ohms for 2.5V and .130A for the laser diode.



IMG_20101025_231844.jpg
 

Toke

0
Joined
Jul 25, 2010
Messages
1,099
Points
0
It looks workable to me, at least for testing.

Your two 1/4W resistors should be able to handle the effect, the diode will get hot, so you better put it in a heatsink or just run it for a sek at a time.

The diode voltage drop is not completely static, but rises a bit with current and drop with temperature. Guess you know that as you are calling this a test setup. :)
 




Top