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Old 09-15-2007, 05:51 PM #1
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Default Circuit causing low wattage with GB LD?

Well, it's my first post after lurking here for a while, so why not start with a question?

Would there be a formula to calculate the wattage of the output of a LD by knowing the voltage and current?
Simple P=IV doesn't seem to work (or am I just doing the math wrong?).

I have a modified (ok, practically changed until it doesn't resemble) Daedal's circuit. Basically, I have a LM317, 10 ohm resistor and 2 silicon diodes in series connected to a cap and LD in parallel. I measure the voltage to be around 2.1, and the current at 200 mA. I can't burn a match, or else I haven't held it there long enough. When I short out one of the diodes with a wire, I get 2.3 V at 250 mA. Yeah, I put it at a really dangerous current, but the voltage seems really low. I can burn a match with the laser after a few seconds, but I'd rather have a long living LD since it's going to be my only one for a while.

So, is the low voltage affected my output? If so, how could I fix that? The circuit is still bare, so I can desolder and resolder some different components if needed.

Sorry, if this is a really stupid question, but I really don't know electronics well. I actually learned more about electronics messing around with the circuit than in my whole life. Anyway, thanks especially to Senkat who supplied this diode


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Old 09-15-2007, 06:26 PM #2
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Default Re: Circuit causing low wattage with GB LD?

Something doesn't add up. If you have a 10 ohm resistor as the sense resistor, then your maximum current should be 125mA. Can you draw a pic of how you have it assembled.

On the wattage question, you have to differentiate between electrical input and light output. There is a conversion loss in the LD. The only real way to know is to do actual measurements.

Quote:
Originally Posted by misoup
Well, it's my first post after lurking here for a while, so why not start with a question?

Would there be a formula to calculate the wattage of the output of a LD by knowing the voltage and current?
Simple P=IV doesn't seem to work (or am I just doing the math wrong?).

I have a modified (ok, practically changed until it doesn't resemble) Daedal's circuit. Basically, I have a LM317, 10 ohm resistor and 2 silicon diodes in series connected to a cap and LD in parallel. I measure the voltage to be around 2.1, and the current at 200 mA. I can't burn a match, or else I haven't held it there long enough. When I short out one of the diodes with a wire, I get 2.3 V at 250 mA. *Yeah, I put it at a really dangerous current, but the voltage seems really low. I can burn a match with the laser after a few seconds, but I'd rather have a long living LD since it's going to be my only one for a while.

So, is the low voltage affected my output? If so, how could I fix that? The circuit is still bare, so I can desolder and resolder some different components if needed.

Sorry, if this is a really stupid question, but I really don't know electronics well. I actually learned more about electronics messing around with the circuit than in my whole life. Anyway, thanks * especially to Senkat who supplied this diode
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Old 09-17-2007, 10:25 AM #3
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Default Re: Circuit causing low wattage with GB LD?

misoup, please check the driver thread.

Make sure you have the LM317 pins lined up right, and make sure the voltage to the diode is at a minimum of 2.8V, otherwise the diode just won't lase! It'll get hot and burn out before it's even gotten useful.

GL;
DDL
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