LM317 Driver question

[anselm]

So you think that I should use 2x 18650 batteries.

Hey, 3 will do fine as well, I suppose you'll have a longer runtime in that case.

I'm employing a variant of the DDL driver, using one lm317, some resistors and two
capacitors (not really needed anyway).
At the moment, I'm running it @250ma, 850ma, 1500-1800ma eek.
But I'll rewire it to get more and more useful modes.

 

[itsmei]

Yes, I will probably run it with 3x 18650 batteries for extra life. I will be running it at 1500mA to give me 1500mw

 

[Cyparagon]

Hey, 3 will do fine as well, I suppose you'll have a longer runtime in that case.

Nope. The chip will just drop the extra voltage as heat.

 

[anselm]

Yeah but shouldn't it take a longer time before the batteries total voltage is run down
so far that the diode doesn't lase anymore?
Of course, they might be a BIT over-discharged at this point. :thinking:
Lets assume driver+diode need ~7V to run:
7V /2 = 3.5 V each.
7V /3 = ~2 V each.

 

[midias]

Yes, I will probably run it with 3x 18650 batteries for extra life. I will be running it at 1500mA to give me 1500mw

I think you will get extra life for this driver you need about 2.5V over the Fwd voltage of the diode

The A130 pulls 1300mW -- 1530mA @ 4.99V so you need about 7.5 volts while the A140 pulls 1500mW -- 1570mA @ 4.45V so yea 7 volts I think you will get longer time out of 3 batteries at full power as you start to get below 2.5V+fwdV you start to loose current.

They recommend +3v here http://www.rog8811.com/laserdriver.htm

 

[itsmei]

So you think I will be better off with 2x 18650 battery to give me 7.4v?