I just tested with 3 old 2000mAH NiMH AAs fully charged to 1.4 V gives me 4.2 V, less the forward Voltage drop of the GB LD I'm playing with which from 160-320mA is about 2.8 V leaves me a max of 1.4 V to drop with a resistor. 1.4 V/300 mA = 4.7 Ohm resistor. The batt voltage quickly drops to 3.72 V less the Voltage drop leaves 0.92 V/4.7 Ohms = 196mA.
In real life the current supplied is a bit lower because of the internal resistance of the batteries. But if someone is intent on sending a diode to an early grave, this would seem to work.
But I get MUCH better results when using a regulated current supply. With 6 V into my 4 component LM317 circuit I can burn everything in sight all day long. With the 3 NiMH and 4.7 Ohm resistor it works great for about 10 seconds, and then drops in power quite a bit. and I can't go any lower than 4.7 Ohms as the current spike on power up is around 370mA which I think would in short order kill the diode.
If you don't have a way to measure the spike on power up and you're intent on driving it this way I'd say start with a pot at around 20 Ohms with 3 fully charged NiMH AAAs and SLOWLY decrease the resistance WHILE measuring the current, when it gets to about 160mA stop and measure the resistance. Use the closest higher value resistor you can find/make.
Also note that your diode may have a VERY different Voltage drop and it needs to be measured. This example was just for my diode.
In real life the current supplied is a bit lower because of the internal resistance of the batteries. But if someone is intent on sending a diode to an early grave, this would seem to work.
But I get MUCH better results when using a regulated current supply. With 6 V into my 4 component LM317 circuit I can burn everything in sight all day long. With the 3 NiMH and 4.7 Ohm resistor it works great for about 10 seconds, and then drops in power quite a bit. and I can't go any lower than 4.7 Ohms as the current spike on power up is around 370mA which I think would in short order kill the diode.
If you don't have a way to measure the spike on power up and you're intent on driving it this way I'd say start with a pot at around 20 Ohms with 3 fully charged NiMH AAAs and SLOWLY decrease the resistance WHILE measuring the current, when it gets to about 160mA stop and measure the resistance. Use the closest higher value resistor you can find/make.
Also note that your diode may have a VERY different Voltage drop and it needs to be measured. This example was just for my diode.