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You've misread the data sheet. Nominal operating current (according to the data sheet) is ~200 mA. In fact, the 400 mA limit is mentioned nowhere in the data sheet, and I'd guess you got it from the eBay listing. A word of advice - when it comes to believing an eBay listing or a data sheet - go with the data sheet. With this in mind, your best bet (for consistent power levels) is

schematicschematic

simulate this circuitsimulate this circuit – Schematic created using CircuitLab

I recommend that you find a copy of the LM317 data sheet and read it. The circuit is one of the application circuits. The biggest drawback of the circuit is that the LM317 will dissipate nearly 2 watts, so you need a decent heat sink on it.

Going with the 5 volts supply/resistor is workable, but the resistor should be 10 ohms, in order to limit the current appropriately.

And don't forget to heatsink the laser.

You've misread the data sheet. Nominal operating current (according to the data sheet) is ~200 mA. In fact, the 400 mA limit is mentioned nowhere in the data sheet, and I'd guess you got it from the eBay listing. A word of advice - when it comes to believing an eBay listing or a data sheet - go with the data sheet. With this in mind, your best bet (for consistent power levels) is

schematic

simulate this circuit – Schematic created using CircuitLab

I recommend that you find a copy of the LM317 data sheet and read it. The circuit is one of the application circuits. The biggest drawback of the circuit is that the LM317 will dissipate nearly 2 watts, so you need a decent heat sink on it.

Going with the 5 volts supply/resistor is workable, but the resistor should be 10 ohms, in order to limit the current appropriately.

And don't forget to heatsink the laser.

You've misread the data sheet. Nominal operating current (according to the data sheet) is ~200 mA. In fact, the 400 mA limit is mentioned nowhere in the data sheet, and I'd guess you got it from the eBay listing. A word of advice - when it comes to believing an eBay listing or a data sheet - go with the data sheet. With this in mind, your best bet (for consistent power levels) is

schematic

simulate this circuit – Schematic created using CircuitLab

I recommend that you find a copy of the LM317 data sheet and read it. The circuit is one of the application circuits. The biggest drawback of the circuit is that the LM317 will dissipate nearly 2 watts, so you need a decent heat sink on it.

Going with the 5 volts supply/resistor is workable, but the resistor should be 10 ohms, in order to limit the current appropriately.

And don't forget to heatsink the laser.

1
source | link

You've misread the data sheet. Nominal operating current (according to the data sheet) is ~200 mA. In fact, the 400 mA limit is mentioned nowhere in the data sheet, and I'd guess you got it from the eBay listing. A word of advice - when it comes to believing an eBay listing or a data sheet - go with the data sheet. With this in mind, your best bet (for consistent power levels) is

schematic

simulate this circuit – Schematic created using CircuitLab

I recommend that you find a copy of the LM317 data sheet and read it. The circuit is one of the application circuits. The biggest drawback of the circuit is that the LM317 will dissipate nearly 2 watts, so you need a decent heat sink on it.

Going with the 5 volts supply/resistor is workable, but the resistor should be 10 ohms, in order to limit the current appropriately.

And don't forget to heatsink the laser.