Can't get enough current for 1W Luexon LED even without resistor

Yes indeed, Jim. There are better solutions than a '317 if you are battery powering, but if you are going to start driving 300mA through the things, you're going to be needing some pretty good batteries anyway. I got the impression that the OP was just trying to test his purchase with a battery. As to the current that is going to pass though the LED, it is not determined by the forward voltage. Rather, it is determined by how much you *allow* it to draw. Once you have enough voltage available across the device, it will settle at whatever value that particular colour and design of LED, normally has. It's then up to you how much current you let it draw. Less than 300mA, and it's not quite so bright, with a longer life expectancy. More than

Arfa

I would not try to use an LM317 to pulse drive a LED. It is better suited as a linear constant current source. Fundamentally, it is actually designed as a variable linear voltage regulator, but its internal topology happens to make it particularly suited to use as a simple (and cheap) constant current source. If you are looking for a 'quick and dirty' experimental set up for pulse driving this LED, you could probably just cobble up a 555 timer IC as an adjustable astable, and use the output to drive a power MoSFET. Stick a suitable resistor in series with the LED to limit the current to say 8A peak, and away you go. Alter the 555's mark space ratio to effectively PWM the current to the LED, and you then are able to control its (invisible) intensity.

You are probably better to put the switching FET in the cathode side of the LED, as you can then return its source straight to ground, which makes the drive arrangement to the gate a lot simpler. Doesn't really matter where you put the current limiting resistor, but I would probably put it in the anode side 'out of the way'.

If your drive circuitry is going to be powered from the same supply as the LED, then you will need to get seriously good with the decoupling on the supply rail to that circuitry. Pulses of 8A or so are going to cause some big spikes to fly about. You would probably be as well to supply the drive electronics via its own regulator - LM7808 or something - with a small choke filter on its input, and all the recommended Cs, especially if you are going to be driving with some very narow pulses. I can't remember what the minimum pulse width from a standard bipolar 555 is, but if not that short, then one of the other versions possibly is. Bear in mind also, that if yiu are going to start switching currents of several amps at those sorts of pulse width, you are quite likely to start generating quite broadband RF noise. You might want to have a little transistor radio nearby, just to make sure that you are not interfering with the local airport ... :-)

Arfa

It makes sense to not use a LM317 as a current source to limit current in a pulse situation.

I have a couple of problems with putting series resistors into the circuit. First of all, I don't know what the forward voltage drop of the LED will be. It will probable change as it self heats during the excitation. And it will vary with the current. Perhaps a very low duty cycle will mitigate the self heating.

Secondly, most of the power resistors in my junk box are wirewound. I'm not sure how the diode would react to the inductive reactance. Yes, I know, put in a clamp diode. But those have a switching time involved. Will a clamp diode that can handle many amperes have a fast transient recovery time?

The IR LED I have acquired is quite old, > 15 yrs. It does not have an integrated switch circuit in it like some of the recent ones I have seen.

Yes, I am doing this as a hobby. I manage to get everything I need from either recycling stations or electronic flea markets. Most of my experiments work. Some just let the smoke out ;-)