Some help with High Powered LEDs

I'm very confused on how to drive LEDs. I am trying to drive a 5 watt infrared LED, here http://canada.newark.com/ledengin/lz1-00r400/led-infrared-5w-850nm/dp/48T1393

It says it needs 2 volts at 1.2 amps. I understand I need a constant current driver, but I can't find one that works at 2 volts. Can the LED take more than 2 volts, as long as the current is limited? (Years ago, I powered LEDs off of the 50v phone line without problem)

Once I find a suitable LED driver, do I put the transistor between the driver and the LED or between the power and the driver? (I am going to be sending some very fast pulses.)

Your driver can be more than 2V output; it's the current that matters. You do want to use a source voltage and driver that matches the Vf of your LED as closely as possible however.

You need to be careful when selecting a driver that the driver is capable of PWM or "blinking" control. Switchmode LED drivers and most all AC mains-powered drivers will react poorly if you try to toggle power to them using a transistor or such. Make sure the driver you choose has either a PWM input or is otherwise described as dimmable.

but I can't find one that works at 2 volts.

It is not the constant current regulator that works at 2V but the LED. So if your constant current regulator can work at a voltage above 2V then it will work. ( no constant current regulator can not work at this voltage ) Basically you are looking the wrong figure. You want a constant current regulator that gives 2A.

Looking for a "2 volt constant-current supply" is completely missing the point.

A constant current driver will supply as many volts as needed to maintain the target current. No more. No less.

I understand now. Thanks.

I still don't get where I should put the transistor.

do I put the transistor between the driver and the LED or between the power and the driver?

between the power and the driver or better between the driver's ground and the real ground.

I am going to be sending some very fast pulses

I think your idea of fast might not match up with what the arduino thinks is fast, your pulses are going to be slow if you expect to light up an LED with them.

Grumpy_Mike:

do I put the transistor between the driver and the LED or between the power and the driver?

between the power and the driver or better between the driver's ground and the real ground.

I am going to be sending some very fast pulses

I think your idea of fast might not match up with what the arduino thinks is fast, your pulses are going to be slow if you expect to light up an LED with them.

Thanks.

Regarding the 'fast' pulses, I am going to be running the TV-B-Gone sketch and have it control my massive infrared LED.

You don’t understand what “fast” means to electronics. Think 50MHz and up!

OK, that’s debatable, but using an adjective instead of a number is likely to lead
to confusion in an area of technology where values vary of many many orders of
magnitude. A fast relay might be 2ms, a fast logic gate might be 0.8ns…