Lamp Driver.

So I've got a lamp that I've completely made myself, from sand casting the base, to lathe work on the bulb-holder, so it's time to get to the electronics of it.

I'm going for a basic XM-L T6 4C bulb from FastTech, but what I really need to find is a suitable driver.

I have a momentary push-button LED switch that needs 3V across it which I am dying to use since it multiplies the coolness (geekiness) factor by over 9000. And I need to use it for a night light. :X

Does anyone know of a driver that:

  • Runs on 3V (since I don't want two seperate transformers for two voltages)
  • Puts out >2.5A
  • Can be run with an soft/electronic momentary switch.
  • Ramps (optional)

So basically, a single LED SRK/Roche driver.

Is there a reason not to just direct drive the XM-L off the 3 volt supply? If you need a driver, it will definitely have to be a boost one; and there aren't many that can supply that much current. :/

I think youre probably going to be stuck hunting for a proper wall wart or charger type power supply. Check ebay for konica, minolta or nikon external inline style chargers. They are cheap chinese clones but might do the job. Just make sure it doesnt overheat under continuous duty if you purchase one.

Also, if you come across one that claims an output of more than 2.5A @ 4.2V, please post a link here. Id like to have one that outputs 3 - 5A.

You might want to consider other options for led instead plain xm-l. Easywhite xm-l or Bridgelux sm-4 should be much easier to “drive”. Plain 12V/1A wall adapter and cheap pt4115 based driver are excellent and very efficient way to do it. I presume that switch needs 3V to run it’s light source (illuminated switch) or ?

Does it really need to be 3V?
A switch with a LED usually contains the LED and a resistor suitable for 3V, you could add an additional resistor to make it work with higher voltages, like 4V, then you could use a NANJG105C with custom firmware suitable for electronic switches.

Yeah, I want it to be bright enough to light a small room. :)
But I could direct drive it off 3.3V for 2.8A like your diagrams say.
But this would mean CV not CC regulation, which shouldn't be a problem because there whole lamp is a heatsink, but in case the turd hits the blades.

This might be cheating:

And the cheat part:


Or this.

I can't customise Nanjg105c :(
Are there any drivers already out there that you know of?

No, it doesn't really need to be 3V, but do I just subtract the LED's reverse voltage and then add resistance to get the same amount of current as before?

Thanks for all your contributions and suggestions you geniuses.


Yes, measure current I at 3V, for new voltage U add a resistor with R=(U-3V)/I

Ok, quick update.

Bought a few drivers from DrJones.
Using 3.04A lumodrv specifically for this project.

This is the momentary switch I am using. -link

Bought a T6-4C and a U3-1B XM-L LED on a 16mm PCB from FastTech.

And I am using this as a power supply.

Current measured at 3.25V was 27.5mA. (The LED uses almost 0.1W). Rounding off values to assume 25mA @ 3V and using formula given by DrJones:

R(additional) = (5.0 Volts - 3.0 Volts) / (25 x 10^-3)

= 80 Ohms. (82R is the closest value I can find.)

Cool Switch. Ive played with some of them before, same style anyway. They can be little buggers to fully depress though.

Not to hijack but, seeing as it pertains to the same subject:
There wouldnt be any Issue in running just an LED off a wallwart right? I want to make a little lamp as well and use it as a night light, but dont quite get it all safety wise.

The transformer takes care of it all correct? So an extra fuse to the LED is not needed, but okay to use none the less?

Should be fine, but read the Current/Voltage graph correctly. 3.3V is just about perfect for 2.8A across a XM-L emitter.

And also, you will get CV across your LED, not CC, which could be catastrophic in a shorting situation.