UBEC as driver?

[Hrvoje]

Hello all, I'm new here but old as flashaholic. Just ordered SSC P7 bare emitter from DX and will try to make custom flashlight. I have small lathe with milling attachment, so most parts will make by myself. As RC modeler, in my electric model I often use UBEC (external battery eliminator circuit) which purpose is to provide current for receiver and servos. I'm interested is it possible to modify that unit to give 3.7 V output. If so, it would be nice driver for P7 on 2-3 Li-Po cell for longer duration.
Here is example of one typical UBEC (I have this one in one of my airplane):

http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=4319

Hrvoje

 

[Spacemarine]

Even if it was possible to set it to 3.7V, you'd still have the problem that the UBEC would output a constant voltage and not a constant current.

Andre

 

[Hrvoje]

Andre, thank you for your answer. What about this device:

http://www.dimensionengineering.com/AnyVolt3.htm

Hrvoje

 

[jsr]

There's nothing wrong with a constant voltage driver, just that the LED's output will vary more than if it were constant current. The variation won't be enough to be noticed by the human eye anyways. A constant current driver is still just a voltage source that has sense and feedback to vary the voltage. As long as the UBEC can supply the voltage and current needed by the LED or your application, it would work fine.

 

[HarryN]

You can always put a 1 or 2 ohm resistor in series with the voltage controller if needed. That is more or less equivalent to a battery with very flat output running a resistored LED light.

Under the right conditions, a resistored light is not that bad for efficiency, and the devil you know, is often better than the one you don't.

I do have to admit, that while most of my homebuilts are resistored lights, I do have some constant current drivers from georges80 (taskled.com) and they do work superbly.