Long Term Test Results for LED Dimmer Light

[jeff1500]

I made a 4 led light with a dimmer that runs on 2AA batteries. You can see it here:
http://edusite10.tripod.com/led3/max757/max757.html

I've been using it for about six months and I find I'm always happier with worn out batteries because the light is dimmer if I turn it on in the middle of the night.

The voltage range has been from 2.75 to 3.5 volts. No good. By normal evening house lighting that's plenty dim, but too bright at the lowest setting for night vision.

I just took it apart and changed the voltage range to 2.4 to 3.5v for a current range from about 0 to 25 mA per led.

Now at the lowest setting it's about like a firefly. We'll see how that goes.

 

[**DONOTDELETE**]

TO Jeff1500 -

I have printed out the schematic for your flashlight dimmer. I can build that if I have to. What I want, in the end, is a dimmable spotlight with a a nice smooth bell curve beam profile, that is as white and circular as possible (maybe like Brock's "Turtle Light 1"?), that can be dimmed way down, and at a distance of about 4 feet has a diameter of about 12" or less at the point where the brightness is halfway down. Or something like that. This does not have to be particularly portable - it can even use a battery adapter plugged into the wall. It should have a big knob for easy dimmer control, and the knob could be in a box remote from the light itself. In fact, that is preferable. Would anyone care to quote price/delivery of such a machine? Please advise via CC to my email address [email protected]. Thanks for your attention.

 

[jeff1500]

I really like the dimmer feature. The max757 chip is good for up to about 200 mA.

My next project is with a much smaller max1674 chip that can go up to about 1000 mA.

I built the max757 light without using the resistors shown on the schematic as R3 that are in series with the leds. Some say they help divide the current more evenly to the leds, but it was just too many pieces to solder. It's been working well.

 

[Darell]

THANK YOU Jeff! Thanks for making the dimmable flashlight a reality. I sure hope the big mfg's catch on to how great this feature is!

 

[Saaby]

Looks nice but if I were to build it I'd be a little uncomforable with the coil part. What's the trick to windings like that? It looks like one of those things that is more complicated than it seems to be but maybe it's as simple as it seems...

 

[jeff1500]

You can either buy something prewound for about $1.50 or make your own inductor coil out of a ferrite bead. The inductor size is in the chip data sheets. If you make your own, I don't think the number of turns of wire or the size of the ferrite bead is all that critical. I've read posts here about people using various size inductors that all seem to work okay in the same circuit.