Dedicated Moonlight Mode Driver

[netprince]

Is there a driver specifically made for moonlight mode?

I'd like to drive an LED at 2mA (regulated) for 20+ days from a AA cell... Am I crazy? See my math below...

LED Vf 3.2
Led mA 2
Led mW 6.4
Cell Mah 3000
Cell V 1.3
Cell mWH 3900
Driver Eff 0.80
Cell Draw (mA) 6.15
runtime days 20.31

 

[netprince]

wife's post removed.

 

[JamisonM]

I don't see why it isn't possible. I wonder if you could solder the right resistors one of the Shoppe's drivers?

 

[jason 77]

wouldn't this be something like one of those "jewel thief" circuits?

 

[netprince]

The joule thief is not regulated, and I'm not sure you can use it with a fresh battery. But yes, the idea is similar...

Will have to look at the shoppe's drivers...

 

[netprince]

Took a quick look at the shoppe, their converter board comparison says the madmax driver is the only board which can use 1.5v input, and it doesn't have an adjustable output...

 

[JamisonM]

Took a quick look at the shoppe, their converter board comparison says the madmax driver is the only board which can use 1.5v input, and it doesn't have an adjustable output...

I don't think that's the minimum imput voltage, but the maximum. Send a question to the Shoppe or contact Dat2zip at their own forum here.

 

[MikeAusC]

If you used 3xAAA with a Resistor you would get the same efficiency.

It would cost more in batteries, but you would save on the Driver.

 

[netprince]

3AAA plus resister will not be regulated... Depending on the resistor, it will either start out bright and burn through the batts faster, or it will start out low and not use the end of the batts...

The AA quark is the best I have found so far, someone reported 13 days runtime on a AA.

 

[Eddie-M]

Supposedly the new maglite XL100 can run 201 hours on low off 3 AAA vs 5.25 hours on high. Thats the only driver similar in concept that I know of. But I don't know much lol.

 

[PCC]

The XL-100 does all this in the tail cap.

The Mad Max driver can handle up to 3V but will drive an LED at less than 1.5V. I haven't tried one on a single AA, yet, but will be doing one soon. I'm wondering if Wayne could resistor one down to an even lower drive level?

I know that the Nite-Ize 3-LED drop-in for the Mini-Mag will work down to about 0.7V and it will draw around 150mA at around 1.2V. It does dim as the battery voltage drops, though.

 

[spencer]

I'm sure Linear or somebody has an IC that would do what you want with very minimal parts. I'll have a look and see what I can find.

 

[jason 77]

If you used 3xAAA with a Resistor you would get the same efficiency.

It would cost more in batteries, but you would save on the Driver.

if you use 3 batteries then you could use Dan Goldwater's CC circuit and have the R3 "sense" resistor be a 220 ohm, the current draw would be 2.2 mA...

 

[spencer]

I have found a potential candidate. Here. See page 8 of the datasheet.

 

[netprince]

Spencer: nice find, that part looks like it would work nicely. I am far from understanding it all, but it doesn't look terribly difficult to figure out...

Jason 77: I had not seen that circuit before, it looks like it would work well for multiple cells...

 

[datiLED]

The ZXLD381 looks to be very efficient at ultra low drive currents. I think that with a larger inductor, the 2mA that you desire could be achieved. Look at the flat regulation at currents from 0.8V to 1.2V. :thumbsup:

 

[netprince]

Wow, that does look good. It looks even easier to build. Nice find.