Forgetting my education

[The PIT]

I've got a weather station that runs off solar power and batteries. The only problem I have is that during Winter the batteries don't have enough power to power the fan overnight.
The fan makes sure that the air where the temperature and humidity centres gets constantly changed and reflects the temperature more accurately. It also ensures a faster response to temperature change as well.
So I bought more powerful Solar station and battery to power this.

The fan runs at 1.2v and draws 40 ma. The new station outputs at 6v and has a 6v 1.25a battery as backup.

To drop the voltage I used a simple voltage divider checked the voltage and this runs at 1.2V offload.

Attaching it to the fan zilch the fan doesn't spin. So I'm presuming that the fan is loading the voltage divider and ballsing up my calculations. Any idea's round this??

[Tjalfe]

use an LM317 with the offset pin set to ground, and it will output 1.26V or there abouts
It is a variable voltage regulator.

http://www.national.com/JS/searchDocument.do?textfield=lm317

not terribly efficient though, if you want to maximize your battery life, you should look at a switching regulator, though they are a tad more complex to set up

[gt40]

or you could just use 7 diodes in series. A voltage divider is not the way to do it.

[The PIT]

Well six volts input voltage would fry the LM317. Yup you're right back to the drawing board.

Found some different specs and it should do the job.

[Tjalfe]

you are looking at the minimum input voltage to the LM317.. it can handle at least 40V

[Jon P. Inghram]

The fan runs at 1.2v and draws 40 ma. The new station outputs at 6v and has a 6v 1.25a battery as backup.

Are you certain it's a 1.2v fan? The lowest voltage DC fan I could find on Digi-Key was 3.3v. Or is it just using one of those little "toy" DC motors?

It might be easiest to just add a small ~1.5v solar panel and hook it up to it's own AA Ni-Cad/Ni-MH battery.

[The PIT]

According to Davis it is and who am I to argue.
Even more annoying due to the fit you're stuck with buying replacements from Davis as well.
It runs of it's own solar panel and batteries. Problem is in winter short days and cloudy skies leaves no juice to charge up the batteries.

[Rakido]

Problem is in winter short days and cloudy skies leaves no juice to charge up the batteries.

install a light source directly above it, should solve that problem