John Waters wrote:

> I want to use my car battery to provide a range of variable d.c. from
> 0-12V,
> but a standard regulator circuit doesn't fulfill the requirement, as I want
> the output voltage to be adjustable by software through a microcontroller,
> could someone suggest how to do that?

The key is: digital POT. Question is whether you can afford a wasteful
linear regulator, or you need a switcher. The LM317 I believe is the
standard for this sort of thing. Of course, you might need an LDO (low
dropout) regulator...see TI, OnSemi, etc. for an adjustable LDO linear
regulator. All of these use some sort of resistive divider to fix
voltage, and with a digital POT in there (Microchip makes some nice
ones, the MCP4xxxx series), you're all set.

If you are looking for switchers, National makes a number of adjustable
ones. I've used the LM2576-ADJ, but that's a high current (3A) part.
They make low-current ones too. Check them out. "dropout", i.e. min
input-output differential is about 3V.

Cheers,
-Ishaan

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