Alice, what pressure sensor are you using and what is the application? I
have a lot of experience with absolute pressure transducers in the 0-15 PSI
range for use in barometers and altimeters. I've been using Sensym and now
Lucas NovaSensor's NPP-301 and NPC-1220 series.

   I normally recommend an instrumentation amp for this application. Either
a dedicated IA amp or individual op-amps. Also, stable bridge excitation.
There are a lot of ways to do this using a single supply.

   The Linear app note (AN43) Chris mentioned, is also in the 1993 Linear
Applications Handbook, Volume II. Another good source is Analog Devices'
Transducer Interfacing Handbook, and Instrumentation Amplifier Application
Guide 2'nd Edition.

   As far as power supplies, there are a variety of solutions that will
provide 5V from 1.5V. Charge pump converters/regulators have come a long
ways since the old '7660. TI, Linear, and Maxim have several with very
little ripple and currents from 50ma to 300ma using 3 or 4 caps. The MAX619,
for example, converts 2-3.6V to 5V regulated at 50ma and consumes 75ua. The
MAX682 converts 2.7-5.5V to 5V at 250ma and uses 100ua.

   - Tom

At 12:08 AM 11/8/99 PST, Alice Campbell wrote:
>Well, i'm about to replace the 9v battery in my datalogger with two
>AA 1.5v and a stepper to 5v, but i was curious how they worked, and
>wanted to see for mysef.  I've been messing with switched capacitor
>circuits, and saw the inductor circuit, but couldnt get it to work.
>Then i wondered if i could run it at 3v, stepped up from 1.5v, and
>let the pressure transducer work ratiometrically. The pressure sensor
>only pulls a few mA, the pic and adc and memory chip only a few mA.
>The problem with the switched cap design is the oscillator part, the
>self-oscillation of the coil looked nicer.
>
>alice


------------------------------------------------------------------------
Tom Handley
New Age Communications
Since '75 before "New Age" and no one around here is waiting for UFOs ;-)