Sine wave generator

[mister_e]

Something that spring to mind using a PIC.

Use a 12F629 or else with an external Crystal. Fed the CLKOUT signal to those OpAmp Filter.

The PIC will manage the Power-on/Off AND monitor the battery voltage. Could be interesting now... well just an idea.

One other using a 12F683.
This one Will produce a PWM signal on GP2 to generate a negative voltage for the OpAmp and do the same things as the previous suggestion.

Unfortunately those baby 10F can't run with an external OSC... that would be perfect here...

[mister_e]

mmpfff, forget the PWM stuff. We can even have +V and -V by designing the power supply another way...just by moving the Ground reference you can have +4V, kinda gnd and -5V if you're using a fix 5Volt regulator.

The main problem will be when the battery voltage will drop... mmm i still prefer the PWM stuff after all

[ChrisMicro]

#12 Of Steve will do the trick