Wow your motor, idea sounds expensive, power hungry and unreliable, I don't know how you got all three in one!

Filter any waveform with a 50% duty cycle enough and you'll get a sinewave. Build a 7555 timer circuit with 50% duty cycle, add a non-inverting buffer to the capacitor, stick a picky enough filter on the end and you'll have a near as damn it perfect sinewave.

__________________
I also post at the following sites:
http://www.stop-microsoft.org http://www.heated-debates.com
Screen name: Aloone_Jonez

 

A switched-capacitor Butterworth lowpass filter IC does wonders to remove harmonics. A square-wave can be filtered with an 8th-order IC and the results are low distortion sine-wave.

My very low distortion sine-wave generator uses a CD4018 to make a stepped sine-wave with 10 steps (10 times over-sampled) then is filtered by an 8th-order Butterworth filter IC. The distortion is 0.01%.

__________________
Uncle $crooge

 

is this gonna be some strictly controlled output? you could keep it simple, LC tank. dang yall love things complicated more than they have to be.

 

No, we all read the requirements - how were you planning making a 0.2Hz to 1.75Hz variable LC oscillator?.

__________________
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

 

with lots of love and hugs.

 

Man, I can just 'feel the love' - but what I can't feel is a low frequency variable sinewave!

__________________
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

 

You could if you played it out of a huge sub woofer but it'd probably make you feel ill rather than lovely.

__________________
I also post at the following sites:
http://www.stop-microsoft.org http://www.heated-debates.com
Screen name: Aloone_Jonez

 

Well if you wind a really large coil around the garage and put it in parallel with a huge capacitor. If you park the car outside the garage you get 2Hz and if you park inside you'll get 0.2Hz. Simple really.

__________________
--- The days of the digital watch are numbered. ---

 

Sorry, but I don't have a garage?

__________________
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

 

It seems like alot of phaser circuits use JFETs. how do they get around the distortion?

 

sounds like overkill for my application; but very cool. I think smoothness is more important for me than perfect sine wave.

 

Distortion isn't a problem with a phaser, it's entire reason for being there is to distort the signal anyway.

Why don't you try googling for phaser circuits, and see how thousands of others have overcome the problems?

On the other hand, although I'm presuming you're wanting to build one for the pleasure of it?, why not just buy one?

http://www.bluearan.co.uk/menu/index...e=manufacturer

Nice box, at less than the parts are goint to cost you!.

__________________
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

 

ha, i already have one.
im having lots of fun with this.

 

OMFG u won the internetz!

 

Even I get lucky like that, sometimes.

That'll work, to get a good sine, for a particular frequency. I just did a quick-n-dirty simulation of it in LTspice and got 0.674% THD after running a 0.1 Hz square wave through five 1st-order 10K/150uF lowpass filters, with four opamps as buffers between the stages.

BUT, he needs the amplitude to stay constant regardless of frequency, from 0.2 Hz to 1.75 Hz if I recall correctly. So, with that approach, either the filter's corner frequency would need to be moved up, to be able to even try to keep the amplitude constant vs frequency, and the filter would need to have many (many) more stages, and it still wouldn't have constant amplitude vs frequency, OR, he'd need to use a smaller bank of adaptive filters, with a variable corner frequency, and some way to control it, and some way to know when and how to control it.

The motorized oscillator idea had a lot of potential problems. But at least it did hold a constant amplitude versus frequency.