On Fri, 26 Nov 2010 14:13:42 -0500, ehsjr
wrote:

John Fields wrote:
On Wed, 24 Nov 2010 21:02:19 -0500, ehsjr
wrote:


John Fields wrote:

Combined filter/coil driver functions and used a spare opamp to get
the Q3 inversion to feed back to D1.

I used LT1677's 'cause they were in the LTspice database, and handy,
but there are probably other parts out there that would work as well,
for less money.

Not a perfect sine wave, but not bad; take a look at the FFT.

---
JF


Nice.

This thing "simulates" nicely on breadboard, as well as spice. :-)

I put it together with stuff I had on hand - the op amp is a 324, no
matched caps or R's - and it actually looks a little better on the
scope than in spice. Not sure if I can get clear waveform photos,
but I'll try if you want.

Ed


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Sure, that would be great!

Thanks :-)

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JF

Ok, here's my "photographic genius" ( :-( ) on display. I tried
taking pictures in the dark last night at ~ 19Hz, but they were awful.
In the daytime, I had to take the pictures under a towel to keep
ambient light out - I would not be surprised to hear there's a better
way. (See Daylight.jpg for no towel) Frequency was ~39 Hz (see Sine
ph1 & 3 on the far right for frequency readout, and Sine ph1 & ph2 for
sweep & V/div).

Aside from the photographic issues, the sine looks pretty good. :-)
I'll bet the op would be happy with your circuit if he tried it.

Ed

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Not bad shots, they show what's going on... :-)

Strange kinda guy; he only made two posts over the course of the
entire thread.

Thanks again for the photos and the real-world testing.

---
JF