Very Very Low Frequency Generator

Discussion in 'Electronic Components' started by [email protected], Dec 25, 2006.

1. Guest

Hi all,
I'm looking after a sine (or triangle) wave generator, but with really
low frequency.
a frequency of only 0.001Hz - That's not enough for me!

I need the whole cycle to take more then 30min = frequency of about
0.0005 Hz.

Thnks, me.

2. JamieGuest

Learn to program a PIC or AVR. They have simply varieties that
can handle what you need.
You need to use a PWM output and some simply code to calculate
the steps needed on the output.

3. Homer J SimpsonGuest

Use a motor driven pot.

4. Salmon EggGuest

Why not just do it with your computer. Compute sin (0.001*¼*t) using your
system clock? Send the output to an D/A converter with a filtering
capacitor, and voila.
-- Fermez le Bush

5. Guest

First thanks.
I see that there is no way to avoid PIC programing (which is new to
me).
But what can you do.. a bit smoke here and there, maybe a burned
circuit or four.. I'll be alright.

6. Michael BlackGuest

Of course there are plenty of other ways. You just have to learn
electronics to get it right.

There is nothing magic about a sinewave where you want, it's just
a matter of scaling things down. But, you will end up with really
large value components. I doubt there is anything intrinsically
wrong with the 8038 at low frequencies, but once you use large
enough value components to get those low frequencies, the 8038 will

Take a 1KHz oscillator using an coil and capacitor and scale those
values down, and it will work. But you'll end up with really large
values.

Take a higher frequency clock, run it through a divider, and then
use some method to convert it to a sinewave. A simple low pass
filter might work, though again you end up with large value
capacitors. A stepped sine wave might be suitable, depending on your
specific use. So you can do the conversion with some resistors and
a ripple counter, or a ROM lookup table and an D/A converter.

But, since you had to ask a general how to do it, then of
course someone's going to suggest a computer to do it, and you have
nothing to put that answer in context.

Michael

7. petrus bitbyterGuest

As (almost) always there are more ways to skin a cat. But scaling down alone
will have a serious drawback: time. It may take seconds for a 1Hz sinewave
oscillator to stabilize. A 0.001Hz sine wave oscillator may need hours, a
0.0005Hz one may need days. You can of course refine the design to handle
the problem. Nevertheless, I doubt someone will build an oscillator like
this using only analog technics these days. But it sure can be done.

petrus bitbyter

8. Homer J SimpsonGuest

ISTR that Don Lancaster has discussed related matters on tinaja.com