# Very Very Low Frequency Generator

• posted

Hi all, I'm looking after a sine (or triangle) wave generator, but with really low frequency. I read about a compennt called ICL8038 which looks really great but had 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.

• posted

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.

```--
"I'm never wrong, once i thought i was, but was mistaken"
Real Programmers Do things like this.```
• posted

Use a motor driven pot.

• posted

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

• posted

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.

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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 start loading down the components and mess things up.

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

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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

• posted

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

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