Low frequency signal generator

[Dirk Bruere at Neopax]

Hi

Looking for a low frequency signal generator chip that can put out a sine wave
varying in frequency from around 1Hz to 100Hz with resolution around 0.01Hz
Any ideas for a cheap solution?

--
Dirk

The Consensus:-
The political party for the new millenium
http://www.theconsensus.org

 

[Dirk Bruere at Neopax]

That's well within the range practical for direct synthesis with a
microcontroller. Well, depending on how good a sine wave you need.

Thanks.
Since it will be feeding an inductive load it doesn't have to be too good.
However, I was hoping for some super chip with some switches as inputs, a sine
o/p and which drives a 4 digit LCD...

--
Dirk

The Consensus:-
The political party for the new millenium
http://www.theconsensus.org

 

[Al Clark]

Hi

Looking for a low frequency signal generator chip that can put out a
sine wave varying in frequency from around 1Hz to 100Hz with
resolution around 0.01Hz Any ideas for a cheap solution?

This is very easy with our dspstak boards. You could also do this with our
DSP-8300 modules. We have an article that discusses the method and also a
working set of examples.

http://www.danvillesignal.com/index.php?id=applications_signalgeneration

The modules are $125 in 100 qty. A dev kit is available for $250.

 

[Spehro Pefhany]

Hi

Looking for a low frequency signal generator chip that can put out a sine wave
varying in frequency from around 1Hz to 100Hz with resolution around 0.01Hz
Any ideas for a cheap solution?

That's well within the range practical for direct synthesis with a
microcontroller. Well, depending on how good a sine wave you need.


Best regards,
Spehro Pefhany

 

[Guy Macon]

Looking for a low frequency signal generator chip that can put out a sine wave
varying in frequency from around 1Hz to 100Hz with resolution around 0.01Hz
Any ideas for a cheap solution?

Since it will be feeding an inductive load it doesn't have to be too good.
However, I was hoping for some super chip with some switches as inputs,
a sine o/p and which drives a 4 digit LCD...

How's this for a super chip that does what you describe?

http://www.basicx.com/
http://www.basicx.com/Products/BX-24/bx24overview.htm
http://www.basicx.com/Products/BX-24/bx24specs.htm
http://www.basicx.com/appnotes/bx-24appnotes.htm
http://www.basicx.com/Products/SLCD/2X16LCDoverview.htm

 

[Jon]

Try the Maxim MAX038 IC. It generates sine, triangle, square, pulse
waveforms from 0.1Hz to 20MHz.

Jon

 

[Ben Bradley]

Try the Maxim MAX038 IC. It generates sine, triangle, square, pulse
waveforms from 0.1Hz to 20MHz.

The OP wants "resolution" of 0.01Hz, which for 1 Hz to 100 Hz would
require a 10-turn pot (and a VERY accurate dial), voltage regulation
and probably temperature compensation as well.
Actually I'm not sure what the OP wants, but if the stated
resolution is an indication of the accuracy he wants, it surely will
take a digital (microcontroller) solution most likely involving an
implementation of the "phase accumulator" concept.

 

[John Larkin]

Hi

Looking for a low frequency signal generator chip that can put out a sine wave
varying in frequency from around 1Hz to 100Hz with resolution around 0.01Hz
Any ideas for a cheap solution?

Analog Devices serial DDS chip, maybe, if you don't mind some
programming to control it.

John

 

[[email protected]]

You might try a four pole switched capacitor filter chip like the
National MF-10. You put in a square wave of the fundamental frequency
and a sample clock of say 64 time higher frequency. You filter out all
(most) of the the harmonics and get out a sine wave .

Dick Hagerman

 

[[email protected]]

You might try a four pole switched capacitor filter chip like the
National MF-10. You put in a square wave of the fundamental frequency
and a sample clock of say 64 time higher frequency. You filter out all
(most) of the the harmonics and get out a sine wave .

Dick Hagerman

 

[Ken Smith]

You might try a four pole switched capacitor filter chip like the
National MF-10. You put in a square wave of the fundamental frequency
and a sample clock of say 64 time higher frequency. You filter out all
(most) of the the harmonics and get out a sine wave .

If you don;t need an exact frequency on the output, you can build an
oscillator with the switched cap filter acting as the frequency
determining components. This removes the need for the extra dividers at
the cost of an added dual diode and a couple of resistors.

Wire up both sections as band pass filters


Connect section #2's input to the BP output of section #1.

Take the HP output of section #2, run it through a simple diode limiter
and use it as the input to the section #1 filter.

 

[Dirk Bruere at Neopax]

Hi

Looking for a low frequency signal generator chip that can put out a
sine wave varying in frequency from around 1Hz to 100Hz with resolution
around 0.01Hz
Any ideas for a cheap solution?

Thanks for all the suggestions guys, and I'll keep them in mind.
However, I have decided the best (ie cheapest and hassle free)method is to use a
program like Audacity on a PC to generate the signal I need to high precision. I
can then either output it directly from the soundcard or convert it to MP3 and
play it from a portable device.

--
Dirk

The Consensus:-
The political party for the new millenium
http://www.theconsensus.org

 

[Ban]

Thanks for all the suggestions guys, and I'll keep them in mind.
However, I have decided the best (ie cheapest and hassle free)method
is to use a program like Audacity on a PC to generate the signal I
need to high precision. I can then either output it directly from the
soundcard or convert it to MP3 and play it from a portable device.

I was just checking out with my old copy of CEP what happens when you add a
1Hz and a 1.01Hz sinewave. nice beat frequency.
The question is if the soundcard can output 1Hz without attenuating it a
bit. You should at least increase the output capacitors, so the lower
frequency -3dB point is 0.1Hz or less.

 

[Dirk Bruere at Neopax]

I was just checking out with my old copy of CEP what happens when you add a
1Hz and a 1.01Hz sinewave. nice beat frequency.
The question is if the soundcard can output 1Hz without attenuating it a
bit. You should at least increase the output capacitors, so the lower
frequency -3dB point is 0.1Hz or less.

Well, as far as I know Audacity can create a tone at a very precise frequency.
However, you are correct about playing very LF stuff.
One solution is to create a stereo track with one channel at f1 and the other at
f2 where f1>f2, feed these into a summing op-amp and follow by some simple
filtering to get f1-f2.

--
Dirk

The Consensus:-
The political party for the new millenium
http://www.theconsensus.org

 

[martin griffith]

Hi

Looking for a low frequency signal generator chip that can put out a sine wave
varying in frequency from around 1Hz to 100Hz with resolution around 0.01Hz
Any ideas for a cheap solution?

To solve the LF cutof problem with a normal soundcard, think FM.
Modulate an audio carrier say at 10KC/S with the LF frequency
required. Stuff the output into a 4046 PLL as an FM detector


martin

 

[Robert Scott]

..as far as I know Audacity can create a tone at a very precise frequency...

Unless you take some steps to calibrate to an external reference, the
generated tone can be no more accurate than the quartz crystal
timebase in your soundcard. And I have found these crystal
oscillators to be off by as much as 1%. That's not very precise. To
be fair, most soundcards are better than that. About .02%.


-Robert Scott
Ypsilanti, Michigan

 

[Robert Baer]

Well, as far as I know Audacity can create a tone at a very precise
frequency.
However, you are correct about playing very LF stuff.
One solution is to create a stereo track with one channel at f1 and the
other at f2 where f1>f2, feed these into a summing op-amp and follow by
some simple filtering to get f1-f2.

That will not work.
In order to get (cerate, or generate) a sum or difference of
frequencies, one needs to use those signals to drive a nonlinear device.
Harmonics are also generated.

 

[Dirk Bruere at Neopax]

That will not work.
In order to get (cerate, or generate) a sum or difference of
frequencies, one needs to use those signals to drive a nonlinear device.

Summing them won't work?

Harmonics are also generated.

The f1+f2 can be filtered out. It should be easy if f1,f2 >> f1-f2

--
Dirk

The Consensus:-
The political party for the new millenium
http://www.theconsensus.org

 

[Dirk Bruere at Neopax]

Unless you take some steps to calibrate to an external reference, the
generated tone can be no more accurate than the quartz crystal
timebase in your soundcard. And I have found these crystal
oscillators to be off by as much as 1%. That's not very precise. To
be fair, most soundcards are better than that. About .02%.

The playback device could be anything from an MP3 player to a boombox.

--
Dirk

The Consensus:-
The political party for the new millenium
http://www.theconsensus.org

 

[Spehro Pefhany]

In order to get (cerate, or generate) a sum or difference of
frequencies, one needs to use those signals to drive a nonlinear device.
Harmonics are also generated.

Some audio editing software allows you to generate a modulated signal.


Best regards,
Spehro Pefhany