scheme for really slow LFO??

[rx5]

stable triangle wave lfo

im planing to build an LFO(low freq oscillator) with a minimum freq of 0.1Hz....traingle wave.. all i could find are much faster(1Hz and above).....

any ideas/links?? 8O

tnx 8)

 

[akouz]

op amp lfo

im planing to build an LFO(low freq oscillator) with a minimum freq of 0.1Hz....traingle wave.. all i could find are much faster(1Hz and above).....
tnx 8)

There is no much difference between 1Hz and 0.1 Hz LFO
If you use a standard OpAmp-based triangle oscillator, just pay attention to some details:
-- Use OpAmp with low input current, such as JFET or CMOS
-- Use timing capacitor with low leakage and low charge absorbtion, such as teflon or polyprophylen capacitors. As soon as 0.1 Hz is not a big deal, you might even use electrolytic caps, preferrably tantalum or low-leakage aluminium. Just bear in mind, electrolytic caps are not quite accurate, also their capacitance is not stable.
-- To prevent leakage, use big clearances on PCB

 

[devrimaksin]

Is triangle wave is a requirement?
If square wave is ok, the easiest way to do it
is to use digital counter (divider)

 

[rx5]

lemme rephrase my prob... a TRIANGULAR wave LFO with freq of 1/32Hz to 2Hz.... cus im gonna use it for my 'flanger' circuit... so square waves are out of the story..

 

[JPR]

Could you use a digital up/down counter (direction switches at end of sweep) with a DAC, running from a higher frequency oscillator? An 8 bit DAC would use an input frequency of 1024Hz to 16Hz. A higher resolution DAC would require faster clocks (12 bit would be 16kHz to 256Hz.

Two options for controlling the rise/fall times:

1- Make the oscillator frequency variable.
2- Run from an even higher frequency, and use a counter with reset to divide the frequency down to the frequency needed for the DAC steps.

 

[echo47]

This is an analog forum, but I would consider building a DDS with a triangle ROM in place of the sine ROM. Extremely precise and repeatable, but it's a non-trivial digital project.

 

[akouz]

a TRIANGULAR wave LFO with freq of 1/32Hz to 2Hz for my 'flanger' circuit...

Use the circuut shown below. R1 is a trimpot, say, 1M. To reduce frequency further, increase C1 as needed, say, to 33 uF ... 100 uF. As far as triangle waveform output is high-impedance, use another OpAmp as a buffer.