# Me Again, Math Again

Started by June 25, 2018

On page 5 of that they have a phase shift oscillator. I would like to use one in  my, well, whatever.

They got the formula there and the way I read it, the frequency is :

1/[2pi times R times C times the square root of 6].

So I want 2 KHz.

2,000=1/[6.28*R*C*2.449...]

If that is correct, then the values you get for R and C are for each of the three stages ? As in 60 degree delay per R/C ?

It seems another way to attack this would be to use ascending values in each subsequent stage. For example only - you need 1K and 0.01. Next stage is 10K and 0.001. Then comes 100K and 0.0001. That doesn't look too good for a bipolar because of current etc., and it might run out of signal and not oscillate. An FET should be alright though.

This has to do with a design I posted a while back. I want to do away with the two stage oscillator. This, like before has the same function, it goes to a buffer that puts out a short pulse to switch the states of the bistable multivibrator. I believe this would be more stable, as the Vcc is  not regulated. What I've seen, correct me if I am wrong, an astable multivibrator frequency is quite dependent on the Vcc. It can be designed out of course but I don't have a hundred years.

I have it now so that changes in battery voltage equally affects the output to the DUT as well as the scale of the detector end. It nulls out, and I AM going to use 2 more diodes and remove the Vf of the detectors.

If the battery gets too low, or I don't get the feedback level right it will clip and that will affect the frequency. I am not putting in a regulator. This damn thing is already going to be 5 times more expensive than I ever wanted it, but it will be cool.

So, where am I right and wrong here. If necessary I can bring u p the old LT file on it, and a new one with the changes.

Your thoughts. Call me an asshole, call me stupid, call me anything you want, but state your case.
On 06/25/18 19:47, jurb6006@gmail.com wrote:
> http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwiSvsnY9-_bAhVDja0KHXHnALoQFggpMAA&url=http%3A%2F%2Fphysics.oregonstate.edu%2F~giebultt%2FCOURSES%2Fph412%2FReading%2Foscillators-1p.pdf&usg=AOvVaw2ID2iftO5An0jNHiC1lYRm > > On page 5 of that they have a phase shift oscillator. I would like > to use one in my, well, whatever. > > They got the formula there and the way I read it, the frequency is : > > 1/[2pi times R times C times the square root of 6]. > > So I want 2 KHz. > > 2,000=1/[6.28*R*C*2.449...] > > If that is correct, then the values you get for R and C are for each > of the three stages ? As in 60 degree delay per R/C ? > > It seems another way to attack this would be to use ascending values > in each subsequent stage. For example only - you need 1K and 0.01. > Next stage is 10K and 0.001. Then comes 100K and 0.0001. That doesn't > look too good for a bipolar because of current etc., and it might run > out of signal and not oscillate. An FET should be alright though. > > This has to do with a design I posted a while back. I want to do away > with the two stage oscillator. This, like before has the same > function, it goes to a buffer that puts out a short pulse to switch > the states of the bistable multivibrator. I believe this would be > more stable, as the Vcc is not regulated. What I've seen, correct me > if I am wrong, an astable multivibrator frequency is quite dependent > on the Vcc. It can be designed out of course but I don't have a > hundred years. > > I have it now so that changes in battery voltage equally affects the > output to the DUT as well as the scale of the detector end. It nulls > out, and I AM going to use 2 more diodes and remove the Vf of the > detectors. > > If the battery gets too low, or I don't get the feedback level right > it will clip and that will affect the frequency. I am not putting in > a regulator. This damn thing is already going to be 5 times more > expensive than I ever wanted it, but it will be cool. > > So, where am I right and wrong here. If necessary I can bring u p the > old LT file on it, and a new one with the changes. > > Your thoughts. Call me an asshole, call me stupid, call me anything > you want, but state your case. >
IIRC the classical vanilla no-frills phase shift oscillator runs at exactly 29/RC, but that's a memory from long ago. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
It's 29/RC ?

The referenced paper says something about 29, feedback gain of the amp beta=1/29.

So that means it is the point where I want my frequency ?

So the amp must be able to handle the load of the feedback network for a voltage gain of 29 ?

???
On Mon, 25 Jun 2018 16:47:20 -0700 (PDT), jurb6006@gmail.com wrote:

>http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwiSvsnY9-_bAhVDja0KHXHnALoQFggpMAA&url=http%3A%2F%2Fphysics.oregonstate.edu%2F~giebultt%2FCOURSES%2Fph412%2FReading%2Foscillators-1p.pdf&usg=AOvVaw2ID2iftO5An0jNHiC1lYRm > >On page 5 of that they have a phase shift oscillator. I would like to use one in my, well, whatever. > >They got the formula there and the way I read it, the frequency is : > >1/[2pi times R times C times the square root of 6]. > >So I want 2 KHz. > >2,000=1/[6.28*R*C*2.449...] > >If that is correct, then the values you get for R and C are for each of the three stages ? As in 60 degree delay per R/C ? > >It seems another way to attack this would be to use ascending values in each subsequent stage. For example only - you need 1K and 0.01. Next stage is 10K and 0.001. Then comes 100K and 0.0001. That doesn't look too good for a bipolar because of current etc., and it might run out of signal and not oscillate. An FET should be alright though. > >This has to do with a design I posted a while back. I want to do away with the two stage oscillator. This, like before has the same function, it goes to a buffer that puts out a short pulse to switch the states of the bistable multivibrator. I believe this would be more stable, as the Vcc is not regulated. What I've seen, correct me if I am wrong, an astable multivibrator frequency is quite dependent on the Vcc. It can be designed out of course but I don't have a hundred years. > >I have it now so that changes in battery voltage equally affects the output to the DUT as well as the scale of the detector end. It nulls out, and I AM going to use 2 more diodes and remove the Vf of the detectors. > >If the battery gets too low, or I don't get the feedback level right it will clip and that will affect the frequency. I am not putting in a regulator. This damn thing is already going to be 5 times more expensive than I ever wanted it, but it will be cool. > >So, where am I right and wrong here. If necessary I can bring u p the old LT file on it, and a new one with the changes. > >Your thoughts. Call me an asshole, call me stupid, call me anything you want, but state your case.
Be warned, phase shift oscillators usually make distorted sine waves. Or no sine waves. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
John Larkin wrote:
>Be warned, phase shift oscillators usually make distorted sine waves. >Or no sine waves.
A question, looking at that circuit: is there a difference between 'high pass' phase shifting networks and 'low pass' phase shifting networks in that respect? Seems to me a high pass, as described, is asking for harmonics to be more amplified, equals distortion. while if you reverse R and C like this: -===---===---===--- | | | === === === | | | /// /// /// then you get a low-pass, and no harmonic can make its way? Same phase shift -. What do you think?
On 06/25/18 20:46, jurb6006@gmail.com wrote:
> It's 29/RC ? > > The referenced paper says something about 29, feedback gain of the > amp beta=1/29. > > So that means it is the point where I want my frequency ? > > So the amp must be able to handle the load of the feedback network > for a voltage gain of 29 ? > > ??? >
That's what I was thinking of, minimum gain is (weirdly) exactly 29. Thanks for the reminder! Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
On Monday, June 25, 2018 at 7:47:25 PM UTC-4, jurb...@gmail.com wrote:

> On page 5 of that they have a phase shift oscillator. I would like to use one in my, well, whatever.
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