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Oscillator

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zefiris2K5

New Member
Hi......
How to fine tune the output of the following oscillator?. Can I connect directly regulator circuit with the following circuit. From the experiment, it seems was a bad idea and the voltage output suddenly drop. Any suggestion are welcome.... :)
 

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Nigel Goodwin

Super Moderator
Most Helpful Member
Assuming you want to prevent the massive distortion shown on your graph?, you need to add some kind of automatic gain control in the feedback path. This is commonly done using a special (expensive!) thermistor or a cheap incandescent light bulb. It can also be done using a FET circuit, or (crudely) with diode clipping.

If you google for 'wien bridge oscillator' you will find plenty of information and many circuits.
 

zefiris2K5

New Member
I think there is nothing wrong with my drawing. The output looks like that. BTW, the incandescent light you mean, any torchlight bulb will do? And I'm experimenting it with my own regulator ckt. check below..... :roll:
 

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Nigel Goodwin

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zefiris2K5 said:
BTW, the incandescent light you mean, any torchlight bulb will do?

No, it has to be fairly specific, usually very low current bulbs are used.

And I'm experimenting it with my own regulator ckt. check below..... :roll:

I don't really see the relevance of that?, what is it supposed to do?, and where does it connect?. A wien bridge oscillator is a VERY old and common circuit, with many examples you can download off the internet, why not use a 'proper' method?.
 

mstechca

New Member
I haven't used pins 4 and 8 of that particular amplifier.

It isn't normal for a waveform to go left when it is supposed to go right.
This should indicate that the oscillator isn't functioning correctly.

What kind of waveform are you trying to achieve?
 

zefiris2K5

New Member
I need to build a cicuit to drive 2 motor. The speed of the 2nd motor dependent with the first motor. However I need to do some operation like comparator and etc. And to do this in analog domain I need AC signal, am I right? Then the oscillator is to serve that purpose. To drive motor, then I need to convert the AC signal into DC.

No, it has to be fairly specific, usually very low current bulbs are used.
As for the bulb, how about this **broken link removed**? Is it OK?

Let me clarify the output, the output is like capacitor charging and discharging with +ve and -ve side execpt it kind of distort (maybe the gain to high).
 

Nigel Goodwin

Super Moderator
Most Helpful Member
zefiris2K5 said:
I need to build a cicuit to drive 2 motor. The speed of the 2nd motor dependent with the first motor. However I need to do some operation like comparator and etc. And to do this in analog domain I need AC signal, am I right?

Your requirements are rather vague, but I wouldn't have thought so?.

Then the oscillator is to serve that purpose. To drive motor, then I need to convert the AC signal into DC.

This sounds even stranger?. Are you using normal DC permanent magnet motors?.

No, it has to be fairly specific, usually very low current bulbs are used.
As for the bulb, how about this **broken link removed**? Is it OK?

Possibly, but I (yet again) suggest you simply get a circuit off the internet, which will specify whatever gain system it uses. But as you're not wanting any quality (wien bridge oscillators are commonly used for very low distortion sinewaves), a simple diode clipping type circuit would be nmore than good enough.

Let me clarify the output, the output is like capacitor charging and discharging with +ve and -ve side execpt it kind of distort (maybe the gain to high).

Yes, because you've left out the most vital part of the circuit, the automatic gain control.

But, from what you've said, I don't see as you have any need for an oscillator at all?.
 

Dr.EM

New Member
I have built this circuit and have found it to be more than good enough. I used polystyrene caps and ordinary resistors matched with a multimeter. It apparently uses a transistor as an AGC. That page explains a lot about how it works if nothing else, but I reccomend using the schematic so long as you don't need variable frequency.

**broken link removed**
 

audioguru

Well-Known Member
Most Helpful Member
Texas Instruments has a pretty good applications note about many kinds of sine-wave oscillators. Their Wien bridge oscillator with a lightbulb for AGC has a serious error:
 

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audioguru

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Your "regulator" is a wonderful circuit to short the output of your "oscillator".
When the output attempts to go more positive than 8.9V, both diodes conduct and short the output.
 

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Roff

Well-Known Member
audioguru said:
Texas Instruments has a pretty good applications note about many kinds of sine-wave oscillators. Their Wien bridge oscillator with a lightbulb for AGC has a serious error:
AG, that's a low-distortion, half-wave oscillator. :wink:
 

audioguru

Well-Known Member
Most Helpful Member
Ron H said:
audioguru said:
AG, that's a low-distortion, half-wave oscillator. :wink:
Excellent! :lol:
TI sell ICs. They want you to make two circuits for each oscillator, one for each half of the sine-wave.
 

mstechca

New Member
If you can build an H-bridge-circuit, you got motor control.
 

zefiris2K5

New Member
Is it? to continue, it seems the discussion is off topic. I think to start new thread after I became clear with my idea (maybe posting it with block diagram). BTW if I don't need to use oscillator, what else you suggesting? Anyway, thanks for the help.... :)
 

audioguru

Well-Known Member
Most Helpful Member
You want one motor to control the speed of another motor?
Then you need the speeds of the motors to be sync'd. You can use a tachometer circuit from the 1st motor to control a speed control circuit for the 2nd motor.

An oscillator and regulator have nothing to do with it.
 

audioguru

Well-Known Member
Most Helpful Member
Ron H said:
AG, that's a low-distortion, half-wave oscillator. :wink:
audioguru said:
Excellent! :lol:
TI sell ICs. They want you to make two circuits for each oscillator, one for each half of the sine-wave.

Ron H said:
:lol: :lol: :lol:
TI was hoping you would ask. They want you to use one of their very expensive DSP chips to glue the two halves of the sinewave together. :lol:
 
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