Quadrature Oscillator on Breadboard

Thread Starter

quique123

Joined May 15, 2015
404
So Im trying to set up this circuit:
Screen Shot 2018-09-14 at 6.15.05 PM.png
which came from this youtube video btw:

Ive made a Fritzing (and attached the fzz.zip file) of it since its the closest I can get to drawing what I have on the actual breadboard. The circuit doesnt work in the sense that it doesnt make the sounds it should. Here are a few caveats:

1. Im using a single 9V battery to power the circuit.
2. Im using a speaker from a wireless home phone.
3. Im actually using the 1uF cap (micro) before the speaker (a polarized type btw), but for the other caps Im using ceramic non polarized caps that are 0.047uF which have a "473" marking on it. I dont have 10nF, but 0.047 works to about 47nF so I figured Id give it a shot.

Im worried about my wiring on the breadboard so I made the fzz file so someone could review it and tell me if it represents the schematic posted above.
Ill post a picture of the breadboard but its a mess! :)

Thanks in advance
 

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Hi,

From your breadboard setup is hard to tell a reasonable answer.
Do you have an oscilloscope to see what's happening in the output with and without the speaker? Sometimes, the signal is clipped in these kind of circuits. Be aware that changes in the capacitors values will affect the frequency as the design formulas suggest.
 

MisterBill2

Joined Jan 23, 2018
7,231
What is this circuit claimed to do? Fritzing has no meaning other than being Fritz. Not trying to be nasty, I am just puzzled as to what it is supposed to do. I did not open the zipped file, I don't open zipped files.
And if your circuit is based on that incredibly messy breadboard, are the LM324 power terminals actually corrected correctly? The appearance suggests that it is intentionally messy to avoid anybody being able to trace it.
Without the speaker connected it might oscillate if both opamps are in their linear region. But it is not obvious that will be the case.If you post the other file unzipped we can look at it.
The circuit is two integrators in a loop, with one set up as inverting. So they will function until the capacitors charge up and then just sit. Not very exciting.
One additional thing is that it appears that the "speaker" in the picture is a piezo device, which has a very high impedance, while the speaker in your circuit has an impedance of possibly 50 ohms, but more likely 8 ohms.
 

MisterBill2

Joined Jan 23, 2018
7,231
OK, and thanks for the picture of the neater circuit. But we still have no explanation of what "works" means in this case. And the neatly wired circuit does prove that on some occasions neatness pays. Not every time, but at least some of the time. The previous version may have had a few open connections , which will usually alter performance of any design..
So is this an oscillator or something else?
 

Thread Starter

quique123

Joined May 15, 2015
404
OK well it works means I get sound from the speaker. I started tinkering with arduino a couple of years ago and I loved it, crossed over to RPi but along the way I ran into some circuits every now and then that caught my attention, circuits or pure electronics concepts that I felt I had to try. The first component I ran into that seemed interesting was an opamp.

The first circuit I tried was a mic amplifier, also from this guy. I couldn't get it to work but since it was just a detour because it was pure electronics and not Arduino related, I left the idea behind. Then I ran into opamp used in a battery indicator circuit, tried reproducing the circuit and failed. A few days ago I ran into oscillators and I finally got this quadrature oscillator to work. So now I gotta go back to the others. When I ran into oscillators I decide to finally order an oscilloscope but that was 2 days ago so it'll be a while til I have it.
 
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