I have tried building a phase shift oscillator, but it won't work

[David lopez]

I built a phase shift oscillator, but it
Won't work. I visit the website https://www.google.com/url?sa=t&sou...FjANegQIChAG&usg=AOvVaw0YoHKumGz0Xl3fYKtIRdFa and copied the schematic I saw. I tried coping the schematic of the op amp implementation. But it won't work.
How do you troubleshoot this?

 

[berkeman]

What power supply rails are you using with the opamp? Which opamp is it? Do you have an oscilloscope to use for debugging?

If you do have an oscilloscope, draw the circuit diagram with the pin numbers shown on the opamp, and use the oscilloscope to probe each of the nodes in the circuit. Write down the DC voltage that you find at each node, and scan and attach that drawing to a reply here. That will help us a lot to guide you to get the circuit working.

What is your target oscillation frequency, BTW?

 

[David lopez]

I don't have an oscilloscope. I use a
18650 Lithium ion cell as a power source. I am trying to get the phase shift oscillator to oscillate at all.

 

[berkeman]

18650 Lithium ion cell

That's a 3.6V battery. I doubt you could get that circuit to work with just a single supply voltage anyway, especially one so low.

That circuit would appear to want to oscillate around ground (given the biasing), so you will need split supply voltages to give the opamp compliance with the power supply rails. Maybe for an experiment, try two 9V batteries hooked in series to give you +/- 9V power supplies to the opamp.

You also did not say yet which opamp you are using, or what component values you chose for what oscillation frequency. Did you build this on a plug-in type breadboard?

I'm guessing this is supposed to oscillate in the audible range? Otherwise, how will you tell if it's working if you don't have an oscilloscope?

 

[davenn]

But it won't work.
How do you troubleshoot this?

Probably because you didn't connect the battery to the power pins of the IC
so it cannot work

 

[tech99]

Circuit diagrams often do not give a beginner the details of how to connect the batteries. Also the load must be fairly high resistance, a few hundred Ohms, not a 35 Ohm speaker for instance.

 

[davenn]

Circuit diagrams often do not give a beginner the details of how to connect the batteries.

yeah and that's where, I'm suggesting, he's probably tripped up in both his threads

 

[David lopez]

I am using a lm244 operational amplifier. I made sure the ground pin
Was connected to the negative terminal. I made sure the voltage supply pin was connected to the Positive terminal. The 18650 lithium ion cell I use have a measured voltage of 4.2 volts roughly. I use a single supply configuration. Each resistor has a value of one kilohm. C1 is 120 μf, c2 is 120 μf, c3 is 6.8 μf.

 

[David lopez]

I can build a frequency divider to measure the frequency.

 

[berkeman]

I am using a lm244 operational amplifier.

Although the input voltage range of the LM224 family of opamps includes ground, it does not tolerate signals that are below ground. Your circuit will oscillate with the average voltage level at ground, so the circuit needs to be able to work with signals that swing below ground.

That means you need split power supplies for this to work. You need two power rails, like the +/- 9V supplies that I already mentioned. Do you understand why this is needed?

And as mentioned by others, be careful not to load the output of this first opamp too much. It would be best to add a follower opamp buffer (use another of the opamps in that quad IC package) before driving any frequency divider or speaker circuits.

 

[David lopez]

Should I use a different operational amplifier? And can the lm224 swing
Below ground?

 

[davenn]

Was connected to the negative terminal. I made sure the voltage supply pin was connected to the Positive terminal.

Hopefully not the + and - terminals as shown in those circuits
They are not the power supply pins

the chip datasheet shows the power connections

Are you really using a LM244 or is it the LM224 as @berkeman said in his response ?

Why did you choose a LM224 they are a quad op-amp, 4 op-amps in one package ?
Why not use just a single op-amp package and make things easier to work out ?
Less chance of doing incorrect wiring

 

[David lopez]

That was a typo. I am using the lm224.
And I have the datasheet. I use the datasheet to make sure the wiring is
Correct.

 

[David lopez]

Do You need two positive rails and two
Negative rails to provide split power
Supplies? I have a breadboard with two positive rails and two negative rails.

 

[berkeman]

I have a breadboard with two positive rails and two negative rails.

What does that mean? Can you post a picture? Does it mean that the breadboard you have can support up to 4 power supply voltages plus ground?

Do You need two positive rails and two
Negative rails to provide split power
Supplies?

You should connect your split +/- 9V power supply voltages to the +/- power input pins of the LM324/whatever. If you were using all 4 opamps in the package, it would look something like this (this is not an oscillator circuit, and you should connect -9V to the IC pin 11 instead of the ground shown in this schematic):

https://bestengineeringprojects.com...istribution-Amplifier-Circuit-using-LM324.jpg

When you use only one opamp out of a quad IC package, it is best practice to tie the other 3 opamps off in a way that minimizes noise and power consumption. You can connect them as followers with ground at their + inputs, for example.

 

[David lopez]

This breadboard can support two
Different voltages.
Do you connect the negative terminal of one battery to the Positive
Terminal of the other battery to make a split power supply?

 

[berkeman]

Ah, yes. Assuming that each of those outside 4 columns are connected vertically, I usually will use the inside two for ground connections (and tie those two columns together at one end), and use the outside two columns for my +/- supply voltages. If I need to support +5V and also +/-12V in the same circuit, then I only get one ground column.

Here is how you connect two 9V batteries to give the split supplies that you need for your oscillator circuit:

https://forum.allaboutcircuits.com/threads/make-create-dual-power-supply-from-two-single-power-supplies.146835/

 

[David lopez]

So you connect the Positive terminal
From battery a to ground and connect
The negative terminal from battery b to the same. Ground

 

[sophiecentaur]

Circuit diagrams often do not give a beginner the details of how to connect the batteries. Also the load must be fairly high resistance, a few hundred Ohms, not a 35 Ohm speaker for instance.

You are right but beginners should realize that they are, in fact, beginners and start from the beginning of the subject. All those bits of knowledge that we get, on the way through a life using electronics, are worth something and it is foolhardy to try to leap into a subject half way through and expect it all to 'go right'.
I blame the dreaded simulators which try hard to make your circuit work by assuming the right supply volts and appropriate supply rail decoupling etc. etc.. Real components are not mathematical functions but the message for beginners seems to be otherwise.

 

[sophiecentaur]

I suspect that the OP is trying to achieve an Electronics Course by means of the Q and A system. It ain't going to work, I'm afraid.

 

[David lopez]

So I connect one voltage to the inverting Terminal and connect the other voltage to the noninverting terminal?

 

[Averagesupernova]

So I connect one voltage to the inverting Terminal and connect the other voltage to the noninverting terminal?

This makes no sense in and of itself. Whatever thought you had prior to making this post we cannot determine. We cannot read your mind. Are you still talking about split power supplies? You need to do better. Inverting and noninverting are inputs and are not considered part of the power supply rails.

 

[sophiecentaur]

So I connect one voltage to the inverting Terminal and connect the other voltage to the noninverting terminal?

This just amplifies the point I made earlier about jumping into a subject too far. Calm down and start at the beginning; save yourself time, overall.
PS Why do you need a phase shift oscillator? That's a pretty sophisticated function for a circuit - much harder than connecting up a power supply to an integrated circuit.

 

[David lopez]

You said start at the beginning. where is the beginner? I need a phase shift oscillator, because I want make a circuit that generates ac current. Where should I start learning
To generate ac current?

 

[berkeman]

I want make a circuit that generates ac current

There are lots of ways to generate an AC current. What frequency range? What amplitude? What is the load that you want too drive? Do you need a sine wave, or would a square wave or triangle wave work for your application?

 

[David lopez]

I want a sine wave. I want to start with
Low frequencies. In the range 1 hertz
To 30, 000 hertz. I think the load I want to drive is both a led and piezoelectric buzzer that I have. Any amplitude will do.

 

[Averagesupernova]

Something that you can vary across that whole spectrum from 1 to 30000 is a tall order especially for a beginner. My suggestion is to start simpler and be happy (for now) with something that generates a sine wave at one frequency. I would also suggest finding some form of oscilloscope if you will be doing these types of projects.

 

[Averagesupernova]

https://www.google.com/search?q=100...oECA4QAQ&biw=360&bih=512#imgrc=QnGs49z58TvCUM-
I typed into google: 1000 Hertz phase shift oscillator and the above is what I got. Should also explain the split power supply. I would assume you can use 9 volt batteries instead of the 15.

 

[sophiecentaur]

You said start at the beginning. where is the beginner? I need a phase shift oscillator, because I want make a circuit that generates ac current. Where should I start learning
To generate ac current?

If you do not know Electronics then buy an oscillator - perhaps from a School Supplier or look on eBay.
You do not say what spec you need - frequency range and output level ( stability etc, etc)
If you want to learn Electronics then a phase shift oscillator is some way down the path.
You have not said what this oscillator is for.

 

[davenn]

You said start at the beginning. where is the beginner? I need a phase shift oscillator, because I want make a circuit that generates ac current. Where should I start learning
To generate ac current?

a phase shift oscillator ISNT what you need ... rather just a plain oscillator

The wien bridge osc you tried building is a tricky one to get working

Hint / suggestion
You seem to be jumping too deep into projects without understanding the basics.
You need to step a long way back and start with very basic circuits that have a low component count
and come to understand the function of the circuit and the individual components in the circuit.

Till you make a BIG effort to do that, these fruitless Q/A posts will continue and you will end up with more non-working projects. you are trying to run before you learn to walk and it, as you have found, not working for you. It won't work for anyone.

Start at the start a battery, a LED and resistor.
Use the info easily available on the net to calculate what resistor value you need when you use a battery of a specific voltage.
Learn WHY you need that value of resistor. SLOWLY increase the complexity of a circuit, and learn at each stage what is occurring in the circuit and why.Dave

 

[David lopez]

But I already have some experience
Making electronic circuit. For example
I worked with operational amplifiers, comparator, circuit that turn leds, built
555 timer circuit in both a astable mode and monostable mode, built circuit that charge a capacitor and discharge a capacitor, built analog to digital converter, built voltage dividers,
Built set- reset circuit, built d-type circuit, built solar powered circuit, have programmed arduino microcontroller, built circuit that turns on buzzer, worked with and gates, quad inverter ic, built no gate out of transistor and resistor, built circuit that turns on small electric motor, worked numeric displays, lcd drivers, pressure sensors and experiment with different arrangement of components. Then I thought I could learn a.c. circuits next.

 

[davenn]

But I already have some experience
Making electronic circuit. For example
I worked with operational amplifiers, comparator, circuit that turn leds, built
555 timer circuit in both a astable mode and monostable mode, built circuit that charge a capacitor and discharge a capacitor, built analog to digital converter, built voltage dividers,
Built set- reset circuit, built d-type circuit, built solar powered circuit, have programmed arduino microcontroller, built circuit that turns on buzzer, worked with and gates, quad inverter ic, built no gate out of transistor and resistor, built circuit that turns on small electric motor, worked numeric displays, lcd drivers, pressure sensors and experiment with different arrangement of components.

yeah, but how many of them did you actually get working ?

so far on the forum, you have come with 4 projects, none of which you have got working
even with the help that has been offered

 

[David lopez]

I got the ones I listed working, except the 4 projects I asked about. Those 4
Are the hard ones.

 

[Nik_2213]

IMHO, phase-shift oscillators can be very fussy beasts. My 'Discrete' versions sometimes failed to start, and even an op-amp's gain might not suffice to initiate oscillation. Akin to oscillator sims that just sit there until you stomp off for a coffee while iteration errors accrue...
Against that, I've had 'accidental' phase-shift oscillators that took patient de-bugging to tame...

OP, may I suggest you Google/Bing at least a dozen versions of your circuit, compare, contrast, calculate their nominal frequency, mutter 'Ah?' and 'Gotcha!' etc etc. IIRC, you'll find that function often requires RC values that are much more restricted than simple theory predicts. Go beyond the 'habitable zone' and, despite correct wiring, appropriate power supplies, loading etc, the circuit may simply not start.

Also, though I've seen some ingenious approaches in eg Graf's multi-volume 'Encyclopaedia of Electronic Circuits', you will be hard-pressed to 'swing' any phase-shift oscillator's working frequency across a significant range as-is. Switching Cs and varying the Rs 'in synch' with a 'dual linear potentiometer' is simplest approach, despite poor stability, non-linearity etc etc...

Given your difficulties to date, I'll not recommend DIY with an '8038' function generator IC.

Get a breadboard phase-shift oscillator working as 'proof of concept', document its quirks & foibles, then get a complete $20 mini-SigGen on-line. With that as a 'sanity check', you may then go back and explore...