Square Wave Oscillator Off-Grid

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  • Last Post 01 August 2023
Jagau posted this 13 August 2020

Hi all
I would like to share with you this little square wave oscillator which works the same as a function generator and which operated on battery which can vary from 6, 9 or 12 volts DC according to your needs.


The heart of the oscillator is a TLC555 from the CMOS series which has very low power consumption and is completely different from the old NE555.

It has a 10K potentiometer to vary the frequency from 13Khz to 130Khz and another 5K potentiometer to increase the amplitude of the signal at will.

 

A drawing of the schematic that I present to you freehand

It can be easily changed by changing a single resistor and a single capacitor.

5 ma on 9 volts battery here

 

The particularity of this oscillator is that the output voltage changes from positive to negative through zero in the center. This is the AC square wave shape.

Most of these freely sold circuits are above zero volts they are only DC square wave and could not be use for experimentation.

Very low or high amplitude at your choice

 

This way you are isolated from the electrical network and have greater freedom of measurements without ground return.

 I also hope for those who would like to join us and experiment with us and do not have a function generator, this is the ideal opportunity, easy to assemble and inexpensive.

Jagau

square-wave off-grid
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Jagau posted this 13 August 2020

Hi all
I would like to share with you this little square wave oscillator which works the same as a function generator and which operated on battery which can vary from 6, 9 or 12 volts DC according to your needs.


The heart of the oscillator is a TLC555 from the CMOS series which has very low power consumption and is completely different from the old NE555.

It has a 10K potentiometer to vary the frequency from 13Khz to 130Khz and another 5K potentiometer to increase the amplitude of the signal at will.

 

A drawing of the schematic that I present to you freehand

It can be easily changed by changing a single resistor and a single capacitor.

5 ma on 9 volts battery here

 

The particularity of this oscillator is that the output voltage changes from positive to negative through zero in the center. This is the AC square wave shape.

Most of these freely sold circuits are above zero volts they are only DC square wave and could not be use for experimentation.

Very low or high amplitude at your choice

 

This way you are isolated from the electrical network and have greater freedom of measurements without ground return.

 I also hope for those who would like to join us and experiment with us and do not have a function generator, this is the ideal opportunity, easy to assemble and inexpensive.

Jagau

square-wave off-grid
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Fighter posted this 01 August 2023

Replying To: Jagau

You had the patience to design, build, test and teach us how to build this device.

Importing the thread here for our entire team is at least I can do to thank you.

There are so many threads we should have imported here. Unfortunately the process can be made only manually, it's time consuming and the available time is limited. In time we'll have more information imported here.

Fighter

"If you want to find the secrets of the universe, think in terms of energy, frequency and vibration."
Nikola Tesla
Jagau posted this 01 August 2023

Thank you for the import you have a patience that I do not have. thanks again

And also with the excellent advice of Yoelmicro becomes a must for your lab

Jagau

Fighter posted this 01 August 2023

With Jagau's approval I imported this thread from the old site archive.

It took some time for importing it but the operation is now complete.

There are two reasons I did this:

  1. It's a very nice tool to have in our Hardware section, useful for low-power off-grid experiments needing true AC pulses with adjustable frequency and voltage;
  2. I intend to use it with my Don Smith Effect experiments and it's useful to have references/details about it here.

Of course in the meanwhile Jagau came with a new more advanced tool, his Arduino MOSFET Driver, but for now this oscillator is a good candidate at least for the beginning of my experiments about the Don Smith effect.

Of course all credits for this device are going to Jagau.

Thanks,

Fighter

"If you want to find the secrets of the universe, think in terms of energy, frequency and vibration."
Nikola Tesla
YoElMiCrO posted this 04 December 2020

Hello everyone.

@Jagau.

With that circuit you shouldn't have problems with distortions
below 500KHz, of course this, according to the mosfet driver
you use.
It can be any driver, inverter or non-inverter and 1Apico
Minimum.
Capacitors must have a minimum value, for example
4.7uF.
What you should do is put a serial potentiometer between
the output of the driver and your POT, look for the resonance frequency
and then adjust your potentiometer in such a way that I accentuated the peaks
tension that appear at the beginning of your waveform,
once this optim in frequency and impedance you calculate a
inductor in such a way that it possesses the same resistive value as the
potentiometer at working frequency.
This way you wouldn't lose coupling power between your POT
and the driver.
This serial inductor should have a value (Serial Potentiometer Value/(2*Pi*Fr)).
And capacitors should be greater than or equal to 1/(4*Pi*Fr* (Serial potentiometer value/10)).
Any doubt you let me know.

YoElMiCrO.

Jagau posted this 03 December 2020

Ok, the differential driver that I proposed has a slew rate too low, it works well up to 10khz but after that it is too slow for the rate of change (slew rate), it is a bit of the problem of most of have operational amplifiers.


So Yoelmicro

I'm going to look at your circuit you offered me, could you please explain me more precisely the proposed circuit.

i thought it was a negative resistance circuit?

I just want to increase the amplitude of the square wave oscillator without distorting it

Thank you Yo

P.S. just a precision when I speak of frequency not exceeding 10khz I am talking about the differential amplifier and not the tlc555 oscillator which easily goes up to 200khz and more


Jagau

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Jagau posted this 01 December 2020

Thanks Yo


 The goal of having a voltage amplitude only of the square wave with a very high impedance input so as not to alter it and also a low consumption at the input.

Thank you will analyse this capacitive divider too if it will do the job


Jagau

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YoElMiCrO posted this 01 December 2020

Hello everyone.

@Jagau.

If I may...
This circuit meets the requirements you need.

As you can see, once you find the necessary serial impedance
and the working frequency, you can replace the resistor with an inductor,
in this way the energy you lost in it becomes null and void!.
I hope it'll do you some good.

YoElMiCrO.

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Jagau posted this 01 December 2020

Hi all

One of the problems encountered nowadays when working with instruments connected to the grid is that often we have to isolate them or even make them work with inverter on batteries. The second next problem is that the batteries drain quickly because the devices draw a lot of current.

To solve this problem with the oscillator above we can already solve the first part of the problem given that it operates at very low voltage and current.

For the other problem I am building an instrument amplifier which I believe will solve the second problem, having a little more power in the square output waveform.
The schematic of the one I am building.

When it is ready I will let you know and we can use it together with the square oscillator with more latitude in the power and being free and well isolated  from the grid .


Jagau

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Jagau posted this 09 November 2020

Hello fighter
nice job, you now have one more tool in your lab, I often use it too.
A recommendation from the manufacturer is this in section 10.1:

10.1 Layout Guidelines
Standard PCB rules apply to routing the TLC555. The 0.1-μF ceramic capacitor in parallel with a 1-μF electrolytic
capacitor must be as close as possible to the TLC555. The capacitor used for the time delay must also be placed as close to the discharge pin. A ground plane on the bottom layer can be used to provide better noise immunity and signal integrity.

For the question of lowering the negative side you will have to make a power supply circuit with a virtual ground, this will correct the problem of voltage difference.
I recommend this simple and efficient one for all the ICs that you will have to use in the future.

This circuit is not mine, it works very well I use it in my setup

Jagau

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Fighter posted this 09 November 2020

This is my build of Jagau's AC Oscillator.

I know that in my build I pushed the frequency range to the limits.

You'll see I placed two sockets so the 10nF capacitor and the 5K variable resistor can be easily replaced with different values to change oscillator's frequency range:

The only modification I made was to add a 2200uF/25V electrolytic capacitor on input.

In the following scope images I'm using a 9V battery on input, an 1nF capacitor and an 2.2K variable resistor which is offering a range starting at 266KHz and ending at 2.05MHz. The scope probes are connected directly on output and there is no other load.

Frequencies shown in the images are (in order): 266KHz, 510KHz, 833KHz, 1.25MHz, 1.76MHz and 2.05MHz.

You'll notice that as I'm forcing the frequency up the square wave is becoming deformed, my electronics knowledge is limited so I don't have a explanation for this but I suppose there is one and this is normal.

Also depending on frequency there seems to be a slight difference between the positive voltage (Max) and the negative voltage (Min), also don't know the cause for that:

But we don't need MHz frequencies for our experiments so it's an excellent oscillator for experiments were real AC is needed even if we're using DC for input.

Just want to thank to Jagau for this excellent AC Oscillator, I intend to use it in QLED-type experiments.

"If you want to find the secrets of the universe, think in terms of energy, frequency and vibration."
Nikola Tesla
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