Waveform Definition

Hello all. I have a question about how to define a waveform. It's closely related to duty cycle.

Let's say that I turn the room light switch on for one second, then off for one second. This light uses DC current. So we get a positive going square wave with a 50% duty cycle.

Now, if I vary the off time only, and never have the off time less than one second, then the period of the duty cycle will change each time I change the off time. The on time remains constant.

What kind of duty cycle(?) or waveform is that? Has any heard of this dynamic?

All comments are welcome.

Pulse width modulation (PWM) - although at such a slow speed it's a flashing light.

You can either vary the width of the pulse, or the space, it makes no difference.

It's VERY, VERY common - which is why many (most?) micro-controllers include them.

Ok, thank you. Is PWM ever done with a constant on duration?

BR-549 said:

Ok, thank you. Is PWM ever done with a constant on duration?

Click to expand...

Yes, as I said - it can be either fixed pulse (on), fixed space (off), or neither fixed.

At very low speeds, such control is sometimes called "Burst fire", often used for such as heating where slow speeds do cause any noticeable pulsing of the heat output due to the slow heat up and cool down times of the elements.

BR-549 said:

Now, if I vary the off time only, and never have the off time less than one second, then the period of the duty cycle will change each time I change the off time. The on time remains constant.

What kind of duty cycle(?) or waveform is that?

Click to expand...

It is PWM with a varying frequency.
Most PWM signals use a constant frequency.

Thank you all. I went back and reviewed PWM methods and parameters, but couldn't find an example for my supposition.

And I didn't see or ever hear of the burst fire function, although I catch the idea. Thanks.

crutschow rang the bell for me. That's exactly what it is, after listening to that description. I have not seen this dynamic before. So If I keep the on time constant, and vary the off time only, it is varying the period of the duty cycle. Thus the F of the duty cycle. And if the duty cycle is equal to the on time, divided by the on time + the off time, ....then the duty cycle will also vary in the same direction as the frequency. If F goes down, then the duty cycle goes down. And if F goes up, duty cycle goes up.

Is that right?

By the way, this has nothing to do with power control or transfer. It's a new premise, trying to plot a target's course, without the use of an active reflection. A passive detection function.

So thank you all for clarifying the waveform for me.

BR-549 said:

Thank you all. I went back and reviewed PWM methods and parameters, but couldn't find an example for my supposition.

And I didn't see or ever hear of the burst fire function, although I catch the idea. Thanks.

crutschow rang the bell for me. That's exactly what it is, after listening to that description. I have not seen this dynamic before. So If I keep the on time constant, and vary the off time only, it is varying the period of the duty cycle. Thus the F of the duty cycle. And if the duty cycle is equal to the on time, divided by the on time + the off time, ....then the duty cycle will also vary in the same direction as the frequency. If F goes down, then the duty cycle goes down. And if F goes up, duty cycle goes up.

Is that right?

By the way, this has nothing to do with power control or transfer. It's a new premise, trying to plot a target's course, without the use of an active reflection. A passive detection function.

So thank you all for clarifying the waveform for me.

Click to expand...

Sounds like a doppler shift function? - a frequency decreases when it's going away, and increases as it's coming closer. It's what's used actively in radar and speed guns etc, and passively when a steam train is approaching blowing it's whistle.

Kinda, sorta, maybe. I am usually classified as a nut case. I believe that I discovered how to emit one "wave"(photon) from a dipole. Which is pretty good, considering that I believe the definition of an emitted wave and a photon is incorrect. And even more important, that the act of emission is an instant affair. Zero duration. The propagated disturbance has a 1/2 period duration, and detection has a duration of one full period. I know it sounds crazy to all.

I am usually dismissed at this point.

Of course we witness a continuous function fed into a dipole, and we see a continuous function appear out of the dipole, it only makes sense that the link between to two.......is a continuous function. However, I think nature has fooled us. And if I am right, then all radio and light measurements can be discerned without a local time concept.

I have an experimental setup and can go deeper in the weeds about all these aspects, but all have dismissed my idea out of hand.

But I can not. I believe I understand how a EM chunk.....can be instantly emitted.

BR-549 said:

Kinda, sorta, maybe. I am usually classified as a nut case. I believe that I discovered how to emit one "wave"(photon) from a dipole. Which is pretty good, considering that I believe the definition of an emitted wave and a photon is incorrect. And even more important, that the act of emission is an instant affair. Zero duration. The propagated disturbance has a 1/2 period duration, and detection has a duration of one full period. I know it sounds crazy to all.

I am usually dismissed at this point.

Of course we witness a continuous function fed into a dipole, and we see a continuous function appear out of the dipole, it only makes sense that the link between to two.......is a continuous function. However, I think nature has fooled us. And if I am right, then all radio and light measurements can be discerned without a local time concept.

I have an experimental setup and can go deeper in the weeds about all these aspects, but all have dismissed my idea out of hand.

But I can not. I believe I understand how a EM chunk.....can be instantly emitted.

Click to expand...

If it sounds crazy, then it usually is - but feel free to experiment as much as you wish, however, don't expect advise here on how to get things to work when they don't.

Certainly it's possible to emit one photon of an EM wave.
It's done with light frequencies all the time.
Whether it can be done practically at RF frequencies, I don't know, but I see no theoretical reason you can't.

Don't see how you consider that incorrect to common theory.

With regard to the original question, unlike pwm your duty value can never be zero.

Mike.
BTW burst control can be seen on (old) electric hobs.

I disagree with Nigel and PWM. Because one part of the cycle is a constant width and the other part varies, I would call this PFM - Pulse Frequency Modulation. The frequency of the overall waveform will vary proportionally (but not directly) with the width of the non-constant portion of the waveform.

Vicor first and/or second gen high density DC/DC converters work this way. Energy through the transformer is a string of constant amplitude, constant width pulses. The heavier the load, the closer together the pulses are. Very efficient, but it made for a much wider bandwidth noise signature.


ak

AnalogKid said:

I disagree with Nigel and PWM. Because one part of the cycle is a constant width and the other part varies, I would call this PFM - Pulse Frequency Modulation. The frequency of the overall waveform will vary proportionally (but not directly) with the width of the non-constant portion of the waveform.

Vicor first and/or second gen high density DC/DC converters work this way. Energy through the transformer is a string of constant amplitude, constant width pulses. The heavier the load, the closer together the pulses are. Very efficient, but it made for a much wider bandwidth noise signature.

Pulse-frequency modulation - Wikipedia

en.wikipedia.org

ak

Click to expand...

I would consider PFM as just a sub-catagory of PWM - particularly as you're still varying the pulse (or space) width.

Thanks ak for the link. Pommie, what is an electric hobs?

I have this dynamic in my mind, but didn't know what terms to use for all to understand. This dynamic is not electrical per-say. It's a physical dynamic. A mechanical dynamic. A Classical dynamic.

It's a constant duration, stimulus strobe, with a variable dead time between the strobe.

That's the classical motion. Like a stationary machine gun and target, the dead time between bullets is controlled by your finger. The dead time is equal to the bullet passage time....at a 50% duty cycle(DC). The bullet passage time is the bullet interaction time and comes from the length of the bullet. It's not the velocity per-say, because with this EM machine gun, all emissions are at the same V. So it's only the length, that effects the interaction time.

If we shoot a constant stream of 50% DC(duty cycle)bullets......and move the target, both the off and on interaction time with target changes at the same rate and distance, and the duty cycle remains at 50%. The rate(F) of the duty cycle changes, going up, if we move target towards emitter and down moving away from emitter.

The bullet length(or duration) never changes with emitter V, because the emission is instant. It emits a chunk of length.

An instant event........is like freezing the V of the emitter at one point in space. The length and duration of the bullet(strobe), can not be changed with emitter V. The velocity of the emitter can not be impinged on the velocity of the propagation. That's why c is constant. Because emission is instant.

These two differences, the emission duration(instant) and the strobe DC dynamic......is in direct contradiction with Maxwell......and Einstein. It would be impossible for the strobes to compress or pile up.....and impossible for the strobe to stretch, with emitter V. Only the dead time could change.....with emitter V.(phase only) The strobe interaction time can only be changed with detector V.

We have all seen the EM animations thru space.....and from a dipole. The dipole looks like a speaker emitting.......and the "wave" is a continuous stream. The dipole takes time to emit.

I believe that the dipole acts like an ignition coil and collapses in an instant. Only the field does not collapse in.......it collapses out into the non-impedance of space. When a field collapses in, it takes time, because of impedance.

For the first 179 degrees of input to the feedpoint, a collective field is grown around the dipole.....then at 180 degrees......it snaps and collapses out. (two emissions per cycle) There are two reasons it is an instant dynamic. When the field is grown, it rotates and is already at propagation V. No acceleration time needed. The collapse is just a change in direction....from angular to linear. Plus the EM field has no mass, no inertia....and therefore can change direction in an instant. Without impedance.

Feed a 180 positive precision one shot into one element with a 180 negative precision one shot to the other element.

What do you detect? One photon. With 1/2 wavelength. That 1/2 wavelength....will ring one full wavelength in your detector. The other half wavelength.....flew in the opposite direction.

A 10 MHz receiver.....is simulated with 1/2 wavelengths and rings in the detector like a tank circuit.....at one wave length.

Think of a class B amp. The collector tank is stimulated with 1/2 wavelengths, but rings a one full wavelength.

An emission is an instant event with no duration. A reflection is an instant event, with a 1/2 period duration. With no movement of reflector. The movement of the reflector can vary the 1/2 period interaction time. And vary the reflected F. Keeping the 50% DC.

It's always been an electro-mechanic cosmos. Absolute time and length.

Time for my medication.

BR-549 said:

Pommie, what is an electric hobs?

Click to expand...

Remember the old electric oven (the top was called a hob) with the spiral heating rings on the top. They could be seen heating and cooling due to a burst controller.

Mike.

Thank you Mike. Just to finish up.......

Waves have one full period of emission duration(think speaker). Propagation for alternation has one full period. Detection has one full period. The emission and propagation are continuously alternating without a break. A stream. This stream can be compressed and stretched with velocity. Because it's a stream. It's a continuous line. A growing stick/vector.

EM radiation has zero emission duration. 1/2 period propagation duration, 1/2 period of dead time. And one full period detection. It's an intermittent strobe. The V of the emitter can only change the dead time. The V of detector changes both the dead time and live time equally. All because of interaction duration.

Imagine a large wagon wheel with 8 spokes. Remove rim. Spin hub and spokes at c. Now hit the release button in the center of the hub. All of the spokes will fly out at c very fast. Now put the spinning hub on an axle and slide it down the axle, while spinning. The spokes have mass/inertia and will resist and take some time......to change direction. That time......gives the spokes a little of the hub sliding direction. The spokes will not be incident or normal from the hub, while the hub is sliding, because of this.

Like the swinging weights around a moving rocket. The weights will gain a little rocket direction with the release. Because of time because of inertia.

But a spinning EM field has no mass/inertia and nothing to resist the change quickly, and not adding any rocket motion to it. The flight is incident/normal from the source. No matter source V. WITH A CONSTANT VELOCITY. If any of the emitter V was impressed on the propagation, we would NOT have a constant V of c.

Oh yeah!!!!!!! THEN what about red shift? The local red shift(satellite) comes from the combination of phase and distance change at emitter and frequency change at detector. AND the gravity gradient. Knowing the proper narrative of light, we should be able to discern and separate the difference.......calculating the rel V of emitter and the rev V of detector. Using a static 50% DC for reference. And adding a gravity fudge factor.

The large reds shifts of starlight probably come from gravity not velocity. I believe that the force of gravity has been decreasing ever since the beginning. Very very fast in the beginning....but at a very slow rate now.....and evermore.

Light and lower F, comes from an oscillation. And all oscillations change with a gravity gradient.

Hard x-ray and gamma come from rotational emission........and should not be affected by gravity. These frequencies should remain normal thru-out the cosmos at all times. When we can detect and generate x-ray and above(gamma) like we can a 10 MHZ oscillator.....we will understand a lot more.

Possibly might even gamma strobe an electron, and see what it looks like.....like a fan blade.

Removing the fuzz and the blur.

Ok I'm done. Let me know if you emit one photon.

Nigel Goodwin said:

I would consider PFM as just a sub-catagory of PWM - particularly as you're still varying the pulse (or space) width.

Click to expand...

Still disagree. In both PWM and PPM (pulse-position modulation), the fundamental frequency does not change with modulation. A 50 kHz PWM signal might vary from 5% to 95% duty cycle (with widely varying power spectra), but the fundamental frequency is a constant. The signal spectrum has a fixed lower limit that is independent of modulation.

In PFM, the fundamental freq changes - a lot. Back to an old Vicor project, I think the fundamental freq varied from something like 50 kHz to 240 kHz with load, a bear to filter to MIL-STD-461.

Using a fixed pulse with variable frequency is called PFM.

Tony Stewart said:

Using a fixed pulse with variable frequency is called PFM.

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As already mentioned in post #13