Open discussion for projects on this forum.

[dR-Green]

PW Vs. PWM

Today we have the good fortune of being able to study PW and PWM in action. In the demonstration setup we have an oscillator producing a square waveform in the audio frequency range, which is given a fixed Pulse Width, duty cycle, or symmetry, in relation to "time" set by the user. The demonstration begins with 50%, the PW knob is turned manually, and the effect is seen on the scope.

Lo and behold, we have PW control, a variable but continuous duty cycle with respect to "time". This may be modulated by hand and therefore by definition would be PWM. However, in application, given the fixed PW and the fact we do not intend to modulate it by hand all day long, it may NOT be called PWM. This is a basic continuous signal, unvarying over time.

We now assign a low frequency oscillator (LFO) to Oscillator 1 symmetry, intensity is set to 100%. With an LFO start frequency of 0.12 cycles/sec already a difference can be seen on the scope and heard through the speakers. The square waveform is no longer continuous over time, the pulse width is being varied at a rate of 0.12 cycles/sec. LFO frequency is increased to maximum of 32 cycles/sec and then brought back down. This situation may go on indefinitely at any frequency requiring no user intervention, the pulse width is continuously being modulated, and is therefore referred to as PWM.

In conclusion, PW and PWM is NOT the same thing.

PW Vs. PWM - YouTube

[citfta]

What??

Ok I will admit occasionally my curiosity will get the better of me and I will look at the last couple of posts in the assymetrical motor thread. So I was just checking to see if anyone has actually had any great success with their motors when I found this statement in a post from Ufo.

Quote:

I have been measuring Amperage on NEGATIVE POLE OF BATTERY....AND THAT IS VERY WRONG!!!...

NEVER, EVER, DC AMPERAGE GETS MEASURED ON THE NEGATIVE SIDE POLE OF LOAD...AS THIS CURRENT...IS...NOTHING MORE, NOTHING LESS...THAN THE MANIFESTED CURRENT BACK TO BATTERY FROM MY MACHINE (THE EXCESS, THE RESIDUAL)...SINCE...CURRENT "MANIFESTS"...NEVER TRAVELS LIKE VOLTAGE DOES...WELL, IT MANIFESTS AS INPUT AS MY MOTOR REQUEST IT ONLY AT POSITIVE TERMINAL OF BATTERIES...NEVER AT NEGATIVE!!

And of course...it results in a different readout..than the one I was measuring all this time...so...all tests thrown out to garbage can...Let's start again fresh...from the beginning...

But that is the way experiments and testing goes...as I really did not have that concept clear either...up to now...

End of quote.

Now I am confused. Does anyone understand what Ufo is saying? I think he is trying to say that the current on the negative side of the load is not the same as the current on the positive side of the load. If that is what he is saying then that goes against what I have been taught and more importantly very much against what I have seen in real life. Has anyone ever seen a system where the current leaving a source is any different than the current going back to the source? Now I have seen situations where the meters didn't always tell the truth, especially with pulsing and quick short duration pulses. But the meters still showed the same whether measuring the positive or negative side of the load.

If anyone has actually seen anything different would you please share with us and tell us about what kind of system or circuit you have.

Respectfully,
Carroll

[citfta]

PW or PWM

Hi dR-Green

I am not exactly sure what you were saying in your post. Are you saying we should not call a PWM a PWM unless we modulate the pulses?

In industrial use a PWM is normally constantly changing the pulse width to control the motor. As the motor is loaded the pulse width is increased to maintain the speed of the motor. Or if the operator asks for a different speed then the motor controller will adjust the pulse width to reach the new speed. So you see the pulse width is being constantly adjusted by the motor control circuit so in effect it is modulating the pulse width. I believe that is why they are called PWMs.

Respectfully,
Carroll

[Matthew Jones]

.....Now I am confused. Does anyone understand what Ufo is saying? .....
Respectfully,
Carroll

!!!Warning!!!

Contemplating "Putts Babble" may cause serious and prolonged permanent damage to the cerebral cortex. And in some cases has caused sudden Mental impairment that might prevent you from operating heavy equipment and/or vehicles. In some cases Death was a side effect, in controlled studies, for those who were already impaired from mental illness and/or Mental retardation.

[Ufopolitics]

Answer Included here.

Ok I will admit occasionally my curiosity will get the better of me and I will look at the last couple of posts in the assymetrical motor thread. So I was just checking to see if anyone has actually had any great success with their motors when I found this statement in a post from Ufo.

Quote:

I have been measuring Amperage on NEGATIVE POLE OF BATTERY....AND THAT IS VERY WRONG!!!...

NEVER, EVER, DC AMPERAGE GETS MEASURED ON THE NEGATIVE SIDE POLE OF LOAD...AS THIS CURRENT...IS...NOTHING MORE, NOTHING LESS...THAN THE MANIFESTED CURRENT BACK TO BATTERY FROM MY MACHINE (THE EXCESS, THE RESIDUAL)...SINCE...CURRENT "MANIFESTS"...NEVER TRAVELS LIKE VOLTAGE DOES...WELL, IT MANIFESTS AS INPUT AS MY MOTOR REQUEST IT ONLY AT POSITIVE TERMINAL OF BATTERIES...NEVER AT NEGATIVE!!

And of course...it results in a different readout..than the one I was measuring all this time...so...all tests thrown out to garbage can...Let's start again fresh...from the beginning...

But that is the way experiments and testing goes...as I really did not have that concept clear either...up to now...

End of quote.

Now I am confused. Does anyone understand what Ufo is saying? I think he is trying to say that the current on the negative side of the load is not the same as the current on the positive side of the load. If that is what he is saying then that goes against what I have been taught and more importantly very much against what I have seen in real life. Has anyone ever seen a system where the current leaving a source is any different than the current going back to the source? Now I have seen situations where the meters didn't always tell the truth, especially with pulsing and quick short duration pulses. But the meters still showed the same whether measuring the positive or negative side of the load.

If anyone has actually seen anything different would you please share with us and tell us about what kind of system or circuit you have.

Respectfully,
Carroll

Measuring Tip & Glossary - KYORITSU

[Matthew Jones]

Low side current measurement. Page 8.

http://www.diodes.com/_files/product...zetex/an39.pdf

[dR-Green]

Hi dR-Green

I am not exactly sure what you were saying in your post. Are you saying we should not call a PWM a PWM unless we modulate the pulses?

In industrial use a PWM is normally constantly changing the pulse width to control the motor. As the motor is loaded the pulse width is increased to maintain the speed of the motor. Or if the operator asks for a different speed then the motor controller will adjust the pulse width to reach the new speed. So you see the pulse width is being constantly adjusted by the motor control circuit so in effect it is modulating the pulse width. I believe that is why they are called PWMs.

Respectfully,
Carroll

Well it depends how specific you want to get I suppose, but to audio people PWM refers to a very specific thing and then conveniently everyone knows exactly what the other guy is talking about with this simple phrase based on the physics of what's happening. The "option" to manually adjust the pulse width of a square wave is another thing. If you were to say "use PWM" then an LFO (or some source of modulation) would be applied to the PW, because that's the definition of it. If you don't want a different result to what you have in mind then you don't ask the audio engineer for PWM.

What I'm referring to here is that in a certain thread the term PWM is thrown about as if something specific is being referred to, but there is no modulation whatsoever, they are actually referring to a basic square wave with fixed PW. It's not adjusting itself in any way and there's no modulation.

[citfta]

Thanks

Hi dR-Green,

Now I understand what you are saying. In my lack of knowledge about audio systems I did not know they used the term PWM. Thanks for telling me about something else I didn't know about. I agree with what you said then. If you are not actually changing the pulse width then it of course is not really PWM only PW.

It seems there are a lot of terms used on this forum and others that are not really understood by the people using them. They probably understand what they mean to say but don't use the term or terms the way they are normally used by people familiar with those terms.

Please feel free to use this thread for any other terms you would like to help clarify.

Thanks,
Carroll

[citfta]

You're Right!!

Hey Matt,

You must be right. I have damaged my few remaining brain cells. I must have, because I read the info about using clamp meters, (which I have used hundreds of times) and I couldn't find a single reference in that info about there being any difference between measuring the low side or the high side. Actually I read the whole thing 3 times and still didn't see anything about that. The only thing even close is a tip about reading DC that said the way you clamp around the wire can give you a positive or negative reading. Oh wait maybe it is my eyesight that is going. I just got new glasses. Maybe I can get a refund on them. Oh well I think I'll sign up for a brain transplant. That might do the trick.

Later,
Carroll

PS: Remind me sometime to tell you about the so called engineer I had to work with for a few days. He clamped the 3000 amp clamp-on ammeter around the outside of a 2 inch piece of sealtight and pegged the meter. Then the sealtight started smoking. Another over educated idiot.

[dR-Green]

Hi dR-Green,

Now I understand what you are saying. In my lack of knowledge about audio systems I did not know they used the term PWM.

Sound/synthesis is all about waves/waveforms. The old analogue synths are nothing but voltage controlled oscillators, filters, amplifiers etc. Everything is set by variable resistors and capacitors and switches, it's just a collection of different electronic parts - a source signal is fed through various processors/modules to "shape" the sound and affect the output waveform, hence "modular" synthesis. It just so happens they're designed for the audio frequency range, but otherwise it's all exactly the same thing. They're basically very nice custom waveform signal generators. In the demo video I'm just using a software equivalent and using only the basic oscillator. If you were to connect a scope to your sound output and play the video you would see the same signal as is shown, increase the frequency and we're back in the familiar territory of this forum.

[Farmhand]

Low side current measurement. Page 8.

http://www.diodes.com/_files/product...zetex/an39.pdf

That's a handy reference Matt.

I'm trying to make sense of UFO's measurements but, it's not clear to me
what is measured where and when and the actual circuit layout.

With respect to actual over C.O.P. > 1 or OU claims ( not so much r&d stuff).
I think we should expect at the least a basic diagram showing the circuit
(could be a block diagram even in some cases) with the measurement points,
what was measured where and in what sequence, all together, or one after
another. Or this was measured then that was connected then "that" was
measured ect. And scope shots to show the input / output wave shapes at the
measurement points, ( I think that is one of the most important things ).

Cheers

[Farmhand]

There is something odd about the output current measurement in this video.

At about 5:50 minutes he reads 43 amps from the neutral line, if the voltage was
120v then that would be 5160 Watts, so the voltage must be less.

OK so 2000 watts divided by 43 amps equals 46 volts across the load.
If the 2000 Watt load had 120 volts across it it would read more like 16.6 amps.

Why not just measure the volts across the lamps ? It would be more accurate and useful info.

MECCALTE IMPERIAL RUN 2 - YouTube

The input measures 71 amps at 31 volts so 2200 Watts.

Cheers

[citfta]

Something is not definitely not right.

There are some other things I saw in that video also that just don't add up besides what you pointed out Farmhand. That appears to be what we in the U.S. call 12 gauge wire on the back of the receptacle that he is measuring the current on. That wire is good for 20 amps or so. If he was in fact drawing 43 amps he couldn't do that for long before the wire would start getting pretty warm and then after a while longer it would get really hot. So I agree that looks like a bad measurement of the current.

The other serious problem I saw was the measurement of the DC current. There again it looks like the clamp meter was clamped around number 12 wire. There is no way you could get 73 amps through that wire without is overheating very quickly. I could be wrong about the second wire with the way the camera was moving around so fast but without taking the time to start and stop the video and really study it it sure looked like that wire was way too small for any 73 amps.

Carroll

[Ufopolitics]

Wires...

There are some other things I saw in that video also that just don't add up besides what you pointed out Farmhand. That appears to be what we in the U.S. call 12 gauge wire on the back of the receptacle that he is measuring the current on. That wire is good for 20 amps or so. If he was in fact drawing 43 amps he couldn't do that for long before the wire would start getting pretty warm and then after a while longer it would get really hot. So I agree that looks like a bad measurement of the current.

The other serious problem I saw was the measurement of the DC current. There again it looks like the clamp meter was clamped around number 12 wire. There is no way you could get 73 amps through that wire without is overheating very quickly. I could be wrong about the second wire with the way the camera was moving around so fast but without taking the time to start and stop the video and really study it it sure looked like that wire was way too small for any 73 amps.

Carroll

Hello Carroll,

The wire at the DC reading was 6 gauge, is the one used for marine batteries...tin wire...not copper.
I said it at video,that the Green AC Clamp was not reading right.(crazy readings)
And yes, absolutely agree, those 41 Amps could never be...
I wrote in my Thread to disregard that video as the measurements...

Regards


Ufopolitics

[citfta]

Thanks

Thanks for the explanation Ufo. Yes 6 gauge wire can easily carry 73 amps. I think you mean tin coated copper wire as I have never seen plain tin wire. Tin coated copper is much easier to solder to and also will not corrode like plain copper wire will in certain environments.

Your AC clamp meter is probably picking up some of the field of the other wires close by. We usually try to separate the wires further than that when using a clamp meter. Also you can get erroneous readings if the clamps do not come completely together. Even a small piece of dirt between the ends of the clamps will cause problems. Hope these tips help you get a good reading.

Respectfully,
Carroll