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PWM benefits?
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stevekos7 Offline
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Post: #1
PWM benefits?
Hi all. I have been looking at the various pros and cons out there regarding PWM's and admit I am a bit confused.

I have a generator that produces around 1.2 lpm at 25 amps. I am happy with the output but the amperage draw is a bit high. I am thinking of a PWM to help reduce the amps. The thing I am a bit confused about is just what the PWM will do.

Will it allow me to retain the same output at lower amps? Will it allow me to increase output to say 1.5 lpm at under 20 amps (which is my goal benchmark)?

I have noticed that there are various PWM designs that allow different variables depending on the number and type of timers that it uses etc. Which design will allow the best results?
07-13-2008 06:16 PM
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CheezWiz Offline
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Post: #2
RE: PWM benefits?
Steve,

I am waiting for one of you guys to answer this myself. I do not want to hear the hype from someone making a buck.
I do not understand how it could produce the same amount. Work can only be done when the electrons flow. The electrons only flow during the active part of the duty cycle on a PWM.

My example:
Say we want to control the speed of a DC motor and we only have these two choices, variable resistor or PWM.
Both will work equally well, but the resistor method will always pull the same amount of current no matter the selected speed of the engine.
So when the motor is going slow, we are relocating the current draw to the variable resistor.

The PWM only pulls current during the on cycle of the square wave pulse. When it is off, the motor is coasting. But since the duty cycle is high, you do not perceive a difference. So when the motor is going slow, we save battery power because it is only on a % of the time.

So the way I see it, it is simply a way to control the current flow (Speed of the motor). It also allows us, depending on circuit design, to maintain a constant current regardless of changing electrolyte resistance. But if you get 1.2 LPM at 25 Amps, then you will only get 1.2 LPM with a PWM at 25 Amps. You are still drawing 25 Amps either way and that will still produce the same amount of heat based on the Power law. Power (in Watts) = Current (In Amps) x Voltage (in Volts).

So the only purpose of a PWM is the ability to control current through the cell more efficiently than using a variable load in-line with the cell and more easily than getting out and adding KOH to the Cell. OR adding a feedback circuit and using it to supply a constant current over changing conditions.

As for making the water split based on a resonant frequency, I have to call BS on that one. If anyone here can reproduce that in front of a room of engineers and physicists, you will be wealthy. That is the holy grail of Hydrogen Power, efficient electrolysis of water.
07-13-2008 06:57 PM
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stevekos7 Offline
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Post: #3
RE: PWM benefits?
CheezWiz Wrote:Steve,

I am waiting for one of you guys to answer this myself. I do not want to hear the hype from someone making a buck.
I do not understand how it could produce the same amount. Work can only be done when the electrons flow. The electrons only flow during the active part of the duty cycle on a PWM.

My example:
Say we want to control the speed of a DC motor and we only have these two choices, variable resistor or PWM.
Both will work equally well, but the resistor method will always pull the same amount of current no matter the selected speed of the engine.
So when the motor is going slow, we are relocating the current draw to the variable resistor.

The PWM only pulls current during the on cycle of the square wave pulse. When it is off, the motor is coasting. But since the duty cycle is high, you do not perceive a difference. So when the motor is going slow, we save battery power because it is only on a % of the time.

So the way I see it, it is simply a way to control the current flow (Speed of the motor). It also allows us, depending on circuit design, to maintain a constant current regardless of changing electrolyte resistance. But if you get 1.2 LPM at 25 Amps, then you will only get 1.2 LPM with a PWM at 25 Amps. You are still drawing 25 Amps either way and that will still produce the same amount of heat based on the Power law. Power (in Watts) = Current (In Amps) x Voltage (in Volts).

So the only purpose of a PWM is the ability to control current through the cell more efficiently than using a variable load in-line with the cell and more easily than getting out and adding KOH to the Cell. OR adding a feedback circuit and using it to supply a constant current over changing conditions.

As for making the water split based on a resonant frequency, I have to call BS on that one. If anyone here can reproduce that in front of a room of engineers and physicists, you will be wealthy. That is the holy grail of Hydrogen Power, efficient electrolysis of water.

Are you on a mission CheezWiz? I understand your frustration though, you do get alot of either deliberate misleading info, or just well-meaning but ignorance from people who just repeat what they heard from someone else. However, there are some truly knowledgeable people around on these forums who do have something constructive to contribute. All I want like anyone else is not to be led on a 'wild goose chase' or get ripped off by some huckster.

That said, regarding the PWM issue, my understanding of things is that the PWM can be used to reduce the applied current by allowing the capacitive characteristic of the electrolyzer cell to be utilized. I am led to believe that the current is pulsed to allow the discharging of the capacitance to assist with the work rather than excessive amperage having to be used, which will not only electrolyze the water, but will also heat the water excessively. Because the stainless steel is a semiconducter and hence also a capacitor, it will only allow so much flow of current, so if we want to deliver current across a number of plates we must 'push' the current through the resistance. This achieves the result, but also heats the water. If it is pused, the built up charge can be allowed to dissipate and maintain the overall current without the same amperage draw in nett terms.

Is this a correct summary of the PMW theory? And more important, does it really work?

If it is true, we should be able to achieve more nett gas output from lower amps, keeping the cell cooler than with brute force electrolysis (or rather, maximum output with lower amperage draw).
07-13-2008 09:01 PM
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Gary Offline
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Post: #4
RE: PWM benefits?
That's what I've read too. Also some discussion about the pulses possibly knocking bubbles off the plates, but at over 10k/sec pulses, I doubt you're gonna get any bubbles to move out of the way that fast, so I'm skeptical. There is also talk about some sweet spot frequency or harmonics therof that does some magical exponential work, but haven't seen any experiment done to verify this ... yet. It would seem to be an easy one to do, with a flowmeter and a variable speed PWM; just hook it up and see where it puts out the most, no?
07-14-2008 04:01 AM
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CheezWiz Offline
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Post: #5
RE: PWM benefits?
I guess like most here, I am on a mission for the truth. I am fact-finding to build a setup from scratch that uses the best design I can find. At the same time, I want to be sure that information is grounded in reality. If I see something blatantly wrong, I feel a need to express that if only to assist others like us in the future. This is definitely a field of play loaded with snake oil mongers making outrageous claims. I have settled on this forum because the people here and the mod seem to have my same desire to communicate honest and grounded information with each other for the benefit of the community.

That is why if one of the folks around here who is not a salesman will actually do some experiments to prove the PWM stuff, I will be more inclined to accept it. Unfortunately I am not in a position to do some of these experiments myself so I am living through others at the moment.

The majority of info here that is misguided is not on purpose or meant to deceive anyone, but that does not mean we should not correct obvious discrepancies with the truth, for the benefit of us all.
07-14-2008 06:09 AM
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a3holerman Offline
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Post: #6
RE: PWM benefits?
Hi,

Just to add a few thoughts. The only practical purpose of a pwm at this time is to control the current. The capitance of the cell has many variables and changes almost constantly. A pwm will allow you to use a higher concentrate of electrolyte and get a good output while cold and still be able to keep the current in check as it warms up. Keep in mind that a pwm needs to be rated at the max current your cell will draw when hot. If you cell draws 25A hot then the pwm will always pulse it at 25A hot even the average current may be only 15A.

Tom
Cape Cod
07-14-2008 06:19 AM
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tomqwest Offline
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Post: #7
RE: PWM benefits?
CheezWiz Wrote:I guess like most here, I am on a mission for the truth. I am fact-finding to build a setup from scratch that uses the best design I can find. At the same time, I want to be sure that information is grounded in reality. If I see something blatantly wrong, I feel a need to express that if only to assist others like us in the future. This is definitely a field of play loaded with snake oil mongers making outrageous claims. I have settled on this forum because the people here and the mod seem to have my same desire to communicate honest and grounded information with each other for the benefit of the community.

That is why if one of the folks around here who is not a salesman will actually do some experiments to prove the PWM stuff, I will be more inclined to accept it. Unfortunately I am not in a position to do some of these experiments myself so I am living through others at the moment.

The majority of info here that is misguided is not on purpose or meant to deceive anyone, but that does not mean we should not correct obvious discrepancies with the truth, for the benefit of us all.

I am building a PWM and have most of the circuits working. It is based on a hybrid of Bob Boyce and Stanley Meyer design. When complete it will provide an adjustable "mark" generator to control duty cycle, utilizing the capacitive nature of the HHO cell. Two adjustable independent frequencies can be "superimposed" on the mark signal.

I have been experimenting with a Save Fuel HHO generator, Sonic Spark Plugs, EFIE. I will be testing EE Fuel shortly. I have invested a considerable amount of time and money on this project and I want to make a living from my research.

I have 5 kids, the oldest is at Yale, the second oldest made me a grandfather a couple of years ago and I still have 3 teenage daughters at home.

The alternative energy field is expected to grow to a multi-billion dollar industry in the next couple of years. You can wait for all the X-Oil guys to make the money or you can try to make an honest living from it yourself. Something like the guy who started this forum, as an example.

When I complete and test this unit and if the results are positive, I will sell the completed units and the schematics to anyone who has enough nerve to get involved with hydrogen.

Probably will be a few disclaimers regarding liability.Crazy
Your thoughts

Tomqwest

Tomqwest http://www.AER2.net
99 Acura 3.0
Sonic Spark Plugs
Save Fuel SL50
EFIE
In test: PWM & EE Fuel
07-14-2008 02:52 PM
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skiers4ever Offline
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Post: #8
RE: PWM benefits?
Great idea tomqwest! Good luck and much success!!! John

2007 Honda Ridgeline 3.5L 4WD
Hydro Super 2 installed on 5/21/08
Colorado - 10,000 Feet!
07-14-2008 03:00 PM
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CheezWiz Offline
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Post: #9
RE: PWM benefits?
tomqwest Wrote:I am building a PWM and have most of the circuits working. It is based on a hybrid of Bob Boyce and Stanley Meyer design. When complete it will provide an adjustable "mark" generator to control duty cycle, utilizing the capacitive nature of the HHO cell. Two adjustable independent frequencies can be "superimposed" on the mark signal.

I have been experimenting with a Save Fuel HHO generator, Sonic Spark Plugs, EFIE. I will be testing EE Fuel shortly. I have invested a considerable amount of time and money on this project and I want to make a living from my research.

I have 5 kids, the oldest is at Yale, the second oldest made me a grandfather a couple of years ago and I still have 3 teenage daughters at home.

The alternative energy field is expected to grow to a multi-billion dollar industry in the next couple of years. You can wait for all the X-Oil guys to make the money or you can try to make an honest living from it yourself. Something like the guy who started this forum, as an example.

When I complete and test this unit and if the results are positive, I will sell the completed units and the schematics to anyone who has enough nerve to get involved with hydrogen.

Probably will be a few disclaimers regarding liability.Crazy
Your thoughts

Tomqwest

Wow 5 Kids, you are a brave man indeed!

I would love to see your work!! Is there anything you can share without compromising your investments at this time? How about non-disclosure agreements for those willing to validate your results?

I agree that it is going to explode very soon or we will doom ourselves to extinction. We have no choice but to innovate. I am trying to finish school while also working full time as an IT guy or I would be all in this stuff. I cannot imagine how you find the time to do any research.

I do not know what kind of library resources you have, but I work at what is primarily an engineering University in Tennessee and have access to a plethora of research journals and similar resources. If you find a site pointing to an article in a journal, I can most likely pull that for you. I have a background in Electrical Engineering and Computer Science as well so I can talk technical... Big Grin

That goes for everyone else around here as well...
(This post was last modified: 07-14-2008 06:27 PM by CheezWiz.)
07-14-2008 03:16 PM
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stevekos7 Offline
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Post: #10
RE: PWM benefits?
My intentions for working on this project are mainly personal, however I have plenty of friends who are interested in me helping them if my system shows real results. I have a part time business marketing 4wd gear, so that is a natural outlet for me, but this is not my main objective. I am just very interested to see the theories work in my real world. It's been fun to tinker with this stuff, and although my progress has been varied and slow, I am starting to get the results I am looking for. My current generator is producing around the mark for a trial installation and test run in my vehicle. If it shows results I will go the next step and look into enhancements like a PWM and EFIE etc.

The trouble seems to be in working out what is necessary to get at least a baseline improvement with a simple system first. I don't want to spend much more money unless I know it is necessary and will offer definite improvements.

Thanks to all contributors for the information and insight that has got me this far.
07-14-2008 09:10 PM
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