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Old 09-09-2008, 11:41 AM   #11
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duty cycle refers to the on time vs the off time.

a 50 percent duty cycle would be on for half and off for half and result in half the voltage (average)

a 10 percent duty cycle would be on for 10 percent and off for 90 resulting in one tenth the voltage (average)

this means that it will use half or a tenth (depending on which example above) of the current that you would use if it were straight wired to the battery.

this in essence keeps the heat down as well.

*edit* I don't get into the whole HHO concept but this is the same thing that they do with variable AC drives and with DC drives (motor drives that is). I know that PWMs work because industrty has been using them for years but to apply it to electrolysis? the concept of lowering the average voltage is still the same, the rest is still up for debate
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Old 09-09-2008, 06:51 PM   #12
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I would think since this is a chemical reaction, the PWM would serve to reduce current but not voltage. If you want to reduce voltage per cell, use more cells in series.

If you just want to use the PWM to adjust L/Hr of hydrogen flow, by all means. But if you're still running 12v on one cell, it's still less efficient than ~3v per cell.
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Old 09-10-2008, 03:42 AM   #13
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Yeah but the higher voltage would cause a faster reaction and for more product in the end. I thought the PWM was there to control how long it was to be running at the higher voltage cause you dont always need to run top voltage.... i dont really know though i could be totally wrong
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Old 09-10-2008, 08:13 AM   #14
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Higher voltage will indeed increase the CURRENT, which will make more HHO to a point. Above a certain point you're making far more heat, which causes you to be making steam instead of mostly HHO. This is why it's best to set your cell voltage to around the ideal (3v per cell I think?) and add more cells or more plate area if you need more HHO. Once your cell is big enough to make the maximum flow of HHO you could possibly need, you can use a PWM to turn it *down* from there for the times you need less. The voltage will still be where it should be, but since it'll only be on part of the time due to the PWM the flow will drop.
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Old 09-10-2008, 09:34 AM   #15
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but if you run a duty cycle of 20 percent on a 12 volt system (more like 14 with the alternator) then you are hitting 2.4 volts (2.8 on 14 volts) depending on the frequency.

that is why your house voltage is 120 volts and not 177. 120 is the average. if you look at the actual sine wave, you will see it go to 177 but that is just at its max.

think of a pwm like a dimmer switch. the light is being pulsed on and off but it is being done so fast that instead of the light flickering on and off it actually looks dimmer. same concept. and just for reference sake, modern dimmer switches don't use resistors but a solid state switch of some sort. I would guess either an SCR or diac. I used to know but college was so long ago.

age will getcha man
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Old 09-10-2008, 09:45 AM   #16
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Yeah thanks for the info guys, im planning on installing a switch so i can control the duty cycle and i also plan on adding a temp gauge in the cell so i can see if it is getting to hot or to the point of boiling cuase i do drive alot so it could be on for awhile
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Old 09-10-2008, 04:27 PM   #17
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BEEF: I'm extremely familiar with how both light dimmers (Phase Angle control) and PWM works. 120vac is 120v RMS, which is different because we're talking sine waves with 120vac, not SQUARE waves like a PWM.

You'll get a lower average voltage across things like inductive loads with a PWM, but you have a CHEMICAL load here. IF you run a 12v PWM on a HHO cell, it'll still see 12v even if only 20% of the time. The rest of the time the cell just turns off. But, the reaction needs much much less than 12v, any more than that, even for a few milliseconds at a time, is excessive and wastes energy.

If you want an idea of my electronics knowledge, I work with these guys on occasion:

http://www.youtube.com/watch?v=bcaf9Qb4ncA
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Old 09-15-2008, 11:46 AM   #18
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if you want an idea of MY electronics knowledge, check out RFMD.COM.

that is where I work and make ICs (power amplifiers to be exact). I think I may know a think or two. but enough about credentials.

if the reaction time isn't fast enough for the "jar", just put a PWM onto a transformer and then rectify the voltage to whatever. then you have an all but pure DC voltage coming out. just make sure you get large enough components so they don't burn up.

*edit* to get technical, you will still have some ripple on the DC but I don't think that small amount will really affect anything. and how is it not different from the dimmer switch? the dimmer cuts half the the wave off (or however much you want) and it is the leading edge. the only difference that I can see is that the load is a "chemical" load as you call it and maybe the reaction time of the "chemical" load is different. I will admit that I don't know much about chemical loads and how fast they react to voltage (be it pulsed DC or constant DC)
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Old 09-15-2008, 01:28 PM   #19
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Cool, please experiment away. I would to but don't have time yet.

As for the correct amount of voltage for a cell, couldn't you just measure the resistance across the terminals?

As for add ins, can you even electrolysize distilled water? I thought it was an insulator.

I remember being told once to try 10-30% sulfuric acid solution and I did and while it did produce more it directly increased required amperage. Now I see people suggesting lye (either potassium hydroxide or sodium hydroxide), though I think potassium hydroxide seems to be the most prefered.

Definately look up the chemical reactions for your choice first! Potassium Hydroxide creates a salt byproduct (iirc) but some, like baking soda, can produce gas by products.

Here, I just attached (edit: too big, here's a link http://www.christopherjwerner.com/files/HHOgen.pdf ) a PDF I found most recently that I was going to use as a guide. I uderstand what PWM is and does (I've built a megasquirt and am building an AC motor controller), but this guy is suggesting PWM to pulsing the inner coil of an alternator and then feeding 3 phase AC to the cells. Can you guys suggest to me the point of this? Plus he's using delta winding, so does this prevent the cells from reversing (I can only picture how 2 leads of a single phase AC looks like as a wave, not how it works when sharing a ground like that).
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Old 09-16-2008, 09:11 AM   #20
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itsjustagame,

as a disclaimer: I don't really get into HHO but I do get into electronics (my career). I have done high freq communications for 5 years now and have done industrial electonics for 4 years total.

that being said, in general, 3 phase is much more efficient than single phase and relatively easy to produce. also look at the 3 phase design as 3 seperate single phase designs. forget about ground but more positive and negative. of course they change phases which reverses the polarity but look at each winding as a single phase seperately. now, they are 120 degrees out of phase which fills in the gaps of your normal single phase system (I wish I had a paper and pencil on this site). also, it doesn't have to be 208 volts or 240 or 480 for that matter. if he is fabricating his own, he can set the voltage to whatever he wants depending on configuration.

I am not a chemical engineer so I don't know how this will affect a chemical reaction as stated above but I believe that is the theory behind it. I am sure that someone will have issues with what I have said but hey, life goes on.

also on a side note: what are you using for the logic on your AC drive. I am sure the front end is simple enough with just a diode bridge and some huge capacitors and the back end the same with some transistors but what kind of logic are you using to fire the transistors (6, one for each half phase). it has been a while since I have played with a drive (2 years or so) and quite a while back, I was trying to figure out the logic to build a simplified one myself. also, for testing, you can use a lamp load with just 3 or 6 light bulbs in a delta formation. in very low frequencies, you can actually see the rotation (the pattern anyway).

good luck to you on the motor drive
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