All About Circuits Forum  

Go Back   All About Circuits Forum > All About Circuits Commmunity Forums > Off-Topic

Notices

Off-Topic A place to discuss anything other than electronics with other members. General conversation allowed, but please have consideration for your fellow members.

Closed Thread   Post New Thread
 
Thread Tools Display Modes
  #111  
Old 09-07-2008, 06:55 AM
SgtWookie's Avatar
SgtWookie SgtWookie is offline
Expert Member
 
Join Date: Jul 2007
Location: In the vast midwest of the USA; CST
Posts: 22,032
Default

Quote:
Originally Posted by Oldtech2 View Post
[SIZE=2]Its good to see others out here working hard, spending their time trying to find a way to do what others say is not possible.
Difficult can be done right away. Impossible just takes a bit longer.

Quote:
To help rather than sitting back, providing out dated data and formulas that history continues to show, formulas often needs to be modified to include additional new revised data.
And that's exactly the problem we're seeing nowadays. No accurate, reliable data from experimenters in this field.
Quote:
If those that criticize, would stop and realize, they are putting themselves in the same category of the stone throwers that criticize Tesla, Madame Curi, the Wright Brothers and so many others, that worked very hard to find solutions that add to the betterment of mankind.
I'm not categorizing myself. However, I have yet to see one single, solid piece of scientifically documented proof that any of these circuits are viable, or repeatable.

Quote:
When working together to make it possible much more can and will improve life for everyone.
True, but it can also result in a lot of very broke people from buying gadgets that don't work.
Quote:
Don’t limit your knowledge to what others thought they knew, keep searching beyond what they have taught you, findind a way to improve what they failed to learn is much more rewarding.
Like, magic?

Quote:
With that said, I would like to ask for assistance to improve a circuit I believe could be of value once improved a bit.
There's always that "slight bit of improvement" necessary. In reality, everything is a trade-off. About the best you can hope for in electronic circuits is 97% efficiency, and that's a handful of hoping. Usually, it's much less.

Quote:
Has anyone here built the current regulated PWM on Zero fossil fuel site? Or can anyone recommend how to improve the current control. It has problems driving the Mosfet gate when setting a max current level you pick.
Made a small correction; I believe you meant "pick" instead of "kick". However, problems abound with circuits found amongst the HHO crowd.
Quote:
Scope shows peak voltage levels decline leading to higher temp of Mosfet.
Check the gate voltage. If it's not >=10v or <=0v, you have a problem.
MOSFETs have a positive temperature coefficient; as they get hot, their Rds increases, which might account for your peak voltage decline. Use a higher-rated MOSFET, increase cooling (water cooling works great!), use multiple MOSFETs in parallel, etc.

Quote:
Manually changing duty cycle works but hard to fine tune and doesn’t hold at set level due to load changes as HHO cell warms up.
You seem to have a number of issues going on here; MOSFET heating, PWM needs changing, etc.

Here's something that is common knowledge, and should be quite helpful:
Water has a higher dielectric constant than air. As water heats up, it's dielectric constant lowers. At room temperature, pure water has a dielectric constant of about 80. Near boiling, it's dielectric constant drops to around 55.
Air has a different set of dielectric properties. It's values may range from 70 down to 30, or perhaps even less. This is standard "air" that we breathe in/out every day, and not specifically HHO. I don't know offhand what the dielectric constant of HHO is.

So, at room temperature with no current applied, you have one dielectric constant; that of pure water. Then you apply current, and your dielectric constant changes, because you begin to get HHO bubbles in the water.

As temperature increases, the dielectric properties of the water changes (decreases), and as HHO production increases, the dielectric properties again decrease (this is pure speculation on my part.)

Quote:
Getting to old to relearn everything that was lost after severe head injury yet still trying ……could use a hand.
Look, I'm not a complete skeptic. I AM skeptical when wild claims are made with incomplete/nonexistant documentation is supplied.

However, I have given you what I believe to be reasonable and rational explanations for the variations you are seeing, with what sparse input you have provided. I am not a miracle worker.

However, if you do some research, you will likely find that my suggestions/assertions are within reasonable limits of practicality.

What I would like from you is much better documentation on what you are doing, schematics, circuit layouts - basically, facts. As many facts as you have.

What this whole area is lacking is facts to back up claims. Claims without facts backing them up are simply lies.
__________________
General info:
If you have a question, please start a thread/topic. I do not provide gratis assistance via PM nor E-mail, as that would violate the intent of this Board, which is sharing knowledge ... and deprives you of other knowledgeable input.

Last edited by SgtWookie; 09-07-2008 at 09:10 PM.
  #112  
Old 09-07-2008, 07:22 AM
SgtWookie's Avatar
SgtWookie SgtWookie is offline
Expert Member
 
Join Date: Jul 2007
Location: In the vast midwest of the USA; CST
Posts: 22,032
Default

An LM324 is being used to charge/discharge the gate of an IRFP064N via a 100 Ohm resistor, with an additional load to ground from a 1k resistor. Abysmal waveforms on the gate should be expected.

An LM324 can only source/sink about 30mA (practical limit) to begin with. If you want your MOSFET to keep cool, you will need a much higher source/sink capability.

I'm quite unimpressed with the circuit.
__________________
General info:
If you have a question, please start a thread/topic. I do not provide gratis assistance via PM nor E-mail, as that would violate the intent of this Board, which is sharing knowledge ... and deprives you of other knowledgeable input.
  #113  
Old 09-08-2008, 01:14 AM
thingmaker3's Avatar
thingmaker3 thingmaker3 is offline
Super Moderator
 
Join Date: May 2005
Location: Rural, Oregon GMT -8
Posts: 5,072
Blog Entries: 6
Default

Quote:
Originally Posted by Oldtech2 View Post
Has anyone here built the current regulated PWM on Zero fossil fuel site? Or can anyone recommend how to improve the current control. It has problems driving the Mosfet gate when setting a max current level you kick.
Try adding a driver (totem pole or some such) between R9 and Q1. Get rid of R13. Tie the free end of VR2 to the wiper arm of same (engines are electronically very noisy environments.)

I also wonder if C4 might be more useful connected to the junction of R10 & R12 instead of R10 and the Op Amp i/p.
__________________
"I want to establish in your mind very clearly that you must not think I deny all that I do not admit. On the contrary, I think there are many things which may be true, and which I shall receive as such hereafter, though I do not as yet receive them; but that is not because there is any proof to the contrary, but that the proof in the affirmative is not yet sufficient for me"
- Michael Faraday
  #114  
Old 09-08-2008, 03:14 PM
SgtWookie's Avatar
SgtWookie SgtWookie is offline
Expert Member
 
Join Date: Jul 2007
Location: In the vast midwest of the USA; CST
Posts: 22,032
Default

There does need to be a pull-down resistor on the gate of Q1, for when there is no power applied to the unit (if power is not completely removed from the cell). Otherwise, the gate could float, turning on Q1, resulting in an accumulation of HHO.

My complaint about R13 was based on it's small value of 1k. Increasing it to 10k or 20k would still allow it to perform it's power-off function, and the gate turn-on times would be improved.

As it is, with the 10v regulator, the output of an LM324 can range from 0v to Vcc -1.5v with a 2k load, meaning the gate's max voltage is <8.5v - when the opamp is at room temp; if Vcc=15v, typical source= -30mA, typ sink= 20mA. Those numbers go way down over the full temp range; -10mA and 5mA - and as everyone should know, automotive environments are among the most severe. As Vcc is 10v instead of 15v, those numbers should be further de-rated.

So, as the opamp heated up, the MOSFET would be operating in the linear region much of the time. As Thingmaker3 noted, a gate driver is a must.

The LM324/LM324A is only rated for operation from 0C to 70C, thus is not appropriate for automotive applications. The LM2902/LM2902Q is rated for -40C to 125C, and would at least satisfy the temperature range requirements.
__________________
General info:
If you have a question, please start a thread/topic. I do not provide gratis assistance via PM nor E-mail, as that would violate the intent of this Board, which is sharing knowledge ... and deprives you of other knowledgeable input.
  #115  
Old 09-09-2008, 02:37 AM
beenthere's Avatar
beenthere beenthere is offline
Senior Member
 
Join Date: Apr 2004
Location: Missouri, USA (GMT -6)
Posts: 15,815
Blog Entries: 10
Default

My favorite quote from the zero fossil fuel site - "All plans shown are intended for educational purposes or off-road use only."

Something like the PWM electrolyzer would be easy to set up on a bench and actually measure the quantity of gas evolved over time. Be easy to demo the truth or falsity of the "magic frequency" or "resonant electrolysis cell". Anything will work as an electrolyte, although current should result more form electrode area than from saturating the water with vinegar or salt. Be a good idea to monitor cell temp, too, to account for evaporative loss. Also a good idea to vent the puppy outside.
__________________
First comes the hardware, then the software.
  #116  
Old 09-09-2008, 04:09 AM
SgtWookie's Avatar
SgtWookie SgtWookie is offline
Expert Member
 
Join Date: Jul 2007
Location: In the vast midwest of the USA; CST
Posts: 22,032
Default

Quote:
Originally Posted by beenthere View Post
My favorite quote from the zero fossil fuel site - "All plans shown are intended for educational purposes or off-road use only."
Well, of course they had to include that. I'm sure they didn't want to get sued. I'm surprised that the disclaimer wasn't much more lengthy.

Quote:
Something like the PWM electrolyzer would be easy to set up on a bench and actually measure the quantity of gas evolved over time.
What would be much more meaningful would be gas_qty/power_consumed.

Quote:
Be easy to demo the truth or falsity of the "magic frequency" or "resonant electrolysis cell".
Not as easy as you might think. I've already mentioned in this thread (yesterday, 2:55am) that the dielectric constant of a "cell" will change considerably over temperature and even more when HHO (forgive the shorthand) is generated. Quite frankly, I do not know what the dielectric constant of "Brown's Gas" is. I only have a "hunch" and a comparison to known statistics on the dielectric properties of a random atmospheric sampling.

In the "purely speculative" department, I've heard "rumors" that this "magic frequency" is in the vicinity of 40kHz under certain conditions - but it doesn't involve an electrolyte, and the water must be absolutely pure.

Quote:
Anything will work as an electrolyte, although current should result more from electrode area than from saturating the water with vinegar or salt.
Many electrolytes will result in hazardous or harmful gasses being emitted, and/or will be very destructive to the equipment. I don't know of an electrolyte offhand that is "perfect" and "inexpensive" to boot. There are disadvantages to both electrolytes that you mentioned, but I am not a chemist.
Quote:
Be a good idea to monitor cell temp, too, to account for evaporative loss.
Along with cell temperature, the level of the water in the cell would be critical to maintaining efficiency. I suggest that water should be added at the same rate as it is turned into Brown's Gas, in an attempt to minimize temperature fluctuations in the cell.
Quote:
Also a good idea to vent the puppy outside.
Even with small amounts of "HHO" generation, it would be quite foolish to attempt an experiment like this in any kind of enclosed space. A breezeway with two open sides, an open carport (3 sides open), or a garage with the main door wide open and a large fan exchanging air with the outside would likely be sufficient. It would not take much "HHO" gas accumulation to produce a large (and very potentially fatal) explosion.

SAFETY must be the primary consideration.

If you like danger, I have a phone number for you.
1-800-MARINES
__________________
General info:
If you have a question, please start a thread/topic. I do not provide gratis assistance via PM nor E-mail, as that would violate the intent of this Board, which is sharing knowledge ... and deprives you of other knowledgeable input.
  #117  
Old 09-09-2008, 06:26 PM
beenthere's Avatar
beenthere beenthere is offline
Senior Member
 
Join Date: Apr 2004
Location: Missouri, USA (GMT -6)
Posts: 15,815
Blog Entries: 10
Default

1. get a cell generating Brown's gas with DC applied to the electrodes. use the same voltage as for the PWM. Measure evolution of gas over time.

2. set up for PWM. Try frequencies around the 43 KHz region (given as the magic freq). Measure rate of gas evolution.

3. This is purely for experiment - long term damage to electrodes due to use of not-so-good-over-the-long-term electrolyte not too significant. The purpose is to see if the claim that PWM beats DC for electrolyzing water is true or false.

4. Wouldn't sweat the outdoor aspect too much - I don't see much gas coming out of the cell with 12 volts applied and a reasonable current. You don't want to pull the battery down with this setup under the hood, so try to figure how much capacity is left over with the lights and defroster full on. Maybe 20 amps? That's only 240 watts.

5. There is a convenient method to measure quantity of gas produced and also lead the gas outside safely. Anybody wants to set up for the experiment let me know and I will describe the apparatus (clear plastic tubing, a wood clothes pin, an IR diode, and a phototransistor).
__________________
First comes the hardware, then the software.
  #118  
Old 09-09-2008, 09:32 PM
Bill_Marsden's Avatar
Bill_Marsden Bill_Marsden is offline
Super Moderator
 
Join Date: Mar 2008
Location: Dallas, TX (GMT-5 w/ DST)
Posts: 19,024
Blog Entries: 5
Default

For precision I would suggest a flow meter, which will measure Cubic whatever/sec. Basically it is a ball enclosed in an acrylic body in a very slowly tapering funnel. The ball moves according to gas flow.



I found this one here.

Many of them come with an needle valve built in, you just adjust if for max and use the meter part.
__________________
..
"Good enough is enemy of the best." An old engineering saying, Author unknown.

General info:
If you have a question, please start a thread/topic. I do not provide gratis assistance via PM nor E-mail, as that would violate the intent of this Board, which is sharing knowledge ... and deprives you of other knowledgeable input. Thanks for the verbage Wookie.
  #119  
Old 09-10-2008, 12:33 AM
beenthere's Avatar
beenthere beenthere is offline
Senior Member
 
Join Date: Apr 2004
Location: Missouri, USA (GMT -6)
Posts: 15,815
Blog Entries: 10
Default

Well, not to suggest that this be too crude, but the experiment I have in mind is to see if some form or frequency of PWM has a positive effect on the rate of electrolysis of water.

The method I am putting forth for tracking the rate of gas flow uses a water filled U bend in tubing and a phototransistor & IR diode to signal the passage of each bubble. More bubbles in a given period means more electrolysis. The bubbles are remarkably uniform, so the results are accurate (we used this to track methane formation in hog waste digesters). All you need is a counter and a time base.

My hypothesis is that interruptions in current mean reduced electrolyzing.

Now I may have to set up a cell. At least doing the PWM might be easier with my old Heathkit signal generator - I can tweak the square wave output above 10 volts and the frequency scan gets easy with all the adjustment knobs. Hopefully it's not something odd like 42,841 HZ for the magic frequency.
__________________
First comes the hardware, then the software.
  #120  
Old 09-10-2008, 04:04 AM
SgtWookie's Avatar
SgtWookie SgtWookie is offline
Expert Member
 
Join Date: Jul 2007
Location: In the vast midwest of the USA; CST
Posts: 22,032
Default

Interesting about the U-shaped tube bubble-counter. It'll make for a good backfire preventer, too. Do you have a tubing size in mind?

Back to the PWM thing; the story I'd read about that is some fellow (who's name I forgot) had this race boat that had a HHO generator in it, that was of course supplied by the alternator. It normally wasn't producing a great deal of gas, but then one day he noticed that a particular engine speed, the volume of gas being produced went way up, and he had no clue why.

He later found out that one of the rectifiers in the bridge of the alternator had failed, so he was actually feeding his gas generator a more-or-less square wave, and it seemed to cause the gas output to increase a great deal somewhere in the low 40kHz range.

That's basically the story. I don't recall what he was using for an electrolyte, or if he even mentioned it. Anyway, I've seen some pretty wild claims and outlandish schematics, but that story might actually have a chance of being more than merely wishful thinking.
__________________
General info:
If you have a question, please start a thread/topic. I do not provide gratis assistance via PM nor E-mail, as that would violate the intent of this Board, which is sharing knowledge ... and deprives you of other knowledgeable input.
Closed Thread   Post New Thread

Tags
,


Related Site Pages
Section Title
Worksheet Microcontroller principles
Worksheet Design Project: Pulse-Width Modulation (PWM) signal generator
Worksheet Signal modulation
Worksheet Power conversion circuits
Textbook Pulse Width Modulation : Dc Motor Drives
Textbook PWM power controller : Analog Integrated Circuits


Similar Threads
Thread Thread Starter Forum Replies Last Post
Sine PWM FBorges22 Programmer's Corner 1 04-04-2012 03:59 PM
About my pwm sine power inverter schematic gaetan8888 The Projects Forum 15 03-02-2012 03:19 AM
simple pwm schematic sheldons General Electronics Chat 2 10-29-2011 08:24 PM
PWM control of an EBM-Pabst G1G170-AB05-20 fuzer_guy The Projects Forum 0 10-27-2011 11:15 PM
PWM Problems Dalaran Embedded Systems and Microcontrollers 12 01-11-2010 11:46 PM

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT. The time now is 06:32 AM.


User-posted content, unless source quoted, is licensed under a Creative Commons Public Domain License.
Powered by vBulletin
Copyright ©2000 - 2014, vBulletin Solutions, Inc.