Temperature and duty cycle controlling PWM help needed!

I am working on a Hydrogen generation project. I am using a PWM (pulse width modulator) to control the Generator from going into thermal runaway. However, the current PWM's on the market dont offer temperature control. Only duty cycle control.

So I need some help here. I need a way to control a potentiometer to increase or decrease resistance based upon a temperature range from 80 to 95 degrees. I dont want this to turn the unit off, only lower the duty cycle when the peak temp is reached. Then also, when the unit is cold on start up, it would release full amps into it until it reached it peak operating temp.

The idea is to make a PWM control the generator via duty cycle (amperage draw) and temperature. Make it a "set it, and forget it" system.

My thoughts are using two surface mount thermostatic switches. One for low limit the other for the high limit. Then a relay and another potentiaometer.

Theory of operation: On initial start up, the generator is offered full amperage draw of 40 amps(100% duty cycle) until it reaches its operating temperature of 80 to 95 degrees. Once it reaches the peak of the operating temp the upper limit switch kicks open causing a relay to offer a differing resistance (80% duty cycle) that would effectively make the PWM still keep producing hydrogen, but cool down. When or if the lower limit of 80 degrees is reached the lower limit thermostat would close allowing again 100% duty cycle to the generator. 
Thus, this system would keep the generator operating at an optimal temperature at all times regardless of outside temperature, and conditions.

Current PWM's require the user to manually get them set. If the outside temps are colder the system will work less effectively. If the outside temps are hotter the temps may cause thermal runaway. All operating conditions require the user to be constantly fiddling with, and keeping an eye on the amp draw, temps, and voltage. This means eyes not on the road while driving.
Bad ju-ju.

I'd like to make this device super simple to operate, and build. With off the shelf items, not custom IC's.

Any ideas?

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frollard4 years ago

eyes on the road?

Please for the love of god tell me you aren't generating hydrogen with your engine to feed fuel into your engine.
ydeardorff (author)  frollard4 years ago
Please, don't start.
I am a 20 year US NAVY aircraft mechanic. I have been working on hydrogen generation via electrolysis for 17 years now. I am now also going to WWU for Vehicle engineering and design degree.

Does electrolysis work? yes (been around for 200 years)
Can you run an engine on hydrogen? Yes you can?
Does putting HHO into your intake save on fuel economy? Yes it does (depending on the volume produced, and how much the generator draws in amperage)

Just like a ton of people out there whom say they have tried it and it didn't work, well operator error is most often the case. Being suckered by a mason jar generator seller is another. Unfortunately, we all have to deal with the charlatans out there. I went to building my own system from scratch, 1, I knew how, and 2, I could control the build quality.

A generator must be fit to the application, and must be adjusted to the current conditions. This isn't an Xbox you can just buy, plug in and expect to give opeac the finger. It requires knowledge, and studying to get it right.
This is an emerging technology, that has applications for creating pure water, fuel, disposal of human waste, etc. We are only scratching the surface with hydrogen generation technology applications.
Before you go knocking things do some reading, like the NASA report, look up Xogen systems. These are real, tangible Hydrogen generation system at work now!
At a minimum, even if a hydrogen generator doesn't give you better mileage, your emissions especially the ones called HC (hydrocarbons) you know the 70+ % of unburned gasoline going out your tail pipe? That's burned almost completely reducing your contributions to the air pollution out there.

So, enough with the naysayers about this and other green tech.
If you think you are not being taken to the cleaners by big business, the gas companies, big banks, or even our own government, think again. In fact I challenge anyone to find out for themselves. Dig, read up, find out for yourself. Just bring a bucket to throw up in.
In closing my rant,
HHO does work, and it works for many applications, not just engines. Why, so little energy is required to gain something that is so volatile. 5 times faster flame front than gasoline, and 4 times the energy release. Dont argue the facts with misinformation. try it yourself, be safe, then once you've got some experience behind you enter into the conversation with some experience behind you to help make this a viable energy source by itself.
dayjunk1 year ago

use a constant-current PWM like that of Zero Fossil's circuit

Buy an off the shelf temperature controller. Feed it with a temperature measurement from a thermistor, or thermocouple, and it will control your load for you.
ydeardorff (author)  steveastrouk4 years ago
Thanks, Ill look into it. Ive worked out a simple circuit using a high and low temp switch, with a potentiometer, and a relay.

I would like a better controller for the PWM.
I can't reply to your comment previous but I can reply here;

Let me be perfectly clear I was not pulling a 'know-more-than-thou' - it's just there simply hasn't been tangible evidence of hho systems increasing efficiency of an internal combustion engine. You might get more power out, like with a turbo or supercharger, but it involves using more fuel generally. Honestly, I'd love to see dymo results with a system like this installed - I'm genuinely interested in seeing the next generation(s) of vehicle power delivery. (Lithium chemistries are very promising)

As for your temperature controller, I second quatch's reply -- go with a microcontroller such as arduino (or my new favourite Teensy, arduino compatible) and search a quick easy sketch that varies pwm with input temperature (thermocouple with amplifier best for these temps, but thermistor would totally work). The linked PID script is really good because once dialed in it helps reach a set temperature without overshooting.
ydeardorff (author)  frollard4 years ago
Did you read the 38 Page NASA report from the 1970's? That's pretty conclusive to me. Nothing has been written up recently though, true.
For instance I managed by accident to create an electrical methane generator, and now am seeking a patent on it. Yet was initially trying to create a better hydrogen generator.
There are too many B.S'ers out there to know what is real or not, faked or fact. That's why I have gone to doing my own experiments, and building my own devices.

I almost picked up a digital thermostat at goodwill for 3 bucks, but wasnt sure if it would be right for what I need.
I like the idea of an arduino though! Designing a soft ramp off, and on based upon amperage and temperature would be perfect.. Then the output could control the potentiometer for the duty cycle on the PWM.
arduino out of the box has 6 pwm outputs - no external digital pot :)
ydeardorff (author)  frollard4 years ago
very cool ill have to check into this as an option.
I just looked into an hho instructable and it intrigued me to do the math; it's very loose math, but I have a big problem with how it works -- simply dilution.

According to http://youtu.be/2LtoW1wYdeg (someone who clearly knows what they're talking about and not inflating numbers) states for about 160 watts you get 1 litre of hho/minute. 10.6V at 15 amps in a strong electrolyte and good catalyst.
1 litre per minute. At 35 amps as per this instructable, you should get about double the output. maybe triple. I'll be totally overkill fair and say 3 litres per minute of hho.

A naturally aspirated 2L engine near idle (say 1000RPM for easy math, best case scenario for this thought) breathes 2 litres per 2 revolutions (4 stroke), Thus, it consumes 2000/2 = 1000 L/m of air (and fuel, which as a mist is only a few mL, negligible)
At high revs (say, 5000rpm) it's consuming 5000L/minute of mostly air.

Air, is
Chemical % by volume
Nitrogen (N2) 78.08
Oxygen (O2) 20.95
Argon (Ar) 0.93
Carbon Dioxide (CO2) 0.033
Other trace elements 0.007
Source is www.scifun.org

780 litres of nitrogen
210 litres of oxygen
10 litres of argon
3 litres of CO2

If you take 1000 litres of air, and add 3 litres of HHO, the percentages go to
780L Nitrogen 79.3%
211L Oxygen 21.5%
10L Argon 1.0%
1.8L Hydrogen. 0.18%
982.8 total
The lower explosive limit for hydrogen is 4% Until you get 4% (to a max of 75% in air) hydrogen will not even explode. An explosion is what makes an internal combustion engine run. It will not increase the burn rate of the air fuel mixture in any measurable way.

At high RPM it's ridiculously lower difference as a percentage.
Yes, the new 'fuel' and 'fuel additive' nature will happen -- straight gasoline will be .2fps, and hydrogen will be .4...but the difference is in the hundredth of a percent. The speeds quoted are for pure hydrogen, and this is a trace amount of hydrogen.

The difference is so astronomically low that it simply won't change the chemistry of how the fuel burns.
Compound the inefficiency of the engine to extract that as mechanical energy (20-30% at best, coupled with the alternator 70% at best, coupled with the HHO generator (I don't know but I suspect since it gets hot 50% at best), you have a 9% efficient system aimed at increasing efficiency. Correct me if I'm wrong, (these are loose quick numbers) but it says a lot.
ydeardorff (author)  frollard4 years ago
Yes even at idle on a 2 liter engine you need a rediculous amount of hydrogen to reach the lower limit for igniting it for its own sake.

With the current generation of generator designs out there some of the better ones are reach 6.0 MMW or a tiny bit better. Most are about 5 to 5.5MMW.

For instance my 5N3 Cell has run at anywhere depending on the test 5.0 through 6.2 MMW.

This is why these are only supplemental systems to augment the overall air fuel ratio.
You can run numbers all day long, and it will not seem to work out because their are too many variables. Just like engineers cannot mathematically explain how a helicopter flies. But it does. To the layman its fairly straight forward.
The easiest way to explain what is happening in the cylinder is the HHO introduced into the air/fuel ratio acts like a fuse lighter for every molecule of gasoline in the cylinder, and also has added pure oxygen to the mix too. Its flame speed and energy is so much higher than gasoline, it simply helps ALL the gasoline burn. Your not getting a boost from the hydrogen, the hydrogen is helping the engines efficiency. That is why when the exhaust gas analyzers are run on HHO augmented cars and trucks they little if any HC emissions. I don't know if that helps.
The same thing can be said for the fuel vaporizing shell gasoline opel. It got 376 mpg in the 70's, yet we dont see a single car on the road with anything resembling fuel vaporization. Hmm. It worked no doubt of that.
Even in that stupidly fobbed mythbusters exploding pants episode. They showed a hose coming off a hydrogen tank would run a car without the aid of gasoline. That hose wasn't putting out hundreds or even thousands of liters per minute. Yet that V8 car fired right up. Given the flame size that came off the end of that hose Id say it was probably 8 to 10 lpm of pure hydrogen. That would need to translate into a Hydrogen generator that could produce about 13 liters a minute.
mathematically we can explain how a helicopter flies. That is a myth.

'pure oxygen in the mix' -- no, it's mixed in with the input air. It adds .5% oxygen, which agreed, stocihiometrically accounts for the hydrogen being introduce, net neutral.

hose going into engine = fuel, not air. you use thousands of litres of AIR per minute, and only a few mL of fuel, when that fuel is expanded to gas form, its bigger, but so long as it's stoich balances the engine will run. 100% hydrogen doesn't burn, period. That mythbusters episode sounds totally legit. It took in thousands of litres of air and several tens or hundreds of litres of hydrogen. fuel + air. (oxygen) Just because it's a gas doesn't mean it isn't fuel.
'would say' 8-10 lpm...
It would be nice if they put a lpm gauge in the line, but I'm certain it was a LOT more than that.

I don't care to do the math right now...I already did. Like I said before. I want someone to take their stock car onto a dymo, show me the horsepower and an engine computer showing the fuel consumption, then repeat the test with an HHO generator. I guarantee the 'at the wheels' horsepower is lower.
ydeardorff (author)  frollard4 years ago
I am familiar of, but not with Arduino's. This is very interesting to me. But Ill have to put it on the back burner for the moment. It will take some studying to see how to utilize the Arduino the best.
In the meantime I'll need something a bit more ghetto, but solid to use. Im thinking for the time being either a thermostat (probably out of an RV, or space heater), or the bimetal switches, and a variable resistor.

Thanks everyone! There are no PWM's available for HHO that monitor both duty cycle and heat of the generator. Im trying to work with the guys from Volo to include Gas flow rates and current draw from the cell to make the next chips even better.
you can do it with an arduino, if that's to your liking. Have a look for arduino PID controllers, such as: http://playground.arduino.cc/Code/PIDLibrary (I've no idea if this one is good. My friend who's given it a try is beyond cell service this week).
ydeardorff (author)  quatch4 years ago
you've got my interest...