Degree of difficulty for novice to build a DC-DC converter?

Discussion in 'General Electronics Chat' started by smp375, Mar 23, 2009.

  1. smp375

    Thread Starter Member

    Mar 21, 2009
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    I'm a novice with electronics. I have a basic understanding of principles and components, I know how to solder, and can read a schematic but I have to look up some of the symbols. I would like to build my own DC-DC buck converter for a project I'd like to undertake. Vin 12vdc Vout 4vdc (+/-2V), and I would need the device to be able to handle 30amps. The unit would be used to power an electrolyzer. I'm curious what the degree of difficulty would be to source parts and assemble a unit, for a novice like me. Any insight and advice would be appreciated.
     
  2. beenthere

    Retired Moderator

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  3. Audioguru

    New Member

    Dec 20, 2007
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    Nobody has proven that adding HHO to a car engine does anything except burn and destroy the valves and pistons.
    The car's emissions management computer gets all mixed up.
    When the mechanic who tests emissions sees your modifications then he is taught to fail the car without testing.
     
  4. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    Do yourself a favor and search the forum for threads related to HHO / Meyer.

    You will find some people spent a large amount of money for nothing.

    If you would like to repeat their experience, that's fine, but please save yourself a lot of time and money by spending a bit of time reading the results from people that weren't trying to sell you something.
     
  5. Audioguru

    New Member

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    Lots of people sell the HHO scam.
     
  6. thatoneguy

    AAC Fanatic!

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    To make up for lost cash? Like an unfortunate pyramid scheme?
     
  7. smp375

    Thread Starter Member

    Mar 21, 2009
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    Yes, this would be for a car; and it would be for an HHO system. I'm no fool, I've been a mechanic for nearly 20 years, I know my way around engine management systems, and know how to avoid catastrophic engine failures. Also, I'm not interested in anything anybody is selling, nor do I listen to any of the ridiculous hype promising me 50mpg for $200. I'm only doing research right now. If I choose to test a system I'll build it myself, and do so in a scientific manner.

    Pistons and valves get burnt with HHO because people who don't know enough, install incomplete systems in a hasty fashion, and allow their engines to run lean, which drives up combustion temperatures melting pistons and valves. A smart person uses an exhaust gas temp gauge, and monitors it for several thousand miles, under a variety of driving conditions, before altering their air/fuel system, and monitors the air:fuel ratio as well. As far as emissions testing is concerned, my car is not subject to a full inspection, and my state's laws on modifications are lenient unless the emissions are increased; in the case of proper HHO injection, emissions are lowered along with combustion temperatures. As far as the "emissions management computer" or ECU getting "all mixed up," the problem is simple; the HHO, increases combustion efficiency leaving behind too much oxygen and not the usual amount of poison. This creates a false lean condition, which is detected by the oxygen sensor and compensated for by the ECU. That compensation results in a true rich condition, which is actually not harmful to the engine; it just wastes fuel and increases hydrocarbon emissions. The problem arises when people use what is called an EFIE (electronic fuel injection enhancer) to modify the signal from the oxygen sensor to the ECU, which is intended to act as an offset to the fuel injection system and provide the proper air:fuel ratio. The problem is that the EFIE is user adjustable, and very sensitive, so far too easy to set lean if not careful. People get excited to see how little fuel they can use, or miscalculate how much HHO they are producing, and bam there goes a valve or a piston. I'm working with the guy who programmed my Saab to see if he can figure out a way to avoid using the EFIE, or at least electronically control it so stoichiometry is maintained at all times, regardless of HHO volume. If I'm successful I expect to realize a 25-30% increase in fuel economy, lower exhaust gas temperatures, and reduced emissions, which all equate to a cooler running engine, which equates to more power. Also, I'll get a great sense of satisfaction from designing and building a high quality, sophisticated piece of equipment.

    I appreciate the insight, as well as the concern for my engine; but I do not intend to do anything to harm my engine. I like the line in that article, "A designer's first DC-DC converter circuit generally has one thing in common with other first attempts: It doesn't work!" That sounds like a challenge!
     
  8. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    That is quite true. Don't let it discourage you though.

    As far as the HHO, if you get it working, I'd be interesting in seeing the setup! It sounds like you are a few steps ahead with engine knowledge vs. most that attempt the project.

    Second: Think about heat from two 100W light bulbs. That is roughly the amount of power you will be controlling.
     
  9. smp375

    Thread Starter Member

    Mar 21, 2009
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    When you mention the heat, and the amount of power I would be controlling, is that in regards to the DC-DC converter?
     
  10. thatoneguy

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    Yes. Usually about 70-90% efficient, dependent on design, frequency, transformer quality, etc. An output of 120-150W will need an input of over 180W as a rough guesstimate.
     
  11. smp375

    Thread Starter Member

    Mar 21, 2009
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    So that's about a 15 amp demand on my alternator, which should have at least 50 amps to spare. That is a significant demand, but it only equates to about 0.24hp. If the converter generated too much heat for a fan/heat sink, I could use a water system to cool it; those can be built cheap.
     
  12. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    While you are here, I have a question about vehicle fuel.

    When an engine is knocking or pinging, it is a sign of detonation, and a higher octane (slower to burn) fuel is used to match the engine's compression and ignition setup.

    Hydrogen burns much faster than gasoline. It is also a fuel, rather than an oxidant. I'm wondering how the presence of hydrogen, or a hydrogen derivative adds power.

    This is a serious question.
     
  13. smp375

    Thread Starter Member

    Mar 21, 2009
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    Detonation can be caused by a variety of factors; high compression, high boost pressure, over-advanced ignition timing, over-advance valve/cam timing, carbon build-up in the cylinder, intake or exhaust ports, or on the valves themselves, etc. In short detonation is autoignition and is bad because it causes multiple flame fronts (inefficient), which results in higher than normal temperatures, and a shock wave within the cylinder (which is the source of the audible ping). It is true that in the case of gasoline, higher octane burns slower. However, octane is not a measurement of burn rate, it is a measurement of any given fuel's resistance to autoignition; the slower burn rate is simply a secondary property of higher octane gasoline. There are plenty of fuels that burn much faster than gasoline, and have a significantly higher octane rating than gasoline. The electrolyzers that are being sold all over the internet, and built by many others are producing brown's gas, which is atomically equivalent to water,just happens to be the proper stoichiometric ratio for burning hydrogen as a fuel, and is >130 octane. I do know that fuel injection systems always run slightly rich, and under high load or wide open throttle (WOT) conditions they are programmed to run quite rich. Blending brown's gas into the intake air stream causes a more efficient burn of all the fuel in the cylinder which can only result in more power and better fuel economy, and the emissions from it are simply water vapor and oxygen. Also, hydrogen contains approximately 2.6 times the energy per unit mass as gasoline which results in more expansion within the cylinder, and it's burn properties create a more even burn throughout the piston downstroke which results in more torque.

    Now, like I mentioned earlier, I'm only doing research right now, and I'm avoiding the hype while only paying attention to scientific data and real-world experience. Think about this in realistic terms; these units are adding a fuel with significantly more potential energy than gasoline to an internal combustion engine along with the necessary oxygen to combust that fuel. An engine's performance is mostly limited by the volume of air:fuel it's able to draw in. In my first paragraph I mentioned that hydrogen contains about 2.6 times more energy than gasoline, which means that for every unit of mass of HHO there are 2.6 fewer units of mass of gasoline required to produce the equivalent reaction.

    In my case, my car is highly modified and produces about 100 horsepower above stock. To achieve this high power output my turbocharger is producing 25 psi of boost pressure, which obviously results in high combustion temperatures and some detonation; my ECU counters that by limiting the boost pressure. If I can add a secondary fuel source with ultra high octane I can utilize higher boost pressures and produce more power.

    I hope this answers your question. I do enjoy a good discussion.
     
    Last edited: Mar 24, 2009
  14. beenthere

    Retired Moderator

    Apr 20, 2004
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    You chemistry is off -
    - is not accurate. There is considerably less energy in a volume of hydrogen than in gasoline.

    Your second statement -
    - is more correct. Gasoline is primarily heptane. Octane burns with less energy, and so allows higher compression and therefore better utilization of the fuel as it becomes possible to lengthen the power stroke by advanced ignition - i.e., before TDC.

    A mixture of hydrogen and oxygen is explosive. Attempting to utilize a significant quantity in an IC engine without significant ignition delay - and wastage of the power stroke - will simply destroy the engine.

    The Germans used nitrous oxide and water injection to enable JU-88's to intercept British high altitude aircraft during WWII. There is a reason why NO2 has a considerable history as an IC engine booster, and hydrogen + oxygen does not.
     
  15. SgtWookie

    Expert

    Jul 17, 2007
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    See the attached; I whipped this simulation up for someone a few months back.

    Don't know if they ever built it, but it seems to work OK in simulation.

    The last attachment is the simulation itself. You can download/install Linear Technology's free LTSpice package and experiment with the simulation.

    The "HHO" cell is simulated by using four high-power Schottky diodes plus a low-value resistor; just my "best guess" at what such a load might look like electrically.

    L1 you'd have to wind yourself, using a large ferrite toroid and heavy-gauge magnet wire.
     
  16. smp375

    Thread Starter Member

    Mar 21, 2009
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    I had realized my mistake, and corrected it; I meant unit of mass as opposed to unit of volume. It seems I did so while you were typing your reply. However, the fact remains that hydrogen contains significantly more energy than gasoline.

    In the meantime I've been reading and calculating. My best calculation is as such, assuming I've calculated correctly:

    Approximately 180 watts per minute are required to produce approximately 2 liters per minute of brown's gas. 180 watts is approximately 0.24 horsepower, and 2 liters of HHO contains approximately 46800 joules, which is equivalent to approximately 0.017 horsepower. So producing HHO on a vehicle, using power from the vehicle's alternator would result in a net loss of approximately 0.223 horsepower. Now, this isn't to say that the different properties and burn characteristics of hydrogen do not deliver a positive result on engine performance, but the mathmatics do not justify spending the money to build a unit to perform any actual tests.

    This is why I research things, and utilize as many minds as I can during my course of research.
     
    Last edited: Mar 24, 2009
  17. smp375

    Thread Starter Member

    Mar 21, 2009
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    This time you are wrong. Gasoline contains little or no heptane. Heptane is far too explosive to be used as, or in, a motor fuel. If heptane was a main component of gasoline octane ratings would be DRASTICALLY lower, resulting in severe preignition and knocking. Heptane is essentially anti-octane.

    Also, advanced ignition would reduce the degree before TDC; I think that's what you meant there, but it's not clear. Fully advanced ignition is 0' BTDC; this is how most vehicles run now, because that obviously allows for maximum power, and advanced engine management systems are able to recognize the detonation associated with it, and retard the timing to compensate.
     
  18. Wendy

    Moderator

    Mar 24, 2008
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    Actually gasoline contains a real witches brew of chemicals, heptane can be one of them. Looking at the MSD sheet the primary ingredient listed (toluene) can vary from 0% to 35%, the rest of the ingredients follow the same pattern. There is no set recipe. Heptane is 8th on a list of 20, and can be 0 to 2%.

    If you're still interested in a SMPS regulator I have a long running thread I'm about to test here.

    You will find most everyone will help you design circuits, but 2H2 O2 (aka HHO) is a common hot button here. Water is the ash from burning hydrogen, you can't get any more energy from it. What hydrogen is is a transport mechanism, if you were to use solar power to crack it it would work OK as a fuel.
     
    Last edited: Mar 28, 2009
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