pwm controller

Discussion in 'The Projects Forum' started by jlscott57, Nov 21, 2009.

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  1. jlscott57

    Thread Starter New Member

    Oct 31, 2009
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    :confused:12v 30a pwm controller what are my options

    OLD SUBJECT,NEW STUDENT -HHO CONTROLLER -I HAVE READ EVERY THREAD ON THIS SIGHT THAT I COULD FIND
    I WOULD APPRECIATE SOME DIRECTION ON WHERE TO START.I AM AWARE OF YOUR THOUGHTS ABOUT HHO AND I AM ASKING FOR HELP ANYWAY.

    BEGINNER IN ELECTRONICS-OLD SCHOOL IN ALL ELSE
     
    Last edited: Nov 21, 2009
  2. SgtWookie

    Expert

    Jul 17, 2007
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    What type of load are you considering powering?

    If inductive (like a motor), PWM would be fine.

    If something else, you need to tell us what it is.
     
  3. SgtWookie

    Expert

    Jul 17, 2007
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    OK.
    This thread is not about "HHO", or the dangers of producing such an explosive combination of gases in a confined space, or the engine damage that you will very likely experience, engine fires that are a very real possibility, the emissions laws that you might violate if you tamper with controls, the minimal return you might get from the use of "HHO" in a vehicle, or anything else of that nature.

    Just a reasonably viable current limiter that will operate in the range of 13v to 15v, and supply a fairly constant 30A to a load that has an unknown resistance, but likely has a voltage drop of approximately 1.7v to 2.7v across it.

    Does that about sum up your requirements?
     
  4. jlscott57

    Thread Starter New Member

    Oct 31, 2009
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    You got that right
     
  5. SgtWookie

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    Jul 17, 2007
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    OK, I need to confirm the voltage drop across your load, the "cell" as it were.

    At some low current (say 2A), you will measure a certain voltage across the cell.
    At a higher current (say, 6A to 10A), you will measure another somewhat higher voltage across the cell.

    A battery charger with selectable output currents and a voltmeter would be one way to get such readings.

    Do you have that information available, or could you make those measurements and post them?
     
  6. jlscott57

    Thread Starter New Member

    Oct 31, 2009
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    My current cell is toast !!!
    I hope to have another one built by noon tomorrow.
    I will provide that info as soon as possible.
     
  7. SgtWookie

    Expert

    Jul 17, 2007
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    Bummer about the cell. Just curious, how much did it cost to build it?

    Anyway, based on my prior guesstimates, I threw together a preliminary experimental schematic and got it to output a reasonably stable 30A. Simulation is attached. The blue trace is the rise/fall times on the MOSFET gate, which are not acceptable. The green trace is the current, which is about 28.7A to 30.4A, right about the range you wanted.

    I don't have a clue what your experience level is. If you haven't had a fair background in electronics, this won't be a good project for you.

    I could probably make a lot of money selling these kinds of things, but I'm giving my advice away for free here.
     
    Last edited: Nov 21, 2009
  8. jlscott57

    Thread Starter New Member

    Oct 31, 2009
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    My cost was minimal,all material was already on hand. So far the new cell has set me back 12 dollars,for 1/2" thick pvc sheet for casing (don't want another meltdown).
    My electronic experience is just above beginner level ,although I have alot of experience with blueprints, and schematics. I'am a pipefitter by trade with 30 years experience (Mostly in Steam Boilers,and Hydronics). I have alot of experience in pneumatic controls, I believe the principals are the same. Ithink I can learn the Theory, with a little tutoring THANKS FOR YOUR QUICK REPLY
     
  9. BMorse

    Senior Member

    Sep 26, 2009
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    HHO generators tend to put out a lot of heat when too much current is run through the plates (Which will only use 1.50 - 2 volts per cell, other 10 to 12 volts dissipated as heat !!) So using PVC is not a good idea for housing your cells.... the PVC tends to soften up at certain temperatures (Thats is why you can not use it in hot water runs only CPVC...) so most likely you will still end up with problems with the PVC if your water solution gets hot.....


    My .02
     
  10. SgtWookie

    Expert

    Jul 17, 2007
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    I agree with BMorses' assertion that PVC is an unsuitable material for you to use in your project.

    The maximum service temperature for CPVC is 140°F, minimum safe temperature is 40ºF.

    Materials and electronics for use in automotive environments must be rated for operation in a temperature range of -40°C to +120°C, or -40°F to 248°F.

    The maximum safe temperature for CPVC is 180°F, so it does not meet the criteria either.
     
  11. jlscott57

    Thread Starter New Member

    Oct 31, 2009
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    Sorry for the delay,we are in the middle of a snowstorm and my wife has a problem with me bringing potentially explosive projects indoors.(I'm not to keen on it myself)
    RESULTS
    2.5 amps-11.70 volts
    6.4 amps-12.20 volts
    10.4 amps-14.24 volts

    Maybe I should limit to 10 amps ???

    More info:
    plate configuration + l l l l - positive-four floating plates-negative
     
  12. SgtWookie

    Expert

    Jul 17, 2007
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    OK, version 2 of the experimental current regulator.

    I wasn't very happy with the switching times of the MOSFET gate on the previous version. This one is loads better.

    I'd initially overestimated the available output current of the LT1017 comparator. This affected both the hysteresis and the gate switching times. Changed the driver to a Darlington configuration, which helped enormously.

    Vref is now derived by a voltage divider across a 1n914 diode with about 4mA of current through it; this will make Vref considerably more stable. Ideally, the diode would be thermally coupled to the temp of the cell; as the cell temp increased, the Vf of the diode would decrease, which would decrease the current output of the regulator.

    There needs to be a couple of safety interlocks:
    1) A normally closed thermostat in the cell that opens before a possibly hazardous temperature is reached.
    2) A normally closed pressure limit switch; above a certain pressure, the switch opens.

    Probably the best place to insert these safety interlock switches would be between Vcc and R1.

    There also needs to be a 35A-40A fuse between Vcc and the circuit, just in case M1 fails shorted, D4 blows open, or other fault that could cause maximum current flow.

    There is no provision for detecting a minimum input voltage for operation. You would not want this operating unless the engine is running. A reasonable minimum threshold voltage would then be 13.3v, as a battery would have to be quite cold to output that much by itself without the alternator running.
     
  13. SgtWookie

    Expert

    Jul 17, 2007
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    By all means, do not operate that cell in an enclosed space, or you invite disaster. The gases must not be allowed to accumulate anywhere. A garage with the door open is not sufficient ventilation.

    Interesting results.

    I don't know what you are using for an electrolyte, or what concentration your solution is. I suspect that your electrolyte concentration is pretty weak.

    As the water is broken down to hydrogen and oxygen by the electrolysis, your concentration will increase - and if the voltage across the cell is held constant, the current through it will increase.

    A typical automotive alternator will generate from between 13.8v to 14.2v when the engine is running. If you're getting 10.4A at 14.24v, your load resistance (cell) is about 1.37 Ohms. You are also dissipating 148.1 Watts of power in the cell as heat.
     
  14. BMorse

    Senior Member

    Sep 26, 2009
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    :eek:


    That is why PVC will NEVER work as a housing for HHO cells......
     
  15. jlscott57

    Thread Starter New Member

    Oct 31, 2009
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    I agree with the suitability of PVC, I am only using it as a test material. Currently my plates are small enough to fit inside a motorcycle battery case, which is what i have been considering. I don't want to put any limitations on this project at the moment.

    I am unwilling to put a glass jar of acid and explosive gas under the hood.

    I am open to any and all suggestions

    This project is more to fill the cold winter evenings ,It would be nice to save a buck or two ,I believe the knowledge gained will outway the time and money spent.
     
  16. SgtWookie

    Expert

    Jul 17, 2007
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    OK, now I'm getting it.
    You basically have 5 cells in series.
    With 2.5A current, you have a Vf of 2.34v/cell.
    With 6.4A current, you have a Vf of 2.44v/cell.
    With 10.4a current, you have a Vf of 2.848v/cell.

    I think that's about in the ranges of what I'd been reading about before.

    Unfortunately, since you are using cells in series, there really isn't a good way to keep the hydrogen and oxygen gases separate.

    Also, continually dissipating 148W of power inside a plastic container will eventually cause a big problem; it's going to melt the plastic. You have to have a way to get rid of the heat, or you will have a disaster on your hands.
     
  17. SgtWookie

    Expert

    Jul 17, 2007
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    Ok, put a 150 Watt lamp inside a PVC box the size of a battery case.

    Plug the lamp in.

    See how long it takes for the lamp to soften up the box.
     
  18. BMorse

    Senior Member

    Sep 26, 2009
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    I have managed to generate 1.5 liters of HHO in 45 seconds using NOTHING but distilled water, no PWM,(just straight 12 volts from a car battery)..... no KOH, NaOH , baking Soda, Salt or any other agent......

    see video here of pure distilled water HHO cell... http://www.youtube.com/mcscoder#p/u/33/5yNl6CeZeSc


    I am not trying to power my truck with the stuff either.... I just like blowing things up!! :)

    http://www.youtube.com/mcscoder#p/u/32/xHyIt8DhC8Q

    My .02
     
  19. beenthere

    Retired Moderator

    Apr 20, 2004
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    An H cell may be constructed with the anodic and cathodic plated separated by a plug of material saturated with the electrolyte so it conducts. The hydrogen will bubble off the cathodes. It may be safely collected if kept free of oxygen. Recall that the Hindenburg burned, but did not explode.

    Simply allow the oxygen to escape from the anode side. There is plenty of oxygen in the air to combust the hydrogen in the cylinder.

    We have had many, many people utter testimonials about the increase in mileage with what appear to be trivial amounts of HHO added to the fuel stream. If you could provide some before and after figures, it would be quite interesting.
     
  20. jlscott57

    Thread Starter New Member

    Oct 31, 2009
    11
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    i agree with your thoughts on PVC, This is just for testing purposes.
    I have been thinking about using the case from an old motorcycle battery.

    I increased the concentration of my electolyte and got the following results:

    2.5 amps- 9.96 volts
    6.4 amps-10.00 volts
    10.4 amps-10.07 volts
     
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