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Help with square wave generator

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galveston

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I want to build a HHO generator, and need a square wave generator to operate the electrodes.

The wave generator will run on 12V DC, and I would like to have an output of 12V and up to 25 Amps. A control to vary the on/off time of the wave would be nice too.

A schematic with valid part numbers for the components would solve my problem.

I know very little about electronics, and any help will be greatly appreciated.

PS. I should mention that I have AutoCad 14 and can receive drawings in that format.

OK. How about plans for a 500W inverter?
 

Here there is a simple schematics.For high power you must add a power mosfet to the output.Be careful with HHO generator remember to add a flashback protector and flashback valve, it's dangerous work with hidrogen.
 

    G

    galveston

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brumi said:
Here there is a simple schematics.For high power you must add a power mosfet to the output.Be careful with HHO generator remember to add a flashback protector and flashback valve, it's dangerous work with hidrogen.
Click to expand...

Thanks, I got the schematic, but still have a few questions. The people at the only supply house near here seem to need numbers to know what I want. What do I ask to get these:
1. The item labeled 1458 (or is that a generic that I can use)?
2. The 8 pin mosfet (?)
3. The value for capacitor "C"
4. The value for resistor "R"
5. The power mosfet to be added to this

And:

Is the 10K symetry the same as a variable resistor?
How do the triangle out and the square out hook to the power mosfet?

And thanks for the tip. I will be cautious with the HHO.
 

The 1458 is a general porpouse operational amplifier.
The capacitor "c" and the resistor "r" determine the operating frequency.
The 10k variable resistor adjust simetry, 50% on - 50% off . Or adjust it to your needs.
See the schematics using the mosfet .

Added after 13 minutes:

Sorry , I forget the schematics.
You must use square output.
And +B is the voltage needed for the load.
The mosfet must be for the load and voltage you need.
The HHO cell use low voltage 12/ 20 volts and N ampere
You need a mosfet for 50/60 volts and Nx2 amperes
 

    G

    galveston

    Points: 2
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brumi said:
The 1458 is a general porpouse operational amplifier.
The capacitor "c" and the resistor "r" determine the operating frequency.
The 10k variable resistor adjust simetry, 50% on - 50% off . Or adjust it to your needs.
See the schematics using the mosfet .

Added after 13 minutes:

Sorry , I forget the schematics.
You must use square output.
And +B is the voltage needed for the load.
The mosfet must be for the load and voltage you need.
The HHO cell use low voltage 12/ 20 volts and N ampere
You need a mosfet for 50/60 volts and Nx2 amperes
Click to expand...

OK. So if I want say 20K frequency, what would "C" and "R" be?
+B would have to be 12V DC, right?
And I'm still foggy as to what I ask for to get the 8 pin component.

I'm getting there. Thanks for being so patient.

Edit:
I have another question while we are at it.
What determines the N ampres?
 

You find the IC 1458 everywhere is a very common component.(MC1458, uA1458 , LM1458 )
The time interval for one half cycle is about R*C .
N is the amperes required by your cell, for safe you must use a mosfet for Nx2 amperes and probably it needs a heathsink.
 

    G

    galveston

    Points: 2
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wht frequency u need,anyways check schmitt trigger oscillator
 

So are you saying that the component on the right in the schematic (the triangle) is a schmitt trigger? That is what the people at the supply house couldn't identify.

And I think a max draw of 25A from the battery source would be ok. Not sure how this relates to amps in the electrode?
 

I still need a techinical name for the component shown as the triangle on the right side of the above schematic.

Thanks again
 

Both triangles are a LM1458 integrated circuit . MC1458 is a double operational amplifier.
 

    G

    galveston

    Points: 2
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Thanks for all the answers.
I have been doing more reading. I read that Myers had good results using very low amps, and apparently higher voltage. So now I am wondering about using a sq wave signal to operate a flyback converter instead of a FET. Couldn't the voltage be raised and thus the amps be reduced? It looks like the voltage is what does the trick.
I am also wondering if the sq wave signal could simply operate a step-up transformer? I definitely need lower amps, as I attached my electrode to a 12V auto battery, and it draws about 80A and the water boils in about 3 seconds.
 

The lousy old 1458 dual opamp is too old and is too slow to make a square-wave output as high as 20kHz. Its output turns into a triangle wave above a few kHz when its output level is fairly high. The ramping triangle wave will quickly overheat the Mosfet.
 

    G

    galveston

    Points: 2
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OK. So far, so good. I'm learning slowly. More questions follow.

i've learned that an IRF540 delivers 10A. Queston: If two of these are hooked in paralell, does that deliver 20A to the load?
 

galveston said:
i've learned that an IRF540 delivers 10A. Queston: If two of these are hooked in paralell, does that deliver 20A to the load?
Click to expand...
The IRF520 Mosfet is very old. Whoever still sells it might charge much more than it costs (RadioShack). Much better Mosfets are available and can drive many more Amps.

If you have some then in parallel yes they can drive 20A.
 

Thanks again. Now another question.

If I use a IRF3704 (20V 77A supposed to give 87W) but I don't understand this, as V times A equals W. Can you explain this?

Also, this is an N channel MOSFET. Can that interchange directly with a P channel?

I have 225 sq. in of .040 gap and want to apply as many watts as possible.
 

The datasheet for the Mosfet says it can conduct 77A when its case is held to 25 degrees C somehow (liquid nitrogen or dry ice on a huge heatsink with a fan?). Note 5 says then its chip is at its max allowed temperature and the case can pass only 75A (maybe 77A will cause a pin to melt).

If you keep it cool and feed it very short duration pulses so it stays cool, its max resistance is 9 milli-ohms. With 77A in the 9 milli-ohms its voltage is only 77 x 0.009= 0.693V, not 20V. It can dissipate a max of 77A squared x 9milli-ohms= 53.4W.

An N-channel Mosfet is the opposite to a P-channel Mosfet.
 

Well, all that doesn't sound too promising. Do you know of a better way to deliver more watts to the electrode?
Everything I'm reading indicates a pulse wave generator, but all the mosfets seem really wimpy.
I can use direct constant current and get a lot of gas, but that also causes a lot of heat too. I keep wondering if there is some way to multiply the volatage (& drop amps) in a system using DC, since (am I right?) no current is going to flow through a step up coil without a pulse. I can't see how to use a step up coil in conjunction with a pulse generator.
This brings up a question you may know the answer to. I tried an ignition coil activated by distributor. The ground wire coming from the electrode will jump a spark an inch, but no HHO is formed. Not enough amps, maybe?
 

Many HHO circuits used many amps of current at only 2V. Since your battery is 12V or 13V then you are throwing away 10V or 11V times the current in heat.
 

I have discovered that by hooking 2 electrodes in series, I can reduce the amps draw drastically and at the same time increase the sq, in of plate surface.

Do you think this is the right direction? To use as large a surface as possible?
 

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