hi Steve,
555 circuit is a standard 555, both resistors are 5k pots. The second one has a diode in parallel to give me full control over pulse width. For the capacitor i have 3 trimmers in parallel so that i can adjust the frequency. I suggest anyone copying to do a spreadsheet to calculate your frequency ranges first.
The output from the 555 goes to a MOSFET i pulled out of an old electric drill i had. this switches the primary on my transformer (dismantled 120v>6v 1500ma max wall socket one). This is connected to my test cell, 2x 5cm long SS316 (i believe they are 316) tubes. Gap is about 1/2mm. My new DMM measures inductance and capacitance (along with others too!!!). According to the calculations for resonance i can just hit the 1/2 mark of my test cell with my setup. by half mark i measured capacitance with the cell in air and it in my water, lowest mark is air highest is water. I get reasonable production about equal to or just under brute force, as the cell produces more and more gas the capacitance changes and i can manually adjust the frequency to "ride" the wave to the point where my 555 (or MOSFET) can't do it any more. At this point the process dies, lasts less than 2-3 seconds of production and is fiddly. If with the increase in Capacitance i can "ride" it for longer before bottoming out i have the idea of using a water pump to force the water through the cell/s. i think this will stabilize the capacitance and decrease the amount of adjusting required on the frequency.
Seb,
I don't see the need for the PLL at the moment, i think that is a circuit that was designed to stabilize the process in the larger cell inviroment, I'm not overly interested in creating a magnificent test cell. Once concept is complete i intend to use the process to create an injector, also utilize the HV created to increase the potency of the gas created. This will mean a more precise amount of gas can be made in a shorter amount of time.
I also have an idea to greatly increase the efficiency on the primary firing side by using a cap->transformer->cap setup. Matching the bounce frequency and using the timer to "Kick" the small amount converted into heat to decrease my bottom line required energy. But that is a project for down the line

Till i have more,