This video shows the structure and operation of my experimental HHO cell setup including PWM, bubbler and flashback arrester. 3 of the 6 cells are operational here. The output is 1.17 litres per minute with a current of 19.5 amps and voltage of 2.34 volts across each cell. The cells are series connected. The electrolyte is NaOH, however, the branded caustic soda I am using contains some additive which is causing some foaming. The gas passes from cell to cell and the output of the final cell is passed into a bubbler for safey. Additional safety is provided by flashback arrestors. These are easily made by packing aquarium airstone inside standard 3/4in plumbing fittings. The PWM shown here is a 50A max model and allows both the duty cycle and the frequency to be set via potentiometers. The water filter housings are warranted to 8 bar pressure, and under test the bubbler did contain a flashback (no flashback arrester was fitted for the test). All components are ‘off the shelf’ and except for some reworking of the filter housings, and a little welding, the construction is within reach of most DIY enthusiasts. I expect to be connecting more cells into the series setup soon and will post an update when this happens. What I expect to achieve is that More cells = more gas while maintaing the current at about 20amps.