Inside an ionic foot detox spa unit

This is the controller for a fake "health" treatment offered by some spas where you place your feet in a bowl of water with an electrode in it, and it draws toxins out of your body via your feet, making the water turn brown in the process. In reality the unit is passing current between two electrodes causing accelerated electrolytic corrosion and colouring the water with chromium, iron and nickel compounds.

I was expecting this to be very cheaply made with maybe just a microcontroller putting on a show with LEDs and perhaps just a simple resistor or current regulator.
I was wrong.  It looks like some serious design has gone into this unit.  That's actually quite common in quack products.  The people designing them are often quite creative.

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