Do you mean pulsating DC? or anything else?alternating DC supply
marc said:Nope, I need the polarity to be logically switched (12V 0.5A) across the electrodes so they won't 'plate' and wear unevenly. I thought of a 555 timer switching a relay but I'm sure there is something better. The timer should time say a minute (+) on the electrode and then switch to (-) for a minute and so on...