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Published on Jun 26, 2010
http://boginjr.com A 555-timer configured to output a square wave between 45 and 100Hz, all this is switched by a transistor with hFE more than 50 and Ic 0.2A to a low-watt mains transformer (12V/230V with a center tap). The schematic is using a PNP transistor, for NPN's reverse C-E and LED diode polarities.