Self-powered Doorbell

  
This very simple and self-powered device was conceived to allow a person to monitor if someone has rung his home door-bell when he was out. As most door-bells use 12Vac supply, the circuit must be simply connected to the two door-bell-coil leads.
Self-powered Doorbell - schematic

Though this device was primarily intended to be used when a person leaves the house for a few hours or a week-end, a number of tests has proven that a minimum of 15 days "memory" can be guaranteed, even using cheap capacitor types. To know if t



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