Patent attributes
An electronic ferrous metal detector with an alarm includes a non-ferrous core positioned circumferentially about an opening in an object, such as a hole in a garbage can lid. A pick-up coil having a sufficient number of windings is wound about the non-ferrous core for detecting magnetized objects passing therethrough and generating a voltage. The voltage is passed through an op-amp and into a comparator/detector, where a preset reference point is compared to the voltage from the op-amp. Once the voltage passes the preset reference point, the comparator goes to a high output and powers a switch, such as a SCR or Triac, which is gated on and carries the current and feeds the voltage to an alarm that provides an audible or visual signal that a magnetized piece of ferrous material has passed through the metal detector.