Patent ID: 6680548
Filing Date: 2004-01-20
Classification: H01H

Abstract:
A circuit of an electronic timer powered by an external power source, wherein the electronic timer controls a connection switch, which allows the external power source to provide a power to a load through the switch, the circuit comprising:an adjustable resistor; a capacitor with sufficiently large capacitance connected to the resistor in parallel; and an electromagnetic relay, connected to the capacitor in parallel to form the electronic timer, wherein the relay controls the connection switch to an on state or an off state, wherein the external power source charges the capacitor and activates the rely to set the switch at the on state, whereby the external power source also provides the power to the load when the switch is at the on state, wherein when the external power source stops powering the electronic timer, the capacitor then activates the rely to maintain the switch at the on state for a duration, wherein the adjustable resistor can be used to adjust the duration.