Electronic delay turn off switch

• US 5,530,301 A
• Filed: 06/06/1994
• Issued: 06/25/1996
• Est. Priority Date: 06/06/1994
• Status: Expired due to Fees

• Current Assignee: Grant V. Baumgardner, Haizhong Fu
• Original Assignee: Grant V. Baumgardner, Haizhong Fu
• Inventors: Fu, Haizhong, Baumgardner, Grant V.
• Primary Examiner(s): Wysocki, Jonathan
• Assistant Examiner(s): KAPLAN, JONATHAN STUART
• Application Number:
  US08/254,748
• Time in Patent Office: 750 Days
• Field of Search: 307/125, 307/139, 307/140, 307/141, 307/141.4, 307/112, 307/113, 307/116, 315/360, 315/362, 315/194, 315/199, 323/265, 323/282, 327/447, 327/448, 327/419
• US Class Current: 307/141
• CPC Class Codes: H03K 17/292 in thyristor, unijunction transistor or programmable unijunction transistor switches

Abstract

An electronic delay turn off switch including a bridgelike array of four diodes disposed between an alternating current power source and a load wherein the diodes have anodes and cathodes in opposing disposition and having an SCR with anode connected to the interconnected cathodes and with cathode connected to the interconnected anodes. A gate isolation diode, a switch, a resistor-capacitor charge mode timer, and a DIAC are interconnected between the SCR anode and gate thereby providing an SCR turn on whenever the switch contacts are closed, and a delayed SCR turn off whenever the switch contacts are opened. In an alternate embodiment a variable resistor is added to enable user selection of the duration of turn off delay.

Claims

1. An electronic delay turn off switch for providing a delayed turn off of an electrical load comprising:

a primary switching circuit having two diode pairs wherein each diode has an anode and a cathode, wherein a first diode pair is electrically coupled having the anodes of the first diode pair interconnected and further connected to a cathode of an SCR and a second diode pair is electrically coupled having the cathodes of the second diode pair interconnected and further connected to an anode of the SCR, and furthermore an anode of the second diode pair and a cathode of the first diode pair connected to the load and the remaining anode of the second diode pair and cathode of the first diode pair connected to an alternating current input common;

an SCR gate control circuit comprises a series arrangement of a diode, a first capacitor whereby the first capacitor is in parallel connection with a single pole single throw switch, the series arrangement further connected to a DIAC, and a second capacitor whereby the second capacitor is connected in parallel with a resistor, and furthermore an anode of said diode is connected to the anode of the SCR and the parallel connection of said second capacitor and said resistor is connected to a gate of the SCR, the SCR gate control circuit further having a manually adjustable variable resistor connected at one end to a junction of the switch and DIAC, and at the other end to the cathode of the SCR providing a switched selectable on state and off state wherein the off state is achievable only after a preselected delay period; and

a housing comprising a substantially cubic polymeric box having ports through which alternating current power lines pass and an aperture for human access to the switch.