The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Apr. 09, 1996
Filed:
May. 31, 1994
Mitchell R Rowlette, Berea, KY (US);
Texas Instruments Incorporated, Dallas, TX (US);
Abstract
An electric control is shown for gas furnaces which controls fan motors and ignition controls based on inputs from a room thermostat (32), a high limit control and an ignition control (14) including a gas valve. A flame sense circuit (42, 42') is coupled to a microprocessor (U2) and includes a flameprobe (P1) energized by line power through a capacitor (C3) via a quick connect (QC31). A capacitor (C4) is charged by a 5 volt DC source through resistor (R12) and inputted to an inverter (U3, S2) which provides a low signal to the microprocessor when no flame is present. When a flame is present the capacitor (C4) discharges through the flame causing the inverter to change state providing a high to the microprocessor indicating that a flame is present. A diagnostic network comprising a low leakage diode (CR10) and serially connected resistor (R11) is coupled between the microprocessor (pin 8) and the input of the inverter (U3) so that the operation of the flame sense circuit can be tested. In an alternate embodiment CMOS switches (S1, S2) are used both to verify that the flame sense circuit is properly wired and to simulate a no-flame condition.