| 摘要 |
First-order failure mode arrangement for driving an actuator coil for a switch element employs a microprocessor controller and a driver circuit that includes an amplifier switching device, such as a transistor, a capacitor that ac-couples the output of the microprocessor to a control electrode of the amplifier switching device, and the actuator coil which is tied between a voltage source and an output electrode of the amplifier switching device. The microprocessor also has a capability of interrogating the on or off condition of the switch element. The switch element can be, for example, the gas valve relay for a gas furnace. The switch element can be tested to ensure that it is capable of both closing and opening when directed, and to ensure that of the switch element is not locked or frozen into a closed condition. If any of the microprocessor output, the capacitor, the switch transistor, or the coil develops a short or an open condition, the drive circuit will be unable to provide drive current to the coil, and the microprocessor will terminate the actuation sequence, and shut down.
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