Abstract:
An annunciator comprises an annunciation and shutdown circuit having input terminals for a first power supply and input terminals for a second power supply. The first and second power supplies are connected to supply power in parallel with each other to the annunciation and shutdown circuit. A logic means responds to a fault signal causing the annunciation and shutdown circuit to switch to low power mode upon sensing that a fault signal has occurred.

Description:
BACKGROUND OF THE INVENTION 
     As annunciators for remotely stationed internal combustion engines become more and more sophisticated, the management of power for activating annunciator circuits becomes more demanding. Existing annunciators are powered from the capacitive discharge (CD) ignition or a magnetic pickup from a fly wheel magnet, for example, from intermittent sources, such as photoelectric generators and from long-life batteries. The distribution of power from these sources to maximize battery life has already been considered. See, for example, U.S. Pat. Nos. 4,181,883; 4,336,463; 5,563,456; and 6,144,116. 
     SUMMARY OF THE INVENTION 
     Briefly, according to the present invention, there is provided an annunciator for an internal combustion engine comprising annunciator and shutdown circuits. The annunciator has input terminals for being powered by first and second power supplies, the second power supply being a long-life battery power supply. The annunciator comprises sensor input circuits sensing electrically detected conditions and generating fault signals in response thereto, a digital display, and switches for outputting a shutdown signal. At the heart of the annunciator and shutdown circuit is a logic device including a programmed microcontroller, which, in response to fault signals generated by the sensor inputs, causes output of a shutdown signal through the switches. The logic device is also configured to cause a digital display to display fault conditions. The annunciator and shutdown circuit is configured into normal and low power modes. In a normal mode, the entire circuit is powered. In the low power mode, the digital display and only portions of the logic device are powered. The logic device is designed to respond to fault signals causing the annunciator and shutdown circuit to switch to the low power mode upon sensing a fault signal has occurred. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further features and other objects and advantages of the present invention will become clear from the following detailed description made with reference to the drawings in which: 
     FIG. 1 is an overall schematic of an annunciator according to the present invention; 
     FIG. 2 is a more detailed electrical schematic of the power supply portion of the annunciator according to the present invention; 
     FIG. 3 is an electrical schematic illustrating a tachometer input circuit useful for the present invention; 
     FIG. 4 is a schematic diagram showing a display driver, and display circuit useful for the present invention; 
     FIG. 5 is a schematic diagram showing a plurality of sensor switches and the powering and polling circuits for the sensor switches useful for the present invention; and 
     FIG. 6 is a shutdown circuit useful for the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIG. 1, there is shown a schematic of an annunciator circuit according to a preferred embodiment of the present invention. The heavier lines connecting boxes representing various circuit elements are power lines. The lighter lines are data and control lines, not all of which are illustrated. 
     At the heart of the annunciator is a program microcontroller  10  with on-board program memory. The data inputs to the microcontroller comprise a tachometer input circuit  11  and sensor input circuit  12 . The data outputs from the microprocessor comprise outputs to a shutdown circuit  13 , outputs to a display  14 , and, optionally, communication outputs to a communication circuit  15 . Each is described in more detail hereafter. 
     Three power sources provide electric power to the microcontroller  10  and associated circuits: a secondary power source  16  that depends upon the running of an internal combustion engine, such as a CD ignition or magnetic pickup power source, a tertiary intermittent power source  17 , such as a photoelectric power source, and a primary power source  18  comprising a long-life battery. The three power sources  16 ,  17 , and  18  are connected through diodes to junction  20 . The secondary and tertiary power sources  16  and  17  are regulated to provide approximately 5 volts output. The battery  18  is chosen to have a lower voltage output, say 3.6 volts. If either the secondary or tertiary supplies are available, the battery will not supply power and will not be drained down. 
     Without the secondary and tertiary power sources, the battery life achieved by the various power saving techniques described hereafter would be approximately 24,000 hours or three years. Assuming the tertiary power source  17  is available 50% of the time, the battery life is extended to six years. Assuming the secondary power source is available 80% of the time, the battery life is extended to five times its normal life. As a practical matter, battery life projections in excess often years are unpredictable. 
     The communications option  15  comprises its own microprocessor or microcontroller that is clocked by a crystal oscillator to enable RS232 and/or RS485 outputs. Since the power consumption for the communication option is substantial, it is only powered by the tertiary power supply and never by the battery or primary power supply. Thus, since the tertiary power supply may only be available when the sun is shining, communications may be available in the daytime only. 
     A feature of the present invention is the management of power used by the tachometer inputs  11 , display  14 , and sensor inputs  12  in response to a fault condition sensed by the microcontroller  10 . The sensors and tachometer inputs are powered through power shutoff switch  21 , which can be activated by an output signal from the microcontroller  10 . For example, after shutdown, there is no need to power the tachometer circuit at all. Hence, the power shutoff switch  21  cuts off power to the tachometer input circuit at shutdown. 
     The sensor inputs  12  comprise a plurality of normally open, normally closed digital inputs or analog inputs. Only the sensors being polled are powered during operation when the internal combustion engine is operating. Of course, at this time, the secondary power source is available. However, after shutdown, power is conserved by only powering sensors during polling and only polling those sensors which are significant after shutdown. Any number of inputs, such as status of apparatus driven by the remote internal combustion engine, need not be polled after shutdown. After shutdown, the display  14  is refreshed at much longer intervals as the conditions being monitored are not changing rapidly. Hence, after a fault signal, the microcontroller writes to the display at less frequent intervals saving power. 
     Referring again to FIG. 1, the output from the tertiary power supply is labeled V DD   C . The output from junction  20  supplied by the primary, secondary, and tertiary power supplies is labeled V DD   B , and the output from the power shutoff switch  21  is labeled V DD   A . 
     Referring to FIG. 2, there is shown a more detailed schematic of the primary, secondary, and tertiary power sources. All three power sources are connected in parallel through diodes to junction  20 . Hence, no power supply can drain another. All three power supplies charge a 2,200 microfarad capacitor so that even if all three power supplies fail at once, the shutdown process will be monitored. The outputs V DD   B  from the junction  20  are applied to the annunciator and shutdown circuit at terminal A. 
     The primary power supply  18  is a long-life 3.6 volt lithium battery and diode  27 . 
     The secondary power supply  16  is illustrated for use with a capacitive discharge ignition. The CD ignition pulse is passed to regulator Q 1  through Zenor diode  28 , resistor  29 , and diode  30 . The output of voltage regulator Q 1  is smoothed by a 15 microfarad capacitor  31  and applied to junction  20  through diode  32 . An alternate source of power to Q 1  is from the tertiary power source through diode  25 . 
     The tertiary power supply  17  would comprise, for example, a photodiode array. The 12/24 volt direct current input is regulated to 5 volts by capacitors  33 ,  34 , diode  35 , and regulator U 2 . The regulated output of the tertiary power supply V DD   C  is supplied to the communications option at terminal B and/or to junction  20  through diode  37 . 
     Referring to FIG. 3, there is shown a block diagram illustration of the tachometer input circuit. It comprises a signal conditioning section that compares the RPM pickup pulse to a threshold level and passes signals exceeding the threshold to a shift register. Each time the threshold is exceeded, the shift register changes state (low/high or high/low). The output from the signal conditioning section is passed to the ripple counter  41 . The carryout  43  of the ripple counter  41  is supplied to an EXCLUSIVE OR gate  42 . The other input to the EXCLUSIVE OR gate is a reset signal  44  output from the microcontroller. The output on line  45  of the EXCLUSIVE OR gate is both a reset signal on line  46  for the ripple counter  41  and an interrupt signal on line  47  to the microcontroller. A gate  48  controls the power to the signal conditioning section, ripple counter, AND EXCLUSIVE OR gate. The gate  48  is controlled by an output from the microcontroller on line  49  which stops power drain in the tachometer input circuit after shutdown. 
     Referring to FIG. 4, the display  14  is comprised of a plural digit seven-segment liquid crystal display  50  and a display driver  51  that converts a serial input signal on the data in line  52  to parallel outputs. Additional outputs to the display driver are the clock-in on line  54  and the data enable on line  53 . These integrated circuits remain powered even after shutdown. However, by reducing the refresh rate controlled by the signals on lines  52 ,  53 , and  54 , which are all individually controlled by output connections on the microcontroller, the power consumption is substantially reduced after shutdown. 
     Referring to FIG. 5, the sensor circuit comprises a plurality of sensor switches  60 . The sensor switches may be normally open or normally closed. The sensor switches are powered by power latch  61 . The outputs of the latch  61  are selected by signals on the data bus  65  and latch enable line  62 . Sensors can be powered in banks. As shown in FIG. 5, the sensors are connected to the power latch  61  in two banks of two sensors, one bank of four sensors and one bank of eight sensors. The sensors are polled through eight-channel analog multiplexer chips  63  and  64 . The multiplexer chips poll the sensor switches through the chip select CS input and the select inputs A, B, C. The condition of a polled switch is output on the OUT line, wherein high=safe and ground=fault. The multiplexer chips  63  and  64  are powered by source V DD   B  which is shut off at the time of a fault signal so as not to draw power after shutdown. The power latch  61 , however, is powered by source V DD   A  which continues to apply a voltage after shutdown. However, when the latch LE is disabled, no power is drained by the chip. Indeed, if the power was not applied from some source, the chip would scavage power from the control line  65  which is connected to the microcontroller. The microcontroller remains powered by V DD   A  during shutdown. 
     Referring to FIG. 6, the shutdown circuit comprises two FET switches  70  and  71  that are controlled by FUEL OUT and IGNITION OUT control lines controlled by the microcontroller. A voltage signal applied to the gate of the FET switch grounds the ignition and shuts off the fuel valve. 
     A unique feature of the present invention is that switch to the low power mode is based upon an output from the microcontroller and is not simply the result of a power source failure. Hence, the switch to the low power mode can have a programmed delay to ensure that shut down is orderly and that conditions are monitored during shut down. Moreover, loss of the secondary and tertiary power supplies does not require immediate shut down and switch to the low power mode. As long as the engine is still running safely, the annunciator may be left in the normal mode and run off the battery while maintaining safe operation. 
     Having thus defined my invention with the detail and particularity required by the Patent Laws, what is desired protected by Letters Patent is set forth in the following claims.