| 摘要 |
An alarm system for a two-cycle internal combustion engine having a lubricating oil pump and an alternator generating electric pulses at a frequency related to engine speed. An integrated circuit configured as a counter has an input connected to receive the alternator pulses. A pressure switch generates an electric signal in response to the oil pressure increase in the pump output each time the pump operates. The integrated circuit has a first output which changes logic state in response to a predetermined count and has a second output which changes value at a frequency related to engine speed. The signal generated by the pressure switch is connected to a reset input to the integrated circuit so the counter is reset to zero in response to each oil pressure signal. An SCR switch controls operation of an alarm horn. A control connected to the integrated circuit and to the SCR operates the horn at a frequency related to engine speed. The control includes a flip-flop circuit connected to an IC output which changes logic at a given count. The control also includes a gate which is connected to a second IC output and is enabled by operation of the flip-flop. In one embodiment, the electric pulses, which are applied to the integrated circuit counter, are derived from pressure variations in fuel supplied to the engine by a fuel pump. |
