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When driving down a busy road, you may not notice a “check engine” indicator light that
suddenly turns on within the car’s instrument panel. You could drive for many miles before noticing the light. To provide an
audible indication of trouble, the hobby circuit below could be added. When connected to a typical automotive check engine indicator
light on the instrument panel, this circuit will sound a loud beeper, when the light turns on. the hobby circuit counts on the fact that
most check engine signals swing from chassis ground potential to +12v. When the signal is at 12v it turns on, the n-channel FET which
activates the beeper. |
