Audible Turn Signal
Q. I am one of those people who does not realize that the turn signal on my car is still operating long after have made the turn. To a void this, can you suggest an audible alarm system that will warn me that the turn signal is still blinking? S. Shore, Brooklyn, NY
A. The audible alarm Circuit shown here uses a Mallory SC1.5 Sonalert that operates at about 3500 Hz, and loud enough to be heard in a moving vehicle.
Connect one power lead to the right and left turn signal lamp circuits and the Sonalert minus terminal to chassis ground. Since the turn signal circuit is supplied with + 12 volts when the turn switch is operated, the alarm sounds off. The diodes isolate each side from the other, while the resistors limit the alarm current. If you have a 6-volt system, reduce the value of the resistors. If you have a positive-ground vehicle, reverse the diodes and alarm.
Copyright by Bill Bytheway, K7TTY February 2012