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Re: Buzzers - Speed Warning, Key Reminder - Theory of Operation?
The cool thing about using a relay with the coil acting as a buzzer is it freaks out radar detectors in the area.
If you'll excuse the crude drawing, I believe this is the way they used to do it.
When the speed warn contact connects to the speedo needle, it closes the circuit. This pulls the relay coil down opening the normally closed contact. This disengages the coil which makes the N.C. contact re-energize the coil.
You must make sure you use a HIGH impedance coil on the relay. 1Kohm or better to limit the current through the circuit. Also not shown is a small cap across the contact to keep RFI down.
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1970 Longhorn, Front Disc, 350/4 bolt, 882 heads, HEI, Edelbrock, 700R4, HO-52/4.11.
1996 Corvette, Collector Roadster, LT4, 396, 450RWHP, 6sp, 4.11/Dana44/posi 5 point roll bar
And let us not grow weary of doing good, for in due season we will reap, if we do not give up. Gal 6:9
Last edited by Longhorn 70; 03-09-2015 at 12:21 PM.
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