> This page is quite interesting at
> <http://www.uoguelph.ca/~antoon/circ/headalrm.html>
> it has plans for building a 'headlight alarm'.
Seems overly complicated to me, especially for what it does. You can
accomplish the same thing with just a buzzer (eg
http://www.radioshack.com/product/index.jsp?productId=2062397 )
and a series diode. One side to the tail lamp circuit, the other to the
ignition circuit. Observe polarity on both diode and buzzer (to match your
ground polarity), so the buzzer sounds only when the lights are on and the
ignition is off.
Or if, like me, you occasionally want to leave the lights on, with the key
off but without the buzzer running; you could add a capacitor and resistor
so the buzzer will only sound for a second or two. 1000 mfd (15 volts)
capacitor bypassed with perhaps 100Kohm resistor should work. The capacitor
goes in series with the buzzer & diode, again observing polarity.
Randall
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