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BUILD THE CHIRPER —
THE BEST TURN SIGNAL
By Mike Huddleston
This little device solves one of the
most aggravating and potentially
dangerous aspects of driving a car
(or riding a motorcycle) —
inadvertently leaving a turn signal
flashing while traveling down the
highway. In many cases, the driver
just doesn't know it's on and may
drive for miles with his turn signal
flashing, confounding other drivers
and compromising driving safety.
Why? Because the driver can't hear
the turn signal beeper. The simple
fact is if the manufacturer's turn
signal alarm volume is tolerable
when the car is stopped, it's
probably too soft to be heard over
road noise at 70 mph. If it's powerful
enough to be heard at highway
speeds, it's uncomfortably loud when
idling at a traffic stop.
Idecided to create this gadget for my vintage motorcycles, although the problem exists with any
vehicle with turn signals. The turn signals on early bikes
don’t automatically cancel, so they continue to flash until
the rider (me) remembers to turn them back off (which I
frequently forget to do). So, the goals of this project were:
1. Effectively solve a real problem.
2. Be easy for the novice builder to construct
(i.e., no surface-mount parts).
3. Be inexpensive.
4. Include no microprocessors or other sequential
digital devices that might be corrupted by the nasty
electrical environment in a vehicle.
5. Have a foolproof design (as much as possible).
6. Be easy to install.
The device described here provides
an obvious solution: It emits a
relatively quiet 'click' when the turn
signal is first activated and you're
sitting at that stop sign; then, in
about 30 seconds, it escalates to a
truly attention-getting mega-CHIRP,
easily heard at highway speeds and
sure to motivate the driver to
cancel the turn signal. It's a simple,
inexpensive, one-evening project
suitable for the novice builder.
How Turn Signals Work
Conventionally, turn signals are straightforward. When
the switch (the lever on the steering column) moves to
connect either the right or left signals, the flasher provides
a slow square wave (about 1 Hz) to all the bulbs on that
side of the circuit, and they all flash in unison. When the
steering wheel swings back from the turn, a mechanical
linkage returns the switch to the ‘off’ position. There are
some safety processes built in. For example, if a bulb has
burned out, the flasher runs faster to signal the driver that
something’s amiss. The beeper may be part of the flasher
circuit or (more often) another circuit connected to this
one. The Chirper’s two wires connect between the ‘left’