either the left- or right-turn signal from
outside the diorama using a momentary contact switch. Do you have any
— Jon Westcot
AIn the original Ford design,
the direction indicator used
a series of cams on a single
shaft that would close then
open three micro switches in sequence
when the shaft was rotated. Essentially, a mechanical timer that turned
on when the turn switch was activated.
Of course, that was 40 years ago,
before they began putting microprocessors in cars.
Today, the solution is a serial
in/parallel out shift register — like the
4015 circuit shown in Figure 5. A shift
register is a series of flip-flops that
moves (“shifts”) a train of pulses from
the input to the output. If you monitor the pulse train at each stage, you
can watch it ripple from the beginning
to the end. This is what a serial in/
parallel out shift register does.
To make a T-Bird signal, the flip-flops are first cleared to zero. The data
input (pin D) is then taken high and
A Reader responds
I decided to try one of your first suggestions —
use a converter box. I’m a dinosaur, still have
tube conversion books, and I’m basically self
taught. But like all electronic buffs, I have
boxes of old “stuff.” Among the junk I found an
old cable converter box — and it works
perfectly. I set the TV to channel 3 and tune
from the converter. — Richard
To start the sequence, you need
to press and hold down the left or
right push-button — depending on
which direction you want to go.
Pressing both at the same time will
give you the brake light effect of the
T-Bird and later the Mercury Cougar.
■ FIGURE 5
JUNK BOX FULL
QI have a small TV that fits
well at my desk/work station.
It’s an older model Panasonic TR-1010P with a
telescoping antenna and no external
antenna connection. Is there a
modification that will allow me to
connect this TV to cable?
— Richard Gravina
t = 2.2RC
transferred to the first flip-flop on the
rising edge of the clock signal (
generated by the 4011 CMOS oscillator).
This sets the Q1 output high. Again,
the data input is set high and clocked
into the first flip-flip. This causes the
data bit in the first flip-flop to advance
and be locked in the second flip-flop.
We now have outputs Q1 and Q2
high and output Q3
low — that is until
the next clock pulse
LED1 which moves the
1K bits one more step
LED2 down the line and 1K Left lights all three
1K Now comes the
fourth clock pulse.
At this point, we
enter another one
(high) into the reg-
Left ister, which causes
Q4 to go high. It
just so happens
that when the reset
Right input (pin R) goes
high —notice it’s
tied to Q4 — it
clears all the out-
1K puts to zero. Lights
out. The next clock
1K Right pulse then inputs a
LED1 Turn one bit into the
1K first flip-flop, and it
begins all over
AA few fixes pop to mind. But
the fact that this is a pocket
TV with a 1.5” screen limits
the choices. As in, it rules out
popping the cover and adding a jack.
The point of entry has to be through
the whip antenna.
If your desk is metallic, or has a
metallic apron or legs, first tie the
braid of the coax from the cable to a
metallic part of the desk. If it’s all
wood, place a piece of aluminum foil
under the TV set (making a ground
plane) and tie that to the braid. Sec-
March 2006 23