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PROJECT HIGHLIGHTS
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Vintage: Late 1990s
Circuit
Designer: Ned Ely
Designer’s Comments: “I do remember the thrills of a CK722
amplified crystal set. I played with them in the '56 to '60 period (12 years of age to 16) and then the
hormones took over, and then college, jobs, wife, kids,
house................
In '94 I dug out a box that had survived time and weather (the possums also
nested in it at some point) that contained all of my electronic stuff from
that period, INCLUDING BLUE CASED CK722's!!!!!!!! All of mine had shortened
leads, but what the heck. When the
$3.00 blue leds hit the surplus market I built a "2 blue led, 2 blue
CK722" flasher. It looks
COOL. Reminds me of that saying:
Something Old, something New, something Borrowed and something Blue!”
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Top View of BLINKIE
There are two blue CK722s on the left and two blue
LEDs on the right – the top LED is glowing!
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PROJECT DETAILS
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Ned’s BLINKIE combines some of most interesting aspects of
hobbyist electronics from the past 50 years. When the battery is connected, the two LEDs will alternately
flash with a bright blue color.
With the component values listed, the “flash rate” is approximately
once a second. In basic operation,
this circuit is known as a bi-stable multivibrator, and is similar to
circuitry used in many of today’s computers. For example, with high precision components, it is possible
to adapt this circuit to provide a fairly accurate time standard or
clock. Other variations of the
circuit (known as a flip-flop) have been used as the basic counting/timing
functions in most digital computers over the past five decades.
The original BLINKIE was constructed on a 3 ˝” by 1 3/8”
rectangular piece of blue Vector board.
There are only ten components (in addition to the battery, wiring
and transistor sockets), so construction should be fairly straightforward –
Ned did a fine, neat wiring and soldering job (see page 2 for details) and
since direct soldering is required, it is strongly recommended that the two
CK722 transistors be mounted in sockets to avoid any potential heat damage
to these wonderful, and increasingly scarce historic devices.
BLINKIE,
Go To Page 2
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