Resistors, 5% tolerance or better: 10kΩ ( 1),
1MΩ ( 1), 200Ω ( 1), 1kΩ ( 2), and 100Ω ( 1)
Capacitors, ceramic: 1μF ( 1), 0.1μF ( 1), 0.33μF ( 1),
and 0.01μF ( 3)
Capacitor, electrolytic, 470μF
IC chips: ALD7555 timers ( 2), 74HC4520 counter
( 1), 74HC4514 decoder ( 1), 74HC4078 OR gates
( 2), M74HC164 shift registers ( 3), ULN2003A
Darlington arrays ( 3), and LM7805 voltage regulator ( 1) Part numbers may be preceded or followed
by other letters identifying the manufacturer or package details; these letters can be ignored, so long as
you’re careful to buy through-hole chips (DIP or PDIP
format), not surface-mount.
LED light bars ( 36) Lite-On model #LTL-2450Y
LED, 5mm for the prompt
Switch, SPST momentary pushbutton for the trigger
Switch, SPST toggle, 3A for a power switch
Switch, DPDT pushbutton for a reset switch that
discharges the large capacitor
Power supply Any plug-in AC adapter with 9V DC
output at a minimum of 1A. I used Triad Magnetics
Optional, recommended for testing:
Breadboards ( 2+)
LEDs ( 30) Chicago 4302F1-5V (or F3 or F5), to show
For the finished project:
Perf board, unplated
Hookup wire, solid core
Plywood or plastic sheet, ¼"
Soldering iron and solder
Wire cutters and strippers
To create broken lines in the hexagram on
the left, we simply leave them switched off.
So, the remaining 8 outputs from the decoder
chip are unconnected — except that 1 time in
those 8 instances, we need to light the center
bar on the right. For this purpose, I connected
one more output from the decoder to the
right-hand OR gate.
; Fig. A: Two possible hexagrams describing your
present and future. The meanings are quoted from
The I Ching: The Book of Answers by Wu Wei.
; Fig. B: For any pair of lines spanning present and
future hexagrams, there are 4 possible combinations,
as shown here. The probability values are simplified
if you toss coins instead of using the more traditional
“yarrow stalks” to generate the lines.
; Fig. C: Block diagram showing the basic compo-
nents of the Ching Thing, and their functions.
So far, I’ve described how to generate one line
on the left and one line on the right. We need
to do this 6 times to build complete hexagrams. Is there a way to memorize the first
combination of lines, then repeat the process
to create the next set of lines?
Yes, all we need is an 8-bit shift register. As
159 Follow us @make