50 millisecond delay introduced by R3
and C2. Note also that U2 ( 11, 12, 13)
provides a short 50 microsecond
“housekeeping” delay to prevent SETD
from setting the flip-flop’s D input (U1-2)
high while /RESET at U1-1 is bringing the
flip-flop out of reset.
■ FIGURE 5. Timing
photograph of the
■ FIGURE 4. Timing diagram of the
pendulum driver electronics.
How To Make It:
See Figures 6.1 and 6. 2 to fabricate the relevant parts.
These involve only simple cuts and a few drilled holes. A
hand vice works well for the drill. Pendulum post I and the
three stanchions, S, use the same dowel stock.
Lightly sand around the bottom circumference of A
and then cement a doughnut magnet C with a 3/8”
diameter hole snugly on to the bottom with general-purpose cement. Alternatively, a hole for a wood screw
has been provided.
Note: The chain is necessary. Do not use an “S” hook
to connect the pendulum arm to the pendulum cantileve,
since this forces the pendulum into a largely fixed plane of
Cantilever F will form a snug fit
through the hole in slide G, but it will still
be moveable as needed. The thumbscrew
H will self-thread through the soft plastic
of the slide.
■ FIGURE 6.1. Pendulum arm parts.
■ FIGURE 6. 2. The
cantilever slide (G).