WAY TO KILL
TUNING THE CIRCUIT
Open the box and remove the circuit board, lid,
and batteries, but keep them connected. Place
the handle of a small brush or other round object
under the middle of one side of the box, with the
rim of the open box supporting the other side. This
arrangement will keep the box from wobbling while
you tune the beam.
Starting at maximum resistance (100kΩ) on
the trimpot, turn the power switch on and flip the
phase switch to make the beam vibrate. Turn the
trimpot in half-turns in both directions until you find
the place where the motion, the system’s instability,
Switch the phase switch to stable. The motion
should stop immediately. Turn the trimpot in
quarter-turns in each direction and lightly flick
the beam. You should be able to find a point
where the beam stops the fastest and added
damping is the highest. Now your beam is smart.
One way to get a closer look at the time and
frequency domain behavior of the smart beam is by
connecting an oscilloscope or spectrum analyzer to
the output of the sensor charge amp, pin 7 on the
op-amp chip (and to the ground at pin 11). You can
also glue a small dental mirror to the tip of the beam,
and position a laser pointer at the base. Project the
laser spot onto a distant wall, and you’ll see a vivid
illustration of the behavior of the beam.
Just imagine how your smart beam could be used
in all kinds of structures to cancel out stresses
from high winds, rough terrain, earthquakes, and
other shocks and jiggles. The sky’s the limit.