cathode displays are now available, but
cost quite a bit more. The smaller
displays are very affordable. It would
be ideal to make available a PCB for
the project, a programmed chip, and a
crystal for the time base. Most DIYers
would have the other parts needed.
The PCB could be made small so that
builders could use a variety of case
sizes depending on the size of the
displays used. It wouldn't hold the
displays themselves; the builder would
mount them as needed. For my old
clocks, I mounted the 4" and 2"
displays on a thin sheet of plywood
painted black in a case made from
pieces of acrylic I got at Tap Plastics.
Thanks for the feedback. We have
the same definition of "big" — I've used
Futurlec displays and other large digits
in my clocks. I'm familiar with 73 and
Nixie displays, as well. I'm sure we share
quite a few experiences. Again, thanks
and — I assume — 73s.
Can’t Get Swing of Math
Regarding the parameter amplifier
article in the June 2014 issue, I haven't
gotten the frequency of a simple
pendulum to equal 1.5 Hz using
Richard Panosh’s equation with the
numbers in the article. I put the
numbers into Excel and it is 10 times
under the 1.5 Hz. I checked my
numbers with XLC and it will draw the
James Thompson II
Sorry to hear you're having trouble
with the expression for the frequency of
this simple pendulum.
Take the free length of the string as
four inches long. Add the radius of the
ball to this to obtain the total length to
the center of mass:
4 inches + 1/2 (3/4 inch ball
diameter = 4.375 inches)
4.375 inches x 1 ft/12 inches = 0.36 ft Hope this clears up the issue.
Thanks for your interest and good
luck in your studies.
READER FEEDBACK Continued from page 8
= 2π = 1.5
=2π √ 1 32. 2 f =2π 0.36 √ 89.444
f=2π l √
The gauntlet has been thrown!
If you’re interested in taking a crack
at this project, email
October 2014 59