An assembly house asked me to look at an existing product that
clipped onto a bicycle wheel and flashed a light every time the
wheel made one revolution. The product consisted of a molded case,
and one printed circuit board with a battery and a light. It also
included a very simple device to sense wheel rotation.
My client wanted to bid on the manufacturing contract for the
device and needed to determine the component costs. The circuit,
which consisted of all through-hole components (viz., several
transistors, resistors, and capacitors), was obviously hand-built
outside of the United States. My client hoped they could be
competitive with surface-mount components and automated assembly.
I found a problem very quickly. One of the transistors was not a
transistor at all, but an integrated timer circuit. To make matters
worse, it was not manufactured in a surface mount package. We looked
into a hybrid or chip-on-board approach, but the numbers did not
work.
This simple project required only a few hours of my time, but
saved the client from a futile bidding effort.
