The piezo-based pads require tapping with drum sticks or
similar items in the conventional "drum" manner. The optical pads can be tapped
by hand, making them easier to use.
We also use an optical pickup for foot-activated sensors. This
is because the system is more robust. A piezo transducer that can be attacked
with a foot pedal may well be destroyed rather quickly.
Each pad type is described in the separate sections following.
Building The Optical PC Board
(left) Fig.5. (Above) Fig.6.
Circuit details were shown in Part 1 but are repeated here for
convenience along with the PC board overlay for the optical sensor (there is no
PC board for the piezo sensor).
The optical sensor PC board is coded 01211053 and measures 52 x
31mm. Once again, before assembly check the underside for any possible shorts
between tracks or breaks in the copper.
As you did for the other boards, install the resistors and diode (as shown),
the PC stakes and the capacitor (which is mounted on its side to allow clearance
above the PC board). Finally, the optical sensor is mounted directly onto the PC
board, making sure it is oriented correctly.