CHAPTER 26 ■ SMOOTHER, SMALLER, CHEAPER- The sensor and headlight potentiometers have been removed. Instead of manually
adjusting and balancing a voltage for a comparator chip, the programmable
microcontroller can normalize readings and trigger points in memory. - The cadmium sulfide photoresistors have been replaced by phototransistors
(QP3-QP7) wired in parallel. Phototransistors use less power, change values faster in
reaction to changes in light, and are manufactured with consistent light sensitivity
(no hand sorting necessary).
Shrinking Packages
By using tiny surface-mount electronics, instead of finger-friendly through-hole packages, the robot’s board
can be considerably smaller, about one-third the size (see Figure 26-6). The board is less expensive and fits
into smaller containers.
Figure 26-6. Comparison of Sandwich implemented using surface-mount parts (smaller board) and
hobbyist-friendly through-hole parts (larger board)
Although it took magnifying glasses, liquid flux, and patience, this small board was soldered by hand
(see Figure 26-7). Automated manufacturing could reduce the spacing between parts and would have
cleaner soldering.