CHAPTER 26 ■ SMOOTHER, SMALLER, CHEAPERSaving Money
The cost difference in the motors is overwhelming. The original motors are 12 V and more powerful but
available from only a single supplier. The replacement motors are 6 V and smaller but available from
multiple suppliers. The specific price I’m quoting is for the knock-offs from an auction web site, rather
than retail.
Interestingly, the need to replace the motors originally came from the desire to run the robot from a
lithium polymer battery. This was fortuitous not only for reasons of price but also because the new motors
have ready-made mounts and wheels available for them (look at the wheels in the earlier Figure 26-4). This
reminds me, yet again, that you often need to start your robot from the motors and work everything else
around them.
The following are the other price differences:
- The printed circuit board is one-third the size but not quite one-third the price
because there is usually a small fixed cost per board regardless of size. - The potentiometers are no longer necessary, so that’s an easy win.
- Toggle switches are more expensive than pushbuttons because they contain more
material and require more complex manufacturing. Although there will always be a
need for physical switches, modern devices use a greater quantity of pushbuttons,
which further reduces their cost because of economies of scale.
It shouldn’t be a surprise that the parts that save money on the modern Sandwich are the same parts
that have been swapped out on other modern devices. Why do fewer consumer electronic devices contain
physical power switches, large motors, large boards, and trimming dials (see Figure 26-10)? Because they
add cost and because alternatives exist.
Figure 26-10. Commonly swapped-out parts for cost reduction