CHAPTER 27 ■ ENCORE
Pushbuttons
Most pushbuttons are spring-loaded switches. Push down and the switch connects, let go and the switch
disconnects. Other than that physical difference, the robot sees switches and pushbuttons identically at an
electrical level.
Pushbuttons (see Figure 27-8) find their place on keyboards as well as mode selectors, reset buttons,
start buttons (stop! buttons), and control pads.
Figure 27-8. Various pushbuttons
Figure 27-7. Resistor network consisting of nine 470 W resistors in one package
Pushbuttons can also be used as “soft” power switches on smart devices. Most consumer electronics work
this way. Unlike a real power switch that totally disconnects power, soft-powered devices often contain an
internal chip constantly receiving power that watches the pushbutton. When the user pushes the button, the
brief continuity causes the chip to enable power (via a relay, transistor, or voltage regulator) to the rest of the
circuits. When the user pushes the button again, the chip disconnects power to all of the circuits but its own.
The soft-power button approach is especially valuable to circuits that can be powered remotely, can
turn themselves off after a period of disuse, or can turn themselves on at a certain time (like a fancy coffee
machine). A soft-power button would be very appropriate for an autonomous robot, so long as the batteries
are physically removed for servicing and long-term storage.
Personally, I select pushbuttons on the basis of how good they look or feel to the finger.