Page 155 - Build Your Own Combat Robot

Build Your Own Combat Robot
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FIGURE 7-7
Standard Futaba
FP-S148 R/C servo.

Radio-Controlled Servos The R/C servo discussed here is the same type of servo
that is commonly found in R/C model airplanes. Figure 7-7 shows a photograph
of one of these servos.
The servo will respond to the signal from the radio transmitter by rotating its
output shaft to various commanded positions. A servo arm (commonly called a
servo horn) attached to the output shaft can be used to move a switch to an on or
off position, which can supply power to the coils of the relays. The most reliable
way to do this is to use a roller-type lever switch and a round servo horn manually
cut into an egg shape. By doing this, the servo horn is being converted into a cam.
Two lever switches positioned on opposite sides of the servo can be used to trigger
two different motor circuits, or to drive a single motor in forward or reverse direc-
tion. The basic R/C servo configuration is shown in Figure 7-8. Microswitches can
be used to drive small motors or to switch relays for driving larger motors.

FIGURE 7-8
Basic circuit
switching using an
R/C servo.