28125 Parallax Inc, 28125 Datasheet - Page 81

• Manufacturer Part Number: 28125
• Description: TEXT ROBOTICS
• Manufacturer: Parallax Inc

Specifications of 28125

• Title: Robotics with the Boe-Bot
• Product: Microcontroller Accessories
• Lead Free Status / RoHS Status: Not applicable / Not applicable

turning. You will then use a screwdriver to adjust them so that they stay still. This is
called centering the servos. After the adjustment, you will test the servos to make sure
they are functioning properly. The test programs will send signals that make the servos
turn clockwise and counterclockwise at various speeds.
Servo Tools and Parts
The Parallax screwdriver shown in Figure 2-21 is the only extra tool you will need for
this activity. Alternately, any Phillips #1 point screwdriver with a 1/8″ (3.18 mm) shaft
should do the trick.
Sending the Center Signal
Figure 2-22 shows the signal that has to be sent to the servo connected to P12 to calibrate
it. This is called the center signal, and after the servo has been properly adjusted, this
signal instructs it to stay still. The instruction consists of a series of 1.5 ms pulses with 20
ms pauses between each pulse.
The program for this signal will be a
DO…LOOP
be
Figuring out the
12, for I/O pin P12. Next, let's figure out what the
argument has to be for 1.5 ms pulses. 1.5 ms is 1.5 thousandths of a second, or 0.0015 s.
Remember whatever number is in the
that number by 2 µs (2 millionths of a second = 0.000002 s), and you will know how long
P12
PAUSE 20
. Figuring out the
for the 20 ms between pulses.
PULSOUT
1.5 ms
command's
PAUSE
20 ms
command from the timing diagram is easy, it's going to
PULSOUT
PULSOUT
Pin
argument isn't that hard either, it's going to be
command and a
command's
Figure 2-21
Parallax
Screwdriver
1.5 ms
PULSOUT
Duration
PAUSE
Figure 2-22
Timing Diagram for
CenterServoP12.bs2
The 1.5 ms pulses
instruct the servo to
remain still.
command's
argument, multiply
command inside a
Duration