Page 104 ·
Robotics with the Boe-Bot
Servo Trouble Shooting
: Here is a list of some common symptoms and how to fix them.
The servo doesn’t turn at all.
√
If you are using a Board of Education Rev C, make sure the 3-position switch is
set to position-2. You can then re-run the program by pressing and releasing the
Reset button.
√
If you are using a BASIC Stamp HomeWork Board, make sure the battery pack
has batteries.
√
Double-check your servo connections using Figure 3-10 on page 100 as a guide.
If you are using a HomeWork Board, you may also want to take a second look at
Figure 2-18 on page 65.
√
Check and make sure you entered the program correctly.
The right servo doesn’t turn, but the left one does.
This means that the servos are swapped. The servo that’s connected to P12 should
be connected to P13, and the servo that’s connected to P13 should be connected to
P12.
√
Disconnect power.
√
Unplug both servos.
√
Connect the servo that was connected to P12 to P13.
√
Connect the other servo (that was connected to P13) to P12.
√
Reconnect power.
√
Re-run
RightServoTest.bs2.
The wheel does not fully stop; it turns slowly.
This means that the servo may not be exactly centered. You can often adjust the
program to make the servo stay still. You can do this by modifying the
PULSOUT
12, 750
command.
√
If the wheel turns slowly counterclockwise, use a value that’s a little smaller than
750.
√
If it’s turning clockwise, use a value that’s a little larger than 750.
√
If you can find a value between 740 and 760 that fully stops your servo, then make
sure to use it anywhere you see the command
PULSOUT 12, 750
.
The wheel doesn’t stop for one second between the clockwise and counterclockwise
rotations.
The wheel might turn rapidly for three seconds in one direction and four in the other. It
might also turn rapidly for three seconds, then just a little slower for one second, then
turn rapidly again for three seconds. Or, it might turn rapidly in the same direction for
seven seconds. Regardless, it means the potentiometer is out of adjustment.
√
Remove the wheels, un-mount the servos and repeat the exercise in Chapter 2
Activity #4: Centering the Servos.
