A set of PCB parts for two Loki legs/feet (no upper legs).
time. Driving servos into their mechanical stops can damage
them. Proceed cautiously. Also be aware that if the battery
discharges too far, erratic servo operation can occur. Turn
off the power immediately!
Power up either Loki’s controller with ONLY servo #0
connected, or a servo driver (Servo Driver Pro). These servo
drivers are reportedly (I don't have one yet) useful in aligning
servos during construction of a robot — just what we need!
Turn on the servo power, being careful to hold up Loki
by the body, and WATCH your fingers!
As mentioned earlier, with the servo horns only allowing
rough squaring, we will record and save a calibration value
for each centered servo position. This calibration will be
dependent upon the controller board and software used.
The intent is to be able to send a 1,500 μs (null) position
request to all servos and have Loki move to the “left foot
forward” posture. This is the “starting” position, and all
of the canned move sequences should both start and
NOTE: Futaba 3004 servos rotate the opposite direction to
Hitec HS-475HB servos! Be sure you account for this if you
change between the servo brands.
Part 2 of this article will discuss the QwikFlash board I
used and the software developed to run Loki.
A better location for the IR and ultrasonic sensors
could be investigated. Maybe rotating sensors! I’ve been
contemplating adding some foot sensors, as well. These
would be great for keeping Loki from walking off the table!
A battery test function would be quite useful. A low
dropout voltage regulator to supply the controller board
would probably allow Loki to run on just a 6V battery pack.
One would have to
check to see what
current the IR and
however. A custom
for Loki is also
Loki with wooden
up in the air.
Loki Crosses the Pond — Part 1
PIC BOOK URL: www.picbook.com
Schematic of QwikFlash board:
Assembly instructions for QwikFlash board:
David Buckley website: http://davidbuckley.net/DB/Loki.htm
Microchip data sheets, ICD 2, MPLAB: www.microchip.com
Board Parts, PCB stock, PIC: www.digikey.com
Hi-Tech PICC- 18 compiler: www.htsoft.com
Servos, IR sensors, battery: www.lynxmotion.com
DT106 Development board:
Aluminum stock: www.onlinemetals.com
Book available on Amazon.com:
Embedded Design with the PIC18F452 Microcontroller
Prentice Hall, 2003
T2 Terminal program:
Docklight Terminal program: www.docklight.de
SERVO 06.2008 55