Jim's Robot - 09/27/2006
|
This is the current state of the robot project.
This labor of love was started three years ago,
shelved for a couple and recently re-started. The
idea for this came over ten years ago and I have
finally found the time and the energy to make
it a reality.
The robot chasis is made of 2x4 H frame and a
2'x2' piece of plywood. The motors and wheels are
from an old Power-Wheels ™ "Barbie Jeep" and
the electronics are hand built and mostly self
designed.
|
Large Size:
GIF or
TIFF
|
This diagram represents a simplified view of the
electronics and logic found on the robot, today.
The robot is controlled by a laptop computer
(not shown) through a serial connection to a
Parallax BS2 microcontroller. All of the
circuits on the board are controlled by the
BS2 after receiving commands from the laptop.
A majority of the circuits on the robot are
controlled through an I2c which allows the BS2
to control several devices through a two line
serial connection. Several of the devices were
built around the PCF8574 - IO Concentrator
from Phillips.
|
|
|
Pictures
|
|
View from the front showing the robot as a whole.
Motors are mounted on an axle on the front and
non-powered wheels are on an axle on the rear.
The angled steel second story (over the battery
box) will be the location for the controlling
laptop.
|
|
This view is of one motor, the BS2 (on a
carrier board), and one of the PWM motor
power boards. The boards are stacked and
under these are additional circuits.
Also visible is one of the two front bumper
supports. The front bumper is pushed out with
springs and push buttons are located on the
bracket and are actuated when the bumper meets
an object.
|
|
This view continues down the front edge and shows
the second PWM motor power board, the I2c bus
connector board (no logic), and the second bumper
support.
Under the Laptop support steel, by the motor
(bottom center), is the inverting relay board and
on the bottom left is a board with two PCF8574
chips. One of these is addressed as 0x42 and is
used to drive the inverting relay board and the
other (0x44) is used for the pull-down switch
and bumper board.
|
|
The two boards on the lower rear of the platform are the compass
carrier board (with compass) and the compass rose board. The rose,
address 0x40, has 8 LEDs arranged in a circle and is used for
various output functions. Ususlly the led pointing to North is
illuminated and this is why it is called the rose.
|
|
Not very good picture from the front. You can see the stacked
controller boards.
|
|
Closeup of the TTM Motor board for Motor 1. Under it you will
see the front edge of the PWM board and to the right you see the
I2c Bus and tne Inverting Relay Controller.
|
|
Closeup view of motor 0 and the BS2 carrier board. In the center middle
you will see the 5v logic power regulator and above it you see the
switch box on the battery box with both logic and motor power switches.
On the wooden support member you will notice a Sharp GP2d02 infra-red
ranger. There are two located on the front supports. In this
picture it is not connected.
|
|
|
Schematics and Details
|
|
5v Logic Power Board
|
|
CMPS01 Module and Board
|
|
Inverting Relay Controller Board
|
|
Switch Pulldown Board
|
|
Pulse Width Modulator (PWM)
|
|
Serial Port and Speaker Board
|
|
TTM Motor Power Control (TTM)
|
|
|
Notes
|
|
The relays shown on the block diagram (r0, r1) are responsible
for forward and reverse for each motor independently. The current
from the TTM board is applied to the relay when open in one
polarity and in a reverse polarity when closed. You can see the
relays on the front of the H frame behind the front bumper near
the motors.
|
Communications from the laptop to the BS2 are sent via an
RS232 cable at 2400,N,8,1. This slow speed is recommended
by Parallax and a higher speed has not been tested.
The laptop sends a string starting with a bang followed
5 bytes (represented as hex). Byte 1 represents a command
and the 4 bytes represent data arguments.
The BS responds with a .1 (for error) or .0 (for success) followed
by 4 bytes (represented as hex) representing result data.
|
