Stensat StenBOT Rover Kit User manual

1
StenBOT Rover Kit
Stensat Group LLC, Copyright 2013

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Legal Stuff
●Stensat Group LLC assumes no responsibility and or liability for the use of
the kit and documentation.
●There is a 90 day warranty for the Quad-Bot kit against component defects.
Damage caused by the user or owner is not covered.
●Warranty does not cover such things as over tightening nuts on
standoffs to the point of breaking off the standoff threads, breaking wires
off the motors, causing shorts to damage components, powering the
motor driver backwards, plugging the power input into an AC outlet,
applying more than 9 volts to the power input, dropping the kit, kicking
the kit, throwing the kit in fits of rage, unforeseen damage caused by the
user owner or any other method of destruction.
●If you do cause damage, we can sell you replacement parts or you can get
most replacement parts from online hardware distributors.
●This document can be copied and printed and used by individuals who
bought the kit, classroom use, summer camp use, and anywhere the kit is
used. Stealing and using this document for profit is not allowed.
●If you need to contact us, go to www.stensat.org and click on contact us.

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Table of Contents
●Overview
●Robot Kit Assembly
●Arduino Programming and Interfacing
●Robot Motor Control
●Robot Sensing
●Robot Remote Control

4
Overview

5
Goals
●The goal of this kit is to have a quad-bot platform that can operate on
uneven terrain and even in sand autonomously or by remote control.
●You will learn basic autonomous operations using the ultrasonic range
sensor.
●For remote operations, you will learn how to configure and program the
quad-bot to be controlled by a TV remote control.

66
Program Overview
●Assemble Kit
●Programming to move
●Learning how to calibrate the motion
●Running the Maze
●Using sensors for collision avoidance
●Running the Maze using collision avoidance
●Remote control

77
Robot Parts
●The robot is made
up structural parts,
mechanical parts
and electronics.
Gear Motors
Wheels
Rocker Arm
Base Plate
Cross Bar and
Linkages
Electronics Plate
Electronics

88
Suspension System
●The rocker arm suspension system is made of a few main components
shown below
Rocker Arms
Cross Bar
Linkages

99
How the Suspension Works
●Two motors are attached to the
ends of the rocker arms. The
center of the rocker arm is
attach to the base plate and
pivots. This lets both wheels
on the same side keep
touching the ground if one
drops in a dip or goes up on
something.
Pivot Point

1010
How the Suspension Works
●When the one rocker arm
changes its angle, the cross
bar is pushed up or down to
push the other rocker arm in
the opposite direction. This
helps keep the wheels on the
other rocker arm touching the
ground. The linkages attach
the rocker arms to the cross
bar. The cross bar is attached
to the base plate so the base
plate changes its angle half
way between the two rocker
arms.
Pivot Point
Cross Bar
Pivot Point
Linkage

1111
How the Electronics Works
●The robot electronics controls the
operations. It consists of a battery for
power, a processor board for the
brains, a motor controller to operate
the motors and an ultrasonic sensor
for detecting obstacles.
●The diagram to the right shows how
the electrical components are
interconnected.
●The battery powers everything.
●The processor board is the brains and
controls everything.
●The motor controller provides the
proper interfaces to the motors for the
processor board to control the motors.
●The radio provides a method for
remote control.
Battery
Battery
Processor
Board
Processor
Board
Motor
Controller
Motor
Controller
Left
Motor
Left
Motor
Right
Motor
Right
Motor
Ultra-
Sonic
Ranger
Ultra-
Sonic
Ranger
Radio
Radio

1212
Battery
●The power source for the robot is a battery. The battery is made up of four
AA cells.
●Multiple types of AA cells can be used in the robot. The simplest is alkaline
cells that cannot be recharged and must be discarded when they are used
up. Alkaline cells generate on average 1.5 volts. With four cells, a total of 6
volts is supplied. It will be noticed that over time, the robot will slow down as
the batteries drain.
●Rechargeable cells can be used. There is Ni-Cad and nickle metal hydride
or Ni-MH. These cells have a slightly lower voltage of 1.25 volts. The benefit
is the cells can be recharged and reused many times. Another benefit is
these cells can deliver more current without dropping the voltage unlike
alkaline cells. These types of batteries also maintain the same voltage
longer than Alkaline batteries. This allows the robot to maintain its speed.
●The four cells are connected in series to create a higher voltage.

1313
Processor Board
●The processor board is the brains of
the robot. It controls everything and
connects to all the sensors. This is the
part that you program to control the
actions of the robot.
●The processor board has multiple
interfaces
●Digital signals
●Servo motor
●Communications
●Analog inputs
●More details will be covered later.

1414
Motor Controller
●The motor controller is the interface between
the motors and the processor board. It has
circuitry to allow control of the motors and can
handle the high currents required to operate
the motors. The processor board cannot
directly power the motors. The controller is
capable of providing the needed current and
is used as the interface.
●The black square in the picture to the right is
the actual controller. It is an integrated circuit
that contains all the circuitry to translate
signals from the processor board to the
operations of the motors. This controller can
operate two sets of motors.
●More details are covered later.

1515
The Motors
●The motors are connected to gears that
translate the high speed of the motors to a
slower rotations speed. This also increases
the power of the motor so the wheels can
turn to move the robot.
●The motor is a small DC brush motor shown
at the bottom. It is inserted into the yellow
gear box.
●At the top side of the picture on the opposite
side is a white shaft. The wheel attaches to
the shaft.
●The gears convert the high speed rotation of
the motor and produces a slower rotating
shaft. The torque is also increased at the
shaft. Motor
Gear box

1616
Ultrasonic Range Sensor
●The ultrasonic range sensor is
a device that sends a short
burst of sound and listens for
the echo.
●The processor board starts the
measurement by generating a
pulse on the Trig pin.
●It them measures the size of
the pulse on the Echo pin.
●The processor calculates the
distance based on the size of
the pulse width.
●Distance is calculated by
dividing the pulse width
measured in microseconds by
58. Answer is in centimeters.
Connections
5 Volt power
Trigger signal
Echo signal
Ground

1717
Ultrasonic Range Sensor Operation
●The ultrasonic range sensor operates in a specific sequence.
●It waits for a trigger signal. The trigger is a 10us pulse. Once the trigger is
detected, the sensor generates a short signal at 40 KHz.
●It then waits for an echo and measures the time from sending the short burst
to receiving the echo.
●The sensor then generates a pulse on the echo with a length proportional to
the delay measured.
Trig
Transducer
Receiver
Echo
10us pulse on Trig pin
40 Khz burst signal
Echo from target Pulse on Echo pin
Delay
distance = pulse width (us) / 58

1818
Base Plate
●The base plate is a fiberglass board with holes arranged in a .5 inch grid
pattern. There are also other holes to mount specific things such as the
suspension systems and the electronics. There are markings on the board
identifying specific functions for the holes.

1919
Electronics Plate
●This is another fiberglass board that is used to hold the processor board and
solderless bread board.

2020
Solderless Bread Board
●The solderless bread board allows you to wire up circuits. It will be used to
connect the motor controller to the motors and the processor board. It is also
used for connecting the sensors.