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Project members: |
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Tim Ring |
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Adam Nelson |
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Scott Bertling |
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Joe
Harrill |
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ACME is an automated highway system. |
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An automated highway system autonomously
navigates a vehicle to a user defined destination. |
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The purpose of this project is to design an
automated highway system on a miniature scale that could lead to further
research. |
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ACME combines a vehicle and highway with
microcontrollers, receivers, transmitters and magnetic sensors. |
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1st presented by General Motors in
1939 at the World’s Fair. |
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During the end of the 1980s, advances in
microprocessors, wireless communications and other electronic sensors
prompted a renewed interest in the automated highway, leading to the
formation of the Intelligent Transportation Society (ITS) of America in 1988. |
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More recently, several pilot tests of automated
highway systems are underway and run by the National Automated Highway
System Consortium. |
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Vehicles travel in “platoons” guided by onboard
sensors. |
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Vehicles communicating on lane changes. |
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Exit beacon transmitting data to vehicles. |
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Two types of navigation. |
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Beginning of AHS implementations. |
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Roadways are dangerous and increasingly
expensive to maintain. |
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Many societies have been very successful at
finding creative alternatives to make their transportation systems safer
and more efficient. |
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The structure of the automated highway system is
a familiar format for the U.S. culture and easily recognizable to its
users. |
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Therefore, a new infrastructure will not be
needed and only retrofitting current systems will be needed. |
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The vehicle’s guidance system is controlled by a
microcontroller and sensor configurations. |
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This system is
guided by signals in the roadway. |
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Exit beacon transmitters relay exit information
to vehicle. |
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On-Board Receivers receive this information and
communicate this to the microcontroller for decision making. |
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User inputs exit # and car follows LHS magnets. |
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Beacon # is tripped when RF car passes. |
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The exit # and beacon data are compared. |
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RF car follows RHS magnets to exit #. |
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Four types of technologies were considered for
navigation in the project: imaging systems, radar, line-trackers and
magnetics. |
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Magnetic systems are the only type that are
transferable to the real world. |
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Sensors are not affected by dirt or mud. |
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Magnetic fields on the roadway operate through
all environmental issues. |
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Magnets will not degrade over time. |
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A magnetometer senses the generated magnetic
field. |
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There are several types of Magnetometers. Our
team selected the digital Hall-Effect Sensors which generates a voltage
when the current flow is perpendicular to the applied magnetic field. |
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We are using the Uni-polar Hall Effect Sensor.
Uni-polar meaning activation by one pole. |
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The output is always on and off in the presence
of a B-field. The turn on strength
needed is 35 G. Switching is done by an internal NPN transistor. |
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Very powerful permanent magnets are needed to
activate magnetometers. |
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These magnets are Ceramic, Alnico, Samarium and
Neodymium. These compounds are mostly found in combination with Iron,
Chrome, Boron and Cobalt. |
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Sufficient strength to activate sensor |
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The left two sensors track the roadway and the
right two sensors track the exits. |
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The left side will operate until interrupted by
the user that an exit is needed. |
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The table applies to the LHS only. RHS table being
10 = Left and 01 = Right. |
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The brains of the project, every system will be
tied into the Microcontroller. |
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The Microcontroller must be: |
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Versatile |
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Sufficient in processing power |
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Easy to use |
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Fairly cheap |
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Processing Power |
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The Microcontroller needs to be able to process
functions simultaneously |
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The Microcontroller needs to process fast enough
for precision timing and accuracy for tracking. |
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Versatility to handle |
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Multiple Sensors |
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Two DC Motors |
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RF Receiver |
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Keypad |
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LCD |
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Parallel Communication |
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Two choices |
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Buy a board |
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Compromise to board configuration |
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Save time (preassembled and tested) |
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Professional layout |
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Make a board |
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Allows for choosing each component |
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Cheap |
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Time consuming; learning software
and hardware, trial and
error, ordering parts, |
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soldering, design |
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Board Criteria |
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Find a board that can easily tie into specified
peripherals |
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Expandable for future application and ideas |
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Uses RS232 or USB port |
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Falls within budget |
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OOBOT40 from |
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Oricom Technologies |
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18 non-dedicated I/O lines |
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4 H-bridges |
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Up to 7 A/D lines |
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Up to 8 servo lines |
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3 High current drivers |
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Will run off a 9V battery |
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Three Main Sub procedures |
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Initial input: Will correspond with the
user interface via LCD
and Keypad |
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Tracking: Follow the magnetic track linking |
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the magnetic sensors to the steering
motor |
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Exiting: Break from the continuous track to
an exiting lane |
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The initial sub procedure will be to link the
LCD and the Keypad (or other input device) together creating a user
interface |
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The system should start out initially by
displaying a message on the LCD screen asking the user for a destination,
and will await for an input from the user. The data will be stored in
memory and the vehicle will be set into motion. |
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The tracking sub procedure will tie the magnetic
sensors to the steering motor. The sensors will guide the vehicle as to
where to go following the magnetic field |
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The system will work by sensing the logic state
of the magnetic sensors; There are four logic states that are used. A
change in logic state will trigger an event or interrupt that will
subsequently call a subroutine that will correct the path of the vehicle. |
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interrupt |
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01 10 |
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00 |
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00 00 |
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interrupt |
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The exiting sub procedure will be much like the
tracking except that tracking from one set of sensors will switch to
another set. |
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The Design of this procedure begins with the
data entered in from the initial sub procedure. When the vehicle falls
within range to the RF signal the data received from the signal will be
cross referenced with destination data. And logic will be emulated to
select the appropriate course of action |
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The Communications systems will be divided into
two major categories. |
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Exit Beacon Transmitter |
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and Vehicle receiver
subsystem. |
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The A.C.M.E. communication system will need to
Transmit Exit data and have it received by the vehicle. |
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Remote Driver control release subsystem. |
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The drive control of the test vehicle will need
to be relinquished from the remote control to the system MCU. |
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The communications in this system will be used
to let the vehicle and driver know when they have arrived at a previously
selected exit from the highway system. |
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It will communicate this information to the main
system MCU so that it may select and follow the exit path. |
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Also, in our configuration we must be able to
remotely change the drive control from the Hand held RC car remote to the
MCU. |
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The RF transmitters and receivers must be: |
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Able to transmit and be received at a distance
of 100 meters. |
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Be programmable. |
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Need only Simplex data transfer. |
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Be completely portable. |
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Small in physical size. |
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Low power consumption. |
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Interface with the A.C.M.E. system
microcontroller. |
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Low Cost. |
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The core of the Communication System will be
determined based on the following considerations: |
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The System will need to transmit an
identification code to identify individual beacons. |
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All of
the systems exit beacons will transmit their specific I.D. codes on the
same RF frequency. |
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This will allow for the vehicles in the system
to be continuously tuned to all of the Beacons in the system. |
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The Beacon transmitter should only operate when
a vehicle is detected in the range of the transmitter. |
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The
best way to meet all of the needs and considerations of the communication
systems is to start with a RF development kit. |
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These will include at least one transmitter and
receiver. |
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Development hardware and software. |
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Programmable components. |
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Kit includes MP lab IDE development environment. |
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Development board, USB to PC interface. |
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Code development in Assembly. |
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Allows for individual component programming or
in-circuit-programming of the module. |
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Transmitter Modules are capable of ICP. |
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Receiver
Modules do not require programming. |
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Enclose Transmitter and Vehicle Detection
switch. |
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Small |
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(2.5” x 2.75” x 5.25”) |
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Weather Proof |
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Manufacturer Unknown |
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Motion Detector Switch |
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Detects vibration from vehicle. |
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No additional power required to operate. |
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Closes circuit on transmitter CCA. |
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Manufacturer Unknown |
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The data that is transmitted will first be
demodulated within the Receiver Module. |
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It is now a PWM data stream at base-band. |
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The PWM data is then decoded to a parallel data
configuration with the programmed decoding PIC. |
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The output from the decoding PIC will now need
to be conditioned for interface with the OOBOT40 microcontroller. |
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The four
bit parallel data that is decoded will be latched for the MCU to detect. |
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This will allow the MCU to accept the data when
it is ready and not interrupt any drive control sequences. |
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Also, the latched data will drive a LED to
indicate it’s condition. |
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The MCU will toggle a conformation bit when it
accepts the data. |
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HPI R/C car-Dash Series |
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Existing Vehicle Power |
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7.2 Volt NiCd battery pack |
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Used to power the drive motor |
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Powers the Steering motor in manual drive |
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Additional power |
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6-10 Volt battery pack to power |
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Micro-controller through 5 volt voltage
regulator |
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H-bridges on evaluation board |
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External H-bridge for drive motor |
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The drive motor for the car is a 7.2 Volt
electric motor with 6 Amps peak current at full throttle moving the car at
speeds of 30mph. |
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3 Amps peak for the operation of this project
due to the minimal velocity. This current occurs when moving the car from
rest. |
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1 Amp continuous during constant minimal
velocity |
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16 pin H-Bridge IC |
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Manufactured by Texas Instruments |
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2 Amp max current |
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1 Amp continuous current |
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Already integrated with the OObot40 board and
the OOpic |
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TPIC0108B |
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20 pin H-bridge |
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Optimized for low power battery operations |
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Input Voltage between 6 and 18 Volts |
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Peak current of 7.5 Amps and continuous current
output of 4.8 Amps |
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Provides overvoltage, over current and over
temperature protection |
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Obtained as a sample from Texas Instruments |
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NIMH-0050 |
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Manufacturer: New Micros |
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5 Amp continuous current |
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6 Amp peak current |
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Separate circuit keeps control board safe from
overloading current. |
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The steering mechanism is powered by an electric
motor that is hooked up to a sensor with a wiper and a pot that determines
the position of the wheels. |
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The electric motor will run off the SN754410
H-bridges currently on the OObot40 board, a high current H-bridge is still
needed to power the drive motor. It
has not been decided between the NIMH-0050 or the TPIC0108B |
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Switching the polarity on the steering motor
effectively steers the car in opposite directions. |
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Vehicle $50.00 |
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Micro-controller $88.00 |
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RF transmitters and receivers $135.00 |
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Miscellaneous parts $40.00 |
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Extra Battery pack $30.00 |
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2 Serial Cables @ $13.00 each $26.00 |
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OOpic programming book $24.00 |
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Unipolar Hall Effect sensors Freebie |
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$393.00 |
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Magnets ($0.28 per 1.87”, 26’ total) $50.00 |
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Highway model materials $60.00 |
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Switches for exit selection $5.00 |
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LCD $40.00 |
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External H-Bridge $30.00 |
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Miscellaneous Components $15.00 |
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Expenses to date $393.00 |
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Total Expenses $593.00 |
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Notes