PC Controlled RC Car

1
PC Controlled RC Car

• Team 12
• Sunil Kondala
• Orbay Tuncay
• Kyle Zars

2
Features

• Wireless Link (75.870 MHz) from Host Computer to
  Car
• On-board Wireless Camera (2.4GHz) with Amplifier
  for Extended Range
• User-Friendly Software Control Interface
• Remote Login Capability

3
Possible Uses

• Visual security for entire home with one unit
• Maneuver and see into small spaces
• Espionage missions
• Can also be implemented on an RC boat, plane or
  helicopter

4
Objectives/Goals

• Make Car Operational Up to 100 ft. (With No
  Obstacles)
• Success Also Operates Up to 58 ft. Through Two
  Brick Walls
• Delay Between Video Frames on Remote Computer
  Less than 500 ms.
• Success
• Delay Less than 100 ms for LAN Connection (MS
  Remote Desktop)

5
Original Design
6
Design Overview
Host PC
Remote Control Circuitry/Transmitter
Breakout Board
Digital Potentiometers
Receiver
Remote PC
Amplifier
Receiver/Car
Camera
7
XR2i Remote Control

• Used for RC Cars, Boats, Airplanes
• Operates at
• 12V, 150mA
• Utilizes Amplitude Modulation (AM)
• 26.995MHz to 75.990MHz
• Channel BW10kHz
• Operates at 75.870MHz
• Channel 84

8
Spectrum Of Tx Signal
9
Interior Components

• Mechanical Potentiometers
• Microprocessor
• RF transmitter board
• Telescopic Antenna

10
Remote Schematic
11
Mechanical Potentiometer

• This potentiometer sweeps through resistances
  from as low as 60 O to as high as
• 5 kO
• W-gt (pin 18 and pin 15) Varies Voltage from 0.8V
  to 3.8V

• Potentiometer

12
Mechanical Potentiometers
13
Microprocessor

• Pin 18 (throttle) -gt Pin 43 of microprocessor
• Pin 15 (steering) -gt Pin 42 of microprocessor
• The ADC in the microprocessor

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Digital Potentiometers

• 10 KO potentiometer
• Operates from 2.7V to 5.5V
• Current through wiper 0.12µA

Maxim DS1866
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Digital Potentiometers

• PIN DESCRIPTION
• H High End terminal
• L Low End terminal
• W Wiper Arm
• P0 LSB data input
• P1 Bit 1 data input
• P2 MSB data input
• Pin 4 Ground
• Pin 8 - VCC

16
Digital Potentiometers
17
Software Interface
18
Software Interface Design

• Buttons vs. Scrollbars or Keyboard
• Parts Decision
• Digital Potentiometers Maxim Part DS1866
• 3 Parallel Inputs (data bus on parallel port is 8
  bits)
• Operates at 5V (same as parallel port signal
  voltage)
• Output Current Same as Mechanical Pots (1-2 µA)
• 10 k? Variable Resistance Range
• Parallel Cable Breakout Board
• Cost
• Easy Terminal Strip/Screw Interface

19
Software Algorithm Overview

• Click on Button takes you to function
• define Data 0x378
• int Bits
• Conditional Statements on Bits
• Holds one channel constant while changing the
  other
• Set Bits to new value
• _outp(Data,Bits)

20
Parallel Port Signals
21
Issues Accessing Parallel Port

• Windows XP does not allow access by default
• Found UserPort software (shareware)
• Configures the Behavior of the Driver

22
Video Transmitting Software

• Clipstream Live (shareware)
• Compresses Video to Transmit Over IE
• Also Conveniently Compresses Enough For MS Remote
  Desktop

23
Capture Card

• ATI TV Wonder Card
• Receives Coax Input From Wireless Camera Receiver
• Clipstream Software Uses this Card for Input of
  Video Signal

24
What we have?

• X-10 2.4GHz Wireless Camera
• Operates w/12V DC, 80mA
• Resolution 310 TV lines
• RF Output of 50,000uV/m _at_3m
• FM modulation
• Receiver operates at 4 channels 2.411GHz to
  2.473GHz
• Channel BW is 18MHz
• Transmission Range 100ft

• ANS-900 2.4GHz Monopole
• 50O input impedance
• 2.5dbi omni-directional gain
• 1.51 VSWR max
• 10W max input power

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How much amplification do we need?

• Amplification Free Space Loss Path Loss
• Friis Transmission Formula
• PR PT DT DR ?2
• 16 p2 d2
• PR Power received by receiving antenna
• PT Power radiated by transmitting antenna
• DT Directivity of the transmitting antenna
• DR Directivity of the receiving antenna
• ? Wave length
• d Separation between antennas

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Free Space Loss

• Using Friis Transmission Formula
• Since PT DT DR ? in Friis Formula doesnt change
  for different separations, power received is
  inversely proportional to separation squared
• Power Ratio PR(55ft) (100ft)2
• PR(100ft) (55ft)2
• Free Space Loss 10 log (Power Ratio) dB
• 5.193dB

27
Path Loss

• Path loss can be estimated as 5dB/wall

• Typical 2 bedroom apartment has 3 walls

http//www.genisysnetworks.com
http//www.imperialsouth.com/2bedroomfloorplan.htm
l
Path Loss 5dB/wall 3 walls 15
dB Amplification needed 20.193 dB
28
X10 transmitter output
Spectrum of video signal (20MHz BW)
Power spectrum of the transmitter output
Output power of the transmitter at 2.411GHz
(channel A) 3.883dBm
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Amplification at the output of transmitter

• Specifications of final power amp
• Operate at 2.4GHz ISM band
• 21dB gain
• High efficiency i.e. low voltage operation
• Low input power i.e. 4dBm
• Max output power of 1W30dBm (limited by FCC)
• Impedance matched to 50O

• Desired power amp RF2163
• 1800MHz to 2500MH operation range
• Operation voltage 3.3V
• 19dB gain w/Pin10dBm
• 30dBm saturated output power
• Impedance matched to 50 O w/impedance matching
  network

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Using what we have MAR8

• Output power of transmitter w/MAR8 and 10dB
  attenuator

• GMAR8(2.4GHz)
• Pout 10dB PTx
• 3.47dBm 10dB 3.883dBm
• 9.587dB
• OR
• Wireless camera range of 100ft in free space and
  1 dry wall
• BW doesnt change
• information is preserved therefore can be
  substituted for RF2163

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Overview of MAR8
Vcc 12V, I 40mA Powered by RS51-0124 battery
32
Characterization of MAR8 Input/Output Missmatch

• Matched to 50O at the input
• S11lt -15dB
• 2.32GHz lt f lt 2.48GHz
• Matched to 50O at the output
• S22lt-15dB
• 2.33GHz lt f lt 2.45GHz

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Characterization Stability

• Unconditional Stability Criteria are satisfied
• K gt 1
• 2.22GHz lt f lt 2.60GHz
• B1 gt 0
• 0 lt f lt 2.60GHz

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Characterization Gain

• S2112dB
• f 2.40GHz
• Measured gain9.5dB
• Since we are operating at power levels 4 dBm,
  cable losses are significant and effect the
  measured gain.

35
Challenges/Problems

• Operation of Potentiometers
• Trouble Figuring Out Correct Configuration
• Added 1 k? Resistors in Series Between Parallel
  Port and Input Pins
• Amplifier
• Was Not Feasible to Build One Given the Time
  Constraint
• Non-Functional Substitutes
• Initialization of RF Signals Being Transmitted
  When Car Is Powered on

36
Thanks To

• Professor Swenson
• Derek Gottlieb
• Professor Steven J. Franke
• Professor Alex Cangellaris
• Chad Carlson
• Josh Potts

37
Questions?