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ECE 485: Electrical Engineering Design I Project. By Group 2: Joel Marcia, Paul Rosensteel, Scott Laminack, and Justin Lanham. Overview: The Problem. To design and implement the hardware and software to control the Trekker Robot in three competitions: Go around outside loop 3 times.

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ece 485 electrical engineering design i project

ECE 485: Electrical Engineering Design I Project

By Group 2: Joel Marcia,

Paul Rosensteel,

Scott Laminack,

and Justin Lanham

overview the problem
Overview: The Problem
  • To design and implement the hardware and software to control the Trekker Robot in three competitions:
  • Go around outside loop 3 times.
  • Go around outside loop at least once, then take the inside loop twice.
  • Evade an obstacle on the track and follow the guidelines from competition 2.
overview specifications
Overview: Specifications
  • OOPic R with a L7806 – 6V Voltage Regulator (TO220 Package)
  • OOPic R Expansion Board

Pictures from

overview specifications1
Overview: Specifications
  • A Sharp GP2D12 IR Sensor
  • A Devantech SRF04 Ultrasonic Ranger
overview specifications2
Overview: Specifications
  • 4 QRB1134 Phototransistors with mounting bracket
  • 2 HiTec HS-422 servos to control the wheels
  • 1 HiTec HS-311 servo to control the ranger or IR sensor

Pictures from

game plan
Game Plan
  • No “If … Then” statements
    • Might be easier getting stated, but more work in the long run
  • Use object codes to create a virtual circuit
    • Simplify the code
    • Easier to debug
    • Changes are easier to make
key object codes used




Key Object Codes Used
  • Designed to control servos or to interface servos with different objects
  • Specifically used with hacked servos
  • Supports URCP values (positive and negative values)
  • Unique property – set Value property to 0, no pulses are sent to the servo (wheels stop completely)
key points using oservosp1
*Key Points using oServoSP1
  • Set the left servo InvertOut property to “1” – sets wheels turning in the same direction
  • Set Refresh property to “1” – doubles the pulses sent to servos (increases torque)
    • Tested using o’scope: 36.2 Hz to 73.53 Hz
  • Designed to use digital sensor inputs (line followers) to determine the location of a black line on a white background
  • Formats URCP readings to express how much it needs turn
    • Range of values +/-8, +/-16, +/-24, +/-32
  • Maximum of four sensor inputs
key points using otracker
*Key Points using oTracker
  • Setting the Width property to “1” allows the use of only three sensors
    • Range of values +/-8, +/-24, +/-32 (no +/-16)
    • The fourth sensor was used to detect the “inner circle” with an oEvent
  • Coverts the information received from oTracker into motor control speed for the servos
    • Takes the predetermined “Speed” value then adds or subtracts the values received from oTracker (URCP values) and send them to the servos
key point using onavcon
*Key Point using oNavCon
  • Set oNavCon to ”0” to turn off the line following subroutine
    • This allowed us to turn off or override the line following subroutine to make adjustments for a special “event”
  • Used with the sonar sensor
  • Triggered depending on distance
  • Compares two numbers (predetermined upper and lower limits) and sets the servo speed values to follow a along a wall or go around a “box”
basic flow diagram
Basic Flow Diagram

Line following


oNavCon on


oNavCon off

oNavCon off

Inner Circle


Go around box




round 1 of line following competition

Round #1 of Line Following Competition

Objective: To complete three laps around the black line track where one lap must be around the outer loop of the track.

the line following circuit
The Line Following Circuit
  • The circuit for an individual line-follower
    • Pull-Up Resistor = 10 kW
    • Rf Resistor = 220 W
    • Line follower Capacitor = 0.1 mF
capacitors used in line following circuit board
Capacitors Used in Line Following Circuit Board
  • We found documentation explaining how capacitors could be included in the line following circuit to reduce noise that the line followers may pick up.
  • The capacitors are connected to the line followers in hopes of leveling out the ripple in the signal out.
no significant difference
No Significant Difference
  • We tested the Trekker with, and without the capacitors in the circuit
  • No significant difference was found.
  • Therefore we chose to remove the capacitors from the line following circuit board.
  • Our design of the circuit board made removal of the capacitors easy, as they were connected from behind using free wires
  • These wires were cut, electronically removing the capacitors from the circuit
servo values s4 and s5
Servo Values S4 and S5
  • The coded values of S4 and S5 refer to server rotational speeds
  • S4’s value directly corresponds with the Right Wheel’s rotational speed
  • S5’s value directly corresponds with the Left Wheel’s rotational speed
finding the center of the servos rotational speed values
Finding the center of the servos rotational speed values
  • From Trekker Experiment #3
  • S4 and S5 relationship with the rotational speed of the wheel was found
reversal of direction
Reversal of Direction
  • Because the left servo and the right servo are opposite of each other, they each travel in opposite directions relative to one another
  • To remedy this, one of the servo’s values is inverted
  • Now both wheels will move the Trekker forward at the same time.
first competition program works
First Competition Program Works!!
  • The initial line following program was uploaded to the OOPic R.
  • The Trekker successfully went around the outer loop of the track
  • First run around the track was very slow
improvements to program
Improvements to Program
  • Had to find a good value for the servo speeds
    • Not too slow, or the Trekker would take too long around the turns. It would have a very “jerky” stop and go manuever.
    • Not too fast, or the Trekker would leave the black line on the turns and not return.
  • A speed value of 31 was found to be the best for what we needed
number of line following sensors
Number of Line Following Sensors
  • The more line following sensors employed in the design, the faster the Trekker should be able to traverse the course
  • Using Four Sensors
    • Time around track = 1 min 6 sec
  • Using Three Sensors
    • Time around track = 1 min 5 sec
  • Three sensors are used in the final design of the Line Following program
three outer loops no inner loops
Three Outer Loops, no Inner Loops
  • Our Trekker made it successfully around the outer loop of the track three times.
  • No inner loop attempt was made
round 1 line following competition results
Round #1 Line Following Competition Results
  • Best time around the track:
    • 01:00.75
  • Competition Ranking:
    • 4th Place overall
    • 8 Points awarded
round 2 of line following competition
Round #2 of Line Following Competition

Competition Objectives:

  • To complete three laps around the black line track
  • One lap around track must be upon the outside loop

Group Objectives:

  • To complete two laps around the inner loop of the track
  • Make a better time around the track three times than in Round #1 of the Line Following Competition
line following and inner track sensors
Line Following and Inner Track Sensors
  • Line Following Sensors
    • Three used, as were used in the Round #1 of the competition
  • Inner Track Sensors
    • One was used away from the three Line Following Sensors
direction of travel and inner loop sensor placement
Direction of Travel and Inner Loop Sensor Placement
  • Direction of Travel around track
    • Clockwise
  • Placement of Inner Loops Sensor
    • On the left side of the Trekker when facing the Trekker front first.
outer loop behavior
Outer Loop Behavior
  • For the first lap, the Inner Loop Sensor will record each time it passes over the inner loop.
inner loop behavior
Inner Loop Behavior
  • After the first lap, and the inner sensors having noted the inner loop twice.
    • Every time the inner loop sensor notices a black line the Trekker will turn to the right, and take the Inner Loop around until it finds the opposite side of the track on the Outer Loop
testing and improvements
Testing and Improvements
  • We needed to make the Trekker have smoother turns around the corners of both the outer and inner loops of the track
    • This was done by changing the coded values for the right servo’s center, the left servo’s center, the oNav.Center, the LeftServo.Value, the RightServo.Value, and the overall speed of the Trekker
round 2 line following competition results
Round #2 Line Following Competition Results
  • Best time around track:
    • 0:50.51
  • Competition Ranking:
    • 3rd Place Overall
    • 18 Points Awarded
round 3 of line following competition
Round #3 of Line Following Competition
  • A familiar problem:
  • Recognize Inner Loop
  • Recognize Tool Box
  • Line Follow: once outer Loop, and twice inner Loop
  • Oh, and navigate at most 8.5 inches from Tool Box
tool box solution

Devantech SRF04 Ultrasonic Range Finder

HiTec HS-311 Servo

Objects to utilize hardware:



oCompare2: Properties (Above, Below and Between)

Tool Box Solution
the set up
The Set Up

1st oCompare2.Input set to oSonar.Value

2nd ReferenceIn1 set to Lower oSonar.Value = 53 and ReferenceIn2 set to Upper oSonar.Value = 58

3rd Allow oCompare to call Sub Routines to maintain 8.5 inches from tool box

  • Operation of Sonar device
  • Maximize sample rate. How? (Link Sonar.Operate to OOPIC.HZ60)
function of sub routines
Function of Sub Routines
  • We had Four Sub Routines:
  • Flag Inner – Used differently than previous competitions.
  • Above - Servo control to turn left.
  • Below – Servo control to turn right.
  • Between – Servo control to go Straight
  • Note: Each Sub controlled operation of oNavcon
competition day
Competition Day
  • What Happened? A) Failed to detect object consistently B) When oCompare operated, Sonar Servo lost sight of object and Our Left Turn Sub routine was called.
  • Possible Solution:

A) First Right Turn was a hard turn, we needed a set up sub routine and a means to return to line follower.

B) Improve Sonar Performance.

overall results
Overall Results
  • Completed two of the three competitions.
  • Placed 2nd in the class overall.
  • Project was a success overall

What we learned:

  • The importance of working as a team.
  • Using indicators in a circuit to help with troubleshooting.
  • Integration of external devices with a microcontroller.
  • Data sheets are helpful in design and implementation.
conclusions continued
Conclusions Continued

What we learned:

  • How an infrared sensor, a sonar sensor, and optical sensor work.
  • Utilization of these devices to accomplish an objective.
  • “OOPic Manual.” Retrieved from
  • “Trekker Robot. Retrieved from ”