Line Follower Robot Racing
Build
Program
Race!
The COLMAC Line Follower Robot has been developed
as a low cost introductory model for students and
educators interested in Robotics.
Line follower robots are used extensively in industry
in areas where parts or materials need to be
constantly delivered from one location to another.
Generally known as AGVs (Automated Guided Vehicles) they are found mainly in the car
manufacturing industry and anywhere that employs large warehousing where the robot follows
tracks to and from the shelves they stock and retrieve from.
The COLMAC line follower robot kit has the following features:

Simple chassis made from acrylic sheet.

Two wheeled easily controlled differential drive and steering.

Significant distance between line sensors and wheels allowing the robot time to react and
reduce the instances of over-shooting.

Line illumination LED.
The following should be noted when using this robot:

All the settings for the LDR sensors indicated in the notes are examples only. Each robot will
require its own settings for the sensors to be found through calibration. They will depend
on the surface it is operating on, the colour of the line being followed, the charge in the
batteries etc. and indeed similar LDRs will differ slightly from each other.

This robot is also suitable for entering the annual Robotics Ireland ©Robot Games Ireland
Tournament in the Line Follower Racing category. See www.colmac.ie for further details.
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Table of Contents
1. Assembling the Line Follower Robot Kit……………………………………………………….................. 3
2.Downloading/Installing GENIE Programming Editor Software ....................................... 21
3. GENIE Programming Editor Interface ........................................................................... 22
4. Connecting the E18 Motor Control Board to your computer ......................................... 23
5. Testing the E18 Motor Control Board ........................................................................... 24
6. Driving the robot forward/reverse............................................................................... 29
7. Turning the robot ........................................................................................................ 32
8. Using the LDRs to detect a line .................................................................................... 35
9. Using the LDRs to follow a line .................................................................................... 43
10. Using a defined loop during a program ...................................................................... 45
11. GENIE Programming Editor Help ................................................................................ 48
12. Troubleshooting Tips ................................................................................................. 49
13. Improving your Line Follower racing……………………………………………………………………………53
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1. Assembling the Line Follower Robot Kit
The following tools which are not supplied are the minimum necessary in order to build the robot:
Minimum 25Watt soldering iron and stand – solder is
supplied in the kit.
SAFETY NOTICE






Never touch tip of soldering iron – it will burn you!
Always return iron to its stand when not in use.
Wear eye protection – solder can ‘spit’
Avoid inhaling fumes – work in a ventilated area
Ensure all parts of the equipment are damage free
See www.colmac.ie for soldering technique video and
other related videos e.g. cable stripping etc.
Small long nosed pliers suitable for electronics.
These can be used for manipulating small components and
stripping cable insulation.
They can also be used for trimming the legs of components once
they have been soldered into the printed circuit board (PCB).
Some method of holding the GENIE E18 printed circuit board (PCB) while components are being
soldered is very useful. Some examples are shown below:
Assembly aids and small vices are
ideal but any method that holds the
PCB while the component is being
soldered is ideal – pieces of Blu-Tack
can even be used!
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The first step is to populate and solder all the components on to the GENIE E18 Motor Control
Board.
When completed, this board is a PIC micro controller. Peripheral Interface Controllers (PIC) are
small computers that can be programmed and reprogrammed using the GENIE Programming Editor
programming language to turn on/off various outputs depending on the state of various inputs.
The outputs being controlled in this case are:

2 x DC motors used to drive and steer the robot

1 x LED used to illuminate the line being followed
The inputs used to control these outputs are:

2 x LDR (Light Dependent Resistors) that act as line following sensors
The processing of all the information from the inputs and the control of the outputs is done by:

1 x GENIE E18 PIC Microcontroller Chip (18 pin shown in red above)
The motors are driven forward/reverse or clockwise/anti using a motor driver chip:

1 x L293D Motor Driver Chip (16 pin shown in yellow above)
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Step 1: Solder in the fixed resistors.
Resistors reduce the flow of electric current and also change the voltage level at different parts of
the circuit. Their size is measured in Ohms (Ω) and usually in thousands of Ohms or Kilo Ohms – this
is usually just written as K e.g. 22K = 22 Kilo Ohms
Fixed resistor size is shown using colour code: http://en.wikipedia.org/wiki/Electronic_color_code
The colour coding of all resistors used in the E18 board is shown below.
Fixed resistors have no polarity i.e. no positive or negative (+ or –) and so can be inserted either
way around.
Insert the resistors in their correct places either
way around as they don’t have a positive or
negative (+ or -).
The size of each resistor is marked on the board and their colour coding is as follows:

0 Ohm – Black – Marked ‘LK’ on PCB

330 Ohm – Orange, Orange, Brown, Gold

4.7K – Yellow, Violet, Red, Gold

10K – Brown, Black, Orange, Gold

22K – Red, Red, Orange, Gold

100K – Brown, Black, Yellow, Gold
NOTE: Many instructional videos including how to solder the printed circuit board (PCB) and the
associated components properly can be found at www.colmac.ie
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Step 2: Solder in the capacitors
Capacitors are devices that store electricity. Their size is measured in Farads, usually a small
fraction of a Farad such as a micro Farad (µF) or nano Farad (nF).
Solder the ceramic capacitors in their correct places either way around as they don’t have a + or -.
These capacitors are used primarily to reduce
electrical noise generated by the motors when
they are running. This electrical noise can
interfere with the operation of the E18
microcontroller.
As such, C3 and C4 are connected directly across the motor output connections Q6/7 and Q4/5.
Note that C5 shown in red is not required for this project.
Solder the electrolytic capacitor in its correct place. It has polarity i.e. a positive and negative.
The negative (-) leg is beside the grey stripe (marked with a minus sign) as shown below.
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Step 3: Solder in the diode
Diodes allow electricity to travel in one direction only.
Solder the diode in its correct place - it has polarity i.e. a positive and negative. The negative (-) leg
is beside the grey band as shown below.
Grey band on negative side
Step 4: Solder the transistor, the reset switch and the USB jack
The transistor operates as an automatic switch.
The USB jack allows the microcontroller to connect to your computer.
The reset switch restarts the program from the beginning.
Flat side
USB
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Step 5: Solder the status LED and chip sockets
Insert the green status LED as shown below – flat side is negative.
The chip sockets to hold the GENIE E18 microcontroller and L293D motor driver microchips should
be inserted as shown. The L293D chip allows the motor turn both clockwise and anti-clockwise
which gives forward/reverse and turning motion in the line follower robot.
Flat side -
Notch
Step 6: Solder the cable terminal blocks.
Insert the terminal blocks as shown – arrows indicate where flying lead cables will be inserted.
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NOTE: Soldering should be neat and uniform. Connections should not touch each other unless they
are supposed to as circled below.
Step 7: Insert E18 and L293D microchips
Try to handle the chip legs as little as possible but ensure that all legs are properly inserted into
their socket.
L293D
E18
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Step 8: Make flying lead connectors for LED, LDRs and motors
Use the coloured cable to make flying lead connectors as shown in the following pictures.
For the LED, cut approx. 170mm of each cable, braid together as shown and remove approx. 5mm
5mm
of insulation from the ends.
Shorten the legs of the LED as shown using snips/pliers etc. in order to minimise the chance of
them touching each other and creating a short circuit.
Braid the individual strands of the exposed cable in order to minimise stray cable strands touching
each other and solder the LED as shown. Take note of which cable is connected to the flat side of
the LED.
Black connected
to flat side of LED
Twist/braid
strands together
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For the LDRs, cut approx. 250mm of each cable, braid together as shown and remove approx. 5mm
of insulation from the ends as before.
As before, shorten the legs of both LDRs as shown to approx.
10mm using snips/pliers etc. in order to minimise the chance
of them touching each other and creating a short circuit.
Braid the individual strands of the exposed cable in order to minimise stray cable strands touching
each other and solder the LED as shown. Take note of
which cable is connected to the flat side of the LED.
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For the motors, cut approx. 150mm of each cable, braid together as shown and remove approx.
5mm of insulation from the ends.
Solder the flying leads to the motors as shown. Be careful with the motor connections as they are
quite delicate.
If possible use similar colour cables
in the positions as shown in order
to program in accordance with the
notes later.
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Step 9: Attach motors to chassis using sticky pads
The motors should be attached to the plastic chassis using two sticky pads on each as shown below.
The motor cables are then fed through the holes as shown.
The edge of the motors should be
positioned on the chassis as seen here.
Line up the edge of the
motor with the edge of
the chassis marked in red.
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Step 10: Attach battery pack/switch to chassis.
Attach 2 sticky pads to the battery pack on the switch side as shown.
Stick down the battery pack as seen below – try to centre on the chassis in order to keep it
balanced.
Battery pack cable
Feed the red (+V) and black (0V)
cables through the holes as shown.
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Step 11: Connect motor flying leads to the E18 PCB
Firstly attach two sticky pads to the bottom of the PCB in each of the approximate positions shown.
2 x sticky pads are used in each case in order to
accommodate the raised soldered joints and
ensure secure fit to the chassis.
Then insert the cable from each motor into the M3 and M4 connectors preferably in the same
manner as shown below in order to correspond with the programming later on. Do not worry
however if they are inserted differently as changes can easily be made to the programming.
Q4=Black
Q5=Yellow
Q6=Black
Q7=Yellow
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Step 12: Insert LED in chassis and connect to E18 PCB
Insert the line illumination LED into the front of the
chassis as shown and feed the flying lead through the
centre cable hole.
Flat side = Negative (-)
Route the LED flying lead through the hole beside the
PCB as shown.
Connect negative (-) cable (black in this case) to the
right side connection of output Q3 and the other cable
+
__
to the left side positive (+) connection.
NOTE: If the LED is connected the wrong way around it
will not be damaged but will simply not work.
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Step 13: Connect battery power leads to the E18 PCB
Connect the red (+V) and black (0V) cables to the relevant connectors as shown below. If the cables
are connected the wrong way around the E18 chip will heat up and may be damaged.
0V +V
Step 14: Insert LDRs in chassis and connect to E18 PCB
Insert the two LDRs into the front of the chassis
as shown and feed the flying lead through the
A0
A2
cable holes.
NOTE: Ensure that the LDR legs do not touch
each other or the legs of the LED which would
result in a short circuit.
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Route the cables through the remaining holes as shown and connect into the input terminals A0
and A2 as shown on page 8.
NOTE: Light Dependent Resistors (LDRs) do not have polarity (positive/negative) which means that
it does not matter how the cables are connected into the terminal blocks.
Finally, using the sticky pads, attach the E18 to the chassis in the position shown.
A0
A2
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Step 15: Attach the rubber bands to the wheels and the wheels to the motors.
The rubber bands are used to increase the grip of the wheels. When attached the wheels should
push fit on to the motor drive shaft.
Step 16: Assemble the rear spoiler and attach to chassis
The 5mm end of the support fits into
the spoiler.
Spoiler
The 3mm end of the support fits into
the chassis.
5mm
Support
3mm
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Congratulations, you have built the COLMAC Line Follower Racing Robot!
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2. Downloading/Installing GENIE Programming Editor Software
GENIE Programming Editor software is required to program the robot and can be downloaded free
of charge from its developers at their website http://www.genieonline.com/
Complete the required details in the online form accessed through the Downloads tab and a link
will be emailed to you – click on the link to download and install the software.
If you encounter any difficulties click on the Support tab and you will be directed to the GENIE
Troubleshooting Guide and the Troubleshooting Tool.
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3. GENIE Programming Editor
To open GENIE Programming Editor click the
GENIE Programming Editor icon on the
desktop or use the start menu to locate the program.
Menu Bar
Tool Bar
Programming
Commands
Microcontroller button
Programming
Area
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4. Connecting the E18 Motor Control Board to your computer
NOTE: It is necessary to use the GENIE USB Plug & Play cable in order to connect your computer to
the GENIE microcontroller. The cable can be used with all GENIE microcontrollers and can be
purchased from http://colmac.ie/product/download-cable/
Connect the GENIE USB Plug & Play cable and the following window should appear:
Select OK
If the confirmation window does not appear then click on the Help button and consult the
Troubleshooting Guide.
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5. Testing the E18 Motor Control Board
Firstly you must tell the software what GENIE chip you are using. Select Microcontroller from the
tool bar followed by Program Settings. Select the GENIE E18 chip.
NOTE: This must be done each time a new program is written unless E18 is set as default.
The Program Settings window provides information about the inputs and outputs available on the
selected E18 chip:
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The E18 chip has the following features:

8 digital outputs labelled Q0 to Q7

We are only using Q3 to Q7 incl. for this line follower robot

These outputs are ‘digital’ in that they are either on (1) or off (0)

3 possible analogue inputs e.g. LDR, Thermistor etc. labelled A0, A1 and A2

5 possible digital inputs e.g. switches labelled D0, D1, D2, D6 and D7

As shown on the chip configuration:
o Input A0 and D0 share Pin 17 – connected to A/D0 on PCB
o Input A1 and D1 share Pin 18 – connected to A/D1 on PCB
o Input A2 and D2 share Pin 1 – connected to A/D2 on PCB

We are only using A/D0 and A/D2 for this line follower robot

Power to the chip can be tested across Pin 5 (0v) and Pin 14 ( should be at least 3.5 to 9v)
NOTE:
We are only using LDR inputs in this
robot but it is possible to use many
other analogue inputs such as a
thermistor, variable resistors etc. with
the GENIE E18.
Similarly it is possible to incorporate
digital inputs such as micro switches
with the robot for obstacle avoidance.
etc. but they are not covered in this
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Connect the GENIE USB Plug & Play cable to the line follower robot and turn on power to the robot
using the on/off switch included in the battery pack.
The green status LED should flash and the software should
indicate that the microcontroller is now connected as shown.
We can now test that both motors and the line illumination LED
are working.
We will use the Control Device command to test these outputs. This command can be activated
from the menu shown above or by clicking the Microcontroller button on the tool bar as shown
below.
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Activating the Control Device command opens the following window in the Program menu.
This indicates that the software recognises that the 2
LDR sensors are connected to A/D0 and A/D2 inputs.
NOTE: If they do not show up immediately, cover the
sensors with your finger or lift the nose of the robot
off the ground.
This indicates that all outputs are currently off (0)
By clicking on output Q3 and changing it from off (0) to on (1) we should be able to activate the line
illumination LED at the front of the line follower robot as shown.
If the LED does not illuminate, check the following:
Is the LED cable connected into the PCB with correct polarity as
shown below?
Is the LED cable connected to the LED with correct polarity i.e.
leg on flat side of LED connected into negative black?
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Now, by turning on (1) and off (0) outputs Q7, Q6, Q5 and Q4 in turn, we should observe the
clockwise and anticlockwise rotation of each motor M4 and M3.
If the motors do not operate then check the following:

Are the 2 cables from M4 connected into Q6 and Q7 on the PCB?

Are the 2 cables from M3 connected into Q4 and Q5 on the PCB?
NOTE: Consult Section 12 Troubleshooting Tips if you still have problems connecting to the board
and using Control Device.
In the next section we will now look at how to write a simple program to operate both motors in
order to create forward and reverse motion.
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6. Driving the robot forward/reverse
We are now ready to write our first program to move the motor forward and reverse.
Construct the following flowchart by left clicking and dragging the programming commands from
the Gallery. Commands will automatically link together when you drop them in place.
The Motor command is located under the Input and Output section of the
flowchart symbols.
The Wait and Stop commands are located under the Program Control section of
the flowchart symbols.
Commands will automatically link together when you drop them in place.
Each command must now be edited in order to complete the program.
NOTE:
The following conventions are used when editing outputs and inputs:

0 Make output low (off)

1 Make output high (on)

T Toggle this output (where high is set to low and low is set to high)

X Leave output alone
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Double click on each of the commands except the Stop and edit as shown below. Remember to set
the type of motor being used to DC:
It is good practice to give
every program a name to
appear in the Start symbol.
Push up the M3 and M4
sliders in order to set both to
forward motion.
NOTE: Depending how you
have connected each motor
polarity you may find that
you need to set the sliders in
the down position or one
slider up and the other down
in order to achieve forward
motion when you download
and Run Live.
Set the Wait time to 3 seconds.
This instructs the program to
continue running the last
command for 3 seconds.
Click on the M3 and M4
buttons to turn both motors
off as shown.
NOTE: The Stop command
stops running the flowchart
program – it will not turn off
the motor if it is already
running!
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In order to download the program to the robot, click on the Microcontroller button and select Run
Live. The Program window will indicate that it is Accessing the PIC chip and then that it is Running
Live. The program will start immediately once it is downloaded. The USB cable can then be
removed and the program rerun by pressing the small reset switch on the PCB.
The following commands and screen will be seen when using Run Live.
As mentioned previously, when you run this program live you may now discover one of the
following scenarios depending on how you have connected the motor polarity either at the motors
or on the PCB:
a) The motor is actually going in reverse. In this case you simply set both M3 and M4 sliders to
the down position instead of the up in order to get forward motion.
b) One motor is going forward and the other going in reverse. In this case you will have to
move M3 slider up and M4 down or vice versa.
EXERCISE 1
Edit the program so that your robot moves forward for 4 seconds AND then reverse for 4 seconds.
Use Run Live to download and run the program.
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7. Turning the robot
The procedure for turning the robot while it is moving is based simply on turning off one motor and
leaving the other running.
Construct and edit the following flowchart as shown. Settings for motor control are shown.
You will see these output
settings appear in the
Multiple Panel View when
we simulate this program.
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Select the Run command
on the tool bar.
You will see each flowchart command highlight as the
program simulates.
The Speed Dial can be rotated to adjust the speed at which
the simulation runs.
Now click on the View several monitor panels at once
command in order to open Multiple Panel View.
This allows us see what each flowchart command is doing as
shown below.
To turn left motor M4 is turned off by
turning off both outputs Q6 and Q7
and motor M3 is left running (output
Q4) in forward direction.
We created this setting earlier while
editing this command using Motor
Properties
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Click on the Microcontroller button and select Run Live in order to download the program to the
robot. The Program window will indicate that it is Accessing the PIC chip and then that it is Running
Live. The program will start immediately once it is downloaded. The USB cable can then be
removed and the program re-run by pressing the small reset switch on the PCB.
EXERCISE 2
Like all learner drivers you need to learn how to complete a 3 point turn.
Edit the previous Turning Ex program to have your robot execute a 3 point turn.
If you’re not sure what a 3-point turn is ask your teacher to explain.
Points to consider:

It is not possible to control the number of revolutions of a DC motor as it is with a servo or
stepper motor.

Controlling the amount your robot turns using the Wait command is accomplished by trial
and error.

It is possible to set the Wait Properties to fractions of seconds by typing the value in rather
than selecting the set values from the drop down menu as shown below.

The turning circle of a robot such as this depends on the diameter of the wheel and the
distance between the wheel centres. This could be the basis for an Applied Math question.
Having completed this exercise why not try to program your robot to drive in a square, drive in a
figure 8 or even set up a parking bay that it must park in using parallel parking!
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8. Using the LDRs to detect a line
Before we can successfully use the LDR sensors to detect a line we must learn how to understand
the digital reading that the LDR creates in the GENIE software.
The resistance of the LDR supplied goes from approx. 1KΩ in normal light to approx. 15KΩ in
normal darkness i.e. the resistance of an LDR increases as it gets darker.
Theoretically it goes from 0KΩ in total brightness to 1MΩ in total darkness.
The GENIE software takes whatever analogue resistance value the LDR has at any given moment
and converts it into a digital reading of between 0 and 255.
A digital value of 0 corresponds to an LDR resistance of 1MΩ i.e. total darkness.
Similarly, a digital reading of 255 corresponds to an LDR resistance of 0KΩ i.e. total brightness.
Turn on your robot, connect it to the USB and select Calibrate Sensor from the Microcontroller
menu on the tool bar. You should see the screen shown below.
Shows the LDRs connected to A0
and A2 and their current reading.
Move the robot around and
observe the reading change as
LDRs pass over bright and dark
surfaces.
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The area underneath the LDRs on the robot will, by virtue of its design, be quite dark. This could
create difficulties when trying to detect a white line on a dark surface. In order to solve this
problem a LED has been installed between them to illuminate the line and surface.
In order to calibrate the LDRs while this LED is on we will use the Debug Live command.
Construct and edit the following ‘Calibrate LDR’ flowchart.
The Outputs command is
The Outputs
used to command
turn on theisLED
used connected
to turn on the
LED Q3.
to output
connected to output Q3.
The back
loop back
toStart
the Start
The loop
to the
keepskeeps
the LED
the tuned
LED tuned
on. on.
To create the loop, firstly left click and hold the mouse over the right connection point on the
Outputs symbol. Drag the connecting line to the right and then upwards to create the first 90˚bend.
To create the second 90˚bend, release the left mouse button and then click again at a point
approximately in line with the Start command. Continue dragging the line to complete loop.
Release and
click again here
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Place your robot on the Calibration Sheet shown on the next page (remove/print/copy if
necessary), turn on and select Debug Live from the Microcontroller menu. You will see the screen
shown below.
Click Start to begin Debug Live. This facility allows you watch your program animate as it runs live
on the microcontroller.
By clicking on View several monitor panels at once as shown
below we can now observe what the LDRs are reading along
with what inputs/outputs etc. are activated.
You could choose to view the inputs/outputs or the analogue
sensor readings etc. on their own but the View several monitor
panels at once option shows nearly everything and is
demonstrated on page 39.
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You should now see the screen as shown.
Indicates that inputs A0 and
A2 are connected.
Indicates that the LED
connected to output Q3 is on.
Readings from LDRs
connected to A0 and A1.
LDRs on the white area.
NOTE: Your readings may be
different
Move the front of the robot on to the thick black line order that the LDRs detect the new reading
associated with the black line. Now, take note of both readings as shown below.
Readings on white area:
A0 = 224
A2 = 231
NOTE: Depending on number of
batteries used and ambient
lighting conditions etc. your
readings may be significantly
different.
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Readings on black line:
A0 = 180
A2 = 184
NOTE: Depending on
number of batteries used
and ambient lighting
conditions your readings
may be significantly
different.
The data gathered in this example shows:

LDRs read a max of approx. 231 on the white surface

LDRs read a max of approx. 184 on the black line
For the purposes of this line follower we can summarise by saying that once the LDR readings go
above 190 then they have definitely moved away from the black line and into the white area.
This allows a little tolerance for ambient lighting, battery power etc.
We can now use this information to create a simple program to stop the robot from driving over
the black line.
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Construct the following program shown below.
The Compare command is found in
the Flow Control section of the
flowchart symbols.
It is used to compare the LDR readings
and decide whether to follow the Yes
(Y) or No (N) route in the program.
The first line connected to the
Compare command will indicate the
Yes (Y) route to follow and the second
line connected will indicate the No (N)
route to follow.
These can be swapped by right clicking
the Compare command and selecting
Swap Yes and No if necessary.
We will now edit this flowchart so that it carries out the following program:
1. Turn on the line illumination LED connected to Q3.
2. Check if the LDR readings are more than 190 (>190).
3. If so then drive the robot forward as it is still on the white surface.
4. If not, i.e. less than 190 then stop the robot as it has detected the black line.
5. The loop will ensure that the program continually checks the readings.
NOTE: The settings used i.e. more than 190 may need to be adjusted to suit the surface and lighting
that your own robot is operating in. Use your own reading found while calibrating using Debug Live
earlier.
The edited flowchart symbols are shown on the next page.
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Tick the ‘and’ box to open the
second expression.
This instructs the program to
compare both readings from A0
and A1 to see if they are more
than 190.
 If they are, then the robot is
still on the white surface and
continues forward.
 If they are less than 190 the
robot has encountered the
black line and stops.
See www.colmac.ie for a video of
the program in operation.
NOTE: The speed of rotation of the motor can be slowed by not pushing up the slider control fully
up or down. Beware of having motors rotate at different speeds as this will cause the robot to veer
off line.
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9. Using the LDRs to follow a line
Before beginning work on programming the line follower to follow a line you should firstly set up a
line course/track for it to follow. The program that follows is based on the COLMAC GP course as
used in competition. The GP course consists of a black line track on a white background as shown
below.
This track is available to purchase from www.colmac.ie and measures approx. 2400mm x 1200mm.
You can create your own track with a roll of standard 20mm wide black
insulating tape and using it to create a track on a lighter coloured floor.
Don’t make the track too difficult initially – keep corner radius large.
In Section 10 we will look at how to deal with difficult tracks.
NOTE: The following program is designed to instruct the line follower follow the black line and
correct itself when it moves on to the white area. It is also possible to program it to stay in the
white each side of the black line and correct itself if it moves on to the black line.
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NOTE: Remember to use
your own LDR readings in
the Compare commands.
Visit
www.colmac.ie
for videos
showing the
program being
tested using
Debug Live and
the robot
following the GP
track.



In the first Compare command the LDRs are set so that if they both read less than 190 i.e. they are
both detecting the black line, then both motors are on moving the robot forward.
In the second Compare command if A0 reads more than 190 then the robot has moved off the line
to the right and motor M3 is turned off in order to turn the robot left and back to the line.
In the third Compare command if A2 reads more than 190 then the robot has moved off the line to
the left and motor M4 is turned off in order to turn the robot right and back to the line.
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10. Using a defined loop during a program
In order to deal with difficult 90˚ bends similar to those highlighted on the COLMAC F1 track
shown below where the robot can lose sight of the line, we need to program it to stop and look for
the line if it loses it completely.
This can be accomplished by instructing the robot to firstly stop, then look left and if it does not
find the line there to then look right until it does.
We could program this in a number of ways but we have chosen to use the defined loop commands
as shown in the program on the following page. Edit the previous program to create the flowchart
shown.
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Initially we need to insert another Compare command that will check if both LDRs A0 and A2 have
lost sight of the black line i.e. if the LDR reading has gone above 190.
We will now look in closer detail at the commands that follow this new Compare command in order
to see how the robot can look for a missing line.
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Once the program detects that the sensors A1 and A0 are both off
the line the motor stops briefly for half a second. This minimises the
amount of over-shoot of the line.
The For command is found in the
Flow Control section of the
flowchart symbols. It runs the
series of commands between it
and the End Loop command
either a set number of times or
for a given number of seconds –
in this case, for 5 seconds.
The Motor command that
follows causes the robot to
perform a two wheeled left turn
in order to look for the line.
Note that the sliders are set
slightly less than max in order to
slow the rotation speed.
The Compare command checks
to see if A2 is on the line during
the left turn. If it is then the
program follows the Y route back
to the main section of the
program.
If not, after the 5 second loop
ends, the motor performs a two
wheeled right turn continuously
until a further Compare
command detects the line in the
other direction. When it does the
program follows the Y route back
to the main section of the
program.
Again that the sliders are set
slightly less than max in order to
slow the rotation speed.
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11. GENIE Programming Editor Help
These notes are only an introduction to GENIE Programming Editor. It contains many more
commands that have not been mentioned at all. Explanations of these other commands can be
found in the Help section of the software by clicking on GENIE Programming Editor Help as shown
below:
Then select Flowchart commands as shown:
This will open a window displaying all current GENIE commands. By clicking on any command the
user will be given a simple explanation of what the command does along with a sample flowchart
showing how the command may be used.
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12. Troubleshooting Tips
The most common problem involves getting the ‘No Device Found’ error when trying to connect to
the GENIE E18 microcontroller using the USB cable. Follow the steps below when trying to resolve
this issue:
Check the USB cable is connected properly using the
Troubleshoot GENIE tool in the Help section.
Follow the steps in the window that opens.
Pin 14 (+V)
Test the supply voltage across pins 5 and
14 of the E18 microchip. These are the
+/- power connections.
There should be at least 3.5V in order for
the chip to work properly and connect to
your computer.
Pin 5 (-V)
NOTE: If the supply voltage is already low (</= 3.5V) it will drop further when the motors are
turned on and this can also cause the chip to turn off and cease controlling/connecting etc.
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If the USB cable is OK and the voltage at the chip is sufficient then the next most common problem
is poor soldered connections. Please consult www.colmac.ie for soldering technique video.
Check your soldering by examining the connections under a magnifying glass. You should see the
following:

The connection should be solid if you try to wiggle it with some tweezers or pliers.

The pad should be covered completely but not overflowing.

The solder should be shiny.
The following are indicators of a poorly soldered joint:

The pad and lead aren't completely covered with solder, enabling you to see through one
side of the hole through which the lead passes.
o You didn't apply enough solder, or the pad wasn't hot enough to accept the solder.

The lead is loose in the hole or the solder isn't firmly attached to the pad.
o You possibly moved the lead before the solder had completely cooled.

The solder isn't shiny.
o
If the solder gets just barely hot enough to melt, then flows over a wire or pad that
isn’t heated sufficiently, it will be dull when it cools.
o Unfortunately, the new lead-free solder almost always cools dull, so it looks like a
bad solder joint even when the joint is good!

Solder overflows the pad and touches an adjacent pad.
o This can happen if you apply too much solder. It can also happen if the pad didn't get
hot enough to accept the solder, which can cause the solder to flow off the pad and
onto an adjacent pad. If solder spills over from one pad to an adjacent pad, your
circuit may not work right.
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Solder not firmly attached to component leg
can be caused by leg moving before solder had
cooled fully.
This is a difficult fault to find and is best
located using a magnifying glass.
Sometimes a pad can break off either during
initial soldering or later de-soldering.
Missing pad
If this happens, scrape off the green protective
coating and reconnect the broken track using
Component leg
cable links soldered to the component leg as
shown.
The photo below shows 6 examples of poorly soldered connections and 2 examples of properly
soldered connections.
Properly soldered connections
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Finally, you may sometimes encounter strange things happening in your programs during either
Debug Live or Run Live such as outputs turning on/off for no apparent reason.
This can be caused by electrical interference generated by the motors during operation. This is a
common problem when motors are being controlled by microcontrollers and is minimised by
attaching a capacitor across the motor connection terminals. This is already done on the PCB with 2
x 100nF ceramic capacitors attached across terminals Q4/Q5 and Q6/Q7 as shown below.
In the event that you still experience these types of issues you can solder a further 100nF capacitor
directly across the terminals of the motor, at the actual motor – they have no polarity so it does not
matter which way around they are connected – an example on a different motor is shown below.
Notice that the cables are also glued to the body of the
motor – this is good practice in order to minimise the chance
of the motor cable connection being damaged through
excessive movement of the cables.
Consult www.colmac.ie for further help with troubleshooting
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Circuit and PCB diagrams courtesy of www.genieonline.com
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14. Improving you Line Follower racing
There are numerous ways of improving the speed of your line follower with a view to entering
competitions such as the annual Robotics Ireland tournament that features both line follower and
mini sumo competitions. Here are some examples:
1. Increase the diameter of the wheels. This will necessitate recalibration of the LDR sensors.
2. Increase the voltage supply to the board. The manufacturers indicate that up to a 12V
battery supply may be used but recommend not to use a 9V PP3 battery. Again, this will
necessitate recalibration and editing of wait times etc.
3. Improve your programming skills and try out other commands such as Analogue, Sub etc.
4. Shield the LDR sensors from external light sources using a shield of your own design. This
will improve the performance of the sensors.
5. Make your line follower as light as possible by removing unnecessary parts.
Further Information
www.colmac.ie
[email protected]
www.roboticsireland.com
www.genieonline.com
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