This robot it's one of the simplest line follower robots in the world.

Only works with 2 NPN Transistors, 3 IR leds and some resistors, easy to build!

Credits: Electrónica CRYA México

Step 1: Materials:

The materials in this proyect it's nearly all used/recycled components, but maybe various you hace to buy in a electronics store, in this proyect you will spend about $10 dollars or less, it depends of the things that you actually have to.

Bill list:

1 cyanoacrylate glue like (kola loka)

1 used lighter

2 telephone cards, old bank, store, cinema cards.

1 9V battery

2 small motors or dvd motors

1 elastic band

2 2N3904 TRANSISTORS

1 9V battery clip

1 resistor of 100 ohms (brown black brown)

1 led diode infrared emitter (like the tv control remote)

2 resistors of 3.3 kilo ohms (orange/orange/red)

2 infrared led receivers with light filter (the black ones)

1 inch of thermofit (it's a plastic tube that reduces it's volumen with the heat). or a black adhesive roll.

INSTRUMENTS YOU WILL NEED:

Rule

a sharpie

sandpaper (for the credit cards)

Nosepliers

solder

soldering iron

a knife (be careful with that)

sissors

drill or dremel if you have one

drill of 5/32

Step 2: Mounting and Mechanic

Take the lighter and open it like the images.

Step 1:

quit the metal protector

step 2:

blend a little the roller support

step 3:

quit the metal roller

step 4:

quit the roller completly,quit the spring and the trigger from the lighter and quit the plastic support

step 5:

mount the metal roller again in the support, cut off the plastic base with the tweezers and cut it, now put a little pegament on the base and mount in the previously cleaned card.

Step 3: Creating the Chassis

step 1:

Take an old bank card, public phone or gift card an clean it from the printed, with the sandpaper until it doenst have any paint like the picture 1

step 2:

with the help of a rule take the sizes of the card like the image 2& 3 and cut it from the card.

step 3;

now blend the T in an angle about 35-45 degrees like the image 4 & 5.

step4:

now put some masking tape to the motors like image 6 & 7.

step 5:

mount it with cyanocrilate glue for to mount above the cars like image 8.

Step 4: Electronic Circuit... the Brain of the Robot!

Picture 1:

The schematic

E1: INFRARED EMITTER

R1: 100 OHMS RESISTOR

IR1=IR2: INFRARED PHOTOTRANSISTOR

R2=R3: 3.3 KiOHMS RESISTORS

Q1=Q2: 2N3904 TRANSISTORS

M1=M2: SMALL DC MOTORS

VCC: POSITIVE POLE OF THE 9V BATTERY (+)

GND: NEGATIVE OF THE 9V BATTERY (-)

IMPORTANT:

FOR IDENTIFY THE IR RECEIVER AND EMITTER IR LEDS TAKE CARE OF THIS:

THE LARGE ONE PIN IS THE POSITIVE IN A LED AND THE SHORT ONE IS THE NEGATIVE, BE CAREFUL TO IDENTIFY THIS BEFORE YOU CUT THE LEADS.

WORKING PRINCIPLE:

it's basic, the ir led emittes a IR light thas only reflected by a white suface and in a black surface will not reflect IR light from the led. when the little car it's following a BLACK LINE IN A WHITE SURFACE one motor will move faster than the other to maintain the car in the line, lef and right depending of the curvature of the line.

it's basically transistor conmuting every time the IR ligth its reflected, and the motors turns depending what IR receiver is working.

Step 5: Assembly of the IR Sensor Bar

Step 1:

using the unused plastic card cut a rectangle about 1cm x 5cm.

Step 2:

IMPORTANT: this step it's important to do good, because it depends the good working of your robot, very important to use a milimetric rule, make a mark in the center of ther rectangle, now 1 cm to right and left side of the center make a mark like picture 1.

(see the simmetry of the marks).

Step3:

Now perforing the marks with a dril,l the hole must be 5 cm for the led, it will fit in it.

Step 4:

introduce the 2 Ir receivers and the IR emitter like the picture 4, solder leads from the IR receivers with the short lead of the IR emitter.

Step 5:

Now blend the short lead of the IR emitter (this lead goes connected to the negative of the battery)

Step 6:

Your final sensor bar should look like pictures 5 & 6.

Step 6: Connecting the Brains of the Robot!

Step 1:

Glue the 2N3904 NPN transistors to the chassis like the picture 1.

Step 2:

Now take the Collector of each transistor and solder to the collector of the other transistor. solder the 2 pins to the (+) of your 9 v Battery connector.

Step3: Now blend each emitter transistor like the picture 3. and solder the 3.3 Kilohms resistors like the picture 3 too.

Step 4:

IMPORTANT: Take the negative pole of the right motor (red/white cable) and the possitive pole of the left motor (black cable) and solder them to the negative pole of the 9v battery clip like the picture 4.

Step 5:

Take the negative cable of the left motor and solder it with the emitter of the transistor of the right in the robot like picture 5.

Step 6:

Take the positive pole of the right motor and solder it with the emitter of the transistor of the left like picture 6.

Step 7:

it's moment of use the sensors bar, Solder the 2 leads of the IR receivers to the base of each transistor and glue the sensor bar to the chassis of the robot, take the short lead of the IR emitter and solder with the negative pole of the battery (-), now use a cable to solder the middle union of the 3.3 kohms resistors to the positive pole of the battery (+), and finally you will solder the 100 ohms resistor to the positive of the IR emitter (anode of the led) and solder the other side to positive pole of the battery (+)-

IF YOU MISS ANY STEP DONT WORRY SEE THE SCHEMATIC AND SEE IF YOU ARE CONNECTING GOOD!!

Step 7: Final Robot and Considerations

The robot is ready to run AF.

This is the final robot, i know it would be better in PCB and SMD, but remember that it's from garbage, and the 2.0 version will be better :)

CONSTRUCTION OF THE HIGHWAY:

The black line should be 8mm.
make the pist in a grand white paper or a good hard surface
You can to use electrical masking tape for to make the line.

ROBOT ADJUSTMENT

If you put the robot on the hightway and it doesn't run well but the motor are spinnin you should change the alture of the battery making more centered to the chassis of the robot.
If the line follower robot doesn't follow well the black line you have to adjust the sensor bar and check the distance of each IR led. if you make wrong the distance of the leds you have to make again the sensor bar.
If the robot turn more in a side that the other, verify the spin of the motor and chek that both motors spin in the same direction.

LIMITATIONS OF THE EASIEST LINE FOLLOWER ROBOT

THIS ROBOT IS A VERY SIMPLE ROBOT AND THE SENSOR SYSTEM ITS NOT THE BEST BUT WORK FINE IN SIMPLE CONDITIONS (NO COMPETITION)
IT'S VERY SUSCEPTIVE TO THE LIGHT, IT MEANS THE PERFECT WORK OF THE ROBOT SHOULD BE IN A DARKER PLACE
IT CAN'T SUPPORT MORE WEIGHT INCLUDING THE BATTERY.
THE WORKING TIME CAN'T EXCEED THE 4 MINUTES, BECAUSE IT DOESN'T HAVE A VOLTAJE REGULATOR AND THE MOTOR WILL BURN IT OUT.

THANKSFOR TO READ MY INSTRUCTABLE, FOR PEOPLE LIKE YOU I'M KEEP WORKING!