Line-Following Mini-Tank

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Line-Following Mini-Tank

Post by pyroelectro on Tue Apr 26, 2011 9:02 pm

The line following robot has been around for a long time because of its all analog design. The fact that the parts to build it are inexpensive does not hurt either.


I had never actually built a line-following robot until now for reasons unknown but I have to say the experience was enlightening. Getting a refresher in some analog circuit design did not hurt either.


Below is a test run of how well the line-following mini-tank works. It is suprising at how simplicity can meet functionality dead on!





Purpose & Overview of this project

The purpose of this project is to build a device that can sense the difference between black and white color so that the robot can follow a black line on a sheet of white paper.

The robot will be low cost and completely made in a DIY style. It will also be able to follow straight and curvy lines alike.

Parts List Details


You may or may not be familiar with the parts above so a picture of each item has been included to help give you an idea of what they look like.
I'll go through and explain the key parts below.


Analog Brains

The 2N2222 and TIP120 transistors are both of the NPN type. As you will see in the schematic portion of this project write-up, these transistors are used to decide what to do when the sensors see black or white. The TIP120 transistors are high-power which makes them perfect for running the motors.

IR Emitter & Phototransistor

These two components combined with a few resistors will tell the circuit whether black or white is currently sensed.
If white is sensed a 0.7-1.0 Volt signal is sent to the analog brains. If black is sensed, 0 Volts is sent.

Tamiya Tank Kit

This kit will give the foundation for the tank tread design of this robot. The treads can be lengthened or shortened but I find that keeping a tank shorter makes it more agile and therefore more mobile.

Tamiya Gearbox

This is the two motor gearbox that will drive the tank forward, backwards, left or right. The two motors are 3v motors which match up nicely with the 3.7v battery that will be used.


Schematic Overview


The Schematic has three main parts to it. The Sensor Circuitry where the accelerometer is wired up to the A/D converters. The second part is the power circuit where we have the On/Off switch, the 9v battery & +5v 7805 Voltage Regualtor. The 3rd part of the circuit is the 3 7-Segment LEDs.



Schematic Specifics

•Motor Circuit
The motor circuit controls the motors depending on the sensor data that comes in through the 'analog brain' circuit. The two motors are 3v and can move moderatley fast. The diode that connects the motors to the battery reduces the voltage at the motors which slows them down a little bit.

•IR Sensor Circuit
The IR Emitter LED and Phototransistor are used for sensing white or black color. The LED emits IR light and the phototransistor receives IR light. Together they work well at see what type of light if any is reflected from a surface.

•Analog Brain Circuit
This part of the circuit connects the sensor circuit and the motor circuit together so that the robot can do its job. A little ASIC logic is used to transfer incoming sensor signals into which motor should be turned on and when.

•Schematic Parts Reference:


Schematic NamePart NameValue/Type
R1Resistor330Ω
R2Resistor360Ω
R3Resistor360Ω
R4Resistor1500Ω
R5Resistor10000Ω
R6Resistor10000Ω
R7Resistor15Ω
R8Resistor10000Ω
R9Resistor5000Ω
R10Resistor10000Ω
R11Resistor150Ω
R12Resistor150Ω
D1DiodeLED-Red (5mm)
D2DiodeLED-IR Emitter (5mm)
D3Diode1N4001
D4Diode1N4001
D5Diode1N4001
D6Diode1N4001
D7DiodeLED-Green (3mm)
D8DiodeLED-Green (3mm)
Q1Transistor2N2222
Q2Transistor2N2222
Q3Transistor2N2222
Q4TransistorTIP120
Q5TransistorTIP120
Q6TransistorIR Phototransistor
C1Capacitor47μF

The Theory

The theory for this project is based upon the 3 main components of the schematic described in the previous page. Below I will run through the theory of how they work with some better illustrations to hammer the theory into your brain.

IR Emitter & Phototransistor Theory



The IR Emitter LED (D2) send outs IR light and the Phototransistor (Q6) receives IR light from the reflected surface.
From high school we learned that white will reflect all colors while black will absorb them. So when the LED emits IR onto white, the Phototransistor is turned on and sends a voltage signal to Q1. When light is reflected off of black color the Phototransistor (Q6) is then turned off and no signal is sent


Looking At The Motor Circuit



The motors are turned on when transistors Q4 or Q5 are switched on with a positive voltage. This happens in one of two cases. When black color is sensed, the circuit switches Q4 off and Q5 on. When white color is sensed the case is reversed with Q4 on and Q5 off. This means the motors are never actually on at the same time and the illusion of driving forward is created by quick back-and-forth movements


Working The Brains



This circuit combines the Motor circuit and the IR Sensor Circuit. Using 3 2N2222's and some resistors a circuit is built that interprets the two cases. When white color is detected Q1 is turned on, which turns off Q2 and Q3 on. In
the opposite case, when black color is detected Q1 is turned off, which means Q2 remains on and Q3 off. Understanding this circuit might take a few minutes staring at the schematic, it is a little complicated.



Hardware Design

With the schematic and a little theory under our belts let us move on to building the circuit and the hardware. First we will build the mini-tank platform. Then we will build the circuit on the breadboard.


Mechanical Hardware

Step (1) - Gather All The Mechanical Parts »



Step (2) - First you will need to cut the plywood, two 6.2mm x 12mm pieces »



Step (3) - Drill holes into the base piece for the gearbox and tank treads »



Step (4) - Cut out a 5.5mm x 6.2mm space for the battery in the roof piece »



Step (5) - Finally, using nuts and bolts, assemble it together »




Electrical Hardware

Step (1) - Gather All The Electrical Parts »



Step (2) - The first thing to build is the power circuit »



Step (3) - Next follow the schematic and assemble the IR circuit »



Step (4) - Now assemble together the analog brain part of the circuit »



Step (5) - Finally, assemble the motor circuit together on the breadboard »



Step (6) - Mount the breadboard on the tank and plugin the motor wires »




for more robotic tutorial just visit our official site
source: PyroElectro.com
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Re: Line-Following Mini-Tank

Post by ultrasonic™ on Mon May 09, 2011 7:50 pm


nyc post pyro.

yan ang needed dito.
post ka pa.. ung basic lng ha

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Re: Line-Following Mini-Tank

Post by pyroelectro on Mon May 23, 2011 8:57 pm

ultrasonic™️ wrote:
nyc post pyro.

yan ang needed dito.
post ka pa.. ung basic lng ha

sir nasaan na iyong pinangako mong points ? lol!
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Re: Line-Following Mini-Tank

Post by ultrasonic™ on Wed May 25, 2011 2:40 am


sigurista pud ka noh..
ito points mu
+1

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Re: Line-Following Mini-Tank

Post by DJFEL on Tue Oct 01, 2013 5:58 pm

weeeeeeee
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