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Components of a Differential Drive

Power

SystemControl

BoxDrive

Mechanism

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Power System

Power

Supply

(220v AC)

Transformer

Rectifier

Circuit

DC Out

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Materials Required

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The following are the most basic requirements for

making a differential drive:

1. 12-0-12 transformer

2. Rectifier circuit

1. Small printed circuit board(PCB)/Bread Board

2. 4 x 1N4001/7 diodes

3. 1 x 1000µF electrolytic capacitor 25v

4. 1 x IC 7805/12( depending on requirement)

5. 2 pin relimates

Materials required (contd.)

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3. Soldering Iron and wire( if using PCB)

4. DC motors

5. Switches

6. Multi /single strand wire

7. Multi-meter

Transformer( Recap)

A transformer is a device that transfers electrical

energy from one circuit to another through inductively

coupled conductors.

To make a simple differential drive, a simple

transformer with following specifications can be used:

1 Amp, C.T. ‐12 V.( it steps down a 220V AC to 12 V

AC.

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Centre Tap Transformer

220 V AC

supply

12V

AC

-12V

AC

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Rectifier Circuit

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PCB

Line matrix PCB Dot matrix PCB

Rectifier Circuit

The top and bottom sections of the

bread board contains slots that are

horizontally shorted, while the

middle section contains slots that are

vertically shorted. www.robotix.in

Bread Board

Rectifier Circuit-Diodes

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Diodes

The usually used rectifier diodes re the 1N4001

and the 1N4007. The only difference between them

is that they have different voltage and current

ratings.

Rectifier Circuit-Capacitor

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Electrolytic Capacitor

Most electrolytic capacitors are polarized, i.e., they

have a positive and negative terminal. Connecting

them to wrong terminals of power supply can destroy

it. Adding to this, these capacitors are used only for

DC voltages.

Fig: A blown capacitor

Rectifier Circuit-Voltage Regulator

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These ICs are voltage regulator integrated circuits.

The voltage regulator IC maintains the output

voltage at a constant value. The xx in 78xx

indicates the fixed output voltage it is designed to

provide. 7805 provides +5V regulated power

supply. Similarly there are several other ICs

available in this category like 7806, 7809, 7812,

7815.

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Rectifier Circuit-Voltage Regulator

Another fact to note about this series of ICs is that

they have a voltage range in which they work. For

any voltage above that range the IC goes into a

thermal shutdown and will give you a very low

arbitrary voltage value. For example, the 7805 IC

has a range between 5V and 16V.

2 31

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Since the IC 78xx series reduces voltage to a constant

value, the remaining voltage is lost as heat. Now, if

the difference between voltages is large, the amount

of heat produced will also be large. Over heating of

the IC can damage it. Hence we often use a heat sink

on the IC. The more heat you want to dissipate, the

more surface area is required for the heat sink.

Rectifier Circuit-Heat Sink

Rectifier Circuit-Relimates

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A relimate is just a connector that can be soldered onto a PCB. It has a female and a male part. There are different kinds of relimates, 2 pin , 3 pin, 4 pin and so on to several pins.

Another point to add is that it is always good to follow the convention that the

black wire is connected to the

ground. This helps in debugging

faults at the end without much

difficulty.

Female

part

Male

part

Rectifier Circuit-Soldering

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A soldering iron is used for melting the solder wire

onto the components. The solder wire is essentially

made up of solder and often it comes with a flux

coating. A flux is used to ensure that the solder does

not stick on the solder iron. The molten solder sticks to

the copper of the PCB when it comes in contact with it.

The practical aspects of soldering will be dealt with in

the hands-on classes of KRAIG.

DC Motors

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DC motors come in different voltage ratings and

rpms. They have to be selected based on the

application. Where speed is necessary, we obviously

need to go for the higher rpm motors. Where torque

is more important, we need to go for low rpm geared

motors. For the purpose of simple DD making we

usually use either the 150 rpm 5V motor or the

100/60 rpm 12V motor. 5V motor

12V motor

Switches

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For the purpose of controlling a differential drive,

the best kind of switch is the three way switch. It has

a central off position with two extreme positions for

two different polarities. Such switches are called

DPDT(Double pole double throw) Centre Off

switches.

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DC power

To motor

Switches

Wires

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There are two kinds of wires available. One is the

multi strand wire in which there are several strands

of copper wire within the plastic insulation. For using

wires to interconnect slots on the bread board, we

have to use the single strand wire. Whereas for

interconnecting wire, multi strand is the best as the

single strand wire may break on twisting.

Multi-meter

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A multi meter is a device used to measure

parameters like voltage( AC/DC), resistance,

capacitance, test short etc. It is a very handy device

when debugging circuits or trying to understand

how a circuit works.

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Rectifier Circuit

Rectifier Circuit

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Let us first see how we can set up a rectifier circuit

on a bread board.(Remember though that this is not

the only way that it can be done).

http://www.youtube.com/watch?v=JEWKufHjAUU&

feature=plcp

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Rectifier Circuit

Drive Mechanism

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Now that we are done with the power system and

the control box we only have the chassis remaining

to assemble.

The chassis can be just about anything. For example

it could even be just a piece of cardboard with

motors attached to it. But then when we take into

consideration the strength of the chassis the best

material is wood or Perspex.

Movement of DD

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MOTION LEFT MOTOR RIGHT MOTOR

FORWARD

BACKWARD

LEFT TURN

RIGHT TURN

Differential Drive Chassis

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Shop Location

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Electronics:

Choudhary Electronics(in Tech Market)

Carpentry:

Tech market

Outside Puri Gate

Prem Bazaar

Umesh Carpenter

Things You Will Need

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Soldering Iron

Soldering Wire

Wire Stripper

Single strand wires

Multi strand wire of appropriate length

PCB (dot or line)

4 Diodes (D1N4007)

1 Electrolytic Capacitor (1000 microfarad)

Step down Transformer (220v- 12V AC)

Two 3 way switches or Two 2 way switches and two push button switches.

2 plastic boxes to encase transformer and for control box

Plug for transformer

2 pin, 4 pin relimates

Insulation Tape

IC 78xx xx=05, 06 or 12 according to your need

DC motors

Breadboard (optional)

Things you will need

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Link to Required materials: http://goo.gl/S8YDr