www.robotix.in
Components of a Differential Drive
Power System
Control Box
www.robotix.in
Drive Mechanism
Power System Power Supply (220v AC)
Rectifier Circuit
Transformer
www.robotix.in
DC Out
Materials Required 
1. 2.
The following are the most basic requirements for making a differential drive: 12-0-12 transformer Rectifier circuit 1. 2. 3. 4. 5.
Small printed circuit board(PCB)/Bread Board 4 x 1N4001/7 diodes 1 x 1000ÂľF electrolytic capacitor 25v 1 x IC 7805/12( depending on requirement) 2 pin relimates www.robotix.in
Materials required (contd.) 3. Soldering Iron and wire( if using PCB) 4. DC motors 5. Switches 6. Multi /single strand wire 7. Multi-meter
www.robotix.in
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.
www.robotix.in
Centre Tap Transformer 12V AC
-12V AC
220 V AC supply
www.robotix.in
Rectifier Circuit PCB Line matrix PCB
Dot matrix PCB
www.robotix.in
Rectifier Circuit Bread Board
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
Rectifier Circuit-Diodes 

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. www.robotix.in
Rectifier Circuit-Capacitor 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 www.robotix.in
Rectifier Circuit-Voltage Regulator 
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.
www.robotix.in
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.
1 2
www.robotix.in
3
Rectifier Circuit-Heat Sink 
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.
www.robotix.in
Rectifier Circuit-Relimates 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 Female ground. This helps in debugging part faults at the end without much difficulty. 
www.robotix.in
Male part
Rectifier Circuit-Soldering 
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.
www.robotix.in
DC Motors 
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
www.robotix.in
Switches 
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.
www.robotix.in
Switches
To motor
DC power
www.robotix.in
Wires 
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.
www.robotix.in
Multi-meter 
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.
www.robotix.in
Rectifier Circuit
www.robotix.in
Rectifier Circuit
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
www.robotix.in
Rectifier Circuit
www.robotix.in
Drive Mechanism 

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.
www.robotix.in
Movement of DD MOTION
LEFT MOTOR
RIGHT MOTOR
FORWARD BACKWARD LEFT TURN
RIGHT TURN
www.robotix.in
Differential Drive Chassis
www.robotix.in
Shop Location Electronics: Choudhary Electronics(in Tech Market) Carpentry:
Tech market Outside Puri Gate Prem Bazaar Umesh Carpenter www.robotix.in
Things You Will Need
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 www.robotix.in Breadboard (optional)
Things you will need 
Link to Required materials: http://goo.gl/S8YDr
www.robotix.in