Tuesday, 15 December 2015

Bend Sensor- Initial iterations and testing

This is the video of the bend sensor designed at the lab for a project on 'Sensor based systems' course at KTH. This is the initial testing of the first such sensor made.

The final demonstration: 

Left hand controls the down-motion (brake) and the right hand controls the acceleration (move forward). Focus of the project was on the sensor-characterization and testing them for repetability, precision etc.

In the video, you can see the Sensors in action. The small green board is the USB keyboard driver board, scrapped from an old dell keyboard. The blue components are solid state relays. 

Wednesday, 4 March 2015

The homemade 'green' LED tent light (Design + field test)

Recently I went looking for a small portable tent-light, that can be used during camping and overnight treks. I was targeting the LED's with a heat sink attached to it. I found a variety of such devices but they were not worth the price I was going to pay. Most of the devices used the 3xAAA size batteries which are quite inconvenient to use, especially in India. So I decided to make something much cheap, at home and as I want it to be, in terms of size, shape, circuit complexity etc. 

This time decided to something with the used batteries. Re-generating the wasted energy with the Joule thief ! Hence the name 'Green'. 

Knob on the left side is to control the intensity.
Right side is the switch.
I have used a small wire to complete the circuit
You can see two small PCB's mounted inside.  
Ultra bright LED!!
Once done, I put the setup inside a used plastic shampoo bottle. Used the empty space to keep the spare batteries as well as to maintain the balance of the bottle. In future I will write a blog on my trekking blog- The Mountain Tamers to describe the performance of this device.

Tuesday, 6 January 2015

A totally random robotics experiment

RF Module (Tx, Rx), LDR's, L293D, PCB manufacturing kit (to design PCB at home), Basic robot chassis

Plan was to control the robot using LDR's basically a light operated robot kinda thing. The driver part was designed and fabricated at home.

The PCB layout of the driver part
The etched PCB board
PCB board with components
The controller part with LDR and RF module
All parts attached 

Tuesday, 21 October 2014

Happy Diwali (The Engineers way)

Its Diwali- the festival of lights! And speaking of lights, I thought that making a LED project would be a best tribute to Isamu Akasaki, Hiroshi Amano and Shuji Nakamura for their 2014 physics Nobel Prize. So its just a small LED project. Lets summon the Batman this Diwali !!

The Bat-lantern in action !
To avoid the intricate circuitry I used a 12V SMPS adapter and a 5V regulator with two capacitors at input and output. Five LED's seems to work perfectly to make the bat-signal. The logo which I used is the one from 'The Dark Knight' movie. And the result was- a super awesome Bat-Signal-Lantern.

Happy Diwali !!

Tuesday, 20 August 2013

Speech, Text Controlled Robot using ARDUINO and VB.Net

Difficulty Rating: 8/10


This is the basic setup of the Speech/Text/Computer controlled Robot. The commands are sent serially over the USB to the ARDUINO Duemilanove. The corresponding signals then drive the two 300 RPM motors with the help of a motor driver IC L293D.


Introduced a RF module so that the Robot can be wireless operated, with only the Receiver mounted on the Robot. The transmitter transmits the signals with the help of ARDUINO and the signals are received by the Receiver on the Robot, which controls the motion of the Robot.

Video of the Software Implementation (Software part):

Video demonstration of the speech commands to the robot (Software part):

Video demonstration of the full project (Hardware + Software):

This is the video of the Computer controlled robot which has following features--
  • Speech command input
  • Text command input
  • Button inputs
  • Keyboard inputs
  • Autonomous mode (to be implemented further)
Please note here that I have implemented here a "Speech controlled mode" and NOT "Voice controlled mode". Hence it can work with anybody's "Speech" and is not a user-specific. I ran a few trials with my friends daughter(8 year old), my uncle (60 years old), mother, father, sister and many friends. It works perfectly!!! Just a few cases of misinterpretation of letters Eg. sometimes letter "a" read out as "d".

In the video please ignore the wagon-wheel effect (strobe effect). Click here for wagon-wheel effect

Stay tuned.
Lots of exciting stuff to come !!!

Sunday, 14 July 2013

Interface for Advance Robotic Controller (iARC) Version 1.00 & 2.00

Difficulty Rating: 7/10

GUI Design: VB.NET
Microcontroller Board: ARDUINO Duemilanov (AtMega 328)
Features: Speech Commands, Text commands, Button Commands, Fully Autonomous Mode
Used for: Robotic Car (iARC V1.00), Robotic Arm (iARC V2.00)

The GUI is designed on Microsoft visual studio 2010 using VB.Net. The commands are serially sent to the ARDUINO Duemilanove, which controls the Robot car. The baud rate is set to 57600bps, which can be changed as per the user convenience. 

I've also added a "Serial communication tester button" to ensure the flawless communication. It simply lights a LED when the serial communication takes place.

Properties used to build the code:
Baudrate: To set Baud rate Eg. 9600, 57600
Databits: Standard length of databits per byte
Encoding: Byte encoding for pre and post transmission of conversion of text
Handshake: Handshaking protocol for serial communication
IsOpen: Value indicating the open or closed status of the Serialport object
Parity: Parity checking protocol
Portname: Port to be used for serial communication with Arduino
Stopbits: Standard number of stopbits per byte

Methods (Functions) used to build the code:
Shared sPort As SerialPort
           sPort.Open( )
           sPort.Write( <Any variables> )
           sPort.Close( )

Speech Recognition Window:

Version 1: To control a Robotic car

Version 2: To control a Robotic Arm

Here is the video of how the GUI works:

Video demonstration of the speech commands to the Robot:

Stay tuned.
More to come..

The code for ARDUINO and the GUI Interface will be made available here for download.

Sunday, 9 June 2013

A Text to Speech App using VB.NET (Microsoft Speech API)

[Software Project]
Difficulty Rating: 4/10
GUI Design: Microsoft Visual Studio 2010 software package.
Back-end program: VB.NET

This is a simple text to speech App designed using Microsoft Speech API. The SAPI is heart of this program (backend). I've added a few features like volume control, speaking rate control and an option to save the speech. The speech can be saved in any file say, mp3 or wav. Eventually, what we have, is a female computer generated Robotic Speech.

SAPI.Volume = TrackBar1.Value
This will control the volume from 10 to 100 in the steps of 10. Properties can be changed as per our convenience. 

SAPI.Rate = TrackBar2.Value
This will control the speed of speaking. Again properties can be changed as per our convenience. 

For those having Resolution 1920 x 1080,
Download STACY: Click here
You will also need Microsoft .NET Framework 4 Web Installer
Download it here: Click here


Monday, 15 April 2013

YAW8: Yet another Windows 8 (Using Microsoft Visual Studio 2010- Express )

Made some changes to the previous version of my VB based Windows 8.

More space for adding extra apps!! Added a fully customized web browser and a search engine. Also developed a dedicated Speech recognition tool and a text-to-speech application. From now on, my computer reads the e-books for me!!

Henceforth don't let Microsoft rule your life. Make your own Windows 8 and make your own applications.

Soon to be made available here for download (Demo Version)
Stay tuned,
More to come.

Monday, 1 April 2013

Windows 8 Metro Apps on Windows 7

Difficulty Rating: 5/10

Don't have a Windows 8? Make one for your own, on Windows 7 itself!!
I made this using VB. 

Serves the purpose, right? It gives me full command over these apps (Metro apps). I have kept these apps enabled with a password. The User/Guest can access the destination path only if the password is correct. A different destination path is set for wrong password entries !!!

Well, I don't wanna offend Microsoft by any means, but come on!! Make your own interface instead of using a pirated version of Windows 8  :)

Here's the video. Hope you like it.


Soon to be available here for download.

Sunday, 17 March 2013

12V 7.2Ah SMF Battery Charger: Smart Approach for Smart devices by Smart People !!

Difficulty Rating: 5/10

This project gives an overview of the Sealed Maintenance-Free (SMF) Lead-Acid Rechargeable Battery charger using 3-pin  IC LM-317 as voltage regulator and opamp IC LM-324.

In case of a simple battery charger, when the battery is fully charged and is left plugged in for more than a day or two, the battery may get damaged. In order to protect the battery from this major risk, the proposed battery charger is designed in such a way that the charging current falls gradually as the charging progresses. So the battery can be left plugged into this charger indefinitely, and it won't bother it in the slightest.

Designing the Circuit: 

Click the image to view the enlarged version
The LM317 is an adjustable three-terminal positive-voltage regulator capable of supplying more than 1.5A over an output-voltage range of 1.25 V to 37 V. It is exceptionally easy to use and requires only two external resistors, R2 and R2”  (R2= R2’+ R2”) to set the output voltage. Furthermore, both line and load regulation is better than standard fixed regulators. In addition to having higher performance than fixed regulators, this device includes on-chip current limiting thermal overload protection, and safe-operating-area protection. All overload protection remains fully functional, even if the ADJUST terminal is disconnected. By connecting a fixed resistor, Rthe ADJUST and OUTPUT terminals, the LM317 can function as a precision current regulator. An optional output capacitor can be added to improve transient response. 

Determining the values: 

Vo is calculated by following formula ,  Vo = Vref * ( 1 + R2/R1 )

Testing of the Circuit: 
The best way to check that the circuit is working is to monitor the current as it flows into your battery. Recall that all the current goes through resistor R3. So you can get a good estimate of the current going into your battery by measuring the voltage drop across the resistor. Use the formula I = V / R (where I = current in amps, V = voltage in volts, R = resistance in ohms) to get the current flowing through the resistor .
Having connected the multimeter probes to the OUTPUT,by adjusting the 500 Ώ Trimpot, output voltage can be varied and optained as wanted( between 12v and 15v ,minimum and maximum charging voltages).To check the regulation of voltage regulator IC LM317,connect the negative probe of the multimeter to the ground ,and observe the voltage at INPUT , OUTPUT and ADJUST pins.While doing so take enough precaution as not to short OUTPUT and ADJUST pins as it may damage the transistor BC 547,whose collector is connected to adjustment pin.

13.7 V
12.47 V
15.01 V

The difference between voltage at output pin and adjustment pin is 1.23 (~1.25) which is the reference voltage Vref.

Current rating of battery to be charged  7.2 Ah 12v, short circuit curent Isc = 720mA .Using multimeter check the short circuit current.If the Isc shows a different value than expected,it can be changed by increasing or decreasing the load connected between the emitter of the transistor T1 and ground.

Circuit Working:
 The circuit uses two LEDs as indicators ; one for signalling charging ON condition ,and the other as an indicator , when charging voltage falls below  its terminal voltage (~12 volts). Terminal voltage can be adjusted by adjusting the 1k Trimpot. The output voltage range can be adjusted by 500 ohm Trimpot.The charging voltage is adjusted such that each cell gets charged at 2.25 – 2.3 v/cell by limiting the charging voltage between 12v and 15v,initial current being less than 0.3CA.

LM324 is  used in comparator circuit ,after the rectifier circuit.Comparator will compare the voltage levels,and if the output voltage is less than the charging voltage ,the voltage across the red LED will go high thus indicating drop in charging voltage.
In the proposed battery charger circuit, minimum voltage is set at ~12v.But if we want to set a different voltage as terminal voltage that can be done by adjusting the 1k Trimpot.

All the details of the project including circuit designing, circuit operation, circuit testing & debugging has been mentioned in detail at this link. Click here 

Saturday, 2 March 2013

L293D: A notion to be cleared

IC L293D, is the Motor Driver IC, which is usually linked to Robotics Applications. Even if you tend to use this guy, few basic questions still arouse in the minds of budding Hobbyists; Like Why 2 supply pins on the IC, How much voltage can be given to the IC, Should I short all the Ground pins of the IC ?????? 

Here, I'll be explaining the Pin description of L293D and not the specifications or other technical details. You can refer datasheet for that. L293D datasheet click here.

To start with, any Microcontroller development Board works with a Max. of 5V, with a few hundreds of mA current. In case of ARDUINO Duemilanov:
DC Current per I/O: 40mA
DC Current for VCC & GND: 200mA 

Is this current sufficient enough to drive a everyday 12V, 200RPM DC motor ?

So what ?
Use a Motor Driver. 

Does it help ?
Yes. It converts low current to high, sufficient to drive a motor.

Pin Conections (Important: Even pro's tend to make mistake here)

Pin 1 & 9:
Pin 1 is Enable 1. Used for enabling working of Motor1 (IN1, IN2, OUT1, OUT2)
Pin 2 is Enable 2. Used for enabling working of Motor2 (IN3, IN4, OUT3, OUT4)

Pin 2, 7 & 10, 15:
Inputs for Motor. 
If pin 2 is +ve, pin 7 is -ve then motor Rotates in one direction. If Pin 2 is -ve, pin 7 is +ve then motor rotates in reverse direction.

Same explanation valid for Pin 10, 15.

Pin 16:
This is the Logic supply voltage for L293D. It should not exceed 7V (recommended rating). But can go Max. upto 36V.

Pin 8:
This is the Output supply voltage. We can give upto 36V (Max), depending on our output voltage requirement.

So, this explains why there are two supply pins on the IC. Pin 16 is usually provided for logic inputs to minimize the device power dissipation.

Pin 4, 5, 12, 13:
These pins are ground pins. They form an on-board Heatsink. Usually these pins are to be shorted  & connected to ground. But, I insist, take a multimeter and test the connectivity of these pins. THEY ARE INTERNALLY SHORTED. We need not short them again, it'll only increase the wire-do of your circuit.  

Please remember that Pin 8 & 16 are totally different. "Pin 8 is supply for left side, Pin 16 is supply for right side" is WRONG. 

Keep prototyping :)

Wednesday, 13 February 2013

Workshop on Computer Controlled RF Rover @ ISTE SAKEC

ORBO V 2.00 to roll during ISTE SAKEC Workshop on 9th March, 2013

ORBO V 1.00

Content of the Workshop:

Intro to Robotics
What is robotics?
How we can use it in day-to day life.

Scope of the workshop:-
Using ATMega168  processors as bot-brain.
Learning about the Arduino environment.
Learning about c++ based processing language IDE.
Learning about 4 channel RF control.
Learning Arduino-Processing interfacing.
PC- Control theory
Processing (An open source Electronic Sketchbook)
Advantages and scope for robotics.
Serial communications.
GUI end user facility. Make Your own programs!.
Controlling methods - Mouse,Pen tablet.
Precision control- Keyboard.
Generic RF module:- Key to open source “hackable”  design.
eg. :- Turbo - using the 5th channel.
Using the Rf module for other purpose - E.g Controlling the home electrical system controlling , Controlling another microprocessor.

(Possibilities for you to explore at  home)

Interactive Q&A Sessions

For more Info. call 
Akshay Narkar: +91 9869209684
Siddhant Betrabet: +91 9167661087

Glimpse of the Workshop:

Saturday, 19 January 2013

A journey from 'UV' to 'Electrical'

A bunch of these just made an entry into my IC box.

S27C64A-20FA is a 64Kb CMOS EPROM (8Kx8), one of the Obsolete Electronic Component manufactured by Signetics. It comes in 28 pin ceramic Dual Inline package (DIP) with Quartz window. 

Thursday, 27 December 2012

Torch Light with Generator

A device that comes in handy during Mountaineering/Trekking

Difficulty Rating: 3/10

Using AA pencil cell to power a torch is too mainstream & also power consuming. And if you are a Mountaineer, where torch-light is vital, replacing these cells becomes too much of pain in the ass. Instead, how about a torch which doesn't need cell replacement in the first place??

The chargeable torch-lights (china made), like this one, have become a commonplace in today's Electronics market.

Commercial Torch-light
(Not mine)

But does anyone have a similar torchlight, which has lasted more than a year?
So I decided to make one for myself, owing to its use during one of the Mountaineering adventures.

My prototype
It works just fine !!!!!

A small pipe, wheel, Long screw (for charging purpose), lots of duct tape, white paper (behind LED)

4.8V Li-ion battery, Toggle switch, push-button switch, 9 high-power LED, Dynamo, PCB, 2 Capacitors 4700uF, IC7805 Regulator, 220 Ohm resistors, 2pin Relimate, Multi strand wire, Rectifier

Self designed electronics: Amplifier, opto coupler, LED drivers (Texas Instruments), Protection circuit for Li-ion battery, charging precautions.

The torch light has a 4.8 V Li-ion battery which is trickle-charged by the hand crank generator.

If you have any queries about designing aspect, or want to know the detailed explanation for the Torch light, feel free to contact me, or drop a comment.

Thursday, 29 November 2012

The Hexapod

Difficulty Rating: 5/10

Hexapod Robot using 12 BO series DC motor (12V-6V and 60RPM)
Microcontroller platform is a ARDUINO (clone) using ATMega 328
Used 6 L293D IC's. 1 IC for driving 2 DC motors.

Sunday, 23 September 2012

Finally Airborne !!!!!

Introducing, JATAYU  (जटायु) a dual-rotor RC chopper. A sweet souvenir from Malaysia!!!
Cost: 120 MYR (Approx. 2000₹)

As the time flies by, day by day, year by year the focus starts drifting from small battery operated toys to the toy cars, the remote controlled cars....... and eventually lands up on the flying models (In my case). And once  you get totally involved in the hobby, even your wildest imagination cannot stop you from thinking about it. From the busiest hour or in your deepest sleep, its still there, somewhere, what you are most inclined to,  wanted thing of your life. For me its RC Heli......

The First Flight
(Also the first crash :p )

A fine sunday morning at Meru Valley, IPOH City Malaysia. Thought, would take Heli for a quick 'morning-flight'. Took the 2 ft. long birdy and kept it on the ground. Slowly moved the throttle stick, and watched as the heli lifts up smoothly. But as it takes off from ground, it runs into a self rotational motion, resulting in a slight 'rotation about own axis'. My fingers reach for the trimmer control, and try to stop the rotational motion. But the logy controlling of an amature Pilot.... It drifts towards right and rams into a nearby tree.

Well Lucky that JATAYU survived. Not much damage done, but a good lesson learnt.

Why I call it Jatayu (जटायु):
In Hindu Mythology, Jatayu is a demi-god, in form of a Vulture, who was known for valour. He gave his life, fighting against a demon (राक्षस) named (रावण), who was abducting Sita (सीता), wife of Lord Raam (राम). For full story click here.

Jatayu (my Heli) has survived many crashes, endured robust flying sessions at different locations. Hence I feel apt to call it Jatayu!!

Flying at Sadashivgad, Karwar (Karnataka): 
Carried out most of the take-off and landings (& crashes). Also did a bit of Night flying here.

Flying at Shivaji Park, Mumbai:
(With Akshay Narkar)

The one with >60ft free-fall. Missing tail fan & loose tail light. But the Heli still flies fine!!

Tuesday, 10 April 2012

Line follower Robot - without using Microcontroller!!

Difficulty Rating : 3/10

Ever wanted to make a Line follower Robot, 'without' using  Microcontroller ???
Then you have visited a right place.


I stumbled upon this Robot in my First year of Engineering during one of the Intercollegiate Robotics Championship (Regional) and ever since, it was my dream to make this Robot on my own. I googled for it & got many designs, but all Microcontroller based. I even shortlisted a few but my senior Pratik Kamat asked me take small steps first and suggested me to make one without the use of Microcontroller and with self designed logic.

Now, as a part of Electronics workshop in Sem-IV (II Year), we were supposed to make a project based on 'Electronics'. Since I was introduced to Microcontrollers at that stage, I made a proposal to make a Microcontroller based LFR( Line follower Robot). But it was rejected by my Batch in-charge as no microcontroller based projects were allowed for current semester. So i decided to make a LFR without using microcontroller. So, started the designing...
And to my surprise, the design was not that tough as it looks. All my friends loved it, batch in-charge appreciated it & (what startled me was the fact that) my immediate Seniors couldn't understand the working at all !!!!

Components : 
  • High power LED (5mm) - 2 to 4
  • LDR's -2 to 4
  • Preset 20k -2 to 4
  • 220 Ohm Resistors -2 to 4
  • L293d -1
  • Geared motors -2
  • Chassis
  • 4.8V NiMh rechargeable battery
  • Burg strip, 2 pin relimat & other secondary stuff..

Circuit diagram:

The Circuit diagram with two pairs of LED-LDR. Click on the image for full-size version.
Click Image for Enlarged View

The Circuit diagram with four pairs of LED-LDR. Click on the image for full-size version.
Click image for enlarged view

Click image for Enlarged view

Working principle:

Our 9th grade science book has taught us that, when light falls on white surface, it gets reflected. When it falls on black surface (or any dark surface) light gets completely absorbed by it. How is this concept applied here? The sensor module has two LED-LDR sensor pair mounted on it (Minimum two is required. You can use any number). The LED or light emitting diode is a semiconductor light source which we will be using. I had used a 5mm white LED for my project. Also, LDR or Light dependent resistor is used here as a Light sensor. It senses the reflected light; i.e light transmitted by the LED and reflected from the surface. If the surface is white, LDR will detect the light. In case the sensor is placed over black surface, LDR cannot detect any light, as the black surface has absorbed all the light.

How Robot follows Line:
(Here I have used two LED-LDR sensor pair instead of four)

Please try to understand that the Left sensor-pair is connected to the left Motor and Right sensor-pair is connected to the right Motor. Notice that the sensor (Either left or right), from which the arrow is pointing outwards is our white LED (transmitter) which emits white light and the one on which arrow is pointed to is LDR or Light dependent resistor (Receiver). This LDR detects the amount of light that will get reflected from the surface, depending on whether the surface is white or black-line.


Left turn

Right turn

How it Works:

This Line Follower Robot basically use a Cadmium Sulphide (CdS) photocell sensor or known as Light Dependent Resistor (LDR) and the high intensity white Light Emitting Diode (5mm LED) to illuminate the area under the LDR sensor to sense the black track line. The LDR will decreases its resistance in the presence of light and increase its resistance in the dark. The region under the LDR is illuminate with a high intensity white LED, the white surface will reflect most of the light to the LDR surface while the black track line will absorb most of the light, therefore less light will reflect to the LDR surface. The 20KOhm trimpot and LDR basically is the voltage divider circuit. When the LDR detects the black track line it will receive less light intensity (LDR resistance increase). Result, the geared DC motor will turn slowly or stop. When the LDR on the white surface it will receive maximum light intensity (LDR resistance decrease) . Result, the geared DC motor will turn fast.

The IC L293D is a motor driver IC, used for boosting current levels, large enough to 'drive' the DC motors.

This is the pic of my 1st prototype using Breadboard (2 LED-LDR sensor)

The sensor mounting

Here's the video of my first Test-Run :


Feel free to comment if you are stuck up, or want to know more about its designing aspects, or if you find any bugs in the circuit diagram.

Friday, 9 March 2012

How to Improve the performances of DC Power supplies & DC motors

Basically  a DC power supply consists of following -
  1. Step down transformer
  2. Rectifier ( Bridge Connection)
  3. Filter
  4. Regulator
  5. Regulated DC output
A standard, general purpose 24V-5Amp power supply is available at Lamington Road, Mumbai. But it consists of only first three elements of power supply i.e. Step down transformer, Rectifier                              (Bridge Connection) and Filter. If you check its rating using a Multimeter, you will find that its actual Voltage Rating & current Rating  is something beyond the specified values. Its actually 35V (DC) 2Amp along with a comparable value of AC voltage !!

 This AC is enough to hamper the performances of the DC devices (mostly DC Motors) which are powered using these messed up power supplies ( It cannot be called blunder as it is serving its purpose of giving DC output ). As the 'DC' Motors run on DC power, the AC voltage does not fit in the bargain, and hence needs to be restrained. And that can be done by adding the remaining two elements (4 & 5) of power supply.

There are many types of voltage regulators, like fixed & adjustable regulators, step up & step down regulators, positive & negative regulators etc. 78xx ICs are series of fixed regulators.Eg. 7805-5V regulator, 7812-12V regulator...L200 is a 5 terminal, voltage and current regulator. Most commonly used adjustable voltage regulators used are LM117, LM217, LM317, LM350 etc. You can either use IC LM7824 ( for 24 volts) or LM 317. LM317 is a 3 terminal adjustable positive voltage regulator capable of supplying greater than 1.5A current over an output voltage range of 1.2 to 37 volts ( For  better flexibility use LM317)

For the datasheet, click here
Refer figure 1 in the datasheet for the circuit diagram and the expressions for Vi & Vo .

Impedance Matching:

Impedance matching is a concept dependent on maximum power transfer theorem, which states that to obtain maximum power at the output, input internal resistance must equals load resistance. 

In case of a DC Motors, what we are concerned about is the current it can draw out of the source. For High torque motors, mainly current matters and not voltage ( That does not mean we should choose any value for voltage, but !5V is standard ). So following techniques can be implemented for better efficiency of DC motors -
  • Use of Flyback Diode
  • Connecting a Capacitor of specific value in parallel with the motor
  • Type of wire used
  • Use of Driver circuits
Use of Flyback Diodes:

The DC motor can be visualized as a coil (inductor coil) connected in series with a resistance of small value, or simply as an electromagnet. When the Motor is disconnected from the supply, the magnetic field which was generated because of inductor coil, decreases as there is no current flowing through the coil. This change in magnetic field gives rise to what is known as back emf. Back emf or counter electromotive force is of several hundreds of volts. The circuitry which is controlling this motor invites an unnecessary risk of damaging the components present on the circuit. Hence to avoid this, we connect a diode across the motors. Flyback diode, freewheeling diode, suppressor diode,  catch diode they all mean the same thing.

Image: wikipedia

In Motor control and Robotics field, back emf is also referred to as the voltage generated in a spinning motor, which hampers the speed of rotation of motor. Even this can be avoided by connecting a diode across the motor, which results in increased effective rating of the DC motor.
But recall that a diode allows the current to flow in only one direction, hence allowing the motor to rotate in only a specific direction.  Hence this  technique is used specially for wireless cars and different programmable robots where we don't require backward motion (But don't use this technique for wired robots).

Connecting a Capacitor of specific value in parallel with the motor:

If you happened to open your remote controlled toy car, you must have seen a small ceramic capacitor connected across the DC motor. Ever wondered, why do we do that???
The DC motor consists of coils, brushes and permanent magnets. The current through the coils pushes them from one magnet to another and this turns the commutator, which switches the current around to continue this process in a cycle. This switching action causes the current drain of battery to vary up and down. The capacitor acts as a reservoir and buffer so that when motor draws little current, the capacitor recharges and when the motor needs high currents the capacitor discharges through the motor. You can use this technique for all kinds of Robots.

Use can also use both, capacitor and diodes for improved results for different competitions.

Type of Wires to be used:

Generally high torque motors require higher currents for their operation. 
According to the equation of current, 
i = dq/dt = n * e * vd  * a
n: No. of electrons
e: Charge on electron i.e. 1.6 x 10 ^ -19
vd: Drift velocity of electrons
a: Area of cross section

If the area of cross section increases, then the current carrying capacity of wire increases. So use copper wire of intermediate thickness for better results.

My Remote control box using thick wires

Driver circuits:

In order to operate a high torque DC motor ( specially used for Robowars & Fifabotix competitions in
MU ) sometimes the rating of even 25 volts and 2 Amp. is  not sufficient. So, in order to tackle this issue there are Driver circuits, available in market. These drivers trade voltages for obtaining higher currents and vice versa. For example 25V and 2 Amp input to a driver can fetch us 15V and >10 Amp. of current!!
Their only disadvantage is that they are damn costly.