Not so deadly BUT painful Taser!!!

Well this is not for the faint hearted. If u wanna make ur own taser (220V or 1KV) this is how u do it(WARNING : Dont try this on any1,before u try it 3times on yourself)...
Taser guns come in various types, but for starters we will keep it simple..Here is what u need for making the 220V Taser-
1) 9V or 12V battery
2) 909 Transformer or 12012 transformer if using the 12V battery
3) 2 BC547 Trasnsistors (Any NPN transistor will do)
4) 2 1/4W 10k carbon resistors
5) 4 1/4W diodes for making Bridge rectifier
6) 100uF 450V rating Capacitor (it is imp u use 450V rating, it just costs 30INR)
7) PCB to put the stuff togethr

Principle and Working:
1)First u make an astable multivibrator using the two transistors and resistors. Then u take this pulsed DC and feed it to the transformer's usual secondary (the side which gives +9,0,-9V when u put 220V in the primary).
2)By doing this u will get 220V pulsed DC in the transformer's ususal Primary...
3)Now put a bridge rectifier in front of the end from where u are getting 220V pulsed DC, to get (220*1.414)V DC...cool....but remember this DC voltage is very high Impedance and thus not at all harmful to any one...
4) Now u must charge a capacitor(450V rating) with this High DC voltage.
5) As soon as the capcitor will be charged ( around 15-20s) u will have a painful voltage strike ready.
6) Diconnect the capacitor from the charging circuit and direct it to two conducting metallic plates or bars.

Make some one touch the ends and see them get a 220V shock...its not deadly but it sure is painful!
Cheers!

Cheap Data Acquisition Hardware (DAQ)

Every one knows about DAQs manufactured by National Instruments and other big MNCs, but these are too expensive to use for small applications where only few channels are required with not much of sampling rate.
The ATMega series has in built 8 channel 10 bit ADC with conversion time of upto 17us. Hence ATMega16 or 32 can be used to make a cheap DAQ. All u need is some skills in computer programming along with time to make the cheap DAQ.
Basically, we have to make an ADC-USART. The algo is simple, first initiate the ADC of the controller to sample the port and give u digital value for the sensor output. As soon as u get the data, store it in a buffer and transmit it serially to the Laptop. You may need a USB to Serial Converter in case u dont have a serial port. use VB6 to make a program which reads the serial port and make a graph out of the readings. Make sure ur baud rate is much above 9600, say 57600 or higher.

Low Cost 2-axis Inertial Navigation System

This is one of my coolest projects till date. I made a 2-axis INS system using a cheap accelerometer interfaced with ATMega32....
First a few words on INS...INS or Inertial Navigation System is used in Missiles, Airplanes (commercial and Military), UAVs, Autonomous vehicles, etc. to calculate real time velocity and distance from a given origin.
Consider a helicopter lying at (0,0) of your co-ordinate axis, you wish to make it fly autonomously to (x,y). How will u do it?well ull need a strapdown-INS system. As the helicopter will take off, your accelerometer will start giving you a reading, which u must convert to digital ( i used in built 10 bit ADC of ATmega32), then integrate with respect to time, and get real time velocity, integrate again to get real time distance....


In the pic u can see the accelerometer, ATM32 and an 16x2 LCD for displaying velocity and distance....i will be uploading the algo shortly....

Robot Control using Cell Phone (DTMF)

DTMF (Dual Tone Multiple Frequency) is a very helpful tool when it comes to controlling any application, say a robot. Standard RC circuits have limited range, on the other hand a mobile phone can be used anywhere, where there is connectivity. Thus interfacing a robot with a Mobile will be quite cool.

For this i used a commonly available DTMF decoder MT8870DE. This IC requires a tone signal which is given by the earphone attached to the Mobile, and it decodes these two tone frequencies and gives digital output, representing the key that was pressed.

Basically on the caller side, it is a dial tone generator. When a key is being pressed on the matrix keypad, it generate a unique tone consisting of two audible tone frequency. For example, if the key '1' is being press on the phone, the tone you hear is actually consist of a 697hz & 1209hz sine signal. Pressing key '9' will generate the tone form by 852hz & 1477hz. The frequency use in the dial tone system is of audible range suitable for transmission over the telephone cable.

On the telephone exchange side, it has a decoder circuit to decode the tone to digital code. For example, the tone of 941hz + 1336hz will be decoded as binary '1010' as the output. This digital output will be read in by a computer, which will then act as a operator to connect the caller's telephone line to the designated phone line. The telephone exchange center will generate a high voltage signal to the receiving telephone, so as to ring the telephone bell, to notified the receiving user that there is an incoming call.
DTMF is a popular project especially in DSP (digital signal processing) subject. DSP software algorithm can be implement to generate as well as to decode DTMF tone.

Virtual Steering Wheel

In this Project I used a 3axis accelerometer interfaced with ATMega32 controller, which was further connected to a secure wireless transmitter, which sent signals to a receiver of a RC car.
I attached the accelerometer to a glove, and as i moved my hand circularly( After wearing the glove), the accelerometer sent analog signal to the ADC of the ATMega32, corresoonding to the direction (ZY plane) in which the hand was moved. The ATMega32 after taking appropriate decision controlled the movement of the car wirelessly.

Securing a Toy Car Radio

Easily available toy cars have a Transmitter and a receiver(in the car), but the receiver can easily catch any stray signal and fire the following circuits. Thus in order to make a secure radio transmission so that any standard radio can be interfaced with any circuit which u want to wireless, I used ATMega32 controllers on each side to encrypt the signal and then send it and subsequently decrypt the signal on the receiving end.

USART-LCD using ATMega32

In this project i used an ATMega32 controller,interfaced with a laptop and a LCD (16X2 alphaneumeric). I used the Laptop to send serial data to the controller and it used to get displayed on the LCD. This project is a good starting point to learn the basics of ATMega32 as it uses both the USART and LCD interfacing.