Hi am kiran i would like to get details on gas detector using ic 555 ppt ..My friend Justin said gas detector using ic 555 ppt will be available here and now i am living at ......... and i last studied in the college ......... and now am doing ....i need help on ......etc

ABSTRACT

LPG gas is supplied in pressurized steel cylinders. As this gas is heavier than air, when it leaks from a cylinder it flows along floor and tends to settle in low spots such as a basement. This can cause fire or suffocation if not dealt with. Here is a circuit that detects the leakage of LPG gas and alerts the user through audio-visual indications.

This LPG Gas Sensor (MQ6), ideal sensor for use to detect the presence of a dangerous Liquefied petroleum gas (LPG) and it has high sensitivity to propane, butane, isobutene, natural gas. The sensor can also be used to detect combustible gases, especially methane. This circuit can detect leakages in your Home, car or in a service station, storage tank environment. This unit can be easily implemented to industrial level by upgrading its ranges.

This project is designed to detect the LPG from 200parts per million (PPM) to 10,000 PPM. Whenever there is LPG concentration of 1000 ppm (parts per million) in the area, the OUT pin of the sensor module goes high. This signal drives timer IC 555, which is wired as an astable multivibrator. The multivibrator basically works as a tone generator. A buzzer is connected to produce audible alert signal.

This LPG Gas Sensor can be used to make wireless Gas leak detector in home security system .The LPG Gas Sensor Module is designed to enable LPG detection interface to Microcontroller without ADC Channels. By providing a GSM modem we can receive “SMS ALERTS” also..



more reference;
http://ollengg.blogspot2012/07/gas-leaka...c-555.html

The 555 timer IC is an integrated circuit (chip) used in a variety of timer, pulse generation, and oscillator applications. The 555 can be used to provide time delays, as an oscillator, and as a flip-flop element. Derivatives provide up to four timing circuits in one package.
Introduced in 1971 by American company Signetics, the 555 is still in widespread use due to its low price, ease of use, and stability. It is now made by many companies in the original bipolar and also in low-power CMOS types. As of 2003, it was estimated that 1 billion units are manufactured every year.[1

Modes

Bistable mode or Schmitt trigger – the 555 can operate as a flip-flop, if the DIS pin is not connected and no capacitor is used. Uses include bounce-free latched switches.
Monostable mode – in this mode, the 555 functions as a "one-shot" pulse generator. Applications include timers, missing pulse detection, bounce-free switches, touch switches, frequency divider, capacitance measurement, pulse-width modulation (PWM) and so on.
Astable (free-running) mode – the 555 can operate as an electronic oscillator. Uses include LED and lamp flashers, pulse generation, logic clocks, tone generation, security alarms, pulse position modulation and so on. The 555 can be used as a simple ADC, converting an analog value to a pulse length (e.g., selecting a thermistor as timing resistor allows the use of the 555 in a temperature sensor and the period of the output pulse is determined by the temperature). The use of a microprocessor-based circuit can then convert the pulse period to temperature, linearize it and even provide calibration means.

Joystick interface circuit using the 558 quad timer

The Apple II microcomputer used a quad timer 558 in monostable (or "one-shot") mode to interface up to four "game paddles" or two joysticks to the host computer. It also used a single 555 for flashing the display cursor.
A similar circuit was used in the IBM PC.[12] In the joystick interface circuit of the IBM PC, the capacitor of the RC network (see Monostable Mode above) was generally a 10 nF capacitor. The resistor of the RC network consisted of the potentiometer inside the joystick along with an external resistor of 2.2 kΩ.[13] The joystick potentiometer acted as a variable resistor. By moving the joystick, the resistance of the joystick increased from a small value up to about 100 kΩ. The joystick operated at 5 V.[14]