9/10/2015 Sensitive LPG Leakage Alarm

http://electronicsforu.com/electronicsforu/circuitarchives/view_article.asp?sno=2204&article_type=1&id=1139 1/3

Design In India Ask Questions!Circuits ∨ Software ∨ Careers ∨ Videos ∨ Stories ∨ Technical Articles ∨ Special ∨ Finder ∨

Automotive Consumer Medical Power Electronics SolarAutomation ∨ Communication ∨ LEDs ∨ Test & Measurement ∨

Related Circuits

Door-Knock or Vibration Alarm Versatile Audio-Visual Alarm

Multi-tone Configurable Alarm Locker-Security Alarm

Hi! Mayur Logout | Advertise | About Us | Search | Contact Us | Search

Home

Aerospace & Defence

H O M E >> C I R C U I T L A B

Select Language ▼

First published on: 1-4-2013

Sensitive LPG Leakage Alarm

D. Mohan Kumar

Here is an ultra-sensitive LPG sensor that generates loud beeps when it senses any gasleakage. It detects vapours of liquefied petroleum gas anywhere between 200 and 10,000ppm and drives a piezobuzzer to catch attention for immediate action. The buzzer beepsuntil the concentration of gas in the air decreases to a safe level. The circuit uses an MQ6gas sensor, which is designed to sense LPG, propane and isobutane gases.

Circuit and workingFig. 1 shows the circuit of the LPG sensor. The circuit is built around 5V voltage regulator7805 (IC1), gas sensor MQ6 (GS1), counter IC 4060 (IC2) and a few discrete components.

GS1 is a six-pin gas sensor that can detect very small traces of LPG in the air and has a swift response time. However, ithas very less sensitivity to alcohol and smoke. The sensor’s output is in the form of resistance.

Fig. 1: Circuit of the sensitive LPG sensor

As indicated in Fig. 1, the pins of GSI are H, A and B, two each on either side. H pins are for the heater with no polarity.Input pins A or B and output pins A or B can be connected either way round.

The coil heater inside the sensor can be easily heated with 5V DC. If pin A is connected to 5V DC through variableresistor VR1, use pin B as the output or vice versa. Both A and B pins can be shorted. In short, H pins are connected topositive and negative rails, A or B pin to 5V DC, and B or A for output.

The resistance value of GSI is different for various kinds and concentration of gases. So when using this sensor,sensitivity arrangement is very important. For accurate detection, it is necessary to calibrate the sensor for 1000 ppm ofLPG concentration in the air with load resistance of about 20 kilo-ohms. (In the datasheet, the load resistance range ofMQ6 is mentioned as 10 kilo-ohms to 47 kilo-ohms.)

Ads by Google ► LPG Gas ► Gas Sensor ► Gas Alarm ► Smoke Alarm

9/10/2015 Sensitive LPG Leakage Alarm

http://electronicsforu.com/electronicsforu/circuitarchives/view_article.asp?sno=2204&article_type=1&id=1139 2/3

Fig. 2: An actual-size, single-side PCB for sensitive LPG sensor

Fig. 3: Component layout for the PCB

Download PCB and Component Layout PDFs: Click Here

Preset VR1 is used to adjust the sensitivity of the sensor to a particular gasconcentration. Output from the sensor is connected to the base of transistor T1,which acts as a switch to trigger the alarm generator built around IC2.

IC2 is a binary counter IC that oscillates using capacitor C2 and resistor R5.Transistor T1 controls the reset pin (pin 12) of IC2. When the reset pin is high IC2does not oscillate, and when this pin goes low IC2 starts oscillating.

Working of the circuit is simple. When the sensor detects LPG in the air, its outputbecomes high and transistor T1 conducts to make reset pin of IC2 low. Thistriggers IC2 to oscillate, which is indicated by LED1. After a few seconds, thebuzzer starts beeping to indicate gas leakage.

The circuit works off 12V DC from a battery (BATT.1) or you can use an adaptor.IC1 provides regulated 5V DC supply for the sensor and IC2.

Construction and testingAn actual-size, single-side PCB for sensitive LPG sensor is shown in Fig. 2 and itscomponent layout in Fig. 3. After assembling the circuit on a PCB, enclose it in asuitable case with an opening to allow the gas to enter. Place the unit near the LPG cylinder or gas stove within adistance of one metre. Vary preset VR1 to adjust the sensitivity of the sensor.

To test the circuit, check 12V at test point TP1 with respect to TP0 to verify the correct power supply. Place the unitnear the gas stove burner and turn on the burner for a few seconds without igniting. Then, turn ’the burner ‘off’ andadjust VR1 until you see LED1 glowing. TP3 should be low at this moment.

The author is an associate professor at Government College for Women, Thiruvananthapuram, Kerala

Related Circuits

Door-Knock or Vibration Alarm Views: 8254

Versatile Audio-Visual Alarm Views: 5483

Multi-tone Configurable Alarm Views: 4450

9/10/2015 Sensitive LPG Leakage Alarm

http://electronicsforu.com/electronicsforu/circuitarchives/view_article.asp?sno=2204&article_type=1&id=1139 3/3

22 33 10 Post Comment | 1 Comments

Priyank Vishnoi 18 days ago

I have made this project but something goes wrong when I connect the battery the LED as well as the buzzer starts withouthaving any concentration of LPG gas in air. Please help me.Thanks in advance.

Reply

Locker-Security Alarm Views: 13081

Magazines

Electronics for YouOpen Source for YouElectronics Bazaar

Portals

electronicsforu.comefytimes.comopensourceforu.com

Directories

Electronics AnnualGuide

Events

EFY EXPOEFY AwardsOSIDAYS Expo

News Verticals

ElectronicsInfotechLinux & OpenSourceConsumerElectronicsScience &TechnologyBPO

Educational Institute

EFY TechcenterKitsnspares.com

© Copyright 2015 EFY Enterprises Pvt. Ltd. All rights reserved.Reproduction in whole or in part in any form or medium without written permission is prohibited. Usage of the content from the web site is subject to terms and Conditions

Ads by Google ► Smoke Alarm ► Door Alarm ► Heater Gas ► Propane Gas