PIC16F84A Gas Detector using GH-312 sensor

Home Projects Test and measurement PIC16F84A Gas Detector using GH-312 sensor

PIC16F84A Gas Detector using GH-312 sensor
author: Rui Cabral - rui.j.cabralgooglemail.com - www.ruijc.webnode.com

Introduction

This is a gas detecting circuit capable of sensing many different types of gases.

The sensor used is the GH-312 and from the datasheet it is capable of sensing gases like smoke, liquefied gas, butane and propane, Methane, alcohol, hydrogen, etc.

Schematic

Parts List

R1                   1K resistor
R2                   1K resistor
P1                    100K potentiometer
C1                   10uF cap
C2                   100nF cap
C3                   100nF cap
C4                   15pF cap
C5                   15pF cap
Xtal                 8Mhz crystal
Led1                3mm red led
Piezo               Piezo
LCD                8X2 LCD
IC1                  16F84A microcontroller
VR1                7805 regulator
GH-312           Gas Sensor

PCB

The PCB used for this Project is single layer and its size is 65.95mm x 59.25mm.

Top Side

Here is the top view with the components

Bottom Side

Here's the bottom side.

I've used a 9V battery for this project because the sensor requires a 9V input. The output when the sensor is triggered is always 5V which is perfect for a direct connection to any microcontroller. Although I've used a 9V battery, any 12V power supply ( a small wall transformer for example ) will work perfectly since the sensor can handle from 9V up to 20V and the microcontroller's voltage is regulated by a 7805 regulator.

Testing

The first tests were made with the circuit mounted on a breadboard. After initialization the circuit will enter a normal state where it detects no gas. The display shows "Sensing...No Gas !".

To test the sensor I used my portable gas soldering iron with the gas coming out pointed to the sensor.

The sensor is able to detect the gas and the microcontroller will trigger a flashing led warning and sound.

The sound is produced by a small piezo and the display show the message "Found Gas".

When the air is clean again and the sensor does not sense any gas, the circuit will return to it's normal state turning off both led and piezo sound.

Photos

Circuit is Initializing

Conclusion

It's a pretty cheap and easy to assemble circuit.

Does not require too many parts and the microcontroller is very easy to find ( the famous 16F84A from microchip ).

Since it's used a small lcd ( 8x2 ) this project can be portable.

Also this sensor senses several types of gas and it's pretty stable.

Source code

The source code is provided in hex format: GASDEMO.HEX

Download

Download project in .DOC format