Interfacing gas sensors with microcontroller

[pratyathedon]

I working on a project where i have interface a gas sensor with uc. My question is that whether gas sensors are affordable or not.do they work efficiently.and Ive searched some sites that they have given the datasheet and that sensor price.the normal Co carbon monooxide sensor costs approx 700 bucks.is it right to use gas sensors.please help ppl.thanks a lot

 

[bobcat1]

Hi

You will need a raw sensor without any additional electronics this will cost less - but you will need to add the electronics to operate the sensor - basically a microcontroller with A/D converter and a transistor switch to control the sensor heating element

All the best

Bobi

The microcontroller specialist

 

[pratyathedon]

Can anybody will give me simple schematic of interfacing of gas sensor with A/D and microcontroller

 

[Tahmid]

Hi,
I know of TGS822 which is an organic solvent vapour sensor, costs around $32.00.
Since you said:

gas sensor with A/D and microcontroller

I assume you're using external ADC, in that case:

The sensor:

 

[ZASto]

Many of the gas sensors are electro-chemical type so for these sensors you need some additional electronics.

Exceptions are Zirconium O2 sensors and CO2 sensors which operate in near IR.

Example for electrochemical sensors: https://www.citytech.com/index.html

HTH

 

[FvM]

I realized, that have mentioned CO measurement in your original post. For CO, the said electrochemical sensors are a rather
simple solution for a low range (ppm) measurement. They have a fair lifetime of 2 to 5 years and are almost selective to CO.
Suitable sensor amplifier circuits can be found e.g. in Citytech application notes.

Figaro has also an electrochemical CO sensor, but it's unusual slow (60 s). https://www.figarosensor.com/products/5042pdf.pdf
They also make SnO2 semiconductor sensors (similar to the above mentioned TGS822) specialized for CO, but they are
still rather unpecific and have considerable cross-sensitivity e.g. to water vapour. https://www.figarosensor.com/products/2442pdf.pdf

For a high (percent) range needed in car emission measurement, IR photometers are needed. Citytech and others have ready
made modules (producing digital concentration data) for it, but they are more complex and expensive.

 

[ZASto]

I realized, that have mentioned CO measurement in your original post. For CO, the said electrochemical sensors are a rather
simple solution for a low range (ppm) measurement. They have a fair lifetime of 2 to 5 years and are almost selective to CO.
Suitable sensor amplifier circuits can be found e.g. in Citytech application notes.

For a high (percent) range needed in car emission measurement, IR photometers are needed. Citytech and others have ready
made modules (producing digital concentration data) for it, but they are more complex and expensive.

You are apsolutely right on sensor type. Electrochemical are mostly used in flue gas analyzers (Testo, Draeger,...), I used to maintain/repair Testo analyzers

 

[pratyathedon]

what will be the o/p of gas A/D converter(assume A/d converter is connected to sensor).do the program to be made for microcontroller will be a tough one.

 

[pratyathedon]

But can anybody plz give me neat schematic diagram using ADC. Coz i have not understood the above schematic.

 

[FvM]

Coz i have not understood the above schematic.

Hm. It's really simple I think. But you can get it much simpler by omitting the external 8-bit ADC and using a PIC
with internal ADC instead, and connect the sensor output directly to the uP. Also the crystal can be save, because
recent PICs have an internal clock oscillator. So the circuit reduces to a TGS822, a resistor, a PIC and a bypass cap.

 

[welove8051]

hi, try this circuit. if you just want to detect the gas just connect the lm358 output to the MC or if you want to measure its value then connect the sensor o/p to adc. for adc programming refer mazidi book its simple.


regards
kj

 

[pratyathedon]

can anybody plz post some prices of different sensors.
like for alcohol sensor,co,co2,LPG sensors.

Added after 30 minutes:

i want to measure the value/ambient level of the gas
so according to above schematic if i use TLC548 A/d conv.
i'm using P89V51RD2 micro-controller.
so pin 5,7,6 of A/D will be connected to port 2.1,2.2,2.3 of microcontroller.
so accordingly can you post a simple assembly program(As a reference) for above schematic.

 

[pratyathedon]

Can plz anybody tell me the temperature range when 5v is applied.i mean what will the max temperature of gas sensor when heater voltage is applied

Added after 14 seconds:

Can anybody tell me the temperature range when 5v is applied.i mean what will the max temperature of gas sensor when heater voltage is applied

 

[pratyathedon]

I live in Pune,Maharashtra,India
So plz tell me that from where to buy these sensor without online buying
any name of the stores.

 

[pranam77]

Contact the dealer on 09448437768 who will arrange send you the said LPG sensor...Cheers

 

[pratyathedon]

Contact the dealer on 09448437768 who will arrange send you the said LPG sensor...Cheers

just tell me whats his name.
and thanks for the reply.i am really angry due to suppliers in our area.
they just double the original price. just tell me his name as soon as possible

 

[pratyathedon]

What will be the maximum output of the LPG gas sensor.

 

[deepakgupta.rf]

hi, try this circuit. if you just want to detect the gas just connect the lm358 output to the MC or if you want to measure its value then connect the sensor o/p to adc. for adc programming refer mazidi book its simple.


regards
kj

hello sir can you tell me more about this gas sensor interfacing.
actually i tried but coudn't get result so plz help me.....
does this lm358 convert the signal in digital .

so plz solve my this problem

 

[welove8051]

yes, lm358 act as comparator. the output will be digital. verify mq6 datasheet for the pin configuration.