Manufacture of Toxic Gas Monitor Based on Internet of Things

Step 1: implement with hardware

Part of the project is mainly handled by the MediaTek linkit one committee.

The MediaTek linkit one board is connected with gas sensors, namely grove LPG sensor and grove air quality sensor. The sensor readings will be sent to the ubidots server.

In the picture, you can see more gas sensors, such as mq-7, mq-135 and mq-138.

However, the linkit one board has only three analog pins. A0, A1 and A2, so up to 3 sensors can be connected.

Because the output of the gas sensor is analog voltage, and our board is a digital system (microcontroller).

We need to convert analog voltage to digital value. This can be done by using an on-board 10 bit ADC.

More information about ADC and gas sensor will be described later.

Step 2: ADC analog to digital conversion

ADC represents analog-to-digital conversion, and the equipment performing the conversion is called analog-to-digital converter.

The most widely used ADC chips are ADC0804 and ADC0808 of Texas Instruments (TI).

Why do we need ADC?

The world we live in is simulated, that is, everything is continuous in time. In order to make these analog signals compatible with digital devices such as microcontrollers, these controllers can only understand digital signals, such as' 0's and '1's.

Therefore, in order to convert analog signals to digital form, we need to use ADC.

How to perform a / D conversion?

Converting an analog signal to digital form involves two steps-

1) Sampling

Sampling means dividing the signal into smaller time slots. For example, if we have a sine wave with a continuous frequency in the time domain, we will sample it, that is, we will obtain the amplitude value of the sine wave at a certain equal time interval, so it looks a bit like the picture

2) Quantification

The second step is to quantify the obtained amplitude value. As with sampling, the amplitude obtained can be any irrational value, such as pi (22 / 7) or 1.33333 or sq.root (2), etc/ p》

These values will never terminate, so if you want to store them, they will require an unlimited amount of memory

So we need to round the number to the nearest position.

This completes the A / D conversion section.

But is this just theory?

How to actually execute ADC?

The answer is by using an IC such as ADC0804 or ADC0808.

The latest microcontroller series such as Arduino and AVR, linkit one, has an on-board ADC, which we will use in our project.

Step 3: use linkit one onboard ADC

A linkit board has three analog input pins, which means that up to three analog devices can be connected to the board.

The word ADC resolution is also important.

The onboard ADC has a 10 bit resolution, which means that the input analog voltage will be represented by values in the range of 0-1023, i.e. a total of 1024 values

How do I get it?

It's simple. A 10 bit ADC means that we will get a 10 bit digital value. That is, 2 ^ 10 = 1024 values.

In the decimal range, it will be 0 to 1023.

How does it assign numeric values?

For an analog input voltage of 0V, we will obtain the corresponding digital value of 0. Analog input voltage, i.e. 5V, we will get the maximum digital value, i.e. 1023.

Any analog input voltage between 0v-5v will have a digital value between 0 and 1023.

This is the formula

ADC reading = (1024 * analog input voltage) / 5

So, as you can see, for 0V, you'll get 1024 when the ADC reads 5V (actually 1023, because you start counting from 0 here.)

Step 4: gas sensors: how do they work?

There are many types of gas sensors. They are classified according to the way gases are detected in the atmosphere.

1) Electrochemical type

The MQ sensor family falls into the following categories: gas sensors. These gas sensors have sensing elements usually made of SnO2 or tin oxide (IV), which is the correct IUPAC name (International Federation of pure and Applied Chemistry) or commonly referred to as tin oxide (not Satan IC).

SnO2 layer is

In this case, this phenomenon is called adsorption, which is very different from. This ceramic matrix is usually made of alumina (Al2O3). Absorption.

Absorption is a surface phenomenon, which means that gas molecules only accumulate on the surface of SnO2 layer.

To increase the adsorption rate, we need heating elements. This is done through the heating coil (wire mesh) on the MQ gas sensor.

Heating can increase the adsorption rate. There is a specific pre heating time for each sensor before use.

As the gas molecules begin to gather on the surface, we get a voltage proportional to the concentration as the output

This is the voltage we will measure to detect the gas.

Now, due to adsorption, that is, molecules accumulate on the sensing elements of the sensors, these sensors become useless after a few months and need to be replaced with new sensors. You cannot clean the sensor because everything happens at the molecular level.

These are the most widely used and available sensors for electronics enthusiasts.

In addition to these sensors, we have four other types

2) Infrared

3) Infrared imaging

4) Semiconductor and

5) Holography

Now, if you see any MQ gas sensor, it will have 6 pins, 4 for heating purposes and 2 for output voltage and ground.

In the picture, you can see the 6 pins of mq-8 gas sensor.

The second picture shows the mq-8 gas sensor which is highly sensitive to H2. It can also be used for the detection of liquefied petroleum gas.

For reference, I attach this data sheet. It is clear from the data sheet that multiple types of gases can be detected using a single mq-8 sensor.

Before continuing, I suggest you read how the gas sensors of the engineer's garage and seeed studio work and how to select gas sensors.

Step 5: hardware requirements

Transmitter side

MediaTek linkit one board

Grove air quality sensor

Grove LPG sensor Click

Software / services

Ubidots

Step 6: register on ubidots

The first step is to create a free ubidots account!!

Ubidots is the cloud service provider we will use.

You are free to use any other service.

If you re-use other services.

Please go to http://www.ubidots.com

Register on the website.

Then follow the instructions in the picture.

Or follow the instructions below-

1) Register on ubidots

2) Click the symbol in the upper right corner to add a new source.

3) Name your source, such as Intel Edison, Arduino, etc.

4) Click source to add a new variable

5) Select the type of variable as the meter and set the minimum and maximum limits

6) Note the variable ID of each variable you create.

7) Now go to your profile and write down the token ID in the API key.

Please note that the pictures are from my other projects. Everything remains the same, except that you need to specify a different name and select the display type accordingly.

Note the variable ID and auth. Token number. You must enter them in the program.

Everyone's numbers are different. Do not copy the image.

Step 7: transmitter

Grove LPG sensor is connected to A0 pin and grove air quality sensor is connected to A1 pin of mediak linkit one board.

The analysisread() function performs the necessary analog-to-digital conversion.

The digital value obtained is between 0-1023 (1024 in total) because the resolution of the ADC is 10 bits.

Use formula

Reading% = (ADC reading / 1024) * 100

The program for the transmitter is written in Arduino ide with. Ino files attached.

Remember to make the following changes in your code.

1) WiFi AP name

2) WiFi password

4) Token ID

, and then upload the code to your development board.

Step 8: Test

This is a short video of my general screen, showing you how the meter reading changes when any sensor value changes.

For demonstration purposes, I connect A0 and A1 pins directly to the 3.3V and 5V pins on the board.

Note: you can also see these values on the Arduino serial monitor as long as the development board is connected to the computer via USB. After removing the USB and using battery power, it will not print values in the serial monitor.

Manufacture of Toxic Gas Monitor Based on Internet of Things 1

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