DIY A FORMALDEHYDE DETECTOR
1078883988 2017-09-20 01:46:28 14722 Views1 Replies HCOH (Formaldehyde) is colorless, poisonous, high water-soluble, high alcohol-soluble and high ether-soluble gas with an obnoxious odor. It is widely used in decoration, such as adhesives, carpeting, decorative paneling and so on. HCOH is a prominent factor in sick-building syndrome as its emissions (accelerated by heat and moisture) irritate eyes and mucous membranes in nose and throat, and cause headache and dizziness. It is widely used in decoration, such as adhesives, carpeting, decorative paneling and so on.
My brotherhave just decorated a new house as the marriage house couple of days ago and he cannot wait for long, for the wedding date is fixed in 1st-Oct. There are many things to check and purify air, kinds of plants and tools. The last time I saw him, he was buying a formaldehyde detector on line, but he complained the inaccuracy of the detector yesterday. As a maker, how could I dfrobot this chance to DIY a simple HCOH detector?
The common solution to measure HCHO in air is the reagent or colorimetric card. But the solution will occupy much time, and used only once. And the result is not very accurate and you just know probably. VOC gas sensor is second-generation solution. it can detect HCHO roughly, because this sensor only expresses the whole concentration of VOC gas, not just HCHO only. There are three kinds of HCOH detectors in the main market, semiconductor sensor, resistance heating and test paper.
Components in Need
Gravity: Formaldehyde (HCHO) Sensor
This one is an electrochemical sensor, which can transform HCOH gas concentration to weak current signal and you can convert a weak current signal to stable current that can be measured by the converter. Compatible with Arduino, it can suppress interference gas and measure HCOH concentration in the air accurately with great stability and high resolution. And the service life is as long as 2 years.
With Gravity interface and wide range power supply, this HCHO sensor supporting analog voltage and serial output. Combined with IOT, it is possible to make an automatic air quality station which can measure HCHO in different sites.
DFRduino UNO R3
Compared to other master boards, DFRduino UNO R3 which compatible withArduino Uno Rev 3 is more cost effective.
Others
Gravity: I2C 16x2 Arduino LCD with RGB Backlight Display
Gravity: IO Expansion Shield for Arduino V7.1
Components Diagram
Circuit Diagram 1-DAC
Switch to DAC, connection diagram is shown as above.
Wiring Diagram1
Caution: In the DAC mode, the measurement accuracy would be influenced by master ADC bit number, reference voltage accuracy. So please charge the main controller with the high precision power supply or the internal reference voltage.
Circuit Diagram2-UART
Switch to UART, connection diagram is shown as above.
Wiring Diagram2
Comparing two modes, I’d love to recommend UART for its better precision.
Sketch
Gravity: I2C 16x2 Arduino LCD with RGB Backlight Display is the combination of 16 million colors, and I chose 4 colors (Green,Red,Yellow,Purple) to represent the distinguish between different HCOH concentration.
The screen display is Green when the HCOH concentration is in a secure range (the indoor air HCOH is lower than 0.08mg/m3 or 0.06ppm)
The screen display is Yellow when the HCOH concentration exceeds a secure range (the indoor air HCOH is higher than 0.06ppm and lower than 0.2ppm), which suggests that you need to take measures to remove HCOH.
The screen display is Red when the HCOH concentration over-exceeds a secure range (the indoor air HCOH is higher than 0.2ppm and lower than 4ppm), which means that you’d better leave it empty for half a year.
The screen display is Red&Purple when the HCOH concentration more than 4ppm (the maximum HCOH measuring range is 5ppm).
Situations
In the 21st century, we meet both harms and benefits. Only when we pay enough attention to health can we age day by day. It is necessary to detect HCOH concentration is many environments, such as bookcase, automobile room, conference room, especially in the newly decorated house.
Bookcase
Automobile room
Conference room
Shelves
Windowsill
Office
Besides these private environments, HCOH detection is also in need in public. For example, building materials, furniture… It can never be too much to mention the damage caused by HCOH, HCOH detectors of civilian values are valued by the public. To satisfy requirements of public, I designed this small, light and cost effective HCOH detector. You can download documents attached in the end page. 
Programs:
HCOH_DAC
My brotherhave just decorated a new house as the marriage house couple of days ago and he cannot wait for long, for the wedding date is fixed in 1st-Oct. There are many things to check and purify air, kinds of plants and tools. The last time I saw him, he was buying a formaldehyde detector on line, but he complained the inaccuracy of the detector yesterday. As a maker, how could I dfrobot this chance to DIY a simple HCOH detector?
The common solution to measure HCHO in air is the reagent or colorimetric card. But the solution will occupy much time, and used only once. And the result is not very accurate and you just know probably. VOC gas sensor is second-generation solution. it can detect HCHO roughly, because this sensor only expresses the whole concentration of VOC gas, not just HCHO only. There are three kinds of HCOH detectors in the main market, semiconductor sensor, resistance heating and test paper.
Components in Need
Gravity: Formaldehyde (HCHO) Sensor
With Gravity interface and wide range power supply, this HCHO sensor supporting analog voltage and serial output. Combined with IOT, it is possible to make an automatic air quality station which can measure HCHO in different sites.
DFRduino UNO R3
Others
Gravity: I2C 16x2 Arduino LCD with RGB Backlight Display
Gravity: IO Expansion Shield for Arduino V7.1
Components Diagram
Wiring Diagram1
Circuit Diagram2-UART
Wiring Diagram2
Sketch
The screen display is Green when the HCOH concentration is in a secure range (the indoor air HCOH is lower than 0.08mg/m3 or 0.06ppm)
The screen display is Yellow when the HCOH concentration exceeds a secure range (the indoor air HCOH is higher than 0.06ppm and lower than 0.2ppm), which suggests that you need to take measures to remove HCOH.
The screen display is Red when the HCOH concentration over-exceeds a secure range (the indoor air HCOH is higher than 0.2ppm and lower than 4ppm), which means that you’d better leave it empty for half a year.
The screen display is Red&Purple when the HCOH concentration more than 4ppm (the maximum HCOH measuring range is 5ppm).
Situations
In the 21st century, we meet both harms and benefits. Only when we pay enough attention to health can we age day by day. It is necessary to detect HCOH concentration is many environments, such as bookcase, automobile room, conference room, especially in the newly decorated house.
Bookcase
Windowsill
Programs:
HCOH_DAC
Code: Select all
HCOH_UART
#define SensorAnalogPin A2 //this pin read the analog voltage from the HCHO sensor
#define VREF 5.0 //voltage on AREF pin
#include "DFRobot_RGBLCD.h"
DFRobot_RGBLCD lcd(16, 2);
void setup()
{
Serial.begin(9600);
lcd.init();
lcd.setRGB(0, 0,255);
lcd.setCursor(1, 0 );
lcd.print("HCHO:");
}
void loop()
{
Serial.print(analogReadPPM());
Serial.println("ppm");
delay(1000);
lcd.setCursor(6,1);
lcd.print(analogReadPPM());
lcd.print("ppm");
lcd.setCursor(6,0);
lcd.print(analogReadPPM()*1.34);
lcd.print("mg/m3");
if(analogReadPPM()<0.06)
{
lcd.setRGB(0, 255, 0);
}
else if(analogReadPPM()<0.2)
{
lcd.setRGB(250, 128, 10);
}
else if(analogReadPPM()<4)
{
lcd.setRGB(255, 0, 0);
}
else
{
lcd.setRGB(255, 0, 0);
delay(250);
lcd.setRGB(0, 0, 0);
}
delay(100);
}
float analogReadPPM()
{
float analogVoltage = analogRead(SensorAnalogPin) / 1024.0 * VREF;
float ppm = 3.125 * analogVoltage - 1.25; //linear relationship(0.4V for 0 ppm and 2V for 5ppm)
if(ppm<0) ppm=0;
else if(ppm>5) ppm = 5;
return ppm;
}
Code: Select all
#include <Wire.h>
#include <DFRobotHCHOSensor.h>
#include <SoftwareSerial.h>
#include "DFRobot_RGBLCD.h"
DFRobot_RGBLCD lcd(16, 2);
#define SensorSerialPin 10 //this pin read the uart signal from the HCHO sensor
SoftwareSerial sensorSerial(SensorSerialPin,SensorSerialPin);
DFRobotHCHOSensor hchoSensor(&sensorSerial);
void setup()
{
sensorSerial.begin(9600); //the baudrate of HCHO is 9600
sensorSerial.listen();
Serial.begin(9600);
lcd.init();
lcd.setRGB(0, 0,255);
lcd.setCursor(1, 0 );
lcd.print("HCHO:");
lcd.setCursor(1, 1 );
}
void loop()
{
if(hchoSensor.available()>0)
{
// delay(1000);
Serial.print(hchoSensor.uartReadPPM());
Serial.println("ppm");
lcd.setCursor(6,1);
lcd.print(hchoSensor.uartReadPPM());
lcd.print("ppm");
lcd.setCursor(6,0);
lcd.print(hchoSensor.uartReadPPM()*1.34);
lcd.print("mg/m3");
if(hchoSensor.uartReadPPM()<0.06)
{
lcd.setRGB(0, 255, 0);
}
else if(hchoSensor.uartReadPPM()<0.2)
{
lcd.setRGB(250, 128, 10);
}
else if(hchoSensor.uartReadPPM()<4)
{
lcd.setRGB(255, 0, 0);
}
else
{
lcd.setRGB(255, 0, 0);
delay(500);
lcd.setRGB(255, 0, 255);
}
delay(100);
}
} 
3.jpg Download(0) 1373_P_1490599039255.jpg Download(0) bgs1.jpg Download(0) DAC.png Download(0) DSC_5521.JPG Download(0) DSC_5522.JPG Download(0) DSC_5525.JPG Download(0) DSC_5556.JPG Download(0) DSC_5582.JPG Download(0) green.JPG Download(0) jq.gif Download(0) Meeting Room.JPG Download(0) PEIJIAN1.jpg Download(0) red.JPG Download(0) SWLJ-DAC.JPG Download(0) UART.png Download(0) UART-LX.JPG Download(0) yellow (2).JPG Download(0) yt.jpg Download(0) zwj.jpg Download(0) 3D printing files and 3D image HCOH Detection.rar Download(0) fixed library files.rar Download(0) 