{"id":1894,"date":"2024-06-28T08:29:41","date_gmt":"2024-06-28T08:29:41","guid":{"rendered":"https:\/\/iotthinghub.com\/?p=1894"},"modified":"2024-08-11T17:19:22","modified_gmt":"2024-08-11T17:19:22","slug":"smoke-sensor-mq3-sensor","status":"publish","type":"post","link":"https:\/\/iotthinghub.com\/?p=1894","title":{"rendered":"Smoke Sensor MQ3 Sensor"},"content":{"rendered":"\n

Flammable Gas & Smoke Sensor- It is suitable for detecting the H2<\/sub>, LPG, CH4<\/sub>, CO, Alcohol or Propane. MQ3 sensor can sense LPG, CO, Smoke etc. For MQ3 sensor if the concentration is high the resistance decrease, if the concentration is low the resistance increase.   <\/p>\n\n\n\n

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D0 <\/sub>: Indicates the presence of combined gases D0 <\/sub>becomes high, when the gas concentration exceeds the threshold value (as set the potentiometer) and low otherwise.<\/p>\n\n\n\n

A0<\/sub> : Produces an analog output proportional to gas concentration so a higher concentrations results in higher voltage and a lower concentration result in lower voltage<\/p>\n<\/div>\n\n\n\n

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For pure air the resistance factor is 9.83. First step is to calculate the resistance in air, suppose it is R0<\/sub>. We use ATtiny85 for full program. <\/p>\n\n\n\n

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\n#define RO_CLEAN_AIR_FACTOR   9.83\nvolatile uint16_t adc_value;\nfloat R0,R0_OLD,Rs;\nvoid R0_resistancs(void)\n{\n\tadc_value=read_adc(2);\n\tR0_OLD=MQResistanceCalculation(adc_value);\n\tR0=R0_OLD\/RO_CLEAN_AIR_FACTOR;\n}\n<\/pre><\/div>\n\n\n
What is the resistance? Here for pure air R = 1, but for normal air the resistance is R0<\/sub> = (1024\/ADC Value)-1. So the function C:> float MQResistanceCalculation(uint16_t raw_adc)<\/p>\n\n\n
\n#define RL_VALUE              1 \/\/define the load resistance on the board, in kilo ohms\n#define ADC_MAX 1023\nfloat MQResistanceCalculation(uint16_t raw_adc)\n{\n\treturn (((float)RL_VALUE*(ADC_MAX-raw_adc)\/raw_adc));\n}\n<\/pre><\/div>\n\n\n
Since the sensor need some time to initialize, so wait in a loop for calculating air resistance. Now look at the datasheet of the MQ3 sensor-<\/p>\n\n\n\n
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From curve the ration Rs<\/sub>\/R0<\/sub> indicates the presence of LPG, CO or Smoke. If we put the Rs<\/sub>\/R0 <\/sub>value in the graph then we get the value of LPG, CO or Smoke in PPM. From the curve the value of slop, transient and constant value as follow-<\/p>\n\n\n
\nfloat LPGCurve[3]  =  {1.413,0.21,-0.473}; \/\/{2.3,0.21,-0.47};\nfloat COCurve[3]  =   {1.413,0.72,-0.34};  \/\/{2.3,0.72,-0.34};\nfloat SmokeCurve[3] = {2.3,0.53,-0.44};  \/\/{2.3,0.53,-0.44};\n<\/pre><\/div>\n\n\n
The desire PPM is – \"\"<\/p>\n\n\n
\nint MQGetPercentage(float rs_ro_ratio, float *pcurve)\n{\n\tpercentage=(pow(10,(((log10(rs_ro_ratio)-pcurve[1])\/pcurve[2]) + pcurve[0])));\n\treturn percentage;\n}\n<\/pre><\/div>\n\n\n
In order to read LPG, CO or Smoke <\/p>\n\n\n
\nfloat MQGetGasPercentage(float rs_ro_ratio, int gas_id)\n{\n\tif ( gas_id == GAS_LPG ) {\n\t\treturn MQGetPercentage(rs_ro_ratio,LPGCurve);\n\t\t} else if ( gas_id == GAS_CO ) {\n\t\treturn MQGetPercentage(rs_ro_ratio,COCurve);\n\t\t} else if ( gas_id == GAS_SMOKE ) {\n\t\treturn MQGetPercentage(rs_ro_ratio,SmokeCurve);\n\t}\n\treturn 0;\n}\n<\/pre><\/div>\n\n\n
So the full function for calculating the PPM of LPG, CO or Smoke in air is<\/p>\n\n\n
\nextern volatile float lpg,co,smoke; \/\/ extern variable\nvoid air_ppm(void)\n{\n\tadc_value=read_adc(2);\n\tRs=MQResistanceCalculation(adc_value);\n\tRs=Rs\/R0;\n\tlpg = MQGetGasPercentage(Rs,GAS_LPG);\n\tco = MQGetGasPercentage(Rs,GAS_CO);\n\tsmoke = MQGetGasPercentage(Rs,GAS_SMOKE);\n}\n<\/pre><\/div>\n\n\n
We have the function ready, now let make a program that buzz when the smoke or lpg or co is present. According to datasheet of ATtiny85 to generate 20KHz fPWM<\/sub> at OC1A pin is-<\/p>\n\n\n
\nvoid Buzzer_init(void)\n{\n\tDDRB|=(1<<DDB1);\n\tTCCR1|=(1<<COM1A1)|(1<<PWM1A); \/\/only OC1B is connected\n\tTCCR1|=(1<<CS12)|(1<<CS10); \/\/FP_PWM=F_CPU\/16\n\tOCR1C=199; \/\/Top value with F_PWM=20KHz\n\tBuzzer_off();\n}\nvoid Buzzer_on(void)\n{\n\tTCCR1|=(1<<PWM1A);\n\tOCR1A=100; \/\/50% duty cycle;\n}\nvoid Buzzer_off(void)\n{\n\tTCCR1&=~(1<<PWM1A); \/\/PWM Mode disable;\n}\n<\/pre><\/div>\n\n\n
We use extern volatile float lpg,co,smoke; -> global variable to display data any file. You can display the data in LCD module, but in this tutorial we chose ATtiny85 which doesn\u2019t have enough pin for controlling LCD. We use OLED for display the data. Connect all the elements according to the connection diagram.<\/p>\n\n\n\n
Let\u2019s look at the main program that will help you in building your own logic-<\/p>\n\n\n
\n\/********************************************************************\n******      D0- Digital Value 1(High Gas Concentration)      *********\n******                        0(Low gas Concentration)       *********\n******      A0- Analog Value of gas presence                 *********\n******      D0 --- N\/C      &       A0-ADC Channel 0         *********\n*********************************************************************\/\n#include <avr\/io.h>\n#include <util\/delay.h>\n#include <stdio.h>\n#include "smoke.h"\nvolatile char display_value[8]="text";\nint main(void)\n{\n    \/* Initialize OLED Display *\/\n    adc_init();\n    init_OLED();\n    reset_display();\n    clear_display();\n    Buzzer_init();\n    \/*  Main program with logo and design *\/\n    OLCD_write_string(0,0,"MQ3 Sensor Init");\n\tfor(uint16_t i=6500;i>=1;i--)\n\t{\n\t\tR0_resistancs();\n\t\tsprintf(display_value,"Time:%d   ",i);\n\t\tOLCD_write_string(1,0,display_value);\n\t\t_delay_ms(1000);\n\t}\n\tclear_display();\n\t_delay_ms(10);\n\tOLCD_write_string(0,0,"Air Materials  ");\n    while(1)\n    {\n\t\tair_ppm();\n\t    sprintf(display_value,"LPG:%d PPM    ",(int)lpg);\n\t    OLCD_write_string(1,0,display_value);\n\t\tsprintf(display_value,"CO:%d PPM     ",(int)co);\n\t\tOLCD_write_string(2,0,display_value);\n\t\tsprintf(display_value,"Smoke:%d PPM   ",(int)smoke);\n\t\tOLCD_write_string(3,0,display_value);\n\t    (((int)lpg>20)|((int)co>20)|((int)smoke>20))? Buzzer_on():Buzzer_off();\n\t    _delay_ms(1000);\n    }\n    return 0;\n}\n<\/pre><\/div>\n\n\n
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download<\/a><\/div>\n<\/div>\n<\/div>\n\n\n\n
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MQ3 Sensor.rar<\/a><\/p>\n<\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"
Flammable Gas & Smoke Sensor- It is suitable for detecting the H2, LPG, CH4, CO, Alcohol or Propane. MQ3 sensor can sense LPG, CO, Smoke etc. For MQ3 sensor if the concentration is high the resistance decrease, if the concentration is low the resistance increase.    D0 : Indicates the presence of combined gases D0 […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[17],"tags":[],"class_list":["post-1894","post","type-post","status-publish","format-standard","hentry","category-adc"],"_links":{"self":[{"href":"https:\/\/iotthinghub.com\/index.php?rest_route=\/wp\/v2\/posts\/1894","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/iotthinghub.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/iotthinghub.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/iotthinghub.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/iotthinghub.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=1894"}],"version-history":[{"count":18,"href":"https:\/\/iotthinghub.com\/index.php?rest_route=\/wp\/v2\/posts\/1894\/revisions"}],"predecessor-version":[{"id":2627,"href":"https:\/\/iotthinghub.com\/index.php?rest_route=\/wp\/v2\/posts\/1894\/revisions\/2627"}],"wp:attachment":[{"href":"https:\/\/iotthinghub.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1894"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/iotthinghub.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1894"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/iotthinghub.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1894"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}