Lluis Nadal
Alcoholmeter with MQ3 sensor
Revision 1:5a58f03abfe9, committed 2011-04-09
- Comitter:
- lnadal
- Date:
- Sat Apr 09 14:15:00 2011 +0000
- Parent:
- 0:05d4673b2832
- Child:
- 2:5bb97fd609cb
- Commit message:
Changed in this revision
| main.cpp | Show annotated file Show diff for this revision Revisions of this file |
--- a/main.cpp Sat Apr 09 14:04:34 2011 +0000 +++ b/main.cpp Sat Apr 09 14:15:00 2011 +0000 @@ -2,14 +2,15 @@ Range: 0-3000 ppm. -************************************************************************************************************************* +**************************************************************************************************** -This project was done in 2010-11 school year in Molins de Rei (Barcelona, Spain) in Lluis de Requesens Secondari School. +This project was done in 2010-11 school year in Molins de Rei (Barcelona, Spain) +in Lluis de Requesens Secondari School. -Tacher: Lluis Nadal. +Teacher: Lluis Nadal. Students: Agnes Garriga, Manel Tuells. -************************************************************************************************************************** +*************************************************************************************************** Sensor: MQ-3 alcohol sensor.(http://www.sparkfun.com/; http://www.bricogeek.com/shop/). @@ -20,8 +21,10 @@ -MQ-3 sensor response is not linear. Calibration was done by passing air (with a fishtank air pump) through a dilute solution of ethanol in water. -The resulting air saturated of ethanol vapor and water vapor, was continuously introduced in an open container containing the sensor. Th voltage across a load resistor was measured. +MQ-3 sensor response is not linear. Calibration was done by passing air (with a fishtank air pump) +through a dilute solution of ethanol in water. +The resulting air saturated of ethanol vapor and water vapor, was continuously introduced in an +open container containing the sensor. Th voltage across a load resistor was measured. A 500 Ohm-1% load resistor was selected in order to achieve a measuring range of 3000 ppm. @@ -31,7 +34,8 @@ ppm = 2.71494E+02*X - 3.10999E+02*X^2 + 6.85051E+02*X^3 - 3.47587E+02*X^4 + 7.47499E+01*X^5 -For more accurate readins is recommended a minimum heating time of 5 minutes (24 hours is recommended for the manufacturer) but 1 minute give satisfactory results. +For more accurate readins is recommended a minimum heating time of 5 minutes (24 hours is recommended +for the manufacturer) but 1 minute give satisfactory results. After heating, the sensor is autozeroed by averaging 5 measures. In heating and in autozero operations the sensor must be left away of alcohol vapors! @@ -79,7 +83,7 @@ TextLCD lcd(p24, p26, p27, p28, p29, p30); // Wiring microcontroller - LCD: // rs(4), e(6), d4(11), d5(12), d6(13), d7(14) (R/W(5) a 0) -DigitalIn pushbutton = p8; // Pushbutton (normally open). Stops initial heating time when it is pressed. . +DigitalIn pushbutton = p8; // Pushbutton (normally open). Stops initial heating time when it is pressed. AnalogOut output(p18); // Analog output to a multimeter or datalogger (1V = 1000 ppm).