The Design And Research Of Portable Gas Detector

A single gas detector which is portable and energy-saving is designed in this paper. The concentration of CO, H2 S or O2 in environment can be detected by the gas sensor which installed in the gas detector, the gas concentration can be showed on the LCD screen in real time, compared with the alarm set point at the same time, determining whether need to give a sound, light and shake alarm.A low power 16-bit chip MSP430F435 is adopted on the detector as microcontroller, the chip has a variety of low power consumption modes that can greatly save energy. A section 1300 mAh 3V lithium battery power supply is used on the detector, which can support detector worke long time and reduce the volume of detector. A customized LCD screen with high contrast is used for screen display. The LCD screen has backlight. When it is under weak light, backlight can be litted according to the keystrokes or alarm status, it is convenient for user. When it is under strong light, backlight will be automatically extinguished, saving electricity. Three types of alarm functions which are sound, light and shake are designed on this detector. Sound component are passive buzzer that drived by PWM wave made by Timer A, by changing the PWM duty cycle, a variety of alarm tones can be given by the buzzer; Luminous components adopt SMD LED lights, LED lights containing red and green colour are used for giving light, which are more likely to fake for attention; small button shaker which have the advantage of strong shock, small size and low power consumption is used on this detector. Single button operation is employed on the detector, which can easily achive these functions including switch machine, sound attenuation, check and calibration, meanwhile reducing the volume of detector. Lower limit, upper limit, short contact time allowable concentration(STEL), average concentration(TWA), super range and battery power shortage alarm are designed on this detector. This detecort can communicate with computer through the serial port that are convenient to modify the alarm point data, etc. The ESD element is designed for preventing electrostatic. The shell of detector is made of wear resistant engineering plastic which coated with rubber buffer layer, it can tolerant high and low temperature environment and 2 meters height of free fall to the ground, it can tolerant the test of bad environment. This detector can detect CO, H2 S or O2 using the same piece of PCB, simply by welding resistance and capacitance or not that made different detection circuit. Double PCB board is designed for this detector, the use of SMT components in small package, the double-sided welding and the reasonable put of component can reduce the volume of detector, which indicates its portability.The detector designed in this paper has high precision, fast response speed, small volume, low power consumption. It is a ultra low power testing instrument that can continuous detect the toxic gas or oxygen concentration in environment, and it will be widely used for many fields, such as petroleum, chemical, mining, environmental protection and city construction.