Giới thiệu Mô-đun cảm biến cảnh báo rò rỉ khí gas oxit cacbon MQ-7
Sensitive for Carbon Monoxide The heater uses an alternating voltage of 5V and 1.4V. A library for the MQ-7 : http://thesis.jmsaavedra.com/prototypes/software/mq-7-breakout-arduino-library/ The MQ307A (also on this page) is like this sensor, but uses a lower heater voltage.
Search for datasheet: http://duckduckgo.com/?q=%22mq-7%22+gas+sensor+filetype%3Apdf
VCC - 5v GND - Ground DO - Digital Output = HIGH /LOW (Sensitive can be adjustable by potentiometer) AO - Analog Output = 0-1023 value (Arduino)